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Slide 1 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007
Slide 2 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice
Slide 3 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. .
Slide 4 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc .
Slide 5 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request
Slide 6 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications
Slide 7 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet .
Slide 8 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge .
Slide 9 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node .
Slide 10 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile .
Slide 11 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network .
Slide 12 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html .
Slide 13 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) .
Slide 14 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 .
Slide 15 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire .
Slide 16 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites .
Slide 17 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. .
Slide 18 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. .
Slide 19 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider .
Slide 20 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries .
Slide 21 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A .
Slide 22 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking
Slide 23 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van .
Slide 24 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11
Slide 25 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS .
Slide 26 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet .
Slide 27 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes .
Slide 28 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001
Slide 29 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005
Slide 30 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000
Slide 31 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput .
Slide 32 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x
Slide 33 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density .
Slide 34 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput
Slide 35 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D .
Slide 36 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000
Slide 37 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? .
Slide 38 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001
Slide 39 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. .
Slide 40 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. .
Slide 41 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. . Baseline comparison of Metrics Single Radio Mesh Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time ETX performs the best Median path length: HOP: 2, ETX: 3.01, RTT: 3.43, PktPair: 3.46 . Draves-MobiCom-2004
Slide 42 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. . Baseline comparison of Metrics Single Radio Mesh Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time ETX performs the best Median path length: HOP: 2, ETX: 3.01, RTT: 3.43, PktPair: 3.46 . Draves-MobiCom-2004 Experimental Setup 23 node testbed Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer Two scenarios: Baseline (Single radio): 802.11a NetGear cards Two radios 802.11a NetGear cards 802.11g Proxim cards WCETT utilizes 2nd radio better than ETX or shortest path Baseline Comparison of Metrics Two Radio Mesh Median path length: HOP: 2, ETX: 2.4, WCETT: 3 . Draves-SIGCOMM-2004
Slide 43 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. . Baseline comparison of Metrics Single Radio Mesh Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time ETX performs the best Median path length: HOP: 2, ETX: 3.01, RTT: 3.43, PktPair: 3.46 . Draves-MobiCom-2004 Experimental Setup 23 node testbed Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer Two scenarios: Baseline (Single radio): 802.11a NetGear cards Two radios 802.11a NetGear cards 802.11g Proxim cards WCETT utilizes 2nd radio better than ETX or shortest path Baseline Comparison of Metrics Two Radio Mesh Median path length: HOP: 2, ETX: 2.4, WCETT: 3 . Draves-SIGCOMM-2004 But with different traffic pattern…. Trace Capture 1 workstations connected via Ethernet Traces captured during 1-month period Trace Replayed Testbed of 22 mesh computers in office environment 2 IEEE 802.11a/b/g cards per computer . Erickson-MobiSys-2006
Slide 44 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. . Baseline comparison of Metrics Single Radio Mesh Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time ETX performs the best Median path length: HOP: 2, ETX: 3.01, RTT: 3.43, PktPair: 3.46 . Draves-MobiCom-2004 Experimental Setup 23 node testbed Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer Two scenarios: Baseline (Single radio): 802.11a NetGear cards Two radios 802.11a NetGear cards 802.11g Proxim cards WCETT utilizes 2nd radio better than ETX or shortest path Baseline Comparison of Metrics Two Radio Mesh Median path length: HOP: 2, ETX: 2.4, WCETT: 3 . Draves-SIGCOMM-2004 But with different traffic pattern…. Trace Capture 1 workstations connected via Ethernet Traces captured during 1-month period Trace Replayed Testbed of 22 mesh computers in office environment 2 IEEE 802.11a/b/g cards per computer . Erickson-MobiSys-2006 The Multicast Problem A multicast group is defined with a unique group identifier. Nodes may leave or join the group anytime In wired networks physical network topology is static In ad hoc multi-hop wireless networks physical topology can change often Need to Integrate with unicast routing protocols Many proposals [Tree-based, Mesh-based, Location-based] which one to use? . - ABAM (On-Demand Associatively-Based Multicast) - FGMP (Forwarding Group Multicast Protocol) - ADMIR (Adaptive Demand-Driven Multicast Routing) - LAM (Lightweight Adaptive Multicast) - AMRIS (Ad hoc Multicast Routing utilizing Increased id-numberS) - MAODV (Multicast AODV) - DCMP (Dynamic Core Based Multicast Routing) - MCEDAR (Multicast CEDAR) - AMRoute (Adhoc Multicast Routing) - MZR (Multicast Zone Routing) - CAMO (Core-Assisted Mesh Protocol) - ODMRP (On-Deman Multicast Routing Protocol) - CBM (Content Based Multicast) - SPBM (Scalable Position-Based Multicast) - DDM (Differential Destination Multicast) - SRMP (Source Routing-based Multicast Protocol) - DSR-MB (Simple Protocol for Multicast and Broadcast using DSR) - … - …
Slide 45 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. . Baseline comparison of Metrics Single Radio Mesh Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time ETX performs the best Median path length: HOP: 2, ETX: 3.01, RTT: 3.43, PktPair: 3.46 . Draves-MobiCom-2004 Experimental Setup 23 node testbed Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer Two scenarios: Baseline (Single radio): 802.11a NetGear cards Two radios 802.11a NetGear cards 802.11g Proxim cards WCETT utilizes 2nd radio better than ETX or shortest path Baseline Comparison of Metrics Two Radio Mesh Median path length: HOP: 2, ETX: 2.4, WCETT: 3 . Draves-SIGCOMM-2004 But with different traffic pattern…. Trace Capture 1 workstations connected via Ethernet Traces captured during 1-month period Trace Replayed Testbed of 22 mesh computers in office environment 2 IEEE 802.11a/b/g cards per computer . Erickson-MobiSys-2006 The Multicast Problem A multicast group is defined with a unique group identifier. Nodes may leave or join the group anytime In wired networks physical network topology is static In ad hoc multi-hop wireless networks physical topology can change often Need to Integrate with unicast routing protocols Many proposals [Tree-based, Mesh-based, Location-based] which one to use? . - ABAM (On-Demand Associatively-Based Multicast) - FGMP (Forwarding Group Multicast Protocol) - ADMIR (Adaptive Demand-Driven Multicast Routing) - LAM (Lightweight Adaptive Multicast) - AMRIS (Ad hoc Multicast Routing utilizing Increased id-numberS) - MAODV (Multicast AODV) - DCMP (Dynamic Core Based Multicast Routing) - MCEDAR (Multicast CEDAR) - AMRoute (Adhoc Multicast Routing) - MZR (Multicast Zone Routing) - CAMO (Core-Assisted Mesh Protocol) - ODMRP (On-Deman Multicast Routing Protocol) - CBM (Content Based Multicast) - SPBM (Scalable Position-Based Multicast) - DDM (Differential Destination Multicast) - SRMP (Source Routing-based Multicast Protocol) - DSR-MB (Simple Protocol for Multicast and Broadcast using DSR) - … - … The Interference Detection Problem When two systems operate on overlapping frequencies, there exists a potential for harmful interference between them Performance degradation on both systems Conflict graph is determined by the “Interference Graph” To determine the Interference Graph, require Knowledge of packet transmission from nodes that are not “visible” Knowledge of physical location of nodes within the network Knowledge of whether or not multiple transmissions increase ot decrease interference? Interference Graph can change as rapidly as the environment when a node leaves or join the network .
Slide 46 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. . Baseline comparison of Metrics Single Radio Mesh Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time ETX performs the best Median path length: HOP: 2, ETX: 3.01, RTT: 3.43, PktPair: 3.46 . Draves-MobiCom-2004 Experimental Setup 23 node testbed Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer Two scenarios: Baseline (Single radio): 802.11a NetGear cards Two radios 802.11a NetGear cards 802.11g Proxim cards WCETT utilizes 2nd radio better than ETX or shortest path Baseline Comparison of Metrics Two Radio Mesh Median path length: HOP: 2, ETX: 2.4, WCETT: 3 . Draves-SIGCOMM-2004 But with different traffic pattern…. Trace Capture 1 workstations connected via Ethernet Traces captured during 1-month period Trace Replayed Testbed of 22 mesh computers in office environment 2 IEEE 802.11a/b/g cards per computer . Erickson-MobiSys-2006 The Multicast Problem A multicast group is defined with a unique group identifier. Nodes may leave or join the group anytime In wired networks physical network topology is static In ad hoc multi-hop wireless networks physical topology can change often Need to Integrate with unicast routing protocols Many proposals [Tree-based, Mesh-based, Location-based] which one to use? . - ABAM (On-Demand Associatively-Based Multicast) - FGMP (Forwarding Group Multicast Protocol) - ADMIR (Adaptive Demand-Driven Multicast Routing) - LAM (Lightweight Adaptive Multicast) - AMRIS (Ad hoc Multicast Routing utilizing Increased id-numberS) - MAODV (Multicast AODV) - DCMP (Dynamic Core Based Multicast Routing) - MCEDAR (Multicast CEDAR) - AMRoute (Adhoc Multicast Routing) - MZR (Multicast Zone Routing) - CAMO (Core-Assisted Mesh Protocol) - ODMRP (On-Deman Multicast Routing Protocol) - CBM (Content Based Multicast) - SPBM (Scalable Position-Based Multicast) - DDM (Differential Destination Multicast) - SRMP (Source Routing-based Multicast Protocol) - DSR-MB (Simple Protocol for Multicast and Broadcast using DSR) - … - … The Interference Detection Problem When two systems operate on overlapping frequencies, there exists a potential for harmful interference between them Performance degradation on both systems Conflict graph is determined by the “Interference Graph” To determine the Interference Graph, require Knowledge of packet transmission from nodes that are not “visible” Knowledge of physical location of nodes within the network Knowledge of whether or not multiple transmissions increase ot decrease interference? Interference Graph can change as rapidly as the environment when a node leaves or join the network . The Transport Layer Problem Majority of the Internet traffic is TCP Packet losses & delays in wireless can occur due to Environmental fluctuations resulting link failures Stochastic link performance due to rapidly changing error rates CSMA/CA assumes loss is due to congestion and back-off’s TCP assumes packet losses are due to congestion Times out when no ACK is received Invokes slow start, when instead the best response would be to retransmit lost packets quickly RTT calculation can change as rapidly as the environment (link) changes Can we solve this problem without changing the end-to-end semantics? .
Slide 47 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. . Baseline comparison of Metrics Single Radio Mesh Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time ETX performs the best Median path length: HOP: 2, ETX: 3.01, RTT: 3.43, PktPair: 3.46 . Draves-MobiCom-2004 Experimental Setup 23 node testbed Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer Two scenarios: Baseline (Single radio): 802.11a NetGear cards Two radios 802.11a NetGear cards 802.11g Proxim cards WCETT utilizes 2nd radio better than ETX or shortest path Baseline Comparison of Metrics Two Radio Mesh Median path length: HOP: 2, ETX: 2.4, WCETT: 3 . Draves-SIGCOMM-2004 But with different traffic pattern…. Trace Capture 1 workstations connected via Ethernet Traces captured during 1-month period Trace Replayed Testbed of 22 mesh computers in office environment 2 IEEE 802.11a/b/g cards per computer . Erickson-MobiSys-2006 The Multicast Problem A multicast group is defined with a unique group identifier. Nodes may leave or join the group anytime In wired networks physical network topology is static In ad hoc multi-hop wireless networks physical topology can change often Need to Integrate with unicast routing protocols Many proposals [Tree-based, Mesh-based, Location-based] which one to use? . - ABAM (On-Demand Associatively-Based Multicast) - FGMP (Forwarding Group Multicast Protocol) - ADMIR (Adaptive Demand-Driven Multicast Routing) - LAM (Lightweight Adaptive Multicast) - AMRIS (Ad hoc Multicast Routing utilizing Increased id-numberS) - MAODV (Multicast AODV) - DCMP (Dynamic Core Based Multicast Routing) - MCEDAR (Multicast CEDAR) - AMRoute (Adhoc Multicast Routing) - MZR (Multicast Zone Routing) - CAMO (Core-Assisted Mesh Protocol) - ODMRP (On-Deman Multicast Routing Protocol) - CBM (Content Based Multicast) - SPBM (Scalable Position-Based Multicast) - DDM (Differential Destination Multicast) - SRMP (Source Routing-based Multicast Protocol) - DSR-MB (Simple Protocol for Multicast and Broadcast using DSR) - … - … The Interference Detection Problem When two systems operate on overlapping frequencies, there exists a potential for harmful interference between them Performance degradation on both systems Conflict graph is determined by the “Interference Graph” To determine the Interference Graph, require Knowledge of packet transmission from nodes that are not “visible” Knowledge of physical location of nodes within the network Knowledge of whether or not multiple transmissions increase ot decrease interference? Interference Graph can change as rapidly as the environment when a node leaves or join the network . The Transport Layer Problem Majority of the Internet traffic is TCP Packet losses & delays in wireless can occur due to Environmental fluctuations resulting link failures Stochastic link performance due to rapidly changing error rates CSMA/CA assumes loss is due to congestion and back-off’s TCP assumes packet losses are due to congestion Times out when no ACK is received Invokes slow start, when instead the best response would be to retransmit lost packets quickly RTT calculation can change as rapidly as the environment (link) changes Can we solve this problem without changing the end-to-end semantics? . The Security Problem Two type of attackers: External malicious node (no crypto keys) Compromised node (attacker captures legitimate node and reads out all cryptographic information) Attacks Selfish behavior, do not forward other node’s packets Denial of Service (DoS) Jamming Resource consumption attack Routing disruption (e.g. Wormhole attack) Inject malicious routing information Ongoing Research Possible solutions: SEAD, Ariadne, SRP, CONFIDANT, … . Hu-MobiCom-2002 Bucheggar-MobiHoc-2002
Slide 48 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. . Baseline comparison of Metrics Single Radio Mesh Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time ETX performs the best Median path length: HOP: 2, ETX: 3.01, RTT: 3.43, PktPair: 3.46 . Draves-MobiCom-2004 Experimental Setup 23 node testbed Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer Two scenarios: Baseline (Single radio): 802.11a NetGear cards Two radios 802.11a NetGear cards 802.11g Proxim cards WCETT utilizes 2nd radio better than ETX or shortest path Baseline Comparison of Metrics Two Radio Mesh Median path length: HOP: 2, ETX: 2.4, WCETT: 3 . Draves-SIGCOMM-2004 But with different traffic pattern…. Trace Capture 1 workstations connected via Ethernet Traces captured during 1-month period Trace Replayed Testbed of 22 mesh computers in office environment 2 IEEE 802.11a/b/g cards per computer . Erickson-MobiSys-2006 The Multicast Problem A multicast group is defined with a unique group identifier. Nodes may leave or join the group anytime In wired networks physical network topology is static In ad hoc multi-hop wireless networks physical topology can change often Need to Integrate with unicast routing protocols Many proposals [Tree-based, Mesh-based, Location-based] which one to use? . - ABAM (On-Demand Associatively-Based Multicast) - FGMP (Forwarding Group Multicast Protocol) - ADMIR (Adaptive Demand-Driven Multicast Routing) - LAM (Lightweight Adaptive Multicast) - AMRIS (Ad hoc Multicast Routing utilizing Increased id-numberS) - MAODV (Multicast AODV) - DCMP (Dynamic Core Based Multicast Routing) - MCEDAR (Multicast CEDAR) - AMRoute (Adhoc Multicast Routing) - MZR (Multicast Zone Routing) - CAMO (Core-Assisted Mesh Protocol) - ODMRP (On-Deman Multicast Routing Protocol) - CBM (Content Based Multicast) - SPBM (Scalable Position-Based Multicast) - DDM (Differential Destination Multicast) - SRMP (Source Routing-based Multicast Protocol) - DSR-MB (Simple Protocol for Multicast and Broadcast using DSR) - … - … The Interference Detection Problem When two systems operate on overlapping frequencies, there exists a potential for harmful interference between them Performance degradation on both systems Conflict graph is determined by the “Interference Graph” To determine the Interference Graph, require Knowledge of packet transmission from nodes that are not “visible” Knowledge of physical location of nodes within the network Knowledge of whether or not multiple transmissions increase ot decrease interference? Interference Graph can change as rapidly as the environment when a node leaves or join the network . The Transport Layer Problem Majority of the Internet traffic is TCP Packet losses & delays in wireless can occur due to Environmental fluctuations resulting link failures Stochastic link performance due to rapidly changing error rates CSMA/CA assumes loss is due to congestion and back-off’s TCP assumes packet losses are due to congestion Times out when no ACK is received Invokes slow start, when instead the best response would be to retransmit lost packets quickly RTT calculation can change as rapidly as the environment (link) changes Can we solve this problem without changing the end-to-end semantics? . The Security Problem Two type of attackers: External malicious node (no crypto keys) Compromised node (attacker captures legitimate node and reads out all cryptographic information) Attacks Selfish behavior, do not forward other node’s packets Denial of Service (DoS) Jamming Resource consumption attack Routing disruption (e.g. Wormhole attack) Inject malicious routing information Ongoing Research Possible solutions: SEAD, Ariadne, SRP, CONFIDANT, … . Hu-MobiCom-2002 Bucheggar-MobiHoc-2002 Packets get dropped! Doesn’t care The Spectrum Etiquette Problem Local behavior affects Global Performance! .
Slide 49 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. . Baseline comparison of Metrics Single Radio Mesh Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time ETX performs the best Median path length: HOP: 2, ETX: 3.01, RTT: 3.43, PktPair: 3.46 . Draves-MobiCom-2004 Experimental Setup 23 node testbed Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer Two scenarios: Baseline (Single radio): 802.11a NetGear cards Two radios 802.11a NetGear cards 802.11g Proxim cards WCETT utilizes 2nd radio better than ETX or shortest path Baseline Comparison of Metrics Two Radio Mesh Median path length: HOP: 2, ETX: 2.4, WCETT: 3 . Draves-SIGCOMM-2004 But with different traffic pattern…. Trace Capture 1 workstations connected via Ethernet Traces captured during 1-month period Trace Replayed Testbed of 22 mesh computers in office environment 2 IEEE 802.11a/b/g cards per computer . Erickson-MobiSys-2006 The Multicast Problem A multicast group is defined with a unique group identifier. Nodes may leave or join the group anytime In wired networks physical network topology is static In ad hoc multi-hop wireless networks physical topology can change often Need to Integrate with unicast routing protocols Many proposals [Tree-based, Mesh-based, Location-based] which one to use? . - ABAM (On-Demand Associatively-Based Multicast) - FGMP (Forwarding Group Multicast Protocol) - ADMIR (Adaptive Demand-Driven Multicast Routing) - LAM (Lightweight Adaptive Multicast) - AMRIS (Ad hoc Multicast Routing utilizing Increased id-numberS) - MAODV (Multicast AODV) - DCMP (Dynamic Core Based Multicast Routing) - MCEDAR (Multicast CEDAR) - AMRoute (Adhoc Multicast Routing) - MZR (Multicast Zone Routing) - CAMO (Core-Assisted Mesh Protocol) - ODMRP (On-Deman Multicast Routing Protocol) - CBM (Content Based Multicast) - SPBM (Scalable Position-Based Multicast) - DDM (Differential Destination Multicast) - SRMP (Source Routing-based Multicast Protocol) - DSR-MB (Simple Protocol for Multicast and Broadcast using DSR) - … - … The Interference Detection Problem When two systems operate on overlapping frequencies, there exists a potential for harmful interference between them Performance degradation on both systems Conflict graph is determined by the “Interference Graph” To determine the Interference Graph, require Knowledge of packet transmission from nodes that are not “visible” Knowledge of physical location of nodes within the network Knowledge of whether or not multiple transmissions increase ot decrease interference? Interference Graph can change as rapidly as the environment when a node leaves or join the network . The Transport Layer Problem Majority of the Internet traffic is TCP Packet losses & delays in wireless can occur due to Environmental fluctuations resulting link failures Stochastic link performance due to rapidly changing error rates CSMA/CA assumes loss is due to congestion and back-off’s TCP assumes packet losses are due to congestion Times out when no ACK is received Invokes slow start, when instead the best response would be to retransmit lost packets quickly RTT calculation can change as rapidly as the environment (link) changes Can we solve this problem without changing the end-to-end semantics? . The Security Problem Two type of attackers: External malicious node (no crypto keys) Compromised node (attacker captures legitimate node and reads out all cryptographic information) Attacks Selfish behavior, do not forward other node’s packets Denial of Service (DoS) Jamming Resource consumption attack Routing disruption (e.g. Wormhole attack) Inject malicious routing information Ongoing Research Possible solutions: SEAD, Ariadne, SRP, CONFIDANT, … . Hu-MobiCom-2002 Bucheggar-MobiHoc-2002 Packets get dropped! Doesn’t care The Spectrum Etiquette Problem Local behavior affects Global Performance! . Consequently we….. Must Increase Range and Capacity Single radio meshes built on 802.11 technologies are not good enough. We must extend the range of radios; we must understand the achievable capacity in an ideal wireless mesh and we must build technology to approach this capacity? Must Improve Routing Performance Routing protocols based on shortest-hop are sub-optimal. We must build a routing protocol that adapts quickly to topology changes, incorporates wireless interference and link quality. Must Provide Security and Fairness Is it possible to ensure fairness and privacy for end-users and security for the network? We must ensure that no mesh nodes starves and that the mesh guards itself against malicious users. Must Provide Self Management An “organic network” should be both self-organizing and self managing? To what extent can we remove the human out of the loop? . Must Develop a Resilient Framework for Applications In a environmentally hostile environment, we must provide a framework for applications to work robustly. .
Slide 50 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. . Baseline comparison of Metrics Single Radio Mesh Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time ETX performs the best Median path length: HOP: 2, ETX: 3.01, RTT: 3.43, PktPair: 3.46 . Draves-MobiCom-2004 Experimental Setup 23 node testbed Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer Two scenarios: Baseline (Single radio): 802.11a NetGear cards Two radios 802.11a NetGear cards 802.11g Proxim cards WCETT utilizes 2nd radio better than ETX or shortest path Baseline Comparison of Metrics Two Radio Mesh Median path length: HOP: 2, ETX: 2.4, WCETT: 3 . Draves-SIGCOMM-2004 But with different traffic pattern…. Trace Capture 1 workstations connected via Ethernet Traces captured during 1-month period Trace Replayed Testbed of 22 mesh computers in office environment 2 IEEE 802.11a/b/g cards per computer . Erickson-MobiSys-2006 The Multicast Problem A multicast group is defined with a unique group identifier. Nodes may leave or join the group anytime In wired networks physical network topology is static In ad hoc multi-hop wireless networks physical topology can change often Need to Integrate with unicast routing protocols Many proposals [Tree-based, Mesh-based, Location-based] which one to use? . - ABAM (On-Demand Associatively-Based Multicast) - FGMP (Forwarding Group Multicast Protocol) - ADMIR (Adaptive Demand-Driven Multicast Routing) - LAM (Lightweight Adaptive Multicast) - AMRIS (Ad hoc Multicast Routing utilizing Increased id-numberS) - MAODV (Multicast AODV) - DCMP (Dynamic Core Based Multicast Routing) - MCEDAR (Multicast CEDAR) - AMRoute (Adhoc Multicast Routing) - MZR (Multicast Zone Routing) - CAMO (Core-Assisted Mesh Protocol) - ODMRP (On-Deman Multicast Routing Protocol) - CBM (Content Based Multicast) - SPBM (Scalable Position-Based Multicast) - DDM (Differential Destination Multicast) - SRMP (Source Routing-based Multicast Protocol) - DSR-MB (Simple Protocol for Multicast and Broadcast using DSR) - … - … The Interference Detection Problem When two systems operate on overlapping frequencies, there exists a potential for harmful interference between them Performance degradation on both systems Conflict graph is determined by the “Interference Graph” To determine the Interference Graph, require Knowledge of packet transmission from nodes that are not “visible” Knowledge of physical location of nodes within the network Knowledge of whether or not multiple transmissions increase ot decrease interference? Interference Graph can change as rapidly as the environment when a node leaves or join the network . The Transport Layer Problem Majority of the Internet traffic is TCP Packet losses & delays in wireless can occur due to Environmental fluctuations resulting link failures Stochastic link performance due to rapidly changing error rates CSMA/CA assumes loss is due to congestion and back-off’s TCP assumes packet losses are due to congestion Times out when no ACK is received Invokes slow start, when instead the best response would be to retransmit lost packets quickly RTT calculation can change as rapidly as the environment (link) changes Can we solve this problem without changing the end-to-end semantics? . The Security Problem Two type of attackers: External malicious node (no crypto keys) Compromised node (attacker captures legitimate node and reads out all cryptographic information) Attacks Selfish behavior, do not forward other node’s packets Denial of Service (DoS) Jamming Resource consumption attack Routing disruption (e.g. Wormhole attack) Inject malicious routing information Ongoing Research Possible solutions: SEAD, Ariadne, SRP, CONFIDANT, … . Hu-MobiCom-2002 Bucheggar-MobiHoc-2002 Packets get dropped! Doesn’t care The Spectrum Etiquette Problem Local behavior affects Global Performance! . Consequently we….. Must Increase Range and Capacity Single radio meshes built on 802.11 technologies are not good enough. We must extend the range of radios; we must understand the achievable capacity in an ideal wireless mesh and we must build technology to approach this capacity? Must Improve Routing Performance Routing protocols based on shortest-hop are sub-optimal. We must build a routing protocol that adapts quickly to topology changes, incorporates wireless interference and link quality. Must Provide Security and Fairness Is it possible to ensure fairness and privacy for end-users and security for the network? We must ensure that no mesh nodes starves and that the mesh guards itself against malicious users. Must Provide Self Management An “organic network” should be both self-organizing and self managing? To what extent can we remove the human out of the loop? . Must Develop a Resilient Framework for Applications In a environmentally hostile environment, we must provide a framework for applications to work robustly. . Handling the Challenges .
Slide 51 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. . Baseline comparison of Metrics Single Radio Mesh Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time ETX performs the best Median path length: HOP: 2, ETX: 3.01, RTT: 3.43, PktPair: 3.46 . Draves-MobiCom-2004 Experimental Setup 23 node testbed Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer Two scenarios: Baseline (Single radio): 802.11a NetGear cards Two radios 802.11a NetGear cards 802.11g Proxim cards WCETT utilizes 2nd radio better than ETX or shortest path Baseline Comparison of Metrics Two Radio Mesh Median path length: HOP: 2, ETX: 2.4, WCETT: 3 . Draves-SIGCOMM-2004 But with different traffic pattern…. Trace Capture 1 workstations connected via Ethernet Traces captured during 1-month period Trace Replayed Testbed of 22 mesh computers in office environment 2 IEEE 802.11a/b/g cards per computer . Erickson-MobiSys-2006 The Multicast Problem A multicast group is defined with a unique group identifier. Nodes may leave or join the group anytime In wired networks physical network topology is static In ad hoc multi-hop wireless networks physical topology can change often Need to Integrate with unicast routing protocols Many proposals [Tree-based, Mesh-based, Location-based] which one to use? . - ABAM (On-Demand Associatively-Based Multicast) - FGMP (Forwarding Group Multicast Protocol) - ADMIR (Adaptive Demand-Driven Multicast Routing) - LAM (Lightweight Adaptive Multicast) - AMRIS (Ad hoc Multicast Routing utilizing Increased id-numberS) - MAODV (Multicast AODV) - DCMP (Dynamic Core Based Multicast Routing) - MCEDAR (Multicast CEDAR) - AMRoute (Adhoc Multicast Routing) - MZR (Multicast Zone Routing) - CAMO (Core-Assisted Mesh Protocol) - ODMRP (On-Deman Multicast Routing Protocol) - CBM (Content Based Multicast) - SPBM (Scalable Position-Based Multicast) - DDM (Differential Destination Multicast) - SRMP (Source Routing-based Multicast Protocol) - DSR-MB (Simple Protocol for Multicast and Broadcast using DSR) - … - … The Interference Detection Problem When two systems operate on overlapping frequencies, there exists a potential for harmful interference between them Performance degradation on both systems Conflict graph is determined by the “Interference Graph” To determine the Interference Graph, require Knowledge of packet transmission from nodes that are not “visible” Knowledge of physical location of nodes within the network Knowledge of whether or not multiple transmissions increase ot decrease interference? Interference Graph can change as rapidly as the environment when a node leaves or join the network . The Transport Layer Problem Majority of the Internet traffic is TCP Packet losses & delays in wireless can occur due to Environmental fluctuations resulting link failures Stochastic link performance due to rapidly changing error rates CSMA/CA assumes loss is due to congestion and back-off’s TCP assumes packet losses are due to congestion Times out when no ACK is received Invokes slow start, when instead the best response would be to retransmit lost packets quickly RTT calculation can change as rapidly as the environment (link) changes Can we solve this problem without changing the end-to-end semantics? . The Security Problem Two type of attackers: External malicious node (no crypto keys) Compromised node (attacker captures legitimate node and reads out all cryptographic information) Attacks Selfish behavior, do not forward other node’s packets Denial of Service (DoS) Jamming Resource consumption attack Routing disruption (e.g. Wormhole attack) Inject malicious routing information Ongoing Research Possible solutions: SEAD, Ariadne, SRP, CONFIDANT, … . Hu-MobiCom-2002 Bucheggar-MobiHoc-2002 Packets get dropped! Doesn’t care The Spectrum Etiquette Problem Local behavior affects Global Performance! . Consequently we….. Must Increase Range and Capacity Single radio meshes built on 802.11 technologies are not good enough. We must extend the range of radios; we must understand the achievable capacity in an ideal wireless mesh and we must build technology to approach this capacity? Must Improve Routing Performance Routing protocols based on shortest-hop are sub-optimal. We must build a routing protocol that adapts quickly to topology changes, incorporates wireless interference and link quality. Must Provide Security and Fairness Is it possible to ensure fairness and privacy for end-users and security for the network? We must ensure that no mesh nodes starves and that the mesh guards itself against malicious users. Must Provide Self Management An “organic network” should be both self-organizing and self managing? To what extent can we remove the human out of the loop? . Must Develop a Resilient Framework for Applications In a environmentally hostile environment, we must provide a framework for applications to work robustly. . Handling the Challenges . Strategies for increasing Capacity Strategy 1: Use all available channels Avoid spectrum waste Strategy 2: Improve modulation, reception, and coding Today ~ 2.5 bits/Hz (.11g), Soon ~ 4.5 bits / Hz (.11n) Network coding Strategy 3: Improve spatial reuse by reducing interference Fine grain transmit power control (Steerable) directional antennas and directional MACs Strategy 4: Navigate around harmful interference Interference aware least cost routing . Will not cover
Slide 52 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. . Baseline comparison of Metrics Single Radio Mesh Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time ETX performs the best Median path length: HOP: 2, ETX: 3.01, RTT: 3.43, PktPair: 3.46 . Draves-MobiCom-2004 Experimental Setup 23 node testbed Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer Two scenarios: Baseline (Single radio): 802.11a NetGear cards Two radios 802.11a NetGear cards 802.11g Proxim cards WCETT utilizes 2nd radio better than ETX or shortest path Baseline Comparison of Metrics Two Radio Mesh Median path length: HOP: 2, ETX: 2.4, WCETT: 3 . Draves-SIGCOMM-2004 But with different traffic pattern…. Trace Capture 1 workstations connected via Ethernet Traces captured during 1-month period Trace Replayed Testbed of 22 mesh computers in office environment 2 IEEE 802.11a/b/g cards per computer . Erickson-MobiSys-2006 The Multicast Problem A multicast group is defined with a unique group identifier. Nodes may leave or join the group anytime In wired networks physical network topology is static In ad hoc multi-hop wireless networks physical topology can change often Need to Integrate with unicast routing protocols Many proposals [Tree-based, Mesh-based, Location-based] which one to use? . - ABAM (On-Demand Associatively-Based Multicast) - FGMP (Forwarding Group Multicast Protocol) - ADMIR (Adaptive Demand-Driven Multicast Routing) - LAM (Lightweight Adaptive Multicast) - AMRIS (Ad hoc Multicast Routing utilizing Increased id-numberS) - MAODV (Multicast AODV) - DCMP (Dynamic Core Based Multicast Routing) - MCEDAR (Multicast CEDAR) - AMRoute (Adhoc Multicast Routing) - MZR (Multicast Zone Routing) - CAMO (Core-Assisted Mesh Protocol) - ODMRP (On-Deman Multicast Routing Protocol) - CBM (Content Based Multicast) - SPBM (Scalable Position-Based Multicast) - DDM (Differential Destination Multicast) - SRMP (Source Routing-based Multicast Protocol) - DSR-MB (Simple Protocol for Multicast and Broadcast using DSR) - … - … The Interference Detection Problem When two systems operate on overlapping frequencies, there exists a potential for harmful interference between them Performance degradation on both systems Conflict graph is determined by the “Interference Graph” To determine the Interference Graph, require Knowledge of packet transmission from nodes that are not “visible” Knowledge of physical location of nodes within the network Knowledge of whether or not multiple transmissions increase ot decrease interference? Interference Graph can change as rapidly as the environment when a node leaves or join the network . The Transport Layer Problem Majority of the Internet traffic is TCP Packet losses & delays in wireless can occur due to Environmental fluctuations resulting link failures Stochastic link performance due to rapidly changing error rates CSMA/CA assumes loss is due to congestion and back-off’s TCP assumes packet losses are due to congestion Times out when no ACK is received Invokes slow start, when instead the best response would be to retransmit lost packets quickly RTT calculation can change as rapidly as the environment (link) changes Can we solve this problem without changing the end-to-end semantics? . The Security Problem Two type of attackers: External malicious node (no crypto keys) Compromised node (attacker captures legitimate node and reads out all cryptographic information) Attacks Selfish behavior, do not forward other node’s packets Denial of Service (DoS) Jamming Resource consumption attack Routing disruption (e.g. Wormhole attack) Inject malicious routing information Ongoing Research Possible solutions: SEAD, Ariadne, SRP, CONFIDANT, … . Hu-MobiCom-2002 Bucheggar-MobiHoc-2002 Packets get dropped! Doesn’t care The Spectrum Etiquette Problem Local behavior affects Global Performance! . Consequently we….. Must Increase Range and Capacity Single radio meshes built on 802.11 technologies are not good enough. We must extend the range of radios; we must understand the achievable capacity in an ideal wireless mesh and we must build technology to approach this capacity? Must Improve Routing Performance Routing protocols based on shortest-hop are sub-optimal. We must build a routing protocol that adapts quickly to topology changes, incorporates wireless interference and link quality. Must Provide Security and Fairness Is it possible to ensure fairness and privacy for end-users and security for the network? We must ensure that no mesh nodes starves and that the mesh guards itself against malicious users. Must Provide Self Management An “organic network” should be both self-organizing and self managing? To what extent can we remove the human out of the loop? . Must Develop a Resilient Framework for Applications In a environmentally hostile environment, we must provide a framework for applications to work robustly. . Handling the Challenges . Strategies for increasing Capacity Strategy 1: Use all available channels Avoid spectrum waste Strategy 2: Improve modulation, reception, and coding Today ~ 2.5 bits/Hz (.11g), Soon ~ 4.5 bits / Hz (.11n) Network coding Strategy 3: Improve spatial reuse by reducing interference Fine grain transmit power control (Steerable) directional antennas and directional MACs Strategy 4: Navigate around harmful interference Interference aware least cost routing . Will not cover Strategy 1: Multi-Channel Communications Goal Assign n non-interfering channels to n pair of nodes such that n packet transmissions can occur simultaneously. . Knobs
Slide 53 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. . Baseline comparison of Metrics Single Radio Mesh Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time ETX performs the best Median path length: HOP: 2, ETX: 3.01, RTT: 3.43, PktPair: 3.46 . Draves-MobiCom-2004 Experimental Setup 23 node testbed Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer Two scenarios: Baseline (Single radio): 802.11a NetGear cards Two radios 802.11a NetGear cards 802.11g Proxim cards WCETT utilizes 2nd radio better than ETX or shortest path Baseline Comparison of Metrics Two Radio Mesh Median path length: HOP: 2, ETX: 2.4, WCETT: 3 . Draves-SIGCOMM-2004 But with different traffic pattern…. Trace Capture 1 workstations connected via Ethernet Traces captured during 1-month period Trace Replayed Testbed of 22 mesh computers in office environment 2 IEEE 802.11a/b/g cards per computer . Erickson-MobiSys-2006 The Multicast Problem A multicast group is defined with a unique group identifier. Nodes may leave or join the group anytime In wired networks physical network topology is static In ad hoc multi-hop wireless networks physical topology can change often Need to Integrate with unicast routing protocols Many proposals [Tree-based, Mesh-based, Location-based] which one to use? . - ABAM (On-Demand Associatively-Based Multicast) - FGMP (Forwarding Group Multicast Protocol) - ADMIR (Adaptive Demand-Driven Multicast Routing) - LAM (Lightweight Adaptive Multicast) - AMRIS (Ad hoc Multicast Routing utilizing Increased id-numberS) - MAODV (Multicast AODV) - DCMP (Dynamic Core Based Multicast Routing) - MCEDAR (Multicast CEDAR) - AMRoute (Adhoc Multicast Routing) - MZR (Multicast Zone Routing) - CAMO (Core-Assisted Mesh Protocol) - ODMRP (On-Deman Multicast Routing Protocol) - CBM (Content Based Multicast) - SPBM (Scalable Position-Based Multicast) - DDM (Differential Destination Multicast) - SRMP (Source Routing-based Multicast Protocol) - DSR-MB (Simple Protocol for Multicast and Broadcast using DSR) - … - … The Interference Detection Problem When two systems operate on overlapping frequencies, there exists a potential for harmful interference between them Performance degradation on both systems Conflict graph is determined by the “Interference Graph” To determine the Interference Graph, require Knowledge of packet transmission from nodes that are not “visible” Knowledge of physical location of nodes within the network Knowledge of whether or not multiple transmissions increase ot decrease interference? Interference Graph can change as rapidly as the environment when a node leaves or join the network . The Transport Layer Problem Majority of the Internet traffic is TCP Packet losses & delays in wireless can occur due to Environmental fluctuations resulting link failures Stochastic link performance due to rapidly changing error rates CSMA/CA assumes loss is due to congestion and back-off’s TCP assumes packet losses are due to congestion Times out when no ACK is received Invokes slow start, when instead the best response would be to retransmit lost packets quickly RTT calculation can change as rapidly as the environment (link) changes Can we solve this problem without changing the end-to-end semantics? . The Security Problem Two type of attackers: External malicious node (no crypto keys) Compromised node (attacker captures legitimate node and reads out all cryptographic information) Attacks Selfish behavior, do not forward other node’s packets Denial of Service (DoS) Jamming Resource consumption attack Routing disruption (e.g. Wormhole attack) Inject malicious routing information Ongoing Research Possible solutions: SEAD, Ariadne, SRP, CONFIDANT, … . Hu-MobiCom-2002 Bucheggar-MobiHoc-2002 Packets get dropped! Doesn’t care The Spectrum Etiquette Problem Local behavior affects Global Performance! . Consequently we….. Must Increase Range and Capacity Single radio meshes built on 802.11 technologies are not good enough. We must extend the range of radios; we must understand the achievable capacity in an ideal wireless mesh and we must build technology to approach this capacity? Must Improve Routing Performance Routing protocols based on shortest-hop are sub-optimal. We must build a routing protocol that adapts quickly to topology changes, incorporates wireless interference and link quality. Must Provide Security and Fairness Is it possible to ensure fairness and privacy for end-users and security for the network? We must ensure that no mesh nodes starves and that the mesh guards itself against malicious users. Must Provide Self Management An “organic network” should be both self-organizing and self managing? To what extent can we remove the human out of the loop? . Must Develop a Resilient Framework for Applications In a environmentally hostile environment, we must provide a framework for applications to work robustly. . Handling the Challenges . Strategies for increasing Capacity Strategy 1: Use all available channels Avoid spectrum waste Strategy 2: Improve modulation, reception, and coding Today ~ 2.5 bits/Hz (.11g), Soon ~ 4.5 bits / Hz (.11n) Network coding Strategy 3: Improve spatial reuse by reducing interference Fine grain transmit power control (Steerable) directional antennas and directional MACs Strategy 4: Navigate around harmful interference Interference aware least cost routing . Will not cover Strategy 1: Multi-Channel Communications Goal Assign n non-interfering channels to n pair of nodes such that n packet transmissions can occur simultaneously. . Knobs Single Radio – Multiple Channels (SR-MC) Distributed: Use a modified RTS/CTS sequence to negotiate channels Problem How does the sender know which channel the receiver is listening on? Solutions Receive on all channels simultaneously Simplest solution but too costly - will not consider here Use a dedicated rendezvous channel Use a synchronized hopping protocol Provide multiple rendezvous opportunities Centralized: Compute channel assignments using global knowledge Scope of Coverage We will cover schemes that work on commodity radios only .
Slide 54 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. . Baseline comparison of Metrics Single Radio Mesh Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time ETX performs the best Median path length: HOP: 2, ETX: 3.01, RTT: 3.43, PktPair: 3.46 . Draves-MobiCom-2004 Experimental Setup 23 node testbed Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer Two scenarios: Baseline (Single radio): 802.11a NetGear cards Two radios 802.11a NetGear cards 802.11g Proxim cards WCETT utilizes 2nd radio better than ETX or shortest path Baseline Comparison of Metrics Two Radio Mesh Median path length: HOP: 2, ETX: 2.4, WCETT: 3 . Draves-SIGCOMM-2004 But with different traffic pattern…. Trace Capture 1 workstations connected via Ethernet Traces captured during 1-month period Trace Replayed Testbed of 22 mesh computers in office environment 2 IEEE 802.11a/b/g cards per computer . Erickson-MobiSys-2006 The Multicast Problem A multicast group is defined with a unique group identifier. Nodes may leave or join the group anytime In wired networks physical network topology is static In ad hoc multi-hop wireless networks physical topology can change often Need to Integrate with unicast routing protocols Many proposals [Tree-based, Mesh-based, Location-based] which one to use? . - ABAM (On-Demand Associatively-Based Multicast) - FGMP (Forwarding Group Multicast Protocol) - ADMIR (Adaptive Demand-Driven Multicast Routing) - LAM (Lightweight Adaptive Multicast) - AMRIS (Ad hoc Multicast Routing utilizing Increased id-numberS) - MAODV (Multicast AODV) - DCMP (Dynamic Core Based Multicast Routing) - MCEDAR (Multicast CEDAR) - AMRoute (Adhoc Multicast Routing) - MZR (Multicast Zone Routing) - CAMO (Core-Assisted Mesh Protocol) - ODMRP (On-Deman Multicast Routing Protocol) - CBM (Content Based Multicast) - SPBM (Scalable Position-Based Multicast) - DDM (Differential Destination Multicast) - SRMP (Source Routing-based Multicast Protocol) - DSR-MB (Simple Protocol for Multicast and Broadcast using DSR) - … - … The Interference Detection Problem When two systems operate on overlapping frequencies, there exists a potential for harmful interference between them Performance degradation on both systems Conflict graph is determined by the “Interference Graph” To determine the Interference Graph, require Knowledge of packet transmission from nodes that are not “visible” Knowledge of physical location of nodes within the network Knowledge of whether or not multiple transmissions increase ot decrease interference? Interference Graph can change as rapidly as the environment when a node leaves or join the network . The Transport Layer Problem Majority of the Internet traffic is TCP Packet losses & delays in wireless can occur due to Environmental fluctuations resulting link failures Stochastic link performance due to rapidly changing error rates CSMA/CA assumes loss is due to congestion and back-off’s TCP assumes packet losses are due to congestion Times out when no ACK is received Invokes slow start, when instead the best response would be to retransmit lost packets quickly RTT calculation can change as rapidly as the environment (link) changes Can we solve this problem without changing the end-to-end semantics? . The Security Problem Two type of attackers: External malicious node (no crypto keys) Compromised node (attacker captures legitimate node and reads out all cryptographic information) Attacks Selfish behavior, do not forward other node’s packets Denial of Service (DoS) Jamming Resource consumption attack Routing disruption (e.g. Wormhole attack) Inject malicious routing information Ongoing Research Possible solutions: SEAD, Ariadne, SRP, CONFIDANT, … . Hu-MobiCom-2002 Bucheggar-MobiHoc-2002 Packets get dropped! Doesn’t care The Spectrum Etiquette Problem Local behavior affects Global Performance! . Consequently we….. Must Increase Range and Capacity Single radio meshes built on 802.11 technologies are not good enough. We must extend the range of radios; we must understand the achievable capacity in an ideal wireless mesh and we must build technology to approach this capacity? Must Improve Routing Performance Routing protocols based on shortest-hop are sub-optimal. We must build a routing protocol that adapts quickly to topology changes, incorporates wireless interference and link quality. Must Provide Security and Fairness Is it possible to ensure fairness and privacy for end-users and security for the network? We must ensure that no mesh nodes starves and that the mesh guards itself against malicious users. Must Provide Self Management An “organic network” should be both self-organizing and self managing? To what extent can we remove the human out of the loop? . Must Develop a Resilient Framework for Applications In a environmentally hostile environment, we must provide a framework for applications to work robustly. . Handling the Challenges . Strategies for increasing Capacity Strategy 1: Use all available channels Avoid spectrum waste Strategy 2: Improve modulation, reception, and coding Today ~ 2.5 bits/Hz (.11g), Soon ~ 4.5 bits / Hz (.11n) Network coding Strategy 3: Improve spatial reuse by reducing interference Fine grain transmit power control (Steerable) directional antennas and directional MACs Strategy 4: Navigate around harmful interference Interference aware least cost routing . Will not cover Strategy 1: Multi-Channel Communications Goal Assign n non-interfering channels to n pair of nodes such that n packet transmissions can occur simultaneously. . Knobs Single Radio – Multiple Channels (SR-MC) Distributed: Use a modified RTS/CTS sequence to negotiate channels Problem How does the sender know which channel the receiver is listening on? Solutions Receive on all channels simultaneously Simplest solution but too costly - will not consider here Use a dedicated rendezvous channel Use a synchronized hopping protocol Provide multiple rendezvous opportunities Centralized: Compute channel assignments using global knowledge Scope of Coverage We will cover schemes that work on commodity radios only . Packets-in-Flight Example Revisited Negotiating Channel with RTS / CTS . 2 3 4 5 7 8 9 1 11 10 RTS (C1,C3,C7) RTS (C3,C5,C7,C11) CTS (C11) CTS (C1, C7) 6 C2 C2 C1 C11 C1 10 nodes are active, 5 packets in flight, 150% improvement!
Slide 55 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. . Baseline comparison of Metrics Single Radio Mesh Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time ETX performs the best Median path length: HOP: 2, ETX: 3.01, RTT: 3.43, PktPair: 3.46 . Draves-MobiCom-2004 Experimental Setup 23 node testbed Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer Two scenarios: Baseline (Single radio): 802.11a NetGear cards Two radios 802.11a NetGear cards 802.11g Proxim cards WCETT utilizes 2nd radio better than ETX or shortest path Baseline Comparison of Metrics Two Radio Mesh Median path length: HOP: 2, ETX: 2.4, WCETT: 3 . Draves-SIGCOMM-2004 But with different traffic pattern…. Trace Capture 1 workstations connected via Ethernet Traces captured during 1-month period Trace Replayed Testbed of 22 mesh computers in office environment 2 IEEE 802.11a/b/g cards per computer . Erickson-MobiSys-2006 The Multicast Problem A multicast group is defined with a unique group identifier. Nodes may leave or join the group anytime In wired networks physical network topology is static In ad hoc multi-hop wireless networks physical topology can change often Need to Integrate with unicast routing protocols Many proposals [Tree-based, Mesh-based, Location-based] which one to use? . - ABAM (On-Demand Associatively-Based Multicast) - FGMP (Forwarding Group Multicast Protocol) - ADMIR (Adaptive Demand-Driven Multicast Routing) - LAM (Lightweight Adaptive Multicast) - AMRIS (Ad hoc Multicast Routing utilizing Increased id-numberS) - MAODV (Multicast AODV) - DCMP (Dynamic Core Based Multicast Routing) - MCEDAR (Multicast CEDAR) - AMRoute (Adhoc Multicast Routing) - MZR (Multicast Zone Routing) - CAMO (Core-Assisted Mesh Protocol) - ODMRP (On-Deman Multicast Routing Protocol) - CBM (Content Based Multicast) - SPBM (Scalable Position-Based Multicast) - DDM (Differential Destination Multicast) - SRMP (Source Routing-based Multicast Protocol) - DSR-MB (Simple Protocol for Multicast and Broadcast using DSR) - … - … The Interference Detection Problem When two systems operate on overlapping frequencies, there exists a potential for harmful interference between them Performance degradation on both systems Conflict graph is determined by the “Interference Graph” To determine the Interference Graph, require Knowledge of packet transmission from nodes that are not “visible” Knowledge of physical location of nodes within the network Knowledge of whether or not multiple transmissions increase ot decrease interference? Interference Graph can change as rapidly as the environment when a node leaves or join the network . The Transport Layer Problem Majority of the Internet traffic is TCP Packet losses & delays in wireless can occur due to Environmental fluctuations resulting link failures Stochastic link performance due to rapidly changing error rates CSMA/CA assumes loss is due to congestion and back-off’s TCP assumes packet losses are due to congestion Times out when no ACK is received Invokes slow start, when instead the best response would be to retransmit lost packets quickly RTT calculation can change as rapidly as the environment (link) changes Can we solve this problem without changing the end-to-end semantics? . The Security Problem Two type of attackers: External malicious node (no crypto keys) Compromised node (attacker captures legitimate node and reads out all cryptographic information) Attacks Selfish behavior, do not forward other node’s packets Denial of Service (DoS) Jamming Resource consumption attack Routing disruption (e.g. Wormhole attack) Inject malicious routing information Ongoing Research Possible solutions: SEAD, Ariadne, SRP, CONFIDANT, … . Hu-MobiCom-2002 Bucheggar-MobiHoc-2002 Packets get dropped! Doesn’t care The Spectrum Etiquette Problem Local behavior affects Global Performance! . Consequently we….. Must Increase Range and Capacity Single radio meshes built on 802.11 technologies are not good enough. We must extend the range of radios; we must understand the achievable capacity in an ideal wireless mesh and we must build technology to approach this capacity? Must Improve Routing Performance Routing protocols based on shortest-hop are sub-optimal. We must build a routing protocol that adapts quickly to topology changes, incorporates wireless interference and link quality. Must Provide Security and Fairness Is it possible to ensure fairness and privacy for end-users and security for the network? We must ensure that no mesh nodes starves and that the mesh guards itself against malicious users. Must Provide Self Management An “organic network” should be both self-organizing and self managing? To what extent can we remove the human out of the loop? . Must Develop a Resilient Framework for Applications In a environmentally hostile environment, we must provide a framework for applications to work robustly. . Handling the Challenges . Strategies for increasing Capacity Strategy 1: Use all available channels Avoid spectrum waste Strategy 2: Improve modulation, reception, and coding Today ~ 2.5 bits/Hz (.11g), Soon ~ 4.5 bits / Hz (.11n) Network coding Strategy 3: Improve spatial reuse by reducing interference Fine grain transmit power control (Steerable) directional antennas and directional MACs Strategy 4: Navigate around harmful interference Interference aware least cost routing . Will not cover Strategy 1: Multi-Channel Communications Goal Assign n non-interfering channels to n pair of nodes such that n packet transmissions can occur simultaneously. . Knobs Single Radio – Multiple Channels (SR-MC) Distributed: Use a modified RTS/CTS sequence to negotiate channels Problem How does the sender know which channel the receiver is listening on? Solutions Receive on all channels simultaneously Simplest solution but too costly - will not consider here Use a dedicated rendezvous channel Use a synchronized hopping protocol Provide multiple rendezvous opportunities Centralized: Compute channel assignments using global knowledge Scope of Coverage We will cover schemes that work on commodity radios only . Packets-in-Flight Example Revisited Negotiating Channel with RTS / CTS . 2 3 4 5 7 8 9 1 11 10 RTS (C1,C3,C7) RTS (C3,C5,C7,C11) CTS (C11) CTS (C1, C7) 6 C2 C2 C1 C11 C1 10 nodes are active, 5 packets in flight, 150% improvement! Note: Hidden Terminal – Multi-Channel Case Let C1 be the rendezvous channel γ can hear traffic on C1 only, doesn’t hear the CTS from β consequently doesn’t know anything about traffic on C6 (δ is too far to hear anything from β) . α β γ δ Possible solution: Use multiple radios So-MobiHoc-2004
Slide 56 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. . Baseline comparison of Metrics Single Radio Mesh Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time ETX performs the best Median path length: HOP: 2, ETX: 3.01, RTT: 3.43, PktPair: 3.46 . Draves-MobiCom-2004 Experimental Setup 23 node testbed Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer Two scenarios: Baseline (Single radio): 802.11a NetGear cards Two radios 802.11a NetGear cards 802.11g Proxim cards WCETT utilizes 2nd radio better than ETX or shortest path Baseline Comparison of Metrics Two Radio Mesh Median path length: HOP: 2, ETX: 2.4, WCETT: 3 . Draves-SIGCOMM-2004 But with different traffic pattern…. Trace Capture 1 workstations connected via Ethernet Traces captured during 1-month period Trace Replayed Testbed of 22 mesh computers in office environment 2 IEEE 802.11a/b/g cards per computer . Erickson-MobiSys-2006 The Multicast Problem A multicast group is defined with a unique group identifier. Nodes may leave or join the group anytime In wired networks physical network topology is static In ad hoc multi-hop wireless networks physical topology can change often Need to Integrate with unicast routing protocols Many proposals [Tree-based, Mesh-based, Location-based] which one to use? . - ABAM (On-Demand Associatively-Based Multicast) - FGMP (Forwarding Group Multicast Protocol) - ADMIR (Adaptive Demand-Driven Multicast Routing) - LAM (Lightweight Adaptive Multicast) - AMRIS (Ad hoc Multicast Routing utilizing Increased id-numberS) - MAODV (Multicast AODV) - DCMP (Dynamic Core Based Multicast Routing) - MCEDAR (Multicast CEDAR) - AMRoute (Adhoc Multicast Routing) - MZR (Multicast Zone Routing) - CAMO (Core-Assisted Mesh Protocol) - ODMRP (On-Deman Multicast Routing Protocol) - CBM (Content Based Multicast) - SPBM (Scalable Position-Based Multicast) - DDM (Differential Destination Multicast) - SRMP (Source Routing-based Multicast Protocol) - DSR-MB (Simple Protocol for Multicast and Broadcast using DSR) - … - … The Interference Detection Problem When two systems operate on overlapping frequencies, there exists a potential for harmful interference between them Performance degradation on both systems Conflict graph is determined by the “Interference Graph” To determine the Interference Graph, require Knowledge of packet transmission from nodes that are not “visible” Knowledge of physical location of nodes within the network Knowledge of whether or not multiple transmissions increase ot decrease interference? Interference Graph can change as rapidly as the environment when a node leaves or join the network . The Transport Layer Problem Majority of the Internet traffic is TCP Packet losses & delays in wireless can occur due to Environmental fluctuations resulting link failures Stochastic link performance due to rapidly changing error rates CSMA/CA assumes loss is due to congestion and back-off’s TCP assumes packet losses are due to congestion Times out when no ACK is received Invokes slow start, when instead the best response would be to retransmit lost packets quickly RTT calculation can change as rapidly as the environment (link) changes Can we solve this problem without changing the end-to-end semantics? . The Security Problem Two type of attackers: External malicious node (no crypto keys) Compromised node (attacker captures legitimate node and reads out all cryptographic information) Attacks Selfish behavior, do not forward other node’s packets Denial of Service (DoS) Jamming Resource consumption attack Routing disruption (e.g. Wormhole attack) Inject malicious routing information Ongoing Research Possible solutions: SEAD, Ariadne, SRP, CONFIDANT, … . Hu-MobiCom-2002 Bucheggar-MobiHoc-2002 Packets get dropped! Doesn’t care The Spectrum Etiquette Problem Local behavior affects Global Performance! . Consequently we….. Must Increase Range and Capacity Single radio meshes built on 802.11 technologies are not good enough. We must extend the range of radios; we must understand the achievable capacity in an ideal wireless mesh and we must build technology to approach this capacity? Must Improve Routing Performance Routing protocols based on shortest-hop are sub-optimal. We must build a routing protocol that adapts quickly to topology changes, incorporates wireless interference and link quality. Must Provide Security and Fairness Is it possible to ensure fairness and privacy for end-users and security for the network? We must ensure that no mesh nodes starves and that the mesh guards itself against malicious users. Must Provide Self Management An “organic network” should be both self-organizing and self managing? To what extent can we remove the human out of the loop? . Must Develop a Resilient Framework for Applications In a environmentally hostile environment, we must provide a framework for applications to work robustly. . Handling the Challenges . Strategies for increasing Capacity Strategy 1: Use all available channels Avoid spectrum waste Strategy 2: Improve modulation, reception, and coding Today ~ 2.5 bits/Hz (.11g), Soon ~ 4.5 bits / Hz (.11n) Network coding Strategy 3: Improve spatial reuse by reducing interference Fine grain transmit power control (Steerable) directional antennas and directional MACs Strategy 4: Navigate around harmful interference Interference aware least cost routing . Will not cover Strategy 1: Multi-Channel Communications Goal Assign n non-interfering channels to n pair of nodes such that n packet transmissions can occur simultaneously. . Knobs Single Radio – Multiple Channels (SR-MC) Distributed: Use a modified RTS/CTS sequence to negotiate channels Problem How does the sender know which channel the receiver is listening on? Solutions Receive on all channels simultaneously Simplest solution but too costly - will not consider here Use a dedicated rendezvous channel Use a synchronized hopping protocol Provide multiple rendezvous opportunities Centralized: Compute channel assignments using global knowledge Scope of Coverage We will cover schemes that work on commodity radios only . Packets-in-Flight Example Revisited Negotiating Channel with RTS / CTS . 2 3 4 5 7 8 9 1 11 10 RTS (C1,C3,C7) RTS (C3,C5,C7,C11) CTS (C11) CTS (C1, C7) 6 C2 C2 C1 C11 C1 10 nodes are active, 5 packets in flight, 150% improvement! Note: Hidden Terminal – Multi-Channel Case Let C1 be the rendezvous channel γ can hear traffic on C1 only, doesn’t hear the CTS from β consequently doesn’t know anything about traffic on C6 (δ is too far to hear anything from β) . α β γ δ Possible solution: Use multiple radios So-MobiHoc-2004 Firmware Packets for C6 TCP/IP, Network Stack Packets for C11 Application Layer User-level Kernel-level Buffer packets, switch between channels Packets for C1 802.11 hardware Implementation Option for SR-MC 802.11 Device Driver Switching logic Channel switching speed: Today - 5 milliseconds Possible - 80 microseconds Chandra-INFOCOM-2004
Slide 57 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. . Baseline comparison of Metrics Single Radio Mesh Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time ETX performs the best Median path length: HOP: 2, ETX: 3.01, RTT: 3.43, PktPair: 3.46 . Draves-MobiCom-2004 Experimental Setup 23 node testbed Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer Two scenarios: Baseline (Single radio): 802.11a NetGear cards Two radios 802.11a NetGear cards 802.11g Proxim cards WCETT utilizes 2nd radio better than ETX or shortest path Baseline Comparison of Metrics Two Radio Mesh Median path length: HOP: 2, ETX: 2.4, WCETT: 3 . Draves-SIGCOMM-2004 But with different traffic pattern…. Trace Capture 1 workstations connected via Ethernet Traces captured during 1-month period Trace Replayed Testbed of 22 mesh computers in office environment 2 IEEE 802.11a/b/g cards per computer . Erickson-MobiSys-2006 The Multicast Problem A multicast group is defined with a unique group identifier. Nodes may leave or join the group anytime In wired networks physical network topology is static In ad hoc multi-hop wireless networks physical topology can change often Need to Integrate with unicast routing protocols Many proposals [Tree-based, Mesh-based, Location-based] which one to use? . - ABAM (On-Demand Associatively-Based Multicast) - FGMP (Forwarding Group Multicast Protocol) - ADMIR (Adaptive Demand-Driven Multicast Routing) - LAM (Lightweight Adaptive Multicast) - AMRIS (Ad hoc Multicast Routing utilizing Increased id-numberS) - MAODV (Multicast AODV) - DCMP (Dynamic Core Based Multicast Routing) - MCEDAR (Multicast CEDAR) - AMRoute (Adhoc Multicast Routing) - MZR (Multicast Zone Routing) - CAMO (Core-Assisted Mesh Protocol) - ODMRP (On-Deman Multicast Routing Protocol) - CBM (Content Based Multicast) - SPBM (Scalable Position-Based Multicast) - DDM (Differential Destination Multicast) - SRMP (Source Routing-based Multicast Protocol) - DSR-MB (Simple Protocol for Multicast and Broadcast using DSR) - … - … The Interference Detection Problem When two systems operate on overlapping frequencies, there exists a potential for harmful interference between them Performance degradation on both systems Conflict graph is determined by the “Interference Graph” To determine the Interference Graph, require Knowledge of packet transmission from nodes that are not “visible” Knowledge of physical location of nodes within the network Knowledge of whether or not multiple transmissions increase ot decrease interference? Interference Graph can change as rapidly as the environment when a node leaves or join the network . The Transport Layer Problem Majority of the Internet traffic is TCP Packet losses & delays in wireless can occur due to Environmental fluctuations resulting link failures Stochastic link performance due to rapidly changing error rates CSMA/CA assumes loss is due to congestion and back-off’s TCP assumes packet losses are due to congestion Times out when no ACK is received Invokes slow start, when instead the best response would be to retransmit lost packets quickly RTT calculation can change as rapidly as the environment (link) changes Can we solve this problem without changing the end-to-end semantics? . The Security Problem Two type of attackers: External malicious node (no crypto keys) Compromised node (attacker captures legitimate node and reads out all cryptographic information) Attacks Selfish behavior, do not forward other node’s packets Denial of Service (DoS) Jamming Resource consumption attack Routing disruption (e.g. Wormhole attack) Inject malicious routing information Ongoing Research Possible solutions: SEAD, Ariadne, SRP, CONFIDANT, … . Hu-MobiCom-2002 Bucheggar-MobiHoc-2002 Packets get dropped! Doesn’t care The Spectrum Etiquette Problem Local behavior affects Global Performance! . Consequently we….. Must Increase Range and Capacity Single radio meshes built on 802.11 technologies are not good enough. We must extend the range of radios; we must understand the achievable capacity in an ideal wireless mesh and we must build technology to approach this capacity? Must Improve Routing Performance Routing protocols based on shortest-hop are sub-optimal. We must build a routing protocol that adapts quickly to topology changes, incorporates wireless interference and link quality. Must Provide Security and Fairness Is it possible to ensure fairness and privacy for end-users and security for the network? We must ensure that no mesh nodes starves and that the mesh guards itself against malicious users. Must Provide Self Management An “organic network” should be both self-organizing and self managing? To what extent can we remove the human out of the loop? . Must Develop a Resilient Framework for Applications In a environmentally hostile environment, we must provide a framework for applications to work robustly. . Handling the Challenges . Strategies for increasing Capacity Strategy 1: Use all available channels Avoid spectrum waste Strategy 2: Improve modulation, reception, and coding Today ~ 2.5 bits/Hz (.11g), Soon ~ 4.5 bits / Hz (.11n) Network coding Strategy 3: Improve spatial reuse by reducing interference Fine grain transmit power control (Steerable) directional antennas and directional MACs Strategy 4: Navigate around harmful interference Interference aware least cost routing . Will not cover Strategy 1: Multi-Channel Communications Goal Assign n non-interfering channels to n pair of nodes such that n packet transmissions can occur simultaneously. . Knobs Single Radio – Multiple Channels (SR-MC) Distributed: Use a modified RTS/CTS sequence to negotiate channels Problem How does the sender know which channel the receiver is listening on? Solutions Receive on all channels simultaneously Simplest solution but too costly - will not consider here Use a dedicated rendezvous channel Use a synchronized hopping protocol Provide multiple rendezvous opportunities Centralized: Compute channel assignments using global knowledge Scope of Coverage We will cover schemes that work on commodity radios only . Packets-in-Flight Example Revisited Negotiating Channel with RTS / CTS . 2 3 4 5 7 8 9 1 11 10 RTS (C1,C3,C7) RTS (C3,C5,C7,C11) CTS (C11) CTS (C1, C7) 6 C2 C2 C1 C11 C1 10 nodes are active, 5 packets in flight, 150% improvement! Note: Hidden Terminal – Multi-Channel Case Let C1 be the rendezvous channel γ can hear traffic on C1 only, doesn’t hear the CTS from β consequently doesn’t know anything about traffic on C6 (δ is too far to hear anything from β) . α β γ δ Possible solution: Use multiple radios So-MobiHoc-2004 Firmware Packets for C6 TCP/IP, Network Stack Packets for C11 Application Layer User-level Kernel-level Buffer packets, switch between channels Packets for C1 802.11 hardware Implementation Option for SR-MC 802.11 Device Driver Switching logic Channel switching speed: Today - 5 milliseconds Possible - 80 microseconds Chandra-INFOCOM-2004 Multi-Channel Medium Access Control (MMAC) . Divide time into beacon intervals Divide a beacon interval into two phase Negotiation Phase: All nodes switch to a pre-defined common channel and negotiate the channel to use Transfer Phase: Once a channel is selected, the source & receiver switch to this channel and data transfer occurs during this phase Idea: Periodically rendezvous on a fixed channel to decide the next channel Issues Requires tight clock synchronization Packets to multiple destinations can incur high delays Congestion on the common channel Common channel goes bad, everything goes bad Not able to handle broadcasts So-MobiHoc-2004
Slide 58 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. . Baseline comparison of Metrics Single Radio Mesh Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time ETX performs the best Median path length: HOP: 2, ETX: 3.01, RTT: 3.43, PktPair: 3.46 . Draves-MobiCom-2004 Experimental Setup 23 node testbed Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer Two scenarios: Baseline (Single radio): 802.11a NetGear cards Two radios 802.11a NetGear cards 802.11g Proxim cards WCETT utilizes 2nd radio better than ETX or shortest path Baseline Comparison of Metrics Two Radio Mesh Median path length: HOP: 2, ETX: 2.4, WCETT: 3 . Draves-SIGCOMM-2004 But with different traffic pattern…. Trace Capture 1 workstations connected via Ethernet Traces captured during 1-month period Trace Replayed Testbed of 22 mesh computers in office environment 2 IEEE 802.11a/b/g cards per computer . Erickson-MobiSys-2006 The Multicast Problem A multicast group is defined with a unique group identifier. Nodes may leave or join the group anytime In wired networks physical network topology is static In ad hoc multi-hop wireless networks physical topology can change often Need to Integrate with unicast routing protocols Many proposals [Tree-based, Mesh-based, Location-based] which one to use? . - ABAM (On-Demand Associatively-Based Multicast) - FGMP (Forwarding Group Multicast Protocol) - ADMIR (Adaptive Demand-Driven Multicast Routing) - LAM (Lightweight Adaptive Multicast) - AMRIS (Ad hoc Multicast Routing utilizing Increased id-numberS) - MAODV (Multicast AODV) - DCMP (Dynamic Core Based Multicast Routing) - MCEDAR (Multicast CEDAR) - AMRoute (Adhoc Multicast Routing) - MZR (Multicast Zone Routing) - CAMO (Core-Assisted Mesh Protocol) - ODMRP (On-Deman Multicast Routing Protocol) - CBM (Content Based Multicast) - SPBM (Scalable Position-Based Multicast) - DDM (Differential Destination Multicast) - SRMP (Source Routing-based Multicast Protocol) - DSR-MB (Simple Protocol for Multicast and Broadcast using DSR) - … - … The Interference Detection Problem When two systems operate on overlapping frequencies, there exists a potential for harmful interference between them Performance degradation on both systems Conflict graph is determined by the “Interference Graph” To determine the Interference Graph, require Knowledge of packet transmission from nodes that are not “visible” Knowledge of physical location of nodes within the network Knowledge of whether or not multiple transmissions increase ot decrease interference? Interference Graph can change as rapidly as the environment when a node leaves or join the network . The Transport Layer Problem Majority of the Internet traffic is TCP Packet losses & delays in wireless can occur due to Environmental fluctuations resulting link failures Stochastic link performance due to rapidly changing error rates CSMA/CA assumes loss is due to congestion and back-off’s TCP assumes packet losses are due to congestion Times out when no ACK is received Invokes slow start, when instead the best response would be to retransmit lost packets quickly RTT calculation can change as rapidly as the environment (link) changes Can we solve this problem without changing the end-to-end semantics? . The Security Problem Two type of attackers: External malicious node (no crypto keys) Compromised node (attacker captures legitimate node and reads out all cryptographic information) Attacks Selfish behavior, do not forward other node’s packets Denial of Service (DoS) Jamming Resource consumption attack Routing disruption (e.g. Wormhole attack) Inject malicious routing information Ongoing Research Possible solutions: SEAD, Ariadne, SRP, CONFIDANT, … . Hu-MobiCom-2002 Bucheggar-MobiHoc-2002 Packets get dropped! Doesn’t care The Spectrum Etiquette Problem Local behavior affects Global Performance! . Consequently we….. Must Increase Range and Capacity Single radio meshes built on 802.11 technologies are not good enough. We must extend the range of radios; we must understand the achievable capacity in an ideal wireless mesh and we must build technology to approach this capacity? Must Improve Routing Performance Routing protocols based on shortest-hop are sub-optimal. We must build a routing protocol that adapts quickly to topology changes, incorporates wireless interference and link quality. Must Provide Security and Fairness Is it possible to ensure fairness and privacy for end-users and security for the network? We must ensure that no mesh nodes starves and that the mesh guards itself against malicious users. Must Provide Self Management An “organic network” should be both self-organizing and self managing? To what extent can we remove the human out of the loop? . Must Develop a Resilient Framework for Applications In a environmentally hostile environment, we must provide a framework for applications to work robustly. . Handling the Challenges . Strategies for increasing Capacity Strategy 1: Use all available channels Avoid spectrum waste Strategy 2: Improve modulation, reception, and coding Today ~ 2.5 bits/Hz (.11g), Soon ~ 4.5 bits / Hz (.11n) Network coding Strategy 3: Improve spatial reuse by reducing interference Fine grain transmit power control (Steerable) directional antennas and directional MACs Strategy 4: Navigate around harmful interference Interference aware least cost routing . Will not cover Strategy 1: Multi-Channel Communications Goal Assign n non-interfering channels to n pair of nodes such that n packet transmissions can occur simultaneously. . Knobs Single Radio – Multiple Channels (SR-MC) Distributed: Use a modified RTS/CTS sequence to negotiate channels Problem How does the sender know which channel the receiver is listening on? Solutions Receive on all channels simultaneously Simplest solution but too costly - will not consider here Use a dedicated rendezvous channel Use a synchronized hopping protocol Provide multiple rendezvous opportunities Centralized: Compute channel assignments using global knowledge Scope of Coverage We will cover schemes that work on commodity radios only . Packets-in-Flight Example Revisited Negotiating Channel with RTS / CTS . 2 3 4 5 7 8 9 1 11 10 RTS (C1,C3,C7) RTS (C3,C5,C7,C11) CTS (C11) CTS (C1, C7) 6 C2 C2 C1 C11 C1 10 nodes are active, 5 packets in flight, 150% improvement! Note: Hidden Terminal – Multi-Channel Case Let C1 be the rendezvous channel γ can hear traffic on C1 only, doesn’t hear the CTS from β consequently doesn’t know anything about traffic on C6 (δ is too far to hear anything from β) . α β γ δ Possible solution: Use multiple radios So-MobiHoc-2004 Firmware Packets for C6 TCP/IP, Network Stack Packets for C11 Application Layer User-level Kernel-level Buffer packets, switch between channels Packets for C1 802.11 hardware Implementation Option for SR-MC 802.11 Device Driver Switching logic Channel switching speed: Today - 5 milliseconds Possible - 80 microseconds Chandra-INFOCOM-2004 Multi-Channel Medium Access Control (MMAC) . Divide time into beacon intervals Divide a beacon interval into two phase Negotiation Phase: All nodes switch to a pre-defined common channel and negotiate the channel to use Transfer Phase: Once a channel is selected, the source & receiver switch to this channel and data transfer occurs during this phase Idea: Periodically rendezvous on a fixed channel to decide the next channel Issues Requires tight clock synchronization Packets to multiple destinations can incur high delays Congestion on the common channel Common channel goes bad, everything goes bad Not able to handle broadcasts So-MobiHoc-2004 Slotted Seeded Channel Hopping (SSCH) Divide time into slots At each slot hop to a different channel Nodes hop across channels to distribute traffic Senders and receivers probabilistically meet & exchange schedules Senders loosely synchronize hopping schedule to receivers Characteristics Distributed: every node makes independent choices Optimistic: exploits common case that nodes know each others’ channel hopping schedules Traffic-driven: nodes repeatedly overlap when they have packets to exchange . Bahl-MobiCom-2004
Slide 59 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. . Baseline comparison of Metrics Single Radio Mesh Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time ETX performs the best Median path length: HOP: 2, ETX: 3.01, RTT: 3.43, PktPair: 3.46 . Draves-MobiCom-2004 Experimental Setup 23 node testbed Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer Two scenarios: Baseline (Single radio): 802.11a NetGear cards Two radios 802.11a NetGear cards 802.11g Proxim cards WCETT utilizes 2nd radio better than ETX or shortest path Baseline Comparison of Metrics Two Radio Mesh Median path length: HOP: 2, ETX: 2.4, WCETT: 3 . Draves-SIGCOMM-2004 But with different traffic pattern…. Trace Capture 1 workstations connected via Ethernet Traces captured during 1-month period Trace Replayed Testbed of 22 mesh computers in office environment 2 IEEE 802.11a/b/g cards per computer . Erickson-MobiSys-2006 The Multicast Problem A multicast group is defined with a unique group identifier. Nodes may leave or join the group anytime In wired networks physical network topology is static In ad hoc multi-hop wireless networks physical topology can change often Need to Integrate with unicast routing protocols Many proposals [Tree-based, Mesh-based, Location-based] which one to use? . - ABAM (On-Demand Associatively-Based Multicast) - FGMP (Forwarding Group Multicast Protocol) - ADMIR (Adaptive Demand-Driven Multicast Routing) - LAM (Lightweight Adaptive Multicast) - AMRIS (Ad hoc Multicast Routing utilizing Increased id-numberS) - MAODV (Multicast AODV) - DCMP (Dynamic Core Based Multicast Routing) - MCEDAR (Multicast CEDAR) - AMRoute (Adhoc Multicast Routing) - MZR (Multicast Zone Routing) - CAMO (Core-Assisted Mesh Protocol) - ODMRP (On-Deman Multicast Routing Protocol) - CBM (Content Based Multicast) - SPBM (Scalable Position-Based Multicast) - DDM (Differential Destination Multicast) - SRMP (Source Routing-based Multicast Protocol) - DSR-MB (Simple Protocol for Multicast and Broadcast using DSR) - … - … The Interference Detection Problem When two systems operate on overlapping frequencies, there exists a potential for harmful interference between them Performance degradation on both systems Conflict graph is determined by the “Interference Graph” To determine the Interference Graph, require Knowledge of packet transmission from nodes that are not “visible” Knowledge of physical location of nodes within the network Knowledge of whether or not multiple transmissions increase ot decrease interference? Interference Graph can change as rapidly as the environment when a node leaves or join the network . The Transport Layer Problem Majority of the Internet traffic is TCP Packet losses & delays in wireless can occur due to Environmental fluctuations resulting link failures Stochastic link performance due to rapidly changing error rates CSMA/CA assumes loss is due to congestion and back-off’s TCP assumes packet losses are due to congestion Times out when no ACK is received Invokes slow start, when instead the best response would be to retransmit lost packets quickly RTT calculation can change as rapidly as the environment (link) changes Can we solve this problem without changing the end-to-end semantics? . The Security Problem Two type of attackers: External malicious node (no crypto keys) Compromised node (attacker captures legitimate node and reads out all cryptographic information) Attacks Selfish behavior, do not forward other node’s packets Denial of Service (DoS) Jamming Resource consumption attack Routing disruption (e.g. Wormhole attack) Inject malicious routing information Ongoing Research Possible solutions: SEAD, Ariadne, SRP, CONFIDANT, … . Hu-MobiCom-2002 Bucheggar-MobiHoc-2002 Packets get dropped! Doesn’t care The Spectrum Etiquette Problem Local behavior affects Global Performance! . Consequently we….. Must Increase Range and Capacity Single radio meshes built on 802.11 technologies are not good enough. We must extend the range of radios; we must understand the achievable capacity in an ideal wireless mesh and we must build technology to approach this capacity? Must Improve Routing Performance Routing protocols based on shortest-hop are sub-optimal. We must build a routing protocol that adapts quickly to topology changes, incorporates wireless interference and link quality. Must Provide Security and Fairness Is it possible to ensure fairness and privacy for end-users and security for the network? We must ensure that no mesh nodes starves and that the mesh guards itself against malicious users. Must Provide Self Management An “organic network” should be both self-organizing and self managing? To what extent can we remove the human out of the loop? . Must Develop a Resilient Framework for Applications In a environmentally hostile environment, we must provide a framework for applications to work robustly. . Handling the Challenges . Strategies for increasing Capacity Strategy 1: Use all available channels Avoid spectrum waste Strategy 2: Improve modulation, reception, and coding Today ~ 2.5 bits/Hz (.11g), Soon ~ 4.5 bits / Hz (.11n) Network coding Strategy 3: Improve spatial reuse by reducing interference Fine grain transmit power control (Steerable) directional antennas and directional MACs Strategy 4: Navigate around harmful interference Interference aware least cost routing . Will not cover Strategy 1: Multi-Channel Communications Goal Assign n non-interfering channels to n pair of nodes such that n packet transmissions can occur simultaneously. . Knobs Single Radio – Multiple Channels (SR-MC) Distributed: Use a modified RTS/CTS sequence to negotiate channels Problem How does the sender know which channel the receiver is listening on? Solutions Receive on all channels simultaneously Simplest solution but too costly - will not consider here Use a dedicated rendezvous channel Use a synchronized hopping protocol Provide multiple rendezvous opportunities Centralized: Compute channel assignments using global knowledge Scope of Coverage We will cover schemes that work on commodity radios only . Packets-in-Flight Example Revisited Negotiating Channel with RTS / CTS . 2 3 4 5 7 8 9 1 11 10 RTS (C1,C3,C7) RTS (C3,C5,C7,C11) CTS (C11) CTS (C1, C7) 6 C2 C2 C1 C11 C1 10 nodes are active, 5 packets in flight, 150% improvement! Note: Hidden Terminal – Multi-Channel Case Let C1 be the rendezvous channel γ can hear traffic on C1 only, doesn’t hear the CTS from β consequently doesn’t know anything about traffic on C6 (δ is too far to hear anything from β) . α β γ δ Possible solution: Use multiple radios So-MobiHoc-2004 Firmware Packets for C6 TCP/IP, Network Stack Packets for C11 Application Layer User-level Kernel-level Buffer packets, switch between channels Packets for C1 802.11 hardware Implementation Option for SR-MC 802.11 Device Driver Switching logic Channel switching speed: Today - 5 milliseconds Possible - 80 microseconds Chandra-INFOCOM-2004 Multi-Channel Medium Access Control (MMAC) . Divide time into beacon intervals Divide a beacon interval into two phase Negotiation Phase: All nodes switch to a pre-defined common channel and negotiate the channel to use Transfer Phase: Once a channel is selected, the source & receiver switch to this channel and data transfer occurs during this phase Idea: Periodically rendezvous on a fixed channel to decide the next channel Issues Requires tight clock synchronization Packets to multiple destinations can incur high delays Congestion on the common channel Common channel goes bad, everything goes bad Not able to handle broadcasts So-MobiHoc-2004 Slotted Seeded Channel Hopping (SSCH) Divide time into slots At each slot hop to a different channel Nodes hop across channels to distribute traffic Senders and receivers probabilistically meet & exchange schedules Senders loosely synchronize hopping schedule to receivers Characteristics Distributed: every node makes independent choices Optimistic: exploits common case that nodes know each others’ channel hopping schedules Traffic-driven: nodes repeatedly overlap when they have packets to exchange . Bahl-MobiCom-2004 Divide time into slots: switch channels at beginning of a slot 3 channels E.g. for 802.11b Ch 1 maps to 0 Ch 6 maps to 1 Ch 11 maps to 2 1 0 2 1 0 2 1 0 0 1 2 0 1 2 0 1 New Channel = (Old Channel + seed) mod (Number of Channels) seed is from 1 to (Number of Channels - 1) Seed = 2 Seed = 1 (1 + 2) mod 3 = 0 (0 + 1) mod 3 = 1 A B Enables bandwidth utilization across all channels Does not need control channel rendezvous . SSCH Rendezvous
Slide 60 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. . Baseline comparison of Metrics Single Radio Mesh Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time ETX performs the best Median path length: HOP: 2, ETX: 3.01, RTT: 3.43, PktPair: 3.46 . Draves-MobiCom-2004 Experimental Setup 23 node testbed Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer Two scenarios: Baseline (Single radio): 802.11a NetGear cards Two radios 802.11a NetGear cards 802.11g Proxim cards WCETT utilizes 2nd radio better than ETX or shortest path Baseline Comparison of Metrics Two Radio Mesh Median path length: HOP: 2, ETX: 2.4, WCETT: 3 . Draves-SIGCOMM-2004 But with different traffic pattern…. Trace Capture 1 workstations connected via Ethernet Traces captured during 1-month period Trace Replayed Testbed of 22 mesh computers in office environment 2 IEEE 802.11a/b/g cards per computer . Erickson-MobiSys-2006 The Multicast Problem A multicast group is defined with a unique group identifier. Nodes may leave or join the group anytime In wired networks physical network topology is static In ad hoc multi-hop wireless networks physical topology can change often Need to Integrate with unicast routing protocols Many proposals [Tree-based, Mesh-based, Location-based] which one to use? . - ABAM (On-Demand Associatively-Based Multicast) - FGMP (Forwarding Group Multicast Protocol) - ADMIR (Adaptive Demand-Driven Multicast Routing) - LAM (Lightweight Adaptive Multicast) - AMRIS (Ad hoc Multicast Routing utilizing Increased id-numberS) - MAODV (Multicast AODV) - DCMP (Dynamic Core Based Multicast Routing) - MCEDAR (Multicast CEDAR) - AMRoute (Adhoc Multicast Routing) - MZR (Multicast Zone Routing) - CAMO (Core-Assisted Mesh Protocol) - ODMRP (On-Deman Multicast Routing Protocol) - CBM (Content Based Multicast) - SPBM (Scalable Position-Based Multicast) - DDM (Differential Destination Multicast) - SRMP (Source Routing-based Multicast Protocol) - DSR-MB (Simple Protocol for Multicast and Broadcast using DSR) - … - … The Interference Detection Problem When two systems operate on overlapping frequencies, there exists a potential for harmful interference between them Performance degradation on both systems Conflict graph is determined by the “Interference Graph” To determine the Interference Graph, require Knowledge of packet transmission from nodes that are not “visible” Knowledge of physical location of nodes within the network Knowledge of whether or not multiple transmissions increase ot decrease interference? Interference Graph can change as rapidly as the environment when a node leaves or join the network . The Transport Layer Problem Majority of the Internet traffic is TCP Packet losses & delays in wireless can occur due to Environmental fluctuations resulting link failures Stochastic link performance due to rapidly changing error rates CSMA/CA assumes loss is due to congestion and back-off’s TCP assumes packet losses are due to congestion Times out when no ACK is received Invokes slow start, when instead the best response would be to retransmit lost packets quickly RTT calculation can change as rapidly as the environment (link) changes Can we solve this problem without changing the end-to-end semantics? . The Security Problem Two type of attackers: External malicious node (no crypto keys) Compromised node (attacker captures legitimate node and reads out all cryptographic information) Attacks Selfish behavior, do not forward other node’s packets Denial of Service (DoS) Jamming Resource consumption attack Routing disruption (e.g. Wormhole attack) Inject malicious routing information Ongoing Research Possible solutions: SEAD, Ariadne, SRP, CONFIDANT, … . Hu-MobiCom-2002 Bucheggar-MobiHoc-2002 Packets get dropped! Doesn’t care The Spectrum Etiquette Problem Local behavior affects Global Performance! . Consequently we….. Must Increase Range and Capacity Single radio meshes built on 802.11 technologies are not good enough. We must extend the range of radios; we must understand the achievable capacity in an ideal wireless mesh and we must build technology to approach this capacity? Must Improve Routing Performance Routing protocols based on shortest-hop are sub-optimal. We must build a routing protocol that adapts quickly to topology changes, incorporates wireless interference and link quality. Must Provide Security and Fairness Is it possible to ensure fairness and privacy for end-users and security for the network? We must ensure that no mesh nodes starves and that the mesh guards itself against malicious users. Must Provide Self Management An “organic network” should be both self-organizing and self managing? To what extent can we remove the human out of the loop? . Must Develop a Resilient Framework for Applications In a environmentally hostile environment, we must provide a framework for applications to work robustly. . Handling the Challenges . Strategies for increasing Capacity Strategy 1: Use all available channels Avoid spectrum waste Strategy 2: Improve modulation, reception, and coding Today ~ 2.5 bits/Hz (.11g), Soon ~ 4.5 bits / Hz (.11n) Network coding Strategy 3: Improve spatial reuse by reducing interference Fine grain transmit power control (Steerable) directional antennas and directional MACs Strategy 4: Navigate around harmful interference Interference aware least cost routing . Will not cover Strategy 1: Multi-Channel Communications Goal Assign n non-interfering channels to n pair of nodes such that n packet transmissions can occur simultaneously. . Knobs Single Radio – Multiple Channels (SR-MC) Distributed: Use a modified RTS/CTS sequence to negotiate channels Problem How does the sender know which channel the receiver is listening on? Solutions Receive on all channels simultaneously Simplest solution but too costly - will not consider here Use a dedicated rendezvous channel Use a synchronized hopping protocol Provide multiple rendezvous opportunities Centralized: Compute channel assignments using global knowledge Scope of Coverage We will cover schemes that work on commodity radios only . Packets-in-Flight Example Revisited Negotiating Channel with RTS / CTS . 2 3 4 5 7 8 9 1 11 10 RTS (C1,C3,C7) RTS (C3,C5,C7,C11) CTS (C11) CTS (C1, C7) 6 C2 C2 C1 C11 C1 10 nodes are active, 5 packets in flight, 150% improvement! Note: Hidden Terminal – Multi-Channel Case Let C1 be the rendezvous channel γ can hear traffic on C1 only, doesn’t hear the CTS from β consequently doesn’t know anything about traffic on C6 (δ is too far to hear anything from β) . α β γ δ Possible solution: Use multiple radios So-MobiHoc-2004 Firmware Packets for C6 TCP/IP, Network Stack Packets for C11 Application Layer User-level Kernel-level Buffer packets, switch between channels Packets for C1 802.11 hardware Implementation Option for SR-MC 802.11 Device Driver Switching logic Channel switching speed: Today - 5 milliseconds Possible - 80 microseconds Chandra-INFOCOM-2004 Multi-Channel Medium Access Control (MMAC) . Divide time into beacon intervals Divide a beacon interval into two phase Negotiation Phase: All nodes switch to a pre-defined common channel and negotiate the channel to use Transfer Phase: Once a channel is selected, the source & receiver switch to this channel and data transfer occurs during this phase Idea: Periodically rendezvous on a fixed channel to decide the next channel Issues Requires tight clock synchronization Packets to multiple destinations can incur high delays Congestion on the common channel Common channel goes bad, everything goes bad Not able to handle broadcasts So-MobiHoc-2004 Slotted Seeded Channel Hopping (SSCH) Divide time into slots At each slot hop to a different channel Nodes hop across channels to distribute traffic Senders and receivers probabilistically meet & exchange schedules Senders loosely synchronize hopping schedule to receivers Characteristics Distributed: every node makes independent choices Optimistic: exploits common case that nodes know each others’ channel hopping schedules Traffic-driven: nodes repeatedly overlap when they have packets to exchange . Bahl-MobiCom-2004 Divide time into slots: switch channels at beginning of a slot 3 channels E.g. for 802.11b Ch 1 maps to 0 Ch 6 maps to 1 Ch 11 maps to 2 1 0 2 1 0 2 1 0 0 1 2 0 1 2 0 1 New Channel = (Old Channel + seed) mod (Number of Channels) seed is from 1 to (Number of Channels - 1) Seed = 2 Seed = 1 (1 + 2) mod 3 = 0 (0 + 1) mod 3 = 1 A B Enables bandwidth utilization across all channels Does not need control channel rendezvous . SSCH Rendezvous Each node broadcasts (channel, seed) once every slot If B has to send packets to A, it adjusts its (channel, seed) Stale (channel, seed) info simply results in delayed syncing 3 channels 1 0 2 1 0 2 1 0 2 0 2 1 0 2 1 0 Seed Seed A B 2 2 2 2 2 2 2 2 1 2 2 2 2 2 2 2 2 2 1 1 B wants to start a flow with A . SSCH Syncing Seeds
Slide 61 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. . Baseline comparison of Metrics Single Radio Mesh Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time ETX performs the best Median path length: HOP: 2, ETX: 3.01, RTT: 3.43, PktPair: 3.46 . Draves-MobiCom-2004 Experimental Setup 23 node testbed Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer Two scenarios: Baseline (Single radio): 802.11a NetGear cards Two radios 802.11a NetGear cards 802.11g Proxim cards WCETT utilizes 2nd radio better than ETX or shortest path Baseline Comparison of Metrics Two Radio Mesh Median path length: HOP: 2, ETX: 2.4, WCETT: 3 . Draves-SIGCOMM-2004 But with different traffic pattern…. Trace Capture 1 workstations connected via Ethernet Traces captured during 1-month period Trace Replayed Testbed of 22 mesh computers in office environment 2 IEEE 802.11a/b/g cards per computer . Erickson-MobiSys-2006 The Multicast Problem A multicast group is defined with a unique group identifier. Nodes may leave or join the group anytime In wired networks physical network topology is static In ad hoc multi-hop wireless networks physical topology can change often Need to Integrate with unicast routing protocols Many proposals [Tree-based, Mesh-based, Location-based] which one to use? . - ABAM (On-Demand Associatively-Based Multicast) - FGMP (Forwarding Group Multicast Protocol) - ADMIR (Adaptive Demand-Driven Multicast Routing) - LAM (Lightweight Adaptive Multicast) - AMRIS (Ad hoc Multicast Routing utilizing Increased id-numberS) - MAODV (Multicast AODV) - DCMP (Dynamic Core Based Multicast Routing) - MCEDAR (Multicast CEDAR) - AMRoute (Adhoc Multicast Routing) - MZR (Multicast Zone Routing) - CAMO (Core-Assisted Mesh Protocol) - ODMRP (On-Deman Multicast Routing Protocol) - CBM (Content Based Multicast) - SPBM (Scalable Position-Based Multicast) - DDM (Differential Destination Multicast) - SRMP (Source Routing-based Multicast Protocol) - DSR-MB (Simple Protocol for Multicast and Broadcast using DSR) - … - … The Interference Detection Problem When two systems operate on overlapping frequencies, there exists a potential for harmful interference between them Performance degradation on both systems Conflict graph is determined by the “Interference Graph” To determine the Interference Graph, require Knowledge of packet transmission from nodes that are not “visible” Knowledge of physical location of nodes within the network Knowledge of whether or not multiple transmissions increase ot decrease interference? Interference Graph can change as rapidly as the environment when a node leaves or join the network . The Transport Layer Problem Majority of the Internet traffic is TCP Packet losses & delays in wireless can occur due to Environmental fluctuations resulting link failures Stochastic link performance due to rapidly changing error rates CSMA/CA assumes loss is due to congestion and back-off’s TCP assumes packet losses are due to congestion Times out when no ACK is received Invokes slow start, when instead the best response would be to retransmit lost packets quickly RTT calculation can change as rapidly as the environment (link) changes Can we solve this problem without changing the end-to-end semantics? . The Security Problem Two type of attackers: External malicious node (no crypto keys) Compromised node (attacker captures legitimate node and reads out all cryptographic information) Attacks Selfish behavior, do not forward other node’s packets Denial of Service (DoS) Jamming Resource consumption attack Routing disruption (e.g. Wormhole attack) Inject malicious routing information Ongoing Research Possible solutions: SEAD, Ariadne, SRP, CONFIDANT, … . Hu-MobiCom-2002 Bucheggar-MobiHoc-2002 Packets get dropped! Doesn’t care The Spectrum Etiquette Problem Local behavior affects Global Performance! . Consequently we….. Must Increase Range and Capacity Single radio meshes built on 802.11 technologies are not good enough. We must extend the range of radios; we must understand the achievable capacity in an ideal wireless mesh and we must build technology to approach this capacity? Must Improve Routing Performance Routing protocols based on shortest-hop are sub-optimal. We must build a routing protocol that adapts quickly to topology changes, incorporates wireless interference and link quality. Must Provide Security and Fairness Is it possible to ensure fairness and privacy for end-users and security for the network? We must ensure that no mesh nodes starves and that the mesh guards itself against malicious users. Must Provide Self Management An “organic network” should be both self-organizing and self managing? To what extent can we remove the human out of the loop? . Must Develop a Resilient Framework for Applications In a environmentally hostile environment, we must provide a framework for applications to work robustly. . Handling the Challenges . Strategies for increasing Capacity Strategy 1: Use all available channels Avoid spectrum waste Strategy 2: Improve modulation, reception, and coding Today ~ 2.5 bits/Hz (.11g), Soon ~ 4.5 bits / Hz (.11n) Network coding Strategy 3: Improve spatial reuse by reducing interference Fine grain transmit power control (Steerable) directional antennas and directional MACs Strategy 4: Navigate around harmful interference Interference aware least cost routing . Will not cover Strategy 1: Multi-Channel Communications Goal Assign n non-interfering channels to n pair of nodes such that n packet transmissions can occur simultaneously. . Knobs Single Radio – Multiple Channels (SR-MC) Distributed: Use a modified RTS/CTS sequence to negotiate channels Problem How does the sender know which channel the receiver is listening on? Solutions Receive on all channels simultaneously Simplest solution but too costly - will not consider here Use a dedicated rendezvous channel Use a synchronized hopping protocol Provide multiple rendezvous opportunities Centralized: Compute channel assignments using global knowledge Scope of Coverage We will cover schemes that work on commodity radios only . Packets-in-Flight Example Revisited Negotiating Channel with RTS / CTS . 2 3 4 5 7 8 9 1 11 10 RTS (C1,C3,C7) RTS (C3,C5,C7,C11) CTS (C11) CTS (C1, C7) 6 C2 C2 C1 C11 C1 10 nodes are active, 5 packets in flight, 150% improvement! Note: Hidden Terminal – Multi-Channel Case Let C1 be the rendezvous channel γ can hear traffic on C1 only, doesn’t hear the CTS from β consequently doesn’t know anything about traffic on C6 (δ is too far to hear anything from β) . α β γ δ Possible solution: Use multiple radios So-MobiHoc-2004 Firmware Packets for C6 TCP/IP, Network Stack Packets for C11 Application Layer User-level Kernel-level Buffer packets, switch between channels Packets for C1 802.11 hardware Implementation Option for SR-MC 802.11 Device Driver Switching logic Channel switching speed: Today - 5 milliseconds Possible - 80 microseconds Chandra-INFOCOM-2004 Multi-Channel Medium Access Control (MMAC) . Divide time into beacon intervals Divide a beacon interval into two phase Negotiation Phase: All nodes switch to a pre-defined common channel and negotiate the channel to use Transfer Phase: Once a channel is selected, the source & receiver switch to this channel and data transfer occurs during this phase Idea: Periodically rendezvous on a fixed channel to decide the next channel Issues Requires tight clock synchronization Packets to multiple destinations can incur high delays Congestion on the common channel Common channel goes bad, everything goes bad Not able to handle broadcasts So-MobiHoc-2004 Slotted Seeded Channel Hopping (SSCH) Divide time into slots At each slot hop to a different channel Nodes hop across channels to distribute traffic Senders and receivers probabilistically meet & exchange schedules Senders loosely synchronize hopping schedule to receivers Characteristics Distributed: every node makes independent choices Optimistic: exploits common case that nodes know each others’ channel hopping schedules Traffic-driven: nodes repeatedly overlap when they have packets to exchange . Bahl-MobiCom-2004 Divide time into slots: switch channels at beginning of a slot 3 channels E.g. for 802.11b Ch 1 maps to 0 Ch 6 maps to 1 Ch 11 maps to 2 1 0 2 1 0 2 1 0 0 1 2 0 1 2 0 1 New Channel = (Old Channel + seed) mod (Number of Channels) seed is from 1 to (Number of Channels - 1) Seed = 2 Seed = 1 (1 + 2) mod 3 = 0 (0 + 1) mod 3 = 1 A B Enables bandwidth utilization across all channels Does not need control channel rendezvous . SSCH Rendezvous Each node broadcasts (channel, seed) once every slot If B has to send packets to A, it adjusts its (channel, seed) Stale (channel, seed) info simply results in delayed syncing 3 channels 1 0 2 1 0 2 1 0 2 0 2 1 0 2 1 0 Seed Seed A B 2 2 2 2 2 2 2 2 1 2 2 2 2 2 2 2 2 2 1 1 B wants to start a flow with A . SSCH Syncing Seeds Using all Available Channels with SSCH Only one of 3 pairs is active @ any given time In current IEEE 802.11 meshes .
Slide 62 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. . Baseline comparison of Metrics Single Radio Mesh Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time ETX performs the best Median path length: HOP: 2, ETX: 3.01, RTT: 3.43, PktPair: 3.46 . Draves-MobiCom-2004 Experimental Setup 23 node testbed Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer Two scenarios: Baseline (Single radio): 802.11a NetGear cards Two radios 802.11a NetGear cards 802.11g Proxim cards WCETT utilizes 2nd radio better than ETX or shortest path Baseline Comparison of Metrics Two Radio Mesh Median path length: HOP: 2, ETX: 2.4, WCETT: 3 . Draves-SIGCOMM-2004 But with different traffic pattern…. Trace Capture 1 workstations connected via Ethernet Traces captured during 1-month period Trace Replayed Testbed of 22 mesh computers in office environment 2 IEEE 802.11a/b/g cards per computer . Erickson-MobiSys-2006 The Multicast Problem A multicast group is defined with a unique group identifier. Nodes may leave or join the group anytime In wired networks physical network topology is static In ad hoc multi-hop wireless networks physical topology can change often Need to Integrate with unicast routing protocols Many proposals [Tree-based, Mesh-based, Location-based] which one to use? . - ABAM (On-Demand Associatively-Based Multicast) - FGMP (Forwarding Group Multicast Protocol) - ADMIR (Adaptive Demand-Driven Multicast Routing) - LAM (Lightweight Adaptive Multicast) - AMRIS (Ad hoc Multicast Routing utilizing Increased id-numberS) - MAODV (Multicast AODV) - DCMP (Dynamic Core Based Multicast Routing) - MCEDAR (Multicast CEDAR) - AMRoute (Adhoc Multicast Routing) - MZR (Multicast Zone Routing) - CAMO (Core-Assisted Mesh Protocol) - ODMRP (On-Deman Multicast Routing Protocol) - CBM (Content Based Multicast) - SPBM (Scalable Position-Based Multicast) - DDM (Differential Destination Multicast) - SRMP (Source Routing-based Multicast Protocol) - DSR-MB (Simple Protocol for Multicast and Broadcast using DSR) - … - … The Interference Detection Problem When two systems operate on overlapping frequencies, there exists a potential for harmful interference between them Performance degradation on both systems Conflict graph is determined by the “Interference Graph” To determine the Interference Graph, require Knowledge of packet transmission from nodes that are not “visible” Knowledge of physical location of nodes within the network Knowledge of whether or not multiple transmissions increase ot decrease interference? Interference Graph can change as rapidly as the environment when a node leaves or join the network . The Transport Layer Problem Majority of the Internet traffic is TCP Packet losses & delays in wireless can occur due to Environmental fluctuations resulting link failures Stochastic link performance due to rapidly changing error rates CSMA/CA assumes loss is due to congestion and back-off’s TCP assumes packet losses are due to congestion Times out when no ACK is received Invokes slow start, when instead the best response would be to retransmit lost packets quickly RTT calculation can change as rapidly as the environment (link) changes Can we solve this problem without changing the end-to-end semantics? . The Security Problem Two type of attackers: External malicious node (no crypto keys) Compromised node (attacker captures legitimate node and reads out all cryptographic information) Attacks Selfish behavior, do not forward other node’s packets Denial of Service (DoS) Jamming Resource consumption attack Routing disruption (e.g. Wormhole attack) Inject malicious routing information Ongoing Research Possible solutions: SEAD, Ariadne, SRP, CONFIDANT, … . Hu-MobiCom-2002 Bucheggar-MobiHoc-2002 Packets get dropped! Doesn’t care The Spectrum Etiquette Problem Local behavior affects Global Performance! . Consequently we….. Must Increase Range and Capacity Single radio meshes built on 802.11 technologies are not good enough. We must extend the range of radios; we must understand the achievable capacity in an ideal wireless mesh and we must build technology to approach this capacity? Must Improve Routing Performance Routing protocols based on shortest-hop are sub-optimal. We must build a routing protocol that adapts quickly to topology changes, incorporates wireless interference and link quality. Must Provide Security and Fairness Is it possible to ensure fairness and privacy for end-users and security for the network? We must ensure that no mesh nodes starves and that the mesh guards itself against malicious users. Must Provide Self Management An “organic network” should be both self-organizing and self managing? To what extent can we remove the human out of the loop? . Must Develop a Resilient Framework for Applications In a environmentally hostile environment, we must provide a framework for applications to work robustly. . Handling the Challenges . Strategies for increasing Capacity Strategy 1: Use all available channels Avoid spectrum waste Strategy 2: Improve modulation, reception, and coding Today ~ 2.5 bits/Hz (.11g), Soon ~ 4.5 bits / Hz (.11n) Network coding Strategy 3: Improve spatial reuse by reducing interference Fine grain transmit power control (Steerable) directional antennas and directional MACs Strategy 4: Navigate around harmful interference Interference aware least cost routing . Will not cover Strategy 1: Multi-Channel Communications Goal Assign n non-interfering channels to n pair of nodes such that n packet transmissions can occur simultaneously. . Knobs Single Radio – Multiple Channels (SR-MC) Distributed: Use a modified RTS/CTS sequence to negotiate channels Problem How does the sender know which channel the receiver is listening on? Solutions Receive on all channels simultaneously Simplest solution but too costly - will not consider here Use a dedicated rendezvous channel Use a synchronized hopping protocol Provide multiple rendezvous opportunities Centralized: Compute channel assignments using global knowledge Scope of Coverage We will cover schemes that work on commodity radios only . Packets-in-Flight Example Revisited Negotiating Channel with RTS / CTS . 2 3 4 5 7 8 9 1 11 10 RTS (C1,C3,C7) RTS (C3,C5,C7,C11) CTS (C11) CTS (C1, C7) 6 C2 C2 C1 C11 C1 10 nodes are active, 5 packets in flight, 150% improvement! Note: Hidden Terminal – Multi-Channel Case Let C1 be the rendezvous channel γ can hear traffic on C1 only, doesn’t hear the CTS from β consequently doesn’t know anything about traffic on C6 (δ is too far to hear anything from β) . α β γ δ Possible solution: Use multiple radios So-MobiHoc-2004 Firmware Packets for C6 TCP/IP, Network Stack Packets for C11 Application Layer User-level Kernel-level Buffer packets, switch between channels Packets for C1 802.11 hardware Implementation Option for SR-MC 802.11 Device Driver Switching logic Channel switching speed: Today - 5 milliseconds Possible - 80 microseconds Chandra-INFOCOM-2004 Multi-Channel Medium Access Control (MMAC) . Divide time into beacon intervals Divide a beacon interval into two phase Negotiation Phase: All nodes switch to a pre-defined common channel and negotiate the channel to use Transfer Phase: Once a channel is selected, the source & receiver switch to this channel and data transfer occurs during this phase Idea: Periodically rendezvous on a fixed channel to decide the next channel Issues Requires tight clock synchronization Packets to multiple destinations can incur high delays Congestion on the common channel Common channel goes bad, everything goes bad Not able to handle broadcasts So-MobiHoc-2004 Slotted Seeded Channel Hopping (SSCH) Divide time into slots At each slot hop to a different channel Nodes hop across channels to distribute traffic Senders and receivers probabilistically meet & exchange schedules Senders loosely synchronize hopping schedule to receivers Characteristics Distributed: every node makes independent choices Optimistic: exploits common case that nodes know each others’ channel hopping schedules Traffic-driven: nodes repeatedly overlap when they have packets to exchange . Bahl-MobiCom-2004 Divide time into slots: switch channels at beginning of a slot 3 channels E.g. for 802.11b Ch 1 maps to 0 Ch 6 maps to 1 Ch 11 maps to 2 1 0 2 1 0 2 1 0 0 1 2 0 1 2 0 1 New Channel = (Old Channel + seed) mod (Number of Channels) seed is from 1 to (Number of Channels - 1) Seed = 2 Seed = 1 (1 + 2) mod 3 = 0 (0 + 1) mod 3 = 1 A B Enables bandwidth utilization across all channels Does not need control channel rendezvous . SSCH Rendezvous Each node broadcasts (channel, seed) once every slot If B has to send packets to A, it adjusts its (channel, seed) Stale (channel, seed) info simply results in delayed syncing 3 channels 1 0 2 1 0 2 1 0 2 0 2 1 0 2 1 0 Seed Seed A B 2 2 2 2 2 2 2 2 1 2 2 2 2 2 2 2 2 2 1 1 B wants to start a flow with A . SSCH Syncing Seeds Using all Available Channels with SSCH Only one of 3 pairs is active @ any given time In current IEEE 802.11 meshes . SSCH Performance Significant capacity improvement when traffic load is on multiple separate flows 100 nodes, IEEE 802.11a, 13 channels, every flow is multihop Avg. per node Throughput Total System Throughput SSCH SSCH IEEE 802.11a IEEE 802.11a .
Slide 63 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. . Baseline comparison of Metrics Single Radio Mesh Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time ETX performs the best Median path length: HOP: 2, ETX: 3.01, RTT: 3.43, PktPair: 3.46 . Draves-MobiCom-2004 Experimental Setup 23 node testbed Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer Two scenarios: Baseline (Single radio): 802.11a NetGear cards Two radios 802.11a NetGear cards 802.11g Proxim cards WCETT utilizes 2nd radio better than ETX or shortest path Baseline Comparison of Metrics Two Radio Mesh Median path length: HOP: 2, ETX: 2.4, WCETT: 3 . Draves-SIGCOMM-2004 But with different traffic pattern…. Trace Capture 1 workstations connected via Ethernet Traces captured during 1-month period Trace Replayed Testbed of 22 mesh computers in office environment 2 IEEE 802.11a/b/g cards per computer . Erickson-MobiSys-2006 The Multicast Problem A multicast group is defined with a unique group identifier. Nodes may leave or join the group anytime In wired networks physical network topology is static In ad hoc multi-hop wireless networks physical topology can change often Need to Integrate with unicast routing protocols Many proposals [Tree-based, Mesh-based, Location-based] which one to use? . - ABAM (On-Demand Associatively-Based Multicast) - FGMP (Forwarding Group Multicast Protocol) - ADMIR (Adaptive Demand-Driven Multicast Routing) - LAM (Lightweight Adaptive Multicast) - AMRIS (Ad hoc Multicast Routing utilizing Increased id-numberS) - MAODV (Multicast AODV) - DCMP (Dynamic Core Based Multicast Routing) - MCEDAR (Multicast CEDAR) - AMRoute (Adhoc Multicast Routing) - MZR (Multicast Zone Routing) - CAMO (Core-Assisted Mesh Protocol) - ODMRP (On-Deman Multicast Routing Protocol) - CBM (Content Based Multicast) - SPBM (Scalable Position-Based Multicast) - DDM (Differential Destination Multicast) - SRMP (Source Routing-based Multicast Protocol) - DSR-MB (Simple Protocol for Multicast and Broadcast using DSR) - … - … The Interference Detection Problem When two systems operate on overlapping frequencies, there exists a potential for harmful interference between them Performance degradation on both systems Conflict graph is determined by the “Interference Graph” To determine the Interference Graph, require Knowledge of packet transmission from nodes that are not “visible” Knowledge of physical location of nodes within the network Knowledge of whether or not multiple transmissions increase ot decrease interference? Interference Graph can change as rapidly as the environment when a node leaves or join the network . The Transport Layer Problem Majority of the Internet traffic is TCP Packet losses & delays in wireless can occur due to Environmental fluctuations resulting link failures Stochastic link performance due to rapidly changing error rates CSMA/CA assumes loss is due to congestion and back-off’s TCP assumes packet losses are due to congestion Times out when no ACK is received Invokes slow start, when instead the best response would be to retransmit lost packets quickly RTT calculation can change as rapidly as the environment (link) changes Can we solve this problem without changing the end-to-end semantics? . The Security Problem Two type of attackers: External malicious node (no crypto keys) Compromised node (attacker captures legitimate node and reads out all cryptographic information) Attacks Selfish behavior, do not forward other node’s packets Denial of Service (DoS) Jamming Resource consumption attack Routing disruption (e.g. Wormhole attack) Inject malicious routing information Ongoing Research Possible solutions: SEAD, Ariadne, SRP, CONFIDANT, … . Hu-MobiCom-2002 Bucheggar-MobiHoc-2002 Packets get dropped! Doesn’t care The Spectrum Etiquette Problem Local behavior affects Global Performance! . Consequently we….. Must Increase Range and Capacity Single radio meshes built on 802.11 technologies are not good enough. We must extend the range of radios; we must understand the achievable capacity in an ideal wireless mesh and we must build technology to approach this capacity? Must Improve Routing Performance Routing protocols based on shortest-hop are sub-optimal. We must build a routing protocol that adapts quickly to topology changes, incorporates wireless interference and link quality. Must Provide Security and Fairness Is it possible to ensure fairness and privacy for end-users and security for the network? We must ensure that no mesh nodes starves and that the mesh guards itself against malicious users. Must Provide Self Management An “organic network” should be both self-organizing and self managing? To what extent can we remove the human out of the loop? . Must Develop a Resilient Framework for Applications In a environmentally hostile environment, we must provide a framework for applications to work robustly. . Handling the Challenges . Strategies for increasing Capacity Strategy 1: Use all available channels Avoid spectrum waste Strategy 2: Improve modulation, reception, and coding Today ~ 2.5 bits/Hz (.11g), Soon ~ 4.5 bits / Hz (.11n) Network coding Strategy 3: Improve spatial reuse by reducing interference Fine grain transmit power control (Steerable) directional antennas and directional MACs Strategy 4: Navigate around harmful interference Interference aware least cost routing . Will not cover Strategy 1: Multi-Channel Communications Goal Assign n non-interfering channels to n pair of nodes such that n packet transmissions can occur simultaneously. . Knobs Single Radio – Multiple Channels (SR-MC) Distributed: Use a modified RTS/CTS sequence to negotiate channels Problem How does the sender know which channel the receiver is listening on? Solutions Receive on all channels simultaneously Simplest solution but too costly - will not consider here Use a dedicated rendezvous channel Use a synchronized hopping protocol Provide multiple rendezvous opportunities Centralized: Compute channel assignments using global knowledge Scope of Coverage We will cover schemes that work on commodity radios only . Packets-in-Flight Example Revisited Negotiating Channel with RTS / CTS . 2 3 4 5 7 8 9 1 11 10 RTS (C1,C3,C7) RTS (C3,C5,C7,C11) CTS (C11) CTS (C1, C7) 6 C2 C2 C1 C11 C1 10 nodes are active, 5 packets in flight, 150% improvement! Note: Hidden Terminal – Multi-Channel Case Let C1 be the rendezvous channel γ can hear traffic on C1 only, doesn’t hear the CTS from β consequently doesn’t know anything about traffic on C6 (δ is too far to hear anything from β) . α β γ δ Possible solution: Use multiple radios So-MobiHoc-2004 Firmware Packets for C6 TCP/IP, Network Stack Packets for C11 Application Layer User-level Kernel-level Buffer packets, switch between channels Packets for C1 802.11 hardware Implementation Option for SR-MC 802.11 Device Driver Switching logic Channel switching speed: Today - 5 milliseconds Possible - 80 microseconds Chandra-INFOCOM-2004 Multi-Channel Medium Access Control (MMAC) . Divide time into beacon intervals Divide a beacon interval into two phase Negotiation Phase: All nodes switch to a pre-defined common channel and negotiate the channel to use Transfer Phase: Once a channel is selected, the source & receiver switch to this channel and data transfer occurs during this phase Idea: Periodically rendezvous on a fixed channel to decide the next channel Issues Requires tight clock synchronization Packets to multiple destinations can incur high delays Congestion on the common channel Common channel goes bad, everything goes bad Not able to handle broadcasts So-MobiHoc-2004 Slotted Seeded Channel Hopping (SSCH) Divide time into slots At each slot hop to a different channel Nodes hop across channels to distribute traffic Senders and receivers probabilistically meet & exchange schedules Senders loosely synchronize hopping schedule to receivers Characteristics Distributed: every node makes independent choices Optimistic: exploits common case that nodes know each others’ channel hopping schedules Traffic-driven: nodes repeatedly overlap when they have packets to exchange . Bahl-MobiCom-2004 Divide time into slots: switch channels at beginning of a slot 3 channels E.g. for 802.11b Ch 1 maps to 0 Ch 6 maps to 1 Ch 11 maps to 2 1 0 2 1 0 2 1 0 0 1 2 0 1 2 0 1 New Channel = (Old Channel + seed) mod (Number of Channels) seed is from 1 to (Number of Channels - 1) Seed = 2 Seed = 1 (1 + 2) mod 3 = 0 (0 + 1) mod 3 = 1 A B Enables bandwidth utilization across all channels Does not need control channel rendezvous . SSCH Rendezvous Each node broadcasts (channel, seed) once every slot If B has to send packets to A, it adjusts its (channel, seed) Stale (channel, seed) info simply results in delayed syncing 3 channels 1 0 2 1 0 2 1 0 2 0 2 1 0 2 1 0 Seed Seed A B 2 2 2 2 2 2 2 2 1 2 2 2 2 2 2 2 2 2 1 1 B wants to start a flow with A . SSCH Syncing Seeds Using all Available Channels with SSCH Only one of 3 pairs is active @ any given time In current IEEE 802.11 meshes . SSCH Performance Significant capacity improvement when traffic load is on multiple separate flows 100 nodes, IEEE 802.11a, 13 channels, every flow is multihop Avg. per node Throughput Total System Throughput SSCH SSCH IEEE 802.11a IEEE 802.11a . How many Channels can we really use? IEEE 802.11{b,g} partitions the allocated 83.5 MHz spectrum into 11 channels Only channels 1, 6 and 11 are mutually non-overlapping But…using only the orthogonal channels may waste spectrum . Banerjee-SIGMETRICS-2006
Slide 64 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer due to interference Too few nodes  route maintenance is difficult disconnections possible Identity and security management is a challenge . The Mesh Networking World Internet Communication Corporate Data Games Shopping Media Web Content Broadband Neighbourhood Mesh Node Mesh Node Mesh Node Mesh Node Home Mesh Mesh Node Traditional Last Mile Territory Mesh Node . Scenario 1: Broadband Internet Access Cost of middle and last miles make physical wired infrastructure not an option in rural areas and many countries Equipment capital cost The scale of touching / maintaining so many endpoints The physics of running cable large distances over unfriendly terrain Political, social and territorial implications Wireless mitigates these issues but introduces others Range Bandwidth Spectrum availability Cost & maintenance issues of new hardware / standards Mesh networking makes wireless workable Range & bandwidth addressed by shorter links Cost & maintenance addressed by building on commodity standards Internet Backbone Middle Mile Last Mile . Scenario 2: A Community Mesh Network Organic – Participants own the equipment and the network . Community Mesh Network Applications Shared broadband Internet access Neighborhood watch (e.g. video surveillance) Shared media content (e.g. neighborhood DVR) Medical & emergency response Neighborhood eBay (garage sales, swaps) Billboards (babysitter/service recommendations, lost cat, newsletter) Bits produced locally, gets used locally Social interaction Distributed backup Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources) Prof. Keith N. Hampton (author of “Netville Neighborhood Study”) URL: http://www.asanet.org/media/neville.html . Scenario 3: Home Mesh Extend Access Point (AP) coverage Better spectrum (re)use  greater capacity Automatic discovery, plug-and-play networked home devices: AV equipment (Cameras, TV, DVD, DVR, satellite/cable) Phones (Cellular and POTS) Traditionally disassociated smart devices (PDAs, AutoPC) Home infrastructure items (Light switches, HVAC controls) . Scenario 4: Blanket City-wide Wireless Coverage Philadelphia picks Earthlink for City Wireless, TechNew World, October 5, 2005 San Francisco Keeps Pushing City Wide WiFi, CNET News.com, August 17, 2005 “San Francisco Mayor Gavin Newsom wants to make Wi-Fi coverage in the city as ubiquitous as the fog that blankets its neighborhoods.” Wi-Fi Hits the Hinterlands, BusinessWeek Online, July 5, 2004 “Who needs DSL or cable? New “mesh” technology is turning entire small towns into broadband hot spots”, Rio Rancho N.M., population 60,000, 500 routers covering 103 miles2 NYC wireless network will be unprecedented, Computerworld, June 18, 2004 “New York City plans to build a public safety wireless network of unprecedented scale and scope, with a capacity to provide tens of thousands of mobile users” Rural Areas need Internet too! Newsweek, June 7, 2004 Issue “EZ Wireless built the country's largest regional wireless broadband network, a 600-square-mile Wi-Fi blanket, and activated it this February”, Hermiston, Oregon, population 13,200, 35 routers with 75 antennas covering 600 miles2 Mesh Casts Its Net, Unstrung, January 23, 2004 “Providing 57 miles2 of wireless coverage for public safety personnel in Garland Texas” PCCW takes Wireless Broadband to London, The Register, September 2, 2005 “Prices for the service in UK start from £10 / month for 256 Kbps to £18 /month for 1 Mbps” Anacapa and Firetide Bring Free Wireless Internet to La Semaine Italienne in Paris, France , Business Wire, 24 May, 2005 Bell Canada and Nortel Networks launch Project Chapleau, designed to evaluate broadband in rural Canada, Optical Networks Daily, 18 July 2005 . Scenario 5: All-Wireless Office No wires No switches No APs Older buildings For small offices (~100 PCs) Rapid deployment Low cost Short-term offices Not a replacement for wire . Scenario 6: Spontaneous “Mesh” Definition A temporary ad-hoc multihop wireless network for exchanging voice, video or data, for collaboration in a locally distributed environment, when no permanent infrastructure or central control is present. Usually between portable wireless devices. 1. Peer Calling & Party Lines P2P calling within local groups – conferences, events, school campus,… 3. Real Time Advisory Drivers need traffic information and advisories generated in real time 2. Public Safety Fire and rescue teams need ad-hoc communication at incident sites . Grass Roots Mesh Deployments Academia The Roofnet Project (MIT, USA) - http://pdos.csail.mit.edu/roofnet/doku.php 802.11 mesh network for broadband IA in cities The CITRIS TIER Project (UC Berkeley, USA) - http://tier.cs.berkeley.edu/ Technology and Infrastructure for emerging regions The Digital Gangetic Plains Project (IIT Kanpur, India) - http://www.iitk.ac.in/mladgp 802.11-based low-cost Networking for rural India The TFA Project (Rice University, USA) - http://taps.rice.edu/index.html Technology for All Project …. Community Mesh Networks Community Network Movement - http://www.scn.org/commnet/ Seattle Wireless - http://www.seattlewireless.net/ Champaign-Urbana Community Wireless Network - http://www.cuwireless.net/ Kingsbridge Link, U.K. - http://www.kingsbridgelink.co.uk/ …. . Industry Breakdown SkyPilot, QualNet (Flarion), Motorola (Canopy) IRoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc. Meshnetworks Inc.,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc. Infrastructure Based Infrastructure-less Architecture effects design decisions on Capacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc. . Industry Deployment Scenarios http://www.unstrung.com/insider/ March 2005, Source: Unstrung Insider . What about WiMAX? IEEE 802.16d for developing/rural use (.16e targets mobile scenarios) Still needs market momentum around hardware optimisation: size, power, efficiency and most important—cost WiMAX as a last-mile solution? In low-density areas, WiMAX requires high-power towers or lots of towers: (=> cost goes up) In NLOS environments, range impacts bandwidth through reduced modulation WiMAX CPE expensive in next 3-5 years (~ $150-250) WiMAX feeding a mesh can be a good solution Mesh extends WiMAX tower reach Mesh simplifies the financials by greatly reducing equipment cost Mesh is robust and deal with network vagaries . 16 QAM 16 QAM 16 QAM 8PSK 16 QAM QPSK FSK WiMAX + Mesh WiFi Meshes can add value to WiMAX in several ways: Reduce CPE costs Extend range of WiMAX tower without compromising speed Replace high-price WiMAX towers with cheaper mesh nodes WiMAX Only 16 QAM WiMAX with Mesh A A . Multi-Hop Wireless Networking Historical Perspective Packet Radio Network (PRNET), 1972-1982 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 km; Speed:100-400 Kbps, Addressing: Flat; Routing: Distance Vector; Scale: 50+ Survivable Adaptive Networks (SURAN), 1983-1992 Band: 1718.4-1840 MHz; Power: 5 W; Range: 10 Km; Speed: 100-400 kbps, Addressing: Hierarchical; Routing: Distance Vector; Scale: 1000+ (Low cost packet radio) Global Mobile Information Systems (GLOMO), 1995-2000 e.g. NTDR, Band: 225-450 MHz; Power: 20 W; Range: 11-20 Km; Speed: 300 kbps, Addressing: Flat; Routing: Link-state / 2-level clusters; Scale: 400+ IETF Mobile Ad Hoc Networks (MANET) Working Group, 1997 – RFC 2501 (Eval), RFC 3561 (AODV), RFC 3626 (OLSR), RFC 3684 (TBRPF), Drafts – DSR, DYMO, Multicast, OLSRv2 MSR Mesh Networking Project (2002 – 2005) IEEE 802.11s Working Group, 2004 - PRNET Van . Challenge: Mesh Networking with IEEE 802.11 2 3 4 5 7 8 9 1 11 10 RTS RTS CTS CTS 6 The MAC Problem – Packets in Flight Example 2 packets in flight! Only 4 out of 11 nodes are active…. Backoff window doubles  RTS RTS RTS . RTS CTS Throughput: Internet Gateway Example RTS RTS Backoff window doubles Backoff window doubles Internet . The Scheduling Problem Conflict graph If future traffic is not known, which one do you schedule first? D Choice 1 Choice 2 yes D yes . The Fairness Problem Information Asymmetry A & C do not have the same information C knows about flow 1 (knows how to contend) A does not know about flow 2 Flow 2 always succeeds, Flow 1 suffers When RTS/CTS is used A’s packets are not acknowledged by B A times out & doubles it’s contention window When RTS/CTS is not used A’s packet collide at B, but Flow 2 is succesful A times out & double it’s contention window Downstream links suffer 1 2 . Gambiroza-MoiCom-2004 Jinyang-MobiCom-2001 The Fairness Problem (2) Location closest to gateway gets the more packets Nodes farthest from the gateway get very little bandwidth and can get starved Possible solution: Rate control on each node with fairness in mind Need topology & traffic information to calculate fair amount Global vs. distributed solution ITAP . Camp-DC-2005 The Fairness Problem (3) MAC attempts to provide fairness at packet level not flow level Capture phenomena Winner of competing flows has a higher chance of winning contention again Different levels of interference at different links (different neighborhood) Highly interfered flows can be drowned Active area of research - MACAW, WFQ, DFS, Balanced MAC, EBF-MAC, PFCR, …. . Qiu-MSRTR-2003 Nandagopal-MobiCom-2000 The Path Length Problem Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time If a connection takes multiple paths over lifetime, lengths are byte-averaged Total 506 points. Impact of path length on throughput . Expected multi-hop b/w based on single-hop b/w Actual Roofnet b/w is often much lower The Collision Problem Robert Morris’s Rooftnet MSR Mesh Summit 2004 Presentation Multi-hop collisions cut b/w by about 2x The Node Density Problem A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other. Round trip delay versus node density . The Power Control Problem A & B do not detect RTS/CTS exchange between C & D B does not detect data transmission from D to C B’s transmission to A results in packet collision at C A B C D . Tight power control reduces interference and increases throughput The Power Control Problem (2) Tight power control reduces interference & increases overall throughput But it also disconnects the network. So what’s the “right” power control algorithm? A B C D A B C D . The Capacity of Mesh Nodes Optimal Case Nodes are optimally located, destinations are optimally located Traffic patterns are fixed Optimally spatio-temporal scheduling, routes, ranges for each transmission As each node obtains bits/sec Average Case Randomly located nodes and destinations Traffic pattern are random Each node chooses same range Each node obtains bits/sec . What is the maximum achievable capacity of a mesh network with N nodes? Gupta-IEEEIT-2000 The Capacity Calculation Problem Gupta and Kumar 2000 Theorem for stationary ad hoc nodes in the worst case traffic scenario Determines asymptotic, pessimistic bounds on performance Every node in the mesh is active (either transmitting or receiving) Does not answer: What is the capacity of a mesh which is using multiple channels, directional antennas, tight power control? . What is the Real Capacity of a Chain? With Ideal MAC, Chain Utilization = 1/3 1 2 3 4 5 6 Source Destination With interferences, Chain Utilization = 1/4 ….but this is achievable only with optimum scheduling and optimum offered load!, …with random scheduling and random load, utilization ~ 1/7 ! …but the radio’s interferance range is > radios communication range . Jinyang-MobiCom-2001 Routing Problem: Which to Choose? Unicast Ad Hoc Multi-hop Routing Protocols ABR (Associativity-Based Routing Protocol) AODV (Ad Hoc On Demand Distance Vector) ARA (Ant-based Routing Algorithm) BSR (Backup Source Routing) CBRP (Cluster Based Routing Protocol) CEDAR (Core Extraction Distributed Ad hoc Routing) CHAMP (CacHing And MultiPath routing Protocol) CSGR (Cluster Gateway Switch Routing) DART (Dynamic Address Routing) DBF (Distributed Bellman-Ford) DDR (Distributed Dynamic Routing) DNVR (Dynamic Nix-Vector Routing) DSDV (Dynamic Destination-Seq. Dist. Vector) DSR (Dynamic Source Routing) DSRFLOW (Flow State in the DSR) DYMO (Dynamic Manet On-Demand) FORP (Flow Oriented Routing Protocol) FSR (Fisheye State Routing) GB (Gafni-Bertsekas) GLS(Grid) (Geographic Location Service) GPSAL (GPS Ant-Like) GSR (Global State Routing) Guesswork HARP (Hybrid Ad hoc Routing Protocol) HSLS (Hazy Sighted Link State) HSR (Hierarchical State Routing) HSR (Host Specific Routing) IARP (Intrazone Routing Protocol) IERP (Interzone Routing Protocol) LANMAR (LANdMARk Routing Protocol) LAR (Location-Aided Routing) LBR (Link life Based Routing) LCA (Linked Cluster Architecture) LMR (Lightweight Mobile Routing) LQSR (Link Quality Source Routing) LUNAR (Lightweight Underlay Network Ad hoc Routing) MMRP (Mobile Mesh Routing Protocol) MOR (Multipoint On-demand Routing) MPRDV (Multi Point Relay Distance Vector) OLSR (Optimized Link State Routing) OORP (OrderOne Routing Protocol) DREAM (Distance Routing Effect Algorithm for Mobility) PLBR (Preferred Link Based Routing) RDMAR (Relative-Distance Micro-discover Ad hoc Routing) Scar (DSR and ETX based) SSR (Signal Stability Routing) STAR (Source Tree Adaptive Routing) TBRPF (Topology dissemination Based on Reverse-Path Forwarding) TORA (Temporally-Ordered Routing Algorithm) WRP (Wireless Routing Protocol) ZHLS (Zone-Based Hierarchical Link State) ZRP (Zone Routing Protocol) …. . The Path Selection Problem Several link quality metrics to select from Hop count Round trip time Packet pair Expected data transmission count incl. retransmission Weighted cumulative expected transmission time Signal strength stability Energy related Link error rate Air Time … Which to select? We still don’t have a interference-aware metric! We still don’t know how to measure interference….. . Baseline comparison of Metrics Single Radio Mesh Experimental Setup 23 node testbed One IEEE 802.11a radio per node (NetGear card) Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer, only one connection at a time ETX performs the best Median path length: HOP: 2, ETX: 3.01, RTT: 3.43, PktPair: 3.46 . Draves-MobiCom-2004 Experimental Setup 23 node testbed Randomly selected 100 sender-receiver pairs (out of 23x22 = 506) 3-minute TCP transfer Two scenarios: Baseline (Single radio): 802.11a NetGear cards Two radios 802.11a NetGear cards 802.11g Proxim cards WCETT utilizes 2nd radio better than ETX or shortest path Baseline Comparison of Metrics Two Radio Mesh Median path length: HOP: 2, ETX: 2.4, WCETT: 3 . Draves-SIGCOMM-2004 But with different traffic pattern…. Trace Capture 1 workstations connected via Ethernet Traces captured during 1-month period Trace Replayed Testbed of 22 mesh computers in office environment 2 IEEE 802.11a/b/g cards per computer . Erickson-MobiSys-2006 The Multicast Problem A multicast group is defined with a unique group identifier. Nodes may leave or join the group anytime In wired networks physical network topology is static In ad hoc multi-hop wireless networks physical topology can change often Need to Integrate with unicast routing protocols Many proposals [Tree-based, Mesh-based, Location-based] which one to use? . - ABAM (On-Demand Associatively-Based Multicast) - FGMP (Forwarding Group Multicast Protocol) - ADMIR (Adaptive Demand-Driven Multicast Routing) - LAM (Lightweight Adaptive Multicast) - AMRIS (Ad hoc Multicast Routing utilizing Increased id-numberS) - MAODV (Multicast AODV) - DCMP (Dynamic Core Based Multicast Routing) - MCEDAR (Multicast CEDAR) - AMRoute (Adhoc Multicast Routing) - MZR (Multicast Zone Routing) - CAMO (Core-Assisted Mesh Protocol) - ODMRP (On-Deman Multicast Routing Protocol) - CBM (Content Based Multicast) - SPBM (Scalable Position-Based Multicast) - DDM (Differential Destination Multicast) - SRMP (Source Routing-based Multicast Protocol) - DSR-MB (Simple Protocol for Multicast and Broadcast using DSR) - … - … The Interference Detection Problem When two systems operate on overlapping frequencies, there exists a potential for harmful interference between them Performance degradation on both systems Conflict graph is determined by the “Interference Graph” To determine the Interference Graph, require Knowledge of packet transmission from nodes that are not “visible” Knowledge of physical location of nodes within the network Knowledge of whether or not multiple transmissions increase ot decrease interference? Interference Graph can change as rapidly as the environment when a node leaves or join the network . The Transport Layer Problem Majority of the Internet traffic is TCP Packet losses & delays in wireless can occur due to Environmental fluctuations resulting link failures Stochastic link performance due to rapidly changing error rates CSMA/CA assumes loss is due to congestion and back-off’s TCP assumes packet losses are due to congestion Times out when no ACK is received Invokes slow start, when instead the best response would be to retransmit lost packets quickly RTT calculation can change as rapidly as the environment (link) changes Can we solve this problem without changing the end-to-end semantics? . The Security Problem Two type of attackers: External malicious node (no crypto keys) Compromised node (attacker captures legitimate node and reads out all cryptographic information) Attacks Selfish behavior, do not forward other node’s packets Denial of Service (DoS) Jamming Resource consumption attack Routing disruption (e.g. Wormhole attack) Inject malicious routing information Ongoing Research Possible solutions: SEAD, Ariadne, SRP, CONFIDANT, … . Hu-MobiCom-2002 Bucheggar-MobiHoc-2002 Packets get dropped! Doesn’t care The Spectrum Etiquette Problem Local behavior affects Global Performance! . Consequently we….. Must Increase Range and Capacity Single radio meshes built on 802.11 technologies are not good enough. We must extend the range of radios; we must understand the achievable capacity in an ideal wireless mesh and we must build technology to approach this capacity? Must Improve Routing Performance Routing protocols based on shortest-hop are sub-optimal. We must build a routing protocol that adapts quickly to topology changes, incorporates wireless interference and link quality. Must Provide Security and Fairness Is it possible to ensure fairness and privacy for end-users and security for the network? We must ensure that no mesh nodes starves and that the mesh guards itself against malicious users. Must Provide Self Management An “organic network” should be both self-organizing and self managing? To what extent can we remove the human out of the loop? . Must Develop a Resilient Framework for Applications In a environmentally hostile environment, we must provide a framework for applications to work robustly. . Handling the Challenges . Strategies for increasing Capacity Strategy 1: Use all available channels Avoid spectrum waste Strategy 2: Improve modulation, reception, and coding Today ~ 2.5 bits/Hz (.11g), Soon ~ 4.5 bits / Hz (.11n) Network coding Strategy 3: Improve spatial reuse by reducing interference Fine grain transmit power control (Steerable) directional antennas and directional MACs Strategy 4: Navigate around harmful interference Interference aware least cost routing . Will not cover Strategy 1: Multi-Channel Communications Goal Assign n non-interfering channels to n pair of nodes such that n packet transmissions can occur simultaneously. . Knobs Single Radio – Multiple Channels (SR-MC) Distributed: Use a modified RTS/CTS sequence to negotiate channels Problem How does the sender know which channel the receiver is listening on? Solutions Receive on all channels simultaneously Simplest solution but too costly - will not consider here Use a dedicated rendezvous channel Use a synchronized hopping protocol Provide multiple rendezvous opportunities Centralized: Compute channel assignments using global knowledge Scope of Coverage We will cover schemes that work on commodity radios only . Packets-in-Flight Example Revisited Negotiating Channel with RTS / CTS . 2 3 4 5 7 8 9 1 11 10 RTS (C1,C3,C7) RTS (C3,C5,C7,C11) CTS (C11) CTS (C1, C7) 6 C2 C2 C1 C11 C1 10 nodes are active, 5 packets in flight, 150% improvement! Note: Hidden Terminal – Multi-Channel Case Let C1 be the rendezvous channel γ can hear traffic on C1 only, doesn’t hear the CTS from β consequently doesn’t know anything about traffic on C6 (δ is too far to hear anything from β) . α β γ δ Possible solution: Use multiple radios So-MobiHoc-2004 Firmware Packets for C6 TCP/IP, Network Stack Packets for C11 Application Layer User-level Kernel-level Buffer packets, switch between channels Packets for C1 802.11 hardware Implementation Option for SR-MC 802.11 Device Driver Switching logic Channel switching speed: Today - 5 milliseconds Possible - 80 microseconds Chandra-INFOCOM-2004 Multi-Channel Medium Access Control (MMAC) . Divide time into beacon intervals Divide a beacon interval into two phase Negotiation Phase: All nodes switch to a pre-defined common channel and negotiate the channel to use Transfer Phase: Once a channel is selected, the source & receiver switch to this channel and data transfer occurs during this phase Idea: Periodically rendezvous on a fixed channel to decide the next channel Issues Requires tight clock synchronization Packets to multiple destinations can incur high delays Congestion on the common channel Common channel goes bad, everything goes bad Not able to handle broadcasts So-MobiHoc-2004 Slotted Seeded Channel Hopping (SSCH) Divide time into slots At each slot hop to a different channel Nodes hop across channels to distribute traffic Senders and receivers probabilistically meet & exchange schedules Senders loosely synchronize hopping schedule to receivers Characteristics Distributed: every node makes independent choices Optimistic: exploits common case that nodes know each others’ channel hopping schedules Traffic-driven: nodes repeatedly overlap when they have packets to exchange . Bahl-MobiCom-2004 Divide time into slots: switch channels at beginning of a slot 3 channels E.g. for 802.11b Ch 1 maps to 0 Ch 6 maps to 1 Ch 11 maps to 2 1 0 2 1 0 2 1 0 0 1 2 0 1 2 0 1 New Channel = (Old Channel + seed) mod (Number of Channels) seed is from 1 to (Number of Channels - 1) Seed = 2 Seed = 1 (1 + 2) mod 3 = 0 (0 + 1) mod 3 = 1 A B Enables bandwidth utilization across all channels Does not need control channel rendezvous . SSCH Rendezvous Each node broadcasts (channel, seed) once every slot If B has to send packets to A, it adjusts its (channel, seed) Stale (channel, seed) info simply results in delayed syncing 3 channels 1 0 2 1 0 2 1 0 2 0 2 1 0 2 1 0 Seed Seed A B 2 2 2 2 2 2 2 2 1 2 2 2 2 2 2 2 2 2 1 1 B wants to start a flow with A . SSCH Syncing Seeds Using all Available Channels with SSCH Only one of 3 pairs is active @ any given time In current IEEE 802.11 meshes . SSCH Performance Significant capacity improvement when traffic load is on multiple separate flows 100 nodes, IEEE 802.11a, 13 channels, every flow is multihop Avg. per node Throughput Total System Throughput SSCH SSCH IEEE 802.11a IEEE 802.11a . How many Channels can we really use? IEEE 802.11{b,g} partitions the allocated 83.5 MHz spectrum into 11 channels Only channels 1, 6 and 11 are mutually non-overlapping But…using only the orthogonal channels may waste spectrum . Banerjee-SIGMETRICS-2006 How many Channels can we really use? Can we use more channels by using partially-overlapped channels? Caution: may increase interference and cause more harm than good Need an appropriate model to capture interference-effects and make correct choices
Slide 65 - Wireless Mesh Networks Victor Bahl http://research.microsoft.com/~bahl Lecture 1 MSR India Summer School on Networking June 15, 2007 These lecture notes are for educating. Feel free to incorporate these slides in your presentations but please cite the source on each borrowed slide and as a courtesy to the author please inform him of such use. Do not post a copy of these slides, or slides derived from these on a web site without the author’s written permission. The contents of this deck may change without notice . Notice Foreword Mobile ad hoc networking and mesh networking is a thriving area of research. The number of solutions & results are simply too large to cover in a short lecture. This is not a lecture on (1) wireless communications (2) MAC protocols, (3) PHY Layer techniques and (3) multi-hop routing protocols. This is quick talk about what I know about building mesh networks. Exhaustive & deep treatment of all existing results is not provided. These notes are an attempt to describe the main problems & the general idea behind some of the promising solutions. At the end of this lecture you should have a reasonably good understanding of the state-of-art in mesh networking. . Topics not covered in this lecture Due to lack of time I was not cover several important research results that you should also be aware of. Some of these are: Modulation and PHY techniques like OFDM, Analog Network Coding etc. Adaptive antenna technologies like MIMO, beam forming, etc. TCP enhancements (for mesh networking) Routing protocols (there are hundreds……) Multicast routing and group communications Topology control and power management Standards including IEEE 802.11s,… Security and Management Directional MACs etc . Roadmap Mesh Networking & Applications Basics of Radio Frequency Communications (already covered by Dr. Ramjee) Multi-hop Wireless Networking Historical background Challenges: Mesh networking with 802.11 Handling the Challenges Capacity Enhancement & Calculation MMAC, SSCH, BFS-CA, HMCP, MUP, Network Coding, conflict graphs, …. Routing Protocols & Link Quality Metrics RFC 2501, RFC 3626, RFC 3684, RFC 3561, RFC 4728, ETX, LQSR, EXoR, HWMP, ETT, WCETT Security & Network Management Mesh Deployments – Discoveries & Innovations MSR’s Mesh, MIT’s RoofNet, IIT’s DGP, Rice’s TFA, UMASS’s DieselNet, UCSB’s Mesh, Madcity’s Mesh, JHU’s SMesh Mesh Networking Standards IEEE 802.11s (IETF standards covered previously) References . Will not cover, tutorial notes available on request Mesh Networking & Applications Wireless Mesh Networking Definition A wireless mesh network is a peer-to-peer multi-hop wireless network in which participant nodes connect with redundant interconnections and cooperate with one another to route packets. Unlike Mobile Ad hoc NETworks (MANETs) where routings node are mobile, in mesh networks routing nodes are stationary. Mesh nodes may form the network's backbone. Other non-routing mobile nodes ("clients") may connect to the mesh nodes and use the backbone to communicate with one another over large distances and with nodes on the Internet . Characteristics of a Mesh Network Classic Hub & Spoke Network Mesh Network Can grow “organically” Does not require infrastructure support Is fault tolerant Requires distributed management Offers higher capacity (via spatial diversity & power management), but Too many nodes  shared bandwidth may suffer