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Wireless LAN and Ad Hoc Wireless Networks PowerPoint Presentation

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On : Nov 15, 2014

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  • Slide 1 - 1 From Ad Hoc to ICEBERG: differences in two wireless network environments Zhigang Gong gong@cs.umn.edu August 9, 2002 Computer Science and Engineering Department University of Minnesota Wireless Networking Seminar
  • Slide 2 - 2 Outline Ad Hoc What is ad hoc network? Why ad hoc network? What are the interesting research topics? ICEBERG What is ICEBERG? Why study ICEBERG? How can we take it further?
  • Slide 3 - 3 What are Ad Hoc Networks In Latin, ad hoc means "for this," further meaning "for this purpose only.” An ad-hoc network is a LAN or other small network, especially one with wireless connections, in which some of the network devices are part of the network only for the duration of a communications session or, in the case of mobile or portable devices, while in some close proximity to the rest of the network.
  • Slide 4 - 4 Definition for Mobile Ad-hoc A "mobile ad hoc network" (MANET) is an autonomous system of mobile routers (and associated hosts) connected by wireless links--the union of which form an arbitrary graph. The routers are free to move randomly and organize themselves arbitrarily; thus, the network's wireless topology may change rapidly and unpredictably. Such a network may operate in a standalone fashion, or may be connected to the larger Internet. -------- IETF
  • Slide 5 - 5 Characteristics of ad hoc wireless network Autonomous (no infrastructure !); Wireless link based; (bandwidth constraint) Dynamic topology; (Due to movement or entering sleep mode); Rely on batteries for energy; (Power-constraint) Limited physical security;
  • Slide 6 - 6 Why ad hoc wireless networking? Technical side: wireless devices need to be connected; increased performance/cost ratio on devices Internet compatible standards-based wireless systems; Market side: mobile computing; wearable computing; military applications; disaster recovery; robot data acquisition
  • Slide 7 - 7 Research Challenges (I) MAC layer problems: Link layer reliability QoS at MAC layer Power conservation Network layer problems: Mobile IP Routing; QoS Power conserving Multicast
  • Slide 8 - 8 Research Challenges (II) Transport layer problems: (TCP over Ad hoc) End-to-end reliability? Congestion control? QoS? Application layer: Security? QoS? Inter-layer interactions; Internetworking with internet;
  • Slide 9 - 9 Main problem: Routing Standard (Mobile) IP needs an infrastructure Home Agent/Foreign Agent in the fixed network DNS, routing etc. are not designed for mobility No infrastructure in Ad hoc networks Main topic: routing no default router available every host (node) should be able to forward packets
  • Slide 10 - 10 Routing in an ad-hoc network N1 N4 N2 N5 N3 N1 N4 N2 N5 N3 good link weak link time = t1 time = t2
  • Slide 11 - 11 Traditional routing algorithms Distance Vector periodic exchange of messages with all physical neighbors that contain information about who can be reached at what distance selection of the shortest path if several paths available Link State periodic notification of all routers about the current state of all physical links router get a complete picture of the network
  • Slide 12 - 12 Problems of traditional routing algorithms Dynamic of the topology frequent changes of connections, connection quality, participants Limited performance of mobile systems periodic updates of routing tables need energy without contributing to the transmission of user data, sleep modes difficult to realize limited bandwidth of the system is reduced even more due to the exchange of routing information Problem: protocols have been designed for fixed networks with infrequent changes and typically assume symmetric links
  • Slide 13 - 13 Routing (Unicast) Table Driven: DSDV, WRP, etc On-demand Driven: AODV, TORA, DSR, ABR, SSR, …… Zone Routing Protocol (ZRP)
  • Slide 14 - 14 DSDV (Destination Sequenced Distance Vector) Expansion of distance vector routing Sequence numbers for all routing updates assures in-order execution of all updates avoids loops and inconsistencies Decrease of update frequency store time between first and best announcement of a path inhibit update if it seems to be unstable (based on the stored time values)
  • Slide 15 - 15 Dynamic source routing (DSR) Split routing into discovering a path and maintaining a path Discover a path only if a path for sending packets to a certain destination is needed and no path is currently available Maintaining a path only while the path is in use one has to make sure that it can be used continuously No periodic updates needed!
  • Slide 16 - 16 Dynamic Source Routing – Internet-Draft Characteristics: On-demand Unidirectional links and asymmetric routes are supported Route Discovery: S-D route is included in the header of each packet. Nodes forwarding or overhearing data packets may cache multiple routes for any D for future use (uni-directional?) Route Maintenance: on-demand Link failure detection: MAC layer (802.11) or Passive ACK or clear request for ACK Link ERR is propagated to source Use an cached new route or rediscover
  • Slide 17 - 17 Dynamic Load-Aware Routing On-demand, backward learning S floods REQ, D choose route by -- Total buffered packets, Average buffered packets, or Least number of congested routers D detects over-loaded route dynamically and initiates route-setup procedure to S. Load information in I is piggybacked periodically on data packets When link failure, the upstream I sends ERR to S and removes its entry. S initiates new route setup procedure. I does not reply REP even it knows a route to D
  • Slide 18 - 18 Mitigating routing misbehavior It is impossible to build a perfect network Routing denial of service Unexpected events, bugs, etc. Incorporate tools within the network to detect and report on misbehavior Route only through trusted nodes Requires a trust relationship Requires key distribution Trusted nodes may still be overloaded or broken or compromised Untrusted nodes might perform well Detect and isolate misbehaving nodes Watchdog detects the nodes Pathrater avoids routing packets through these nodes
  • Slide 19 - 19 Routing (Multicast) Multicast is still a hot topic even in Internet; In Ad Hoc, besides of those problems in traditional Internet, such as congestion control, routing for multicast is another big problem;
  • Slide 20 - 20 Other researches on Routing QoS support routing; Power conserving routing;
  • Slide 21 - 21 ICEBERG http://iceberg.cs.berkeley.edu/ ICEBERG: Internet-based core for CEllular networks BEyond the thiRd Generation Internet-based integration of telephony and data services spanning diverse access networks Leverage Internet’s low cost of entry for service creation, provision, deployment and integration
  • Slide 22 - 22 Why ICEBERG 3G+ will enable many communication devices and networks – diversity Mobility for transparent information access New applications: audio, video, multimedia
  • Slide 23 - 23 Design Goals Potentially Any Network Services (PANS): Network and device independent Personal Mobility: person as communication endpoint; requires a single identity for an individual - iUID Service Mobility: seamless mobility across different devices in the middle of a service session Easy Service Creation and Customization Scalability, Availability and Fault Tolerance Operation in the Wide Area Security, Authentication and Privacy
  • Slide 24 - 24 ICEBERG Architecture Overview PSTN GSM Pager Access Network Plane ICEBERG Network Plane ISP Plane ISP1 ISP2 ISP3 Clearing House
  • Slide 25 - 25 ICEBERG Components ICEBERG Access Point (IAP): A gateway serves as a bridge Call Agent (CA): call setup and control Name Mapping Service (NMS): mapping between communication endpoint and the iUID Preference Registry (PR): stores user profile Personal Activity Coordinator (PAC): tracks dynamic info of a person that is of her interest Automatic Path Creation Service (APC): establishes and manipulates data flow
  • Slide 26 - 26 iPOP on Cluster Computing Platforms Ninja Base and Active Service Platform (AS1) Clusters of commodity PCs interconnected by a high-speed SAN, acting as a single L-S computer mask away cluster management problems Load balancing, availability, failure management Ninja: highly available service initiation Redirector stub Good for long running services such as web servers AS1: fault tolerant service session Client heartbeat with session state Good for session-based services such as video conferencing
  • Slide 27 - 27 An Illustration Alice Bob IAP PR NMS PR NMS IAP Clearing House 2
  • Slide 28 - 28 What’s their difference? ICEBERG is an integrated service architecture to link any digital network with the Internet. Ad Hoc is in the wireless network domain. Put them together, some amazing application may be available.
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Description : Computer Science and Engineering Department University of Minnesota Wireless Networking Seminar From Ad Hoc to ICEBERG: differences in two wireless network environments

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