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Augmenting Mobile 3G Using WiFi PowerPoint Presentation

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On : Nov 13, 2014

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  • Slide 1 - Augmenting Mobile 3G Using WiFi Aruna Balasubramanian Ratul Mahajan Arun Venkataramani University of Massachusetts Microsoft Research
  • Slide 2 - Mobile data is growing exponentially http://www.totaltele.com http://www.readwriteweb.com CISCO VNI 2010 ratul | UW | May '10 2
  • Slide 3 - Demand projected to outstrip capacity ratul | UW | May '10 3
  • Slide 4 - Is more spectrum the answer? “In light of the limited natural resource of spectrum, we have to look at the ways of conserving spectrum” -- Mark Siegel (AT&T) ratul | UW | May '10 4 http://www.nyt.com
  • Slide 5 - The BET of spectrum scarcity Behavioral Economic Technical Increase efficiency Reduce usage http://blogs.chron.com/ http://pro.gigaom.com/ ratul | UW | May '10 5 http://connectedplanetonline.com
  • Slide 6 - Augmenting Mobile 3G using WiFi Offload data to WiFi when possible We look at vehicular mobility ratul | UW | May '10 6
  • Slide 7 - Our work First joint study of 3G and WiFi connectivity Can WiFi usefully augment 3G capacity? Conducted across three cities Wiffler: A system to offload data to WiFi Increase offloaded data but respect app constraints Deployed on 20 vehicles ratul | UW | May '10 7
  • Slide 8 - Measurement study Vehicular nodes with 3G and WiFi (802.11b) radios Amherst: 20 buses Seattle: 1 car SFO: 1 car ratul | UW | May '10 8
  • Slide 9 - WiFi availability is low ratul | UW | May '10 9 90 12 5 Availability (%)
  • Slide 10 - WiFi loss rate is higher ratul | UW | May '10 10 Cumulative fraction WiFi 3G
  • Slide 11 - WiFi (802.11b) throughput is lower ratul | UW | May '10 11 Cumulative fraction Cumulative fraction WiFi 3G WiFi 3G Upstream Downstream
  • Slide 12 - Implications for offloading data to WiFi Straightforward design: use WiFi when available Offloads only 10% of the data Hurts application performance ratul | UW | May '10 12
  • Slide 13 - Key techniques in Wiffler Prediction-based offloading Exploit the delay tolerance of apps to increase data offloaded to WiFi Fast switching Combat poor WiFi connectivity ratul | UW | May '10 13
  • Slide 14 - Prediction-based offloading Delay data transfers only if that reduces 3G usage Transfer requirements: S bytes by D seconds W = Predicted WiFi capacity over future D seconds Send data on 3G only when (W < S · c) Send data on WiFi whenever available ratul | UW | May '10 14
  • Slide 15 - Predicting WiFi capacity Based on (# of APs) x (capacity per AP) Observation: future AP encounters depend on recent past Predict # of APs based on the last N encounters ratul | UW | May '10 15
  • Slide 16 - Error in predicting # of APs ratul | UW | May '10 16 Relative error N=1 N=4 N=8
  • Slide 17 - Fast switching Poor WiFi connectivity will hurt demanding apps such as VoIP and video streaming Send the packet on 3G if WiFi does not succeed within a threshold Link-layer retransmissions take time Losses are bursty ratul | UW | May '10 17
  • Slide 18 - Implementation of Wiffler ratul | UW | May '10 18 Wiffler proxy
  • Slide 19 - Evaluation Deployment on 20 vehicular nodes Trace-driven simulations ratul | UW | May '10 19
  • Slide 20 - Deployment results ratul | UW | May '10 20 Transfer size: 5MB; Delay tolerance: 60 secs; Inter-transfer gap: random with mean 100 secs VoIP-like traffic: 20-byte packet every 20 ms
  • Slide 21 - Trace-driven evaluation Yields results comparable to deployment Vary workload, AP density, delay tolerance, switching threshold Alternative strategies Impatient: use WiFi when available Patient: waits until the delay threshold Breadcrumbs: mobility prediction + location history Oracle: perfect future knowledge ratul | UW | May '10 21
  • Slide 22 - Wiffler increases data offloaded to WiFi Performance of Wiffler is comparable to optimal More complicated predictions do not help ratul | UW | May '10 22 Patient, Oracle Breadcrumbs Wiffler Impatient Fraction of data offloaded to WiFi
  • Slide 23 - Prediction reduces completion time ratul | UW | May '10 23 Completion time (secs) Patient Wiffler Breadcrumbs Oracle Impatient
  • Slide 24 - More offloading in urban centers ratul | UW | May '10 24 Fraction of data offloaded to WiFi 24% WiFi availability 12% WiFi availability
  • Slide 25 - Fast switching improves performance of demanding applications ratul | UW | May '10 25 % time with good voice quality Oracle Only 3G Wiffler No switching
  • Slide 26 - Possible extensions Reduce energy cost of searching for usable WiFi Predict what a user will access and prefetch Recommend content to users based on what is cached (courtesy Romit Roy) ratul | UW | May '10 26
  • Slide 27 - Conclusions Offloading to WiFi can augment mobile data transfer capacity and reduce pressure on cellular spectrum But must overcome the low WiFi availability and performance Prediction-based offloading and fast switching can tackle these challenges Offloads a third of the data if 1-min delays are tolerable ratul | UW | May '10 27

Description : Augmenting Mobile 3G Using WiFi. Aruna Balasubramanian . Ratul MahajanArun Venkataramani. University of MassachusettsMicrosoft Research

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