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RainDrop: A Multi-Rate Multi-Channel Wireless LAN

RainDrop: A Multi-Rate Multi-Channel Wireless LAN. Tianbo Kuang Qian Wu Carey Williamson. Department of Computer Science University of Calgary. Outline. Problem Statement and Motivation Multi-Rate Multi-Channel (MRMC) protocol Simulation Evaluation of MRMC Summary and Conclusions.

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RainDrop: A Multi-Rate Multi-Channel Wireless LAN

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  1. RainDrop: A Multi-Rate Multi-Channel Wireless LAN Tianbo Kuang Qian Wu Carey Williamson Department of Computer Science University of Calgary

  2. Outline • Problem Statement and Motivation • Multi-Rate Multi-Channel (MRMC) protocol • Simulation Evaluation of MRMC • Summary and Conclusions

  3. AP when sharing the same physical channel 11Mbps MH MH 11Mbps MH MH 1 Mbps 1 Mbps Problem Statement • The IEEE 802.11b WLAN supports automatic rate selection • Each station dynamically chooses its transmission rate of either 1, 2, 5.5, or 11 Mbps, depending on channel conditions (e.g., rate selection algorithm in Lucent’s WaveLAN-II) • This is both a good thing and a bad thing...

  4. Performance Anomaly of IEEE 802.11b [Heusse et al. 2003] • An ns-2 network simulation experiment showing the problem Node 0 Server start at time = 150 s start at time = 0 s Node 1 100 Mbps AP Range = 45m Node 2 Node 3 < 8 m 35 m

  5. Throughput of Node 0 versus time (before vs after)

  6. Our Solution – Multi-Rate Multi-Channel (MRMC) WLAN • Use multiple physical channels (3 or 4) simultaneously at AP, each with a different transmission rate (static or dynamic) 1 Mbps 2 Mbps 5.5 Mbps 11 Mbps

  7. AP 11 Mbps 5.5 Mbps 2 Mbps 1 Mbps RainDrop: A Multi-Rate Multi-Channel WLAN Notes: 4x antenna “cost” (?) +77% capacity

  8. Multi-Rate Multi-Channel (MRMC) MAC protocol • Channel association algorithm 1. Beacon (channel, transmission rate, SNR threshold) 2. Get SNR 3. Channel association frame MH AP 4. Channel association grant SNRavg = αlpha * SNRavg + (1- αlpha) * SNRnew

  9. stationary scenario: Server AP 100 Mbps 5, 15, 25, 35m MH Simulation Evaluation of the MRMC protocol (ns-2) Experiment 1. Effect of αlpha on throughput

  10. stationary scenario: mobile scenario: Server AP 100 Mbps 100 Mbps 5, 15, 25, 35m < 45m MH Simulation Evaluation of the MRMC protocol (ns-2) Experiment 1. Effect of αlpha on throughput

  11. stationary scenario: mobile scenario: Server AP 100 Mbps 100 Mbps 5, 15, 25, 35m < 45m MH Simulation Evaluation of the MRMC protocol (ns-2) Experiment 1. Effect of αlpha on throughput

  12. stationary scenario: mobile scenario: Server AP 100 Mbps 100 Mbps 5, 15, 25, 35m < 45m MH Simulation Evaluation of the MRMC protocol (ns-2) Experiment 1. Effect of αlpha on throughput

  13. Experimental Factors • Experiment 1: Effect of alpha Wireless Channel Model: Rayleigh fading, Jakes’ method

  14. stationary mobile Simulation Results: Effect of αlpha on Throughput SNRavg = αlpha * SNRavg + (1- αlpha) * SNRnew

  15. Simulation Evaluation of the MRMC Protocol (ns-2) Expt 2. MRMC performance in a stationary scenario (comparison to results for previousproblem scenario)

  16. Simulation Evaluation of the MRMC Protocol (ns-2) Experiment 3. Static scenario with N mobile hosts Server Node N AP < 45m 100 Mbps < 45m Node 1

  17. Experimental Factors and Performance Metrics • Factors • Number of nodes N: 2, 4, 6,…50 • MAC layer protocols: MRMC, WaveLAN-II • Metrics: • Total throughput of nodes (99% confidence intervals) • Mean throughput for each node

  18. Total Throughput Per-Node Throughput Simulation Results

  19. Node 20 Node 1 Simulation Evaluation of the MRMC Protocol (ns-2) Experiment 4. Mobile scenario with 20 hosts Server AP < 45m 100 Mbps < 45m

  20. Node 20 Node 1 Simulation Evaluation of the MRMC Protocol (ns-2) Experiment 4. Mobile scenario with 20 hosts Server AP < 45m 100 Mbps < 45m

  21. Node 20 Node 1 Simulation Evaluation of the MRMC Protocol (ns-2) Experiment 4. Mobile scenario with 20 hosts Server AP < 45m 100 Mbps < 45m

  22. Node 20 Node 1 Simulation Evaluation of the MRMC Protocol (ns-2) Experiment 4. Mobile scenario with 20 hosts Server AP < 45m 100 Mbps < 45m

  23. Experimental Factors and Performance Metrics • Factors • Mean moving speed: 0.5 m/s, 1 m/s, 2 m/s, 3 m/s, 4 m/s • MAC layer protocols: MRMC, WaveLAN-II • Metrics: • Total throughput of nodes (99% confidence intervals)

  24. Simulation Results

  25. Conclusions • The proposed MRMC protocol is promising • Performance is not very sensitive to value of alpha • With 4 channels and 4 rates, the MRMC protocol offers a 450% throughput advantage over the WaveLAN-II IEEE 802.11b MAC protocol • Super-linear throughput improvement (450%) from 77% increase in channel capacity (4x cost?) • Primary benefit: isolating low-rate/high-rate users

  26. Future Work: Multiple APs

  27. Questions?

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