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. 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... AP MH 1 Mbps 11Mbps 1 Mbps when sharing the same physical channel

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

5. Throughput of Node 0 versus time (before vs after)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 Mbps2 Mbps5.5 Mbps11 Mbps

7. 1 Mbps 2 Mbps 5.5 Mbps 11 Mbps RainDrop: A Multi-Rate Multi-Channel WLAN AP 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 4. Channel association grant SNRavg = αlpha * SNRavg + (1- αlpha) * SNRnew AP MH

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

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

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

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

13. Experimental Factors Experiment 1: Effect of alpha Stationary Mobile Distance to AP5m, 15m, 25m, 35m< 45m Mobile Speed0 m/s0.5m/s, 1m/s, 2m/s, 3m/s, 4m/s αlpha0, 0.1,…0.9, 0.92, 0.94,…0.98 Wireless Channel Model: Rayleigh fading, Jakes’ method

14. Simulation Results: Effect of αlpha on Throughput stationarymobile 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 previous problem scenario)results for previousproblem scenario

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

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. Simulation Results Total Throughput Per-Node Throughput

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

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

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

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

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