Reducing Congestion Effects in Wireless Networks by Multipath Routing

1. ICNP 2006 Reducing Congestion Effects in Wireless Networks by Multipath Routing Presented by Dian Zhang Lucian Popa, Costin Raiciu, University of California, Berkeley

2. Outline • Problem statement and assumptions • BGR • congestion control mechanism • IPS • EPS • Performance evaluation • Conclusions

3. Overview a point-to-point communication in a large Wireless Network

4. Overview

5. Overview Goal: Split flows and reduce congestion by having less traffic in a contention/interference area. • Improve overall throughput • Improve fairness

6. Multipath Routing-related work • We need alternate paths to avoid congested hotspots • Existing solutions not satisfactory • Way points • Simple • Course Grained • Trajectory Based Forwarding [Niculescu03] • Fine Grained • Complex and resource consuming

7. Biased Geographical Routing (BGR) • Idea • Insert a “bias” inside the packet as a measure of the deviation from the greedy path • Achieve different paths by using different biases large bias small bias bias = 0

8. BGR Details • Bias = Angle • Route greedy towards a close by point projected at “bias” angle • Decrease bias at each step • Quadratic dependence on distance to destination • Stop decreasing when it reaches zero bias1 Destination

9. BGR Details • Bias = Angle • Route greedy towards a close by point projected at “bias” angle • Decrease bias at each step • Quadratic dependence on distance to destination • Stop decreasing when it reaches zero bias2 Destination

10. BGR Details • Bias = Angle • Route greedy towards a close by point projected at “bias” angle • Decrease bias at each step • Quadratic dependence on distance to destination • Stop decreasing when it reaches zero bias3 Destination

11. Overview We propose two algorithms to deal with congestion 1. IPS - In-network Packet Scatter • Local algorithm • Lightweight – no per flow state • Suited for short flows or light congestion 2. EPS – End-to-end Packet Scatter • End to end – rate control, relies on receiver feedback • Suited for long flows and widespread congestion

12. IPS (In-network packet scatter) Learn about congested neighbors

13. IPS (In-network packet scatter) Deviate uniformly traffic to congested nodes on three paths

14. EPS (End-to-end packet scatter) Destination Source

15. EPS (End-to-end packet scatter) Destination Congested node Source

16. EPS (End-to-end packet scatter) Destination feedback Source

17. EPS (End-to-end packet scatter) Destination Source

18. EPS (End-to-end packet scatter) Central path is prioritized Destination Exterior paths are less aggressive than the central one Source

19. EPS (End-to-end packet scatter) Most traffic on least congested path Destination Source

20. IPS+EPS • The two algorithms can be used • Independently • Combined

21. ns2 setup • 400 nodes grid • 802.11 wireless • Random source-destination pairs • Success measured as received number of packets

22. Throughput vs Hop Count Increase on AIMD(%)

23. Throughput vs No. Transmissions

24. Testbed • Mirage sensor network testbed • ~100 nodes • But too “narrow” – interference on one side • Thus, our main goal was to estimate in practice potential for throughput increase

25. Testbed metodology • Throughput of vs

26. Testbed results • % Increase in received packets for two BGR paths of 40 degree bias compared to single paths

27. Conclusions • BGR • An efficient and practical multipath algorithm for wireless networks with location information • IPS, EPS • Two mechanisms to increase fairness and throughput by multipath routing • Practical tests

28. ICNP 2006 Thank you!