Reducing Congestion Effects in Wireless Networks by Multipath Routing Presented by Dian Zhang Lucian Popa, Costin Raiciu, University of California, Berkeley ICNP 2006
Outline Problem statement and assumptions BGR congestion control mechanism IPS EPS Performance evaluation Conclusions
Overview a point-to-point communication in a large Wireless Network
Overview
Goal: Split flows and reduce congestion by having less traffic in a contention/interference area. Improve overall throughput Improve fairness
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
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 bias = 0 small bias large bias
BGR Details Destination bias1 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
BGR Details Destination bias2 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
BGR Details Destination bias3 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
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
IPS (In-network packet scatter) Learn about congested neighbors
IPS (In-network packet scatter) Deviate uniformly traffic to congested nodes on three paths
EPS (End-to-end packet scatter) Source Destination
EPS (End-to-end packet scatter) Source Destination Congested node
EPS (End-to-end packet scatter) Source feedback Destination
EPS (End-to-end packet scatter) Source Destination
EPS (End-to-end packet scatter) Source Central path is prioritized Destination Exterior paths are less aggressive than the central one
EPS (End-to-end packet scatter) Source Most traffic on least congested path Destination
IPS+EPS The two algorithms can be used Independently Combined
ns2 setup 400 nodes grid wireless Random source-destination pairs Success measured as received number of packets
Throughput vs Hop Count Increase on AIMD(%)
Throughput vs No. Transmissions
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
Testbed metodology Throughput of vs
Testbed results RateLQI 80LQI 82LQI 84LQI packets/s packets/s packets/s % Increase in received packets for two BGR paths of 40 degree bias compared to single paths
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
Thank you! ICNP 2006