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