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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
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 GrainedComplex 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
Destinationbias1
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
Destinationbias2
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
OverviewWe 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
EPS (End-to-end packet scatter)
Source
Central path is prioritizedDestination
Exterior paths are less aggressive than the central one
ns2 setup
400 nodes grid 802.11 wireless Random source-destination pairs Success measured as received number of
packets
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 results
Rate LQI 80 LQI 82 LQI 84 LQI 86
40 packets/s 167 11 72 4233 packets/s 120 -12 17 -820 packets/s 93 -3 -2 -12
% 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