Reducing Congestion Effects in Wireless Networks by Multipath Routing

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

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 pointsSimple 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 congestion1. 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 prioritizedDestination

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 802.11 wireless Random source-destination pairs Success measured as received number of

packets

Throughput vs Hop Count

Incr

ease

on

AIM

D(%

)

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

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

Thank you!Thank you!

ICNP 2006ICNP 2006