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Interplay of Spatial Reuse and SINR-determined Data Rates in CSMACA-based, Multi-hop, M

ulti- rate Wirless Networks

Ting-Yu Lin and Jennifer C. HouDepartment of Computer Science University

of Illinois at Urbana-Champaign

IEEE INFOCOM 2007

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Outline

Introduction Network Model and Signal Propagation/In

terference Model Network Capacity as A Function of Tcs, SI

NR and β[i] Validation of Analytic Model Conclusions

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Introduction

How does the collision be avoided in CSMA-CA-based wireless network? Physical carrier sense Binary exponential back off

mechanism Data rate adjustmentNetwork throughput : 1. Transmission time

2. Spatial reuse

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Spatial reuse

Tuning the carrier-sensing threshold Tcs Spatial reuse Computes the accumulated interference Tcs vs. Data rate Increase simultaneous transmissions

Within carrier sense range

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Network Model and Signal Propagation/Interference Model

Network Model Multi-hop Multi-rate Based on IEEE 802.11 DCF

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Network Assumption

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Virtual transmission time

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Network Capacity as A Function of Tcs, SINR and β[i]

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Attempt Probability

is derived in Calí’s model

Radio propagation

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Interference

dpg

dcs

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Interference Model

1st –tier interference nodes

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SINR vs. β[i]

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Collision Zone

Extra interference By simultaneous transmissions within the dc

s

SINR perceived at the receiver >β[i] Accumulative interference

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Revision all accumulated interference

Prcv (≧ Isim,dcz,dcs+ Icon,dcs,dpg +η) *β

, ,

[ ]con dcs dpg

GDPi

I

Spatial Reuse

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Numerical Results-1

Setting 500 nodes 500*500 m2

1125 Bytes/packet DSR =50m dpg=302m

dcs = 153m CW=64

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Numerical Results-2_1

200 nodes 500*500 m2

dcs=153 m CW =64~128

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Numerical Results-2_2 62 nodes 500*500 m2

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Numerical Results-2_3 10 nodes 500*500 m2

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Experiments with Settings (Tcs, CW, r)

Tcs : Optimal value r= 6 or 54

Number of nodes: 25 125

Field : 500*500 Single hop CBR conn

ection (225Bytes)

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Validation of Analytic Model

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Conclusions In this paper

Investigate Relation between PHY- and MAC-layer parameters

Derive Analytic model about the characters of IEEE 802.11

DCF A corresponding SINR

Achieve Spatial reuse Sustainable data rates