Tuning the Carrier Sensing Range of IEEE 802.11 MAC

Jing Deng,Ben Liang and Pramod K. Varshney

Univ. of New OrleansGlobecom 2004

Outline

Problem of Fixed Carrier Sensing Range

Carrier Sensing Range Optimization PERFORMANCE EVALUATION CONCLUSIONS

Problem of Fixed Carrier Sensing Range The transmission range (R)

The range inside which nodes are able to receive or overhear the packet transmission

The carrier sensing range (Rs) The range inside which nodes are able to

sense the signal, even though correct packet reception may not be available

Problem of Fixed Carrier Sensing Range The interference range (Ri)

The range inside which any new transmission may interfere with the packet reception

Problem of Fixed Carrier Sensing Range Rs is a tunable parameter. In NS2

Rs = 2.2 R

Problem of Fixed Carrier Sensing Range

Problem of Fixed Carrier Sensing Range

Problem of Fixed Carrier Sensing Range

Node C is free to start any transmission when node B is receiving. Node C is not a hidden term

inal Distant Terminal Problem

Carrier Sensing Range Optimization larger Rs

packet collision rate to decrease leads to a lower level of spatial frequency

reuse

Carrier Sensing Range Optimization η = NS – cNd

NS

The channel throughput Nd

Total amount of transmitted data

PERFORMANCE EVALUATION NS2 simulator CPThreshold

10 dB The transmission range

250m The data packet length

2000 Bytes The simulation time

4 seconds

Effect of Carrier Sensing Range

2560 /( N-1 ) m

PERFORMANCE EVALUATION

PERFORMANCE EVALUATION

Carrier Sensing Range Optimization N nodes are uniformly distributed in

Y m2 network The value of Y is set to 50N.

All traffic are sent to a randomly selected immediate neighbor.

PERFORMANCE EVALUATION

PERFORMANCE EVALUATION

PERFORMANCE EVALUATION

PERFORMANCE EVALUATION

CONCLUSIONS Using this model, we can determine t

he optimal carrier sensing range of CSMA for any ad hoc network.

Our study shows that an optimally chosen carrier sensing range can Increase the network throughput Decrease the number of data packet colli

sions