1. Tuning the Carrier Sensing Range of IEEE 802.11 MAC Jing Deng,Ben Liang and Pramod K. Varshney Univ. of New Orleans Globecom 2004

2. Outline Problem of Fixed Carrier Sensing Range Carrier Sensing Range Optimization PERFORMANCE EVALUATION CONCLUSIONS

3. 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 (R s ) The range inside which nodes are able to sense the signal, even though correct packet reception may not be available

4. Problem of Fixed Carrier Sensing Range The interference range (R i ) The range inside which any new transmission may interfere with the packet reception

5. Problem of Fixed Carrier Sensing Range R s is a tunable parameter. In NS2 R s = 2.2 R

6. Problem of Fixed Carrier Sensing Range

8. Node C is free to start any transmission when node B is receiving. Node C is not a hidden terminal Distant Terminal Problem

9. Carrier Sensing Range Optimization larger R s packet collision rate to decrease leads to a lower level of spatial frequency reuse

10. Carrier Sensing Range Optimization η = N S – cN d N S The channel throughput N d Total amount of transmitted data

11. PERFORMANCE EVALUATION NS2 simulator CPThreshold 10 dB The transmission range 250m The data packet length 2000 Bytes The simulation time 4 seconds

12. Effect of Carrier Sensing Range 2560 /( N-1 ) m

13. PERFORMANCE EVALUATION

15. Carrier Sensing Range Optimization N nodes are uniformly distributed in Y m 2 network The value of Y is set to 50N. All traffic are sent to a randomly selected immediate neighbor.

16. PERFORMANCE EVALUATION

20. CONCLUSIONS Using this model, we can determine the 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 collisions