Yongning Zhang, Bassel Alawieh , Chadi Assi

1. A Novel Physical Carrier Sensing Scheme for enhancing Spatial Reuse in Multihop Wireless Networks Yongning Zhang, BasselAlawieh, ChadiAssi Dept. of Science & Engineering, Concordia University in the U.S.A. World of Wireless, Mobile and Multimedia Networks(WoWMoM), 2008

2. Outline • Introduction • Protocol • Simulation • Conclusion

3. Introduction rc Higher CSth C B A

4. Introduction rc lower CSth C B A

5. Introduction d C B A

6. Introduction C B A

7. Introduction ri C B A

8. Protocol • Scenario 1 failure C B A

9. Protocol • Interference from concurrent transmissions • Collisions which are due to contending hosts which initiate their transmissions simultaneously

10. Protocol • transmits T times • A times are successful • Pc is collision probabilities • Pe is error probabilities • Nbusy and Nidle represent respectively the number of time slots in which a node senses the channel as busy/idle

11. Protocol • Pc is collision probabilities • Pe is error probabilities

12. Protocol • If Pe is above a certain threshold PF ,a node decreases its CSth. • If Peis below a certain threshold PS, a node increases its CSth.

13. Protocol • Scenario 2 failure failure C B A

14. Protocol C B A

15. Protocol C B A

16. Protocol

17. Protocol • Switch from 4-way to 2-way handshake • If this transmission is successful, the 2-way handshake will be activated for the next transmission attempt. • otherwise, a node will keep on using the 4-way handshake until the transmission is successful.

18. Simulation • Simulator : Qualnet • Propagation model : 2-ray mode • Routing protocol : AODV • Dynamic CCA adaptation : 11Mbps • Spatial Backoff : default CSth=-84dbm

19. Simulation

20. Simulation

21. Simulation

22. Simulation

23. Conclusion • The paper proposed a novel scheme that balances the tradeoff between collision and spatial reuse in multihop wireless networks.