1. Full auto rate MAC protocol for wireless ad hoc networks Z. Li, A. Das, A.K. Gupta and S. Nandi School of Computer Engineering Nanyang Technological University Singapore IEE Proceedings-Communications, Vol. 152, No. 3, June 2005

2. Outlines Introduction Motivation Modified Virtual Carrier Sensing (MVCS) Full Auto Rate (FAR) algorithm Analytical modeling Simulation Conclusion

3. Introduction IEEE 802.11 standards provide high raw bandwidth and support multiple transmission rates Several rate-adaptation algorithms had been proposed to improve the throughput  Increase the utilization of bandwidth  Suit the channel condition

4. Introduction (cont.) However, these schemes considered the rate adaptation for the data frame only The overhead of control frames which transmitted in the basic rate is considerable

5. Motivation

6. Motivation (cont.)

7. We could estimate the throughput by

8. Maximum throughput in IEEE 802.11b

9. Bandwidth utilization

10. Objective In this paper, the protocol aims to transmit the control frames at an acceptable higher rate

11. MVCS

12. MVCS (cont.) When a MAC frame did not correctly be received with a correct FCS value, EIFS shall be used Since EIFS = SIFS + DIFS + Tx(ACK)  EIFS is long enough for transmitting any control frame at any rate  RTS and ACK should be always transmitted at the highest rate under the given channel conditions

13. MVCS (cont.) If (L data / R data ) < EIFS  CTS should be transmitted at acceptable highest rate  The higher data rate, the higher probability Otherwise, CTS should be transmitted at the lowest basic rate

14. FAR RTS CTS S R Data ACK SIFS RTSCTSDATAACK CachedCached or basic-rate Piggy backed in CTS Piggy backed in Data Data lengthL/Chosen rate ACK/Chosen rate 0 CTS*Basic-rateDuration value Tx Rate Duration Field Defer Time

15. Analytical modeling Throughput : RBAR+MVCS vs. RBAR

16. Improvements of MVCS

17. Analytical modeling (cont.) Throughput : FAR vs. RBAR+MVCS

18. FAR vs. RBAR+MVCS

19. Analytical modeling (cont.) Throughput : FAR vs. RBAR

20. FAR vs. RBAR

21. Simulation NS-2 Transmission range/Carrier sensing range  250m Mobility  Random way-point mobility model  Pause time = 0  Maximum speed = 5m/s

22. Single flow within single-hop 2 nodes 200 * 200

23. Multiple flows within single-hop 10 nodes 200 * 200

24. Multiple flows within multi-hop 20 nodes 1000 * 500

25. Conclusion This paper proposed a new rate adaptation algorithm: FAR  Transmit all the frames at the highest rate under the given channel conditions To ensure the correct operation of VCS, MVCS is proposed

26. Conclusion (cont.) Both analytical and simulation show that the FAR algorithm greatly improves the performance of IEEE 802.11 Routing protocol should be considered in the future work

27. Thank you !