A Novel Random Backoff Algorithm to Enhance the Performance of IEEE 802.11 DCF

The Probability Distribution of Slot Selection (PDoSS) of IEEE 802.11 DCF is extremely uneven, which makes the packet collision probability very high. In this paper, we propose a novel RWBO+BEB backoff algorithm for 802.11 DCF to make the PDoSS even and thus decrease the packet collision probability. A Markov model is built for analyzing RWBO+BEB's PDoSS and saturation throughput. The model's correctness is validated by simulation. The performance of RWBO+BEB is also evaluated by simulation in terms of PDoSS, saturation throughput, packet collision probability and packet delay. The simulation results indicate that RWBO+BEB can decrease the packet collision probability to a large extent, utilize the channel more efficiently, and make the packet delay jitter much lower comparing to 802.11 DCF. Moreover, we analyze the relation of saturation throughput and packet collision probability to walking probability (p_d) and contention windows (w), respectively. The analysis indicates that RWBO+BEB has a remarkable feature: its saturation throughput keeps high, and packet collision probability keeps very low (which under 0.1) in a large range of p_d and w, this allows us to configure p_d and w more flexibly. Supported by the Program for New Century Excellent Talents in University (NCET 2005), the Research Project of Chongqing Municipal Education Commission of China (KJ050503), the Research Grants by the Science & Tech. Commission of Chongqing (8817) and the National Science Foundation of China (90304004). Li Yun was born in 1974. He is currently a Ph.D. candidate in University of Electronic Science and Technology of China. His research interests are in MAC protocol improvement and QoS in wireless ad hoc networks. Long Ke-Ping was born in 1968. He received his Ph.D. from University of Electronic Science and Technology of China in 1999. He is a professor Ph.D. supervisor in special research Centre for Optical Internet and Wireless Information Networks (COIWIN) at ChongQing University of Posts and Telecommunications. He was an IEEE member. He has over 120 research publications and 4 patents application. His research interests include: Optical Burst switching, modeling of optical networking, IP QoS mechanisms (Diffserv and Intserv, MPLS), WDM/SDH/ATM networks survivability, TCP/IP enhancements in wireless networks, and Mobile IP. Zhao Wei-liang was born in 1962 and received his Ph.D. degree from University of Electronic Science and Technology of China in 2001. He is a professor and a post-doctoral fellow in Beijing University of Posts & Telecommunications of China. His current interest lies in wireless communications.