Improvement of WLAN Contention Resolution by Loss Differentiation (TW04-712, Final Version) Qixiang Pang 1 , Victor C. M. Leung 1 , Fellow, IEEE, Soung C. Liew 2 , Senior Member, IEEE {qixiangp@ece.ubc.ca, vleung@ece.ubc.ca, soung@ie.cuhk.edu.hk} 1. Department of Electrical and Computer Engineering The University of British Columbia 2. Department of Information Engineering The Chinese University of Hong Kong Abstract – In a realistic WLAN environment, frame losses may be caused by collisions or channel noise. The existence of noise-induced losses reduces the effectiveness of the standard WLAN backoff algorithm for contention resolution, which assumes that all losses are caused by collisions and always doubles the contention window to reduce contention upon a frame loss. In this paper, we propose new backoff algorithms that take advantage of a new capability to differentiate the losses, and thereby sharpen the accuracy of the contention resolution process. Analytical models are developed to analyze the performance of these algorithms under heterogeneous link conditions in a WLAN. Both analysis and simulation results show that significant improvement of throughput and fairness can be obtained for WLANs in which contention resolution is enhanced by the loss differentiation ability. Index Terms – WLAN, MAC Protocol, Contention Resolution, Backoff Algorithm, Loss Differentiation Correspondence to: Qixiang Pang Email: qixiangp@ece.ubc.ca; Tel: +1-604-8224985 2332 Main Mall, Vancouver, BC, V6T 1Z4, CANADA This work was sponsored by the Canadian Natural Sciences and Engineering Research Council under grant STPGP 257684-02 and the AoE scheme under the University Grant Committee of Hong Kong (AoE/E- 01/99).