Performance Analysis and Enhancement of IEEE 802.11 DCF Contention Window Backoff Scheme in the Presence of Noise *

The paper presents an in-depth analysis on IEEE 802.11 DCF in the presence of noise. Based on the analysis, the Back to back Retransmission (BR) scheme is proposed. The main idea of the new scheme is to adopt different MAC protocol behaviors to the failures caused by collisions and those by channel errors. Based on the mathematical models, system saturation throughputs and maximum achievable throughputs of DCF and BR are analyzed using numerical methods. Then, ns-2 simulations are performed to study the impact of such factors as bit-error-rate, number of contending nodes on the performance of BR and DCF. Both the numerical calculation results and simulation results have shown that the proposed BR scheme outperforms DCF in the presence of noise.