Performance Evaluation of Binary Negative-Exponential Backoff Algorithm in IEEE 802.11 WLAN

IEEE 802.11 has employed distributed coordination function (DCF) adopting carrier sense multiple access with collision avoidance (CSMA/CA). To effectively resolve collisions, DCF uses binary exponential backoff (BEB) algorithm with three parameters, i.e., backoff stage, backoff counter and contention window. If a collision occurs, stations involving in the collision increase their backoff stages by one and double their contention window sizes. However, DCF with BEB wastes wireless resource when there are many contending stations. Therefore, in this paper, we propose a binary negative-exponential backoff (BNEB) algorithm which maintains a maximum contention window size during collisions and reduces a contention window size half after successful transmission of a frame without retransmissions. We also compare the performance of DCF with BEB to that with BNEB. From the results, BNEB yields better performance than BEB when the number of contending stations is larger than 4.