Enhanced backoff scheme in CSMA/CA for IEEE 802.11

Abstract

An enhanced CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) protocol to be used in the Medium Access Control (MAC) layer of the IEEE 802.11 standard for wireless local area networks (wireless LANs) is proposed in this work. In wireless LANs, the CSMA/CA protocol supports asynchronous data transfer, and adopts an acknowledgement mechanism to confirm successful transmissions and a handshaking mechanism to reduce collisions. In both cases, a binary exponential backoff mechanism is used. The enhanced protocol improves the exponential backoff scheme by dynamically adjusting the contention window (CW) around the optimal value. Moreover, an analytical model based on the Markov chain is developed to analyze the system performance in terms of throughput and delay. Numerical results are presented to show the effect of the proposed backoff mechanism.