Optimized backoff algorithm of IEEE 802.11 DCF for collision resolution

Abstract

IEEE802.11 DCF (Distributed Coordination Function) protocol adopts binary exponential backoff (BEB) algorithm to reduce the probability of collision. However, when the network reaches saturation, throughput declines sharply with the increase of the number of stations (STAs) because of more collisions. In order to further avoid collisions and optimize the system, this paper proposes an improved algorithm based on the RTS / CTS (request to send /dear to send) mechanism. A STA intended to send packet sets an appropriate contention window (CW) and selects a backoff value different from that of other STAs according to the result of previous packet and the current backoff value of other STAs in the network. Theoretical analysis and OPNET simulation results show that the new algorithm outperforms BEB in performance of throughput, network delay and data dropped.