Synchronized Contention Windows-based Backoff Algorithm in IEEE 802.11 Wireless Networks

Binary Exponential Backoff (HER) algorithm is utilized to resolve the channel contention for IEEE 802.11 wireless networks. However, BEB algorithm does not meet the user expectation due to the large collision probability and the poor network fairness when the number of stations is large. To overcome the problems, a novel synchronized contention windows-based backoff algorithm is proposed, i.e., SCW. In SCW algorithm, each station (STA) actively tracks the transmission cases of the network and when the channel state is changed, the contention window (CW) of each station which participates in the competition is synchronized by resetting the CW, which makes each station get the medium access grant with the same probability in next channel contention. The experimental results show that with the increase of the number of the stations, the fairness index of the SCW algorithm is nearly equal to 1 and always keeps stable, and when the number of stations is large (nearly 36 STAs), the throughput and delay of the network are respectively increased and reduced by nearly 11% and 6% than the conventional BEB algorithm. The proposed algorithm can effectively improve the performance of throughput and delay, and it has an excellent fairness of network. Therefore, it is especially suitable the wireless networks with the dense stations.