An Enhanced MAC Backoff Algorithm for Heavy User Loaded WLANs

As average user load in wireless local area network (WLAN) becomes heavy, the fundamental CSMA#x002F;CA mechanism based on binary exponential backoff (BEB) in the 802.11 protocol is under stress. When a large number of users associate with WLAN, the network suffers from severe throughput deterioration and poor short-term fairness due to the inappropriate BEB algorithm. In this paper, we provide an enhanced backoff (EBO) algorithm to improve the performance of WLANs. Our main motivation is based on the observation that disjointing backoff intervals in different backoff stage can greatly reduce the collision probability. In EBO, the size of backoff interval increases by the initial value of contention window after an unsuccessful transmission, and backoff intervals in different backoff stage are disjoint. Meanwhile, to improve the short-term fairness, we slow down the decrement of contention window by resetting the contention window to initial value after T consecutive successful transmissions. Simulation results show that EBO improves the throughput and short-term fairness effectively comparing with BEB in heavy user loaded WLANs.