Performance evaluation of the Quasi-FIFO back-off scheme for wireless access networks

Binary Exponential Back-off (BEB) scheme is widely adopted in both wire and wireless networks for collision resolution. Since the back-off windows among competing users are not synchronized, BEB algorithm results in "capture effect" and, in the limit as the number of users approaches infinity, BEB is unstable for every arrival rate greater than 0. Taking the advantage that a common back-off window size can be broadcast by the base-station or access point in wireless networks, capture effect can be substantially alleviated. We first show that maximum throughput can be achieved when the back-off window size is equal to the number of competing users and there are on the average 2.3922 users involved in each collision. Then, a novel Quasi-FIFO back-off scheme is proposed not only to improve the fairness in bandwidth usage, but also to maximize the throughput. In Quasi-FIFO, packets generated in the current cycle are guaranteed to be serviced in the next cycle and FIFO principle can be semi-accomplished.