Quasi-FIFO back-off scheme for collision resolution in wireless networks

This paper proposes a quasi-FIFO (QFIFO) back-off scheme for collision resolution in wireless networks. The proposed scheme takes advantage of the central unit (CU) in a wireless network to broadcast a common back-off window size to all the users, significantly alleviating the unfairness of bandwidth utilization in conventional binary exponential back-off (BEB) schemes. Since the maximum throughput is achieved when the back-off window size equals the number of users, the average number of users involved in each collision slot is derived to estimate the number of simultaneously competing users. In the QFIFO scheme, service time is divided into a series of cycles. Packets arrive in the current cycle are guaranteed to be serviced prior to any packet generated in the next cycle and the first-in-first-out (FIFO) principle can thus be semi-accomplished. Simulation results demonstrate that the unfairness of bandwidth utilization in the BEB is significantly mitigated and the throughput can be maintained at 0.368 when the number of users approaches infinity. The capture effect even further improves system performance.