A New Distributed Contention Control Protocol for the IEEE 802.11 MAC Layer - Project of ATCRC Application Programms

The famous binary backoff algorithm in IEEE 802.11 MAC layer can forget the contention level between each successfully transmitted data frame and hence suffers significant performance degradation when the contention level is high. In IEEE 802.11 standard, a distributed contention control (DCC) algorithm is proposed to address this problem by observing how many of slots in the last backoff period were busy, i.e. slot utilization. The introduction of slot utilization can provide good estimation of the most recent congestion dynamics, i.e. transient fluctuations of the traffic. However, it is inaccurate to estimate the overall traffic pattern as one backoff period is too short to obtain accurate stationary statistics. In this paper, a new DCC algorithm is proposed that can combine transient and stationary characteristics, which provides better estimation of congestion level of the medium. Extensive simulation by using NS-2 simulator has shown that our scheme has better throughput and low collisions compared with original binary backoff MAC protocol and slot utilization algorithm (Nononi, Conti and Donatiello, 1998).