An Efficient Multi Access Protocol for Wireless Networks

In this paper, we propose and evaluate an efficient multi-access protocol for cell-based wireless networks. Our protocol addresses the problems in existing random-access protocols for wireless networks: long-term fairness as well as short term fairness in accessing a shared channel and the detection of hidden and exposed collisions. Our proposed protocol is a limited contention protocol in which the set of contending mobiles are chosen based on a global common contention window maintained by every mobile station. The contention window is adjusted based on three possible channel states: no transmission, success, and collision. We assume that the channel state at the end of each contention slot is broadcast by a base station in a control channel. We show analytically that the time interval between two successive accesses to the channel by any station is geometrically distributed, and that each station has equal chance to access the channel in every contention period. This is significantly better than existing random-access protocols based on the binary exponential backoff algorithm, which results in large variances in inter-access delays. Our experimental results also show that the number of contention slots to resolve collisions is constant on the average, independent of the number of contending stations.