Performance analysis of an efficient MAC protocol with multiple-step distributed in-band channel reservation

It is well known that the performance of most of contention-based medium-access-control (MAC) protocols are significantly influenced by packet collisions. In this paper, we propose an efficient MAC protocol for wireless local area networks (LANs) to handle packet collisions. Different from traditional reservation-based MAC protocols, where only one-step channel reservation is considered, we propose a multiple-step distributed in-band channel-reservation mechanism, which is called m-DIBCR, where m represents the number of steps considered in the channel reservation. In m-DIBCR, each node maintains m timers, each of which serves as the backoff timer for one of the next m packets to be sent. A node broadcasts the values of these timers by piggybacking them in data packets, and simultaneous transmissions can be avoided when its neighboring nodes overhear these values. Another contribution of this paper is that important performance measurements such as packet collision probabilities and average packet transmission delays are obtained based on in-depth analyses. Moreover, practical implementation methods such as an efficient virtual packet collision resolution scheme and a simple packet delay variation control scheme, are proposed. Results obtained from both performance analyses and simulations show that, compared with one-step channel reservation, the system throughput is significantly improved by multiple-step channel reservation, particularly in networks with high transmission error probabilities and/or a large number of contending nodes.