Improved Opportunistic Auto Rate Media Access Protocol for Multi-Rate Ad Hoc Networks

Fairness of performance has been considered as a key object in multi-rate ad hoc networks. Some researchers proposed opportunistic auto rate (OAR) media access protocol, which is based on IEEE 802.11, to implement fair performance for each sender. However, OAR protocol still cannot avoid unfair performance in some topologies. In this paper, we improve OAR protocol in order to satisfy fair performance as far as possible. This modified OAR protocol is called improved opportunistic auto rate (IOAR) protocol. IOAR protocol consists of two interactive components: an equiprobable auto rate (EAR) protocol and a probabilistic mechanism. IOAR ensures equal bandwidth utilization rate, and each transmitter can share bandwidth according to its transmission rate. We perform a set of ns-2 simulations to study the efficiency of IOAR