A Distributed Cooperative MAC Protocol with Relay Collision Avoidance for Wireless Ad Hoc Networks

In wireless ad hoc networks, cooperative transmission is an efficient way to increase information reliability and improve network throughput. However, the packet collisions caused by the contention of multiple cooperative nodes limit this advantage. In this paper, a distributed cooperative MAC (CMAC) protocol with relay collision avoidance is proposed. Based on the statistical probability of the channel gains between any two nodes, a new method for calculating the contention waiting time of multiple cooperative nodes is proposed. Each cooperative node relays the packet of the sender according to its cooperation capability. The method can guarantee that the node with higher cooperation capability accesses the channel earlier, and greatly decrease the collision probability of the cooperative nodes with the similar cooperation capability (i.e., similar access waiting times). Simulation results show that compared with the energy aware CMAC and random CMAC protocols, the proposed protocol can reduce the collision probability, and achieve the optimal normalized throughput and energy utilization.