A Delay-Tolerant MAC Protocol with Collision Avoidance for Underwater Acoustic Networks

The hostile seawater channel condition poses research challenges in the area of underwater acoustic networks, especially limited bandwidth and high propagation delay of acoustic waves make networks poor performance. Due to low efficiency of traditional handshaking protocol, in this paper, we propose a new delay-tolerant medium access control (MAC) protocol called UMACAW, in which a node is able to exchange messages with multiple other nodes during one RTS-CTS-DATAACK exchange period, while busy durations of neighbors are achieved. The proposed scheme improves channel utilization by taking advantage of long propagation delay over underwater acoustic channel, and also alleviates the hidden terminal and exposed terminal problems. Simulation tests on OPNET radio modeler show that UMACAW protocol has much higher throughput and lower delay than MACAW protocol.