MAC Protocols For Underwater Acoustic Sensor Networks

With the rapid development of wireless sensor networks on the ground and the world’s increasing emphasis on the research and development in the field of the ocean, Underwater Acoustic Sensor Networks (UWASNs) have been emerged. As an important part of UWASNs, MAC Protocols should be designed as suitably for UWANs.UWASNs can be used in various kinds of applications, such as, disaster forecasting, oil monitoring, resource discovery, underwater creature tracking, underwater environmental motoring, marine salvage and military applications etc.. Thus, UWASNs have been widely studied in the last decades and have already obtained lots of results. However, the characteristics of underwater communication, e.g., bandwidth limitations, multi-path propagation, padding, long end-to-end propagation delay, high BET, temporary loss of connectivity, and limited battery power etc., still limit UWASNs.Media Access Control (MAC) protocols, as an important part of Underwater Acoustic Sensor Networks, suffer from latency that is five orders-of-magnitude larger than that in radio networks. And the high transmit power consumption of acoustic transceivers makes the MAC protocols of UWASNs have to not only focus on the throughput, but also pay attention to reducing energy consumption for energy limited underwater devices and hard charging environment. Therefore, kinds of MAC protocols have been proposed for UWASNs by far. However, seldom of them consider the sleep and wake-up mechanism to conserve energy. Even some of them using the signal to wake up nodes (i.e., T-Lohi), it only considers distributed topologies of UWASNs. Considering the UWASNs of multi-hop topology, a MAC protocol, named Multi-hop T-Lohi (MT-Lohi), was proposed in this paper. MT-Lohi is a contention-based MAC and suitable for the UWASNs of multi-hop topology. MST-Lohi and MUT-Lohi are the two variants of MT-Lohi. Our simulation suggested that MT-Lohi improves throughput, energy consumption, end to end delay, the probability of successfully sending packets for the UWASNs of multi-hop topology.