A Comparative Performance Evaluation of Distributed Collision-free MAC Protocols for Underwater Sensor Networks

The design of Medium Access Control (MAC) protocols for UWSNs poses many challenges because of their long propagation delay, high mobility, limited bandwidth, and high bit error rate. Due to these unique acoustic channel characteristics, most contention-based MAC protocols are costly. Thus, collisions and retransmissions should be efficiently handled at the MAC layer in order to reduce the energy cost and to improve throughput and fairness across the network. As a consequence, they do not perform as efficiently as their achieved performance in terrestrial networks. In this paper, we evaluate the performance of three recently reported distributed collision-free MAC protocols; namely, ED-MAC, DL-MAC, and GC-MAC under various operational conditions. An extensive simulation study is carried out to compare the performance of these MAC protocols in terms of packet delivery ratio (PDR), throughput, and energy consumption with different scenarios (narrow and shallow networks) under varying traffic rates and numbers of nodes. Our study results showed that ED-MAC reaches the best energy efficiency in a narrow scenario with a light load than DL-MAC and GC-MAC protocols. While DL-MAC is a suitable choice for both scenarios among others in terms of flexibility. In terms of reliability and scalability, GC-MAC achieves the best performance in both scenarios than other protocols.