A Dual Channel Medium Access Control (MAC) Protocol for Underwater Acoustic Sensor Networks Based on Directional Antenna

Medium access control (MAC) protocol is an important link for achieving networks function in any wireless networks; an efficient and reliable MAC protocol is crucial for an effective underwater acoustic sensor networks (UASNs). Significant differences between UASNs and terrestrial sensor networks (TSNs) render the traditional MAC protocols applied on land inapplicable underwater. Existing MAC protocols for UASNs use the omnidirectional antenna, which wastes energy, restricts the network’s coverage range, and brings about unnecessary interferences in neighbor nodes. This paper proposes a dual channel MAC protocol for UASNs based on directional antenna (DADC-MAC), which increases the network coverage range, efficiently utilizes space, and reduces node interference compared to the omnidirectional antenna. The DADC-MAC protocol divides the channel into a data transmission channel and busy prompt message channel; the node uses the former to transmit the control frame and DATA package while the sending node and receiving node use the latter channel to inform the neighbor nodes of on-going communications to prevent DATA package collision. A neighbor discovery mechanism and directional network allocation vector are applied to resolve hidden terminal and deafness problems. Simulation results show that the DADC-MAC protocol could improve network throughput and reduce end-to-end delay, is efficient, performs well, and is well suited to both symmetrical and asymmetrical UASNs topology.