Distributed Channel Sensing MAC Protocol for Multi-UUV Underwater Acoustic Network

The media access control (MAC) protocol is a primary technology to achieve a collision-free transmission and improve the channel utilization for underwater acoustic networks (UANs). Most relative studies currently focus on solving underwater acoustic sensor networks (UASNs) with a limited mobility and fixed topology, where nearly all the data is transmitted from the network edge to the sink node. However, multiple underwater unmanned vehicle (multi-UUV) networks have complex and variable topologies and usually contain both unicast and multicast transmission. The MAC protocol designed for it should be flexible and achieve a low latency while avoiding signal collisions. This article proposes a distributed channel sensing MAC (DCSM) protocol based on the aforementioned requirement, which allows each node to sense changes in surrounding traffic by sharing the slot usage table. The proposed adaptive transmission scheduling algorithm makes each vehicle select the optimal transmission slot based on a predictive value function, which utilizes long propagation delays to achieve spatial-temporal reuse and is adaptive to the network load. The simulation results demonstrate that compared to the other four distributed MAC protocols, DCSM had significant advantages in the transmission success rate (15% higher) and throughput (35% higher) and achieved a short latency. The adaptability and flexibility of DCSM have also been verified through simulations.