FDBUL: A Delay-Aware Full-Duplex MAC Protocol for Underwater Acoustic Sensor Networks

Underwater networks rely primarily on acoustic waves for communication, but acoustic waves produce long propagation delays and have greater attenuation, posing a challenge for research of media access control (MAC) protocols. As self-interference (SI) cancellation techniques continue to mature, most existing underwater full-duplex (FD) MAC protocols do not take into account the actual system of FD modems, i.e., the long transmission delay. Accordingly, we propose an FD MAC protocol for both unidirectional link (U-Link) and bidirectional link (B-Link) within a channel access in underwater acoustic sensor networks (UASNs) and theoretically analyze its throughput performance. At the beginning of the phase, the handshake of control packets is carried out first, and the nodes obtain the delay between the neighbors and themselves and the delay table between the neighbors and their neighbors. Based on the time delay between nodes, the node selects the destination node with the best effect to establish an FD or half-duplex link. Accordingly, packet scheduling is performed, and the data packet sending process is judged to be delayed or not. Analysis and simulation results show that the full-duplex MAC protocol for both B-Links and U-Links in UASNs (FDBUL) protocol can achieve better performance in throughput, average packet reception delay, and average energy consumption. Taking slotted floor acquisition multiple access (SFAMA) as an example, FDBUL protocol has about 60%–80% performance improvement in throughput.