An Adaptive Mobile Access MAC Protocol for Underwater Sensor Networks

Deploying both static and mobile nodes simultaneously is a practical solution for the Underwater Acoustic Network (UAN). Nevertheless, the mobility of nodes challenges MAC protocols’ design. (1) Mobile access: existing schemes allocate additional time slots to access mobile nodes, which decreases data transmission efficiency because of the long propagation delay. (2) Transmission resource assignment: node mobility alters the network topology dynamically. Therefore, if we assign transmission resources statically, it may cause inefficient transmission and unequal resource distribution. To address these issues, this paper proposes an Adaptive Mobile-Access MAC (AMA-MAC) protocol. In AMA-MAC, by exploiting the long propagation delay, mobile nodes monitor and access the network implicitly during regular data transmission. This approach eliminates unnecessary handshakes and enhances transmission efficiency. Furthermore, AMA-MAC provides a power and bandwidth joint optimization algorithm for adaptive transmission resource assignment. This algorithm dynamically adjusts bandwidth and power based on transmission distance, the rest of the energy, and the Value of Information (VoI). To evaluate the performance of AMA-MAC, we conduct simulations comparing average end-to-end delay, energy efficiency, and throughput, against other existing protocols. Our simulation results indicate that AMA-MAC effectively reduces average end-to-end delay, enhances transmission efficiency, and energy efficiency.