A Trigger-Based Time Division MAC Protocol for Mobile Underwater Sensor Networks With Heterogeneous Traffic

This paper presents a novel trigger-based medium access control (MAC) protocol for mobile underwater sensor networks (UWSNs) that operate under high propagation delay and heterogeneous traffic. Unlike conventional MAC schemes that rely on carrier sensing or frequent handshaking, our approach leverages pre-calculated propagation delays and sink-initiated trigger messages to coordinate packet transmissions with minimal control overhead. Each sensor node registers with the sink via a lightweight initialization process, enabling the sink to estimate the one-way delay and assign time slots accordingly. Time slots are dynamically adjusted based on the node’s data generation rate, estimated using an exponential weighted moving average (EWMA). By synchronizing trigger transmissions with delay-compensated timing, the protocol ensures that sensor packets arrive precisely within their assigned slots. The simulation results show that our protocol improves the throughput, end-to-end delay, collision rate, and energy efficiency while providing robust performance under mobility and varying traffic loads.