DSSS: A TDMA-based MAC protocol with Dynamic Slot Scheduling Strategy for underwater acoustic sensor networks

In underwater acoustic sensor networks, sensors are usually deployed for sensing task, and the sensed data is able to be transmitted in a direct or multi-hop relaying manner to the sink in a single-hop topology. Considering the energy consumption model, the signal transmitted in a longer range will cost much energy than that in a shorter range. Therefore, three transmission types, sink-to-nodes, node-to-node, and node-to-sink are taken into consideration in the paper. However, due to the nature of the sound wave, the major issues of medium access control (MAC) are how to facilitate the concurrent transmission and to avoid the data collisions in underwater acoustic sensor networks. As a result, a TDMA-based MAC protocol with Dynamic Slot Scheduling Strategy (DSSS) is proposed for underwater acoustic sensor networks in this paper. DSSS can not only improve the channel utilization by increasing concurrent transmissions but also take the transmissions of sink-to-node, node-to-node, and node-to-sink into account to increase the network scalability. Simulation results verify that DSSS outperforms UD-TDMA, USS-TDMA and Original-TDMA in terms of the channel utilization and average delay.