Impact of Time-Varying Underwater Acoustic Channels on the Performance of Routing Protocols

The recent development of underwater acoustic modems has enabled multihop networking capabilities that can be used in important military and civilian applications. For this reason, routing protocols for underwater acoustic networks (UANs) have recently been proposed and evaluated. However, the interactions between channel dynamics and networking performance are not well understood. In this paper, we investigate and quantify the effect of the time-varying (TV) link quality on routing protocols in static UANs. In order to do so, we simulate the considered routing protocols in several network scenarios, obtained by changing the network density, the number of packet retransmissions, the packet length, the modulation type, and the power level with both TV and time-invariant (TI) channel conditions. Results confirm that, when evaluating the performance of routing protocols, it is important to understand the TV behavior of the channel quality over intervals of time sufficiently long to accommodate multihop communications. Finally, we also present experimental results, confirming the outcome of the simulations. The experiments have been conducted in collaboration with the NATO Centre for Maritime Research and Experimentation (CMRE) during the CommsNet12 sea trial.