Scheduling granularity in underwater acoustic networks

Abstract

Underwater acoustic networks have many distinct channel characteristics when compared to terrestrial networks. Long propagation delay, one such characteristic, allows scheduling methods with varying granularity that tradeoff schedule quality with protocol overhead. This work examines several channel scheduling methods to determine at what point protocols find the best balance between performance and overhead. To accomplish this, five scheduling options are detailed and then compared through numerical and simulation results between themselves and to other protocols. The results indicate that scheduling links provides the best performance for the resource investment and that other scheduling options either require significant overhead or provide insufficient performance. While the results show that direct sequence spread spectrum techniques, common at the physical layer in underwater networks, do not yield an improved schedule, they do reduce protocol overhead and scheduling complexity by reducing conflicts in the network.

A collision-analysis-based energy-efficient routing protocol in 3D underwater acoustic sensor networks

“…On the MAC layer, the propagation delay and packet collisions have been the most studied factors. Carrier sense multiple access (CSMA) does not work well in underwater networks because long propagation delays prevent nodes from obtaining the current channel state [20]. CSMA/CA also suffers degradation in underwater environments as nodes reserve and occupy channels for probing, which result in a large overhead when transferring packets [21].…”