Improving energy efficiency performance of ALOHA based underwater acoustic sensor networks

The goal of this paper is to explore the throughput and energy efficiency of ALOHA based underwater acoustic sensor networks (UASNs). Primarily, we frame analytical expressions for the throughput and energy efficiency of UW-ALOHA for single hop UASN. We then procure closed form expression for the optimal channel attempt rates that maximize energy efficiency and throughput Independently. In this case, we notice that the attempt rate that maximizes the energy efficiency leads to drop in the network throughput and vice versa. We then consider a cross layer energy optimization problem with the objective of maximizing the energy efficiency of the network while meeting an SNR constraint at the PHY layer and a throughput constraint at the MAC layer. We also consider underwater acoustic channel specific parameters like distance dependent bandwidth and spreading losses for the analysis. Using Karush-Kuhn Tucker conditions, we derive closed form solution for the optimal channel attempt rates that meet the desired objectives. Extensive performance evaluation results show that sensible selection of the attempt rates by the sensor nodes can improve the energy efficiency of the network significantly.