Performance Enhancement of SWIPT by Utilizing the Distance Dependent Bandwidth of Underwater Channel for Cooperative NOMA based UASNs

Underwater acoustic sensor networks (UASNs) support a variety of oceanic applications but suffer from limited communication bandwidth, reliability, and energy efficiency. Cooperative non-orthogonal multiple access (CNOMA) with simultaneous wireless information and power transfer (SWIPT) schemes are proposed for UASNs to meet these constraints. The unique characteristic of underwater acoustic channels compared to terrestrial wireless channels is the distance-dependent bandwidth, which provides additional bandwidth to the near user compared to the far user in NOMA-based UASNs. In this research work, we propose to enhance the performance of power splitting (PS) and time switching (TS) SWIPT schemes by utilizing this additional bandwidth at the near user in NOMA-based UASNs. We consider a CNOMA-based UASN and derive closed-form expressions for average achievable rates, energy efficiency, and outage probability with improved PS-SWIPT and TS-SWIPT schemes. From the analytical results, it is evident that the average achievable rate, energy efficiency and outage probability performances are significantly improved with the proposed methods. The analytical results are corroborated with extensive simulation studies.