Full-duplex cooperative relaying with NOMA for the performance enhancement of underwater acoustic sensor networks

Abstract

Cooperative relaying scheme is identified as an efficient method for improving the reliability and energy efficiency of underwater acoustic sensor networks (UASNs) by exploiting the spatial diversity. Unlike the existing research works, we propose a full-duplex cooperative relaying with NOMA (FD-CR-NOMA) for UASNs. We derive accurate mathematical equations for the calculation of ergodic rate, outage probability, and energy efficiency in UASNs by considering the underwater specific characteristics, namely distance-dependent usable bandwidth, acoustic spreading, propagation losses, and fading effects. Analytical and simulation results show that the FD-CR-NOMA can significantly improve the performance of energy-constrained and bandwidth-limited UASNs in terms of ergodic rate, outage probability, and energy efficiency compared to the other existing cooperative relaying schemes. We analyse the impacts of residual self-interference and imperfect successive interference cancellation on the performance of FD-CR-NOMA. Later, we examine the impact of change in relay position on the FD-CR-NOMA and also the effects of wind speed and shipping activities on the proposed FD-CR-NOMA. It is also observed from results that the high-speed winds and high shipping activities considerably degrade the ergodic sum rate and energy efficiency of the FD-CR-NOMA. In addition, we jointly optimise the signal frequency and power allocation coefficient for the FD-CR-NOMA with respect to the transmission distance using particle swarm optimisation, to further enhance the ergodic rate.