Wireless Information and Power Transfer for Underwater Acoustic Time‐reversed NOMA

The acoustic signal transmission over the underwater channel has a limited sum rate and it consumes high power due to the properties of the underwater environment. This study attempts to use the non‐orthogonal multiple access (NOMA) technologies for underwater communications. NOMA can be an attractive candidate for underwater communication due to its high spectral efficiency, resistance for carrier frequency offset, and efficient energy consumption. To cope with the hard‐recharging capability of the underwater wireless sensor nodes caused by the ocean environment, this study proposes a novel transmission scheme called time‐reversed NOMA (TR‐NOMA) for underwater communication. In the proposed TR‐NOMA, a single‐input multiple‐output NOMA scheme with a passive‐time reversal technique is proposed to reduce the time–frequency dispersion of the underwater acoustic channels. Consequently, simultaneous wireless information and power transfer (SWIPT) can be applied for underwater TR‐NOMA. In this study, a SWIPT‐NOMA is postposed to harvest energy in downlink transmission from the transmitted signal. The bit error rate (BER) and the outage probability are used to characterise the performance of the proposed TR‐NOMA scheme and simulation results show how the proposed TR‐NOMA significantly outperforms the conventional NOMA schemes. Additionally, a mathematical framework for the average BER of TR‐NOMA is delineated.