Exploiting FD/HD Cooperative-NOMA in Underlay Cognitive Hybrid Satellite-Terrestrial Networks

Abstract

This paper investigates the performance of an underlay cognitive hybrid satellite-terrestrial network comprising a primary satellite source with its multiple terrestrial primary receivers and a secondary transmitter with its pre-paired users that are deployed on the ground based on a cooperative non-orthogonal multiple access (C-NOMA) scheme. Herein, the nearby NOMA user works in full-duplex (FD) mode while employing a decode-and-forward relaying strategy for improving the performance of the far-away NOMA user. Importantly, we consider the realistic assumptions of FD-based loop self-interference and NOMA-based imperfect successive interference cancellation (SIC). By exploiting the mutual interference and the pertinent hybrid channels, we analyze the performance of the secondary network in terms of outage probability (OP), ergodic sum rate, and throughput. Further, to perform a more comprehensive analysis, both perfect SIC (pSIC) and imperfect SIC (ipSIC) situations are taken into account for the FD mode and the benchmark half-duplex (HD) mode for comparison purposes. Also, we examine the asymptotic OP behaviour at a high signal-to-noise ratio (SNR) to assess the achievable diversity orders. Our results manifest that FD C-NOMA outperforms HD C-NOMA for the case of ipSIC, whereas for the case of pSIC, HD C-NOMA can outperform FD C-NOMA in the high SNR regime.