Performance of user-assisted nonlinear energy harvesting NOMA network with Alamouti/MRC?

Abstract

This paper focuses on evaluating the outage performance of a dual-hop single-phase non-orthogonal multiple-access (NOMA) system. The base station employs the Alamouti space-time block coding technique (Alamouti-STBC), enabling simultaneous communication with two mobile users, and the far user employs a maximal ratio combining (MRC) scheme. In this setup, the near user serves as a full-duplex (FD) (or half-duplex (HD)) energy harvesting (EH) relay, adopting decode-and-forward (DF) protocol for the far user, thereby enhancing spectral efficiency and energy sustainability-key requirements for fifth generation and beyond (5G+) networks. The study involves the development of a system model and closed-form equations of exact and asymptotic outage probabilities (OP) over Nakagami-m fading channels with and without direct link considering a threshold-based nonlinear EH relaying model and imperfect successive interference cancellation. Moreover, the sum throughput and energy efficiency metrics have been examined to evaluate the overall system performance. We verify analytical results by Monte Carlo simulations and show that the presence of a direct link in the system enhances the performance of the far user considerably by mitigating the degradation caused by the self-interference in the near user. These results offer valuable insights into designing energy-efficient, reliable NOMA-based relay systems suitable for emerging 5G+ applications, such as Internet of Things connectivity.