Constructive Non-Orthogonal Multiple Access: Outage Performance and Ergodic Rate

To address the limitations associated with the need for successive interference cancellation (SIC) in non-orthogonal multiple access (NOMA) systems, this paper explores a transmit antenna selection (TAS)-based constructive interference (CI)-assisted NOMA framework comprising two tailored schemes: (i) CI-enhanced fairness, which strengthens the far user without compromising the performance of the near user, and (ii) CI-reduced complexity, which preserves the performance of the near user while easing SIC requirements. Specifically, the interference signal power is constructively projected onto the desired signal, effectively mitigating the reliance on SIC and thereby significantly improving the operational efficiency of NOMA systems. The performance of the two proposed schemes for enhancing user fairness and reducing SIC complexity is evaluated by analyzing the exact and asymptotic outage probabilities (OPs) as well as the ergodic rate of the users. Simulation results demonstrate that the CI-enhanced fairness and CI-reduced complexity schemes improve the outage and ergodic rate performance for the far and near users over conventional NOMA, respectively, although stringent phase-alignment constraints somewhat restrict further gains in outage performance.