NOMA performance enhancement-based imperfect SIC minimization using a novel user pairing scenario involving three users in each pair

Abstract

Due to the non-uniform distribution of users in a cellular area, there are users with similar channel conditions. In non-orthogonal multiple access (NOMA) systems, a small difference in channel gains of paired users can cause interference in end users, which so-called imperfect successive interference cancellation (SIC) and correspondingly, it causes serious degradation in the system capacity. In NOMA, most of the user pairing algorithms focus on pairing near and far users with each other, and about mid-users there are two options. First, pairing these users together over a common frequency band, which makes some degradation in capacity, due to imperfect SIC. Second, unpairing these users together, which makes mid-users cannot enjoy the benefits provided by the NOMA strategy. In this article to address these issues, a novel user pairing approach is proposed where all far, near, and mid-cell users can pair together based on the interference mitigation, and enjoy the advantages of NOMA. To evaluate the performance of this scenario, the ergodic sum capacity is calculated in both perfect and imperfect SIC modes, and also compared with the benchmark scheme. In addition, we provide a performance analysis of the proposed scheme in terms of user fairness and outage probability, and also investigate the effect of the resources (power/bandwidth) distribution among users on the system performance. Analytical computations and corresponding simulation results, confirm the performance enhancement of the proposed scheme in terms of the system capacity, outage probability, and user fairness.