Performance analysis of AF relaying assisted NOMA system with imperfect CSI and SIC

Abstract

This paper investigates an amplify-and-forward (AF) relaying assisted non-orthogonal multiple access (NOMA) system over Nakagami-m fading channels, where both imperfect channel state information (CSI) and imperfect successive interference cancellation (SIC) are taken into account. To evaluate the performance of AF relaying assisted NOMA system, we derive the closed-form expressions for exact and asymptotic outage probabilities of a pair of users. Additionally, the system throughput and energy efficiency under three different levels of residual interference signal are analyzed in detail. The numerical simulation results reveal that: (1) Error floors exist in outage probabilities due to channel estimation error under imperfect CSI; (2) The outage performance decreases as the channel estimation error μ increasing, and is even lower than that of conventional orthogonal multiple access (OMA) once μ goes beyond 0.008; (3) The optimal location for relay is close to the base station in AF relaying assisted NOMA system; and (4) Due to the effect of residual interference, there are throughput ceiling in delay-limited transmission mode. Moreover, AF relaying assisted NOMA with perfect SIC is capable of outperforming AF relaying NOMA with imperfect SIC on the sum throughput in low SNR region.