Performance Analysis of Selective DF Cooperative NOMA in Presence of Practical Impairments

In this article, we investigate a selective decode-and-forward (DF)-aided cooperative nonorthogonal multiple access (NOMA) system performance in the presence of practical impairments using imperfect successive interference cancellation (SIC) and channel estimation error (CEE). The base station communicates directly and via a relay with the two NOMA users in two-time phases. In particular, the selective DF with synchronized direct and relay transmission relaying protocol is proposed for the considered downlink NOMA system to offer enhanced quality of service and improved data reliability compared with the conventional NOMA and DF NOMA systems. The closed-form of exact and asymptotic expressions of the average bit error rate (ABER) at both NOMA users are derived considering the impact of imperfect SIC and CEE. Furthermore, the outage probability is also obtained. Finally, the improvement in the system performance acquired by the proposed scheme over the existing methods is corroborated by Monte Carlo simulations.