Outage analysis of NOMA-based cooperative relay systems with imperfect SIC

In fifth-generation (5G) wireless communication systems, non-orthogonal multiple access (NOMA) has been considered as a promising multiple access technique. In this paper, a NOMA-based cooperative relay system (CRS) is proposed and analyzed. In contrast to the conventional cooperative relay NOMA system (system model in Kim and Lee (2015)), the proposed NOMA-based CRS allows a source and a relay to transmit a superimposed signal in the first and second time slots, respectively. The proposed scheme gives more reliable communication by fully leveraging the concepts of NOMA and cooperative relaying. The exact closed-form expressions for the outage probability are derived in a Rayleigh fading environment with imperfect successive interference cancellation (SIC) at the relay and destination. The outage performance of the proposed scheme is compared with the existing CRS-NOMA schemes. The paper also investigates the impact of various parameters on the outage performance of the proposed system. The accuracy of the analytical results is verified through simulations. (C) 2020 Elsevier B.V. All rights reserved.