Cooperative multi-relay non-orthogonal multiple access for downlink transmission in 5G communication systems

In this paper, we propose a new setup for a cooperative multi-relay non-orthogonal multiple access scheme (CMR-NOMA) to enhance the downlink performance of non-orthogonal multiple access, while operating in severe fading. We compare the performance of the proposed scheme to an existing cooperative non-orthogonal multiple access scheme (CNOMA) in terms of the user-average bit error rate, the ergodic sum-rate and the fairness index level, with a conventional NOMA system serving as the baseline for comparison. We also propose the use of a modified successive interference cancellation (SIC) technique at the mobile equipment in coded systems to reduce the highly-complex processing inherent in the recovery of NOMA signals.