Performance analysis of 5G Downlink Cooperative NOMA network with multi-antenna relay

In this paper, a 5G Downlink Cooperative amplify-and-forward (AF) NOMA communication system with multi-antenna relay is investigated. By exploring the advantage of multiple antenna, the best antenna selecting and switching scheme at relay is considered. Then the analytical expressions for outage probability and ergodic sum rate are derived, and the asymptotic result for outage probability is also obtained to give easy evaluation. Based on the results, the effects of the important system parameters, such as antenna number, the outdated channel side information(CSI), power allocation, are analyzed. From the asymptotic formula, we find that the system can get the diversity order N, which is the antenna number at the relay, when perfect CSI can be obtained. And the diversity order decreases to one when outdated CSI appears, regardless of multi-antenna. Computer simulations are also done to validate the correctness of theoretical analysis.