No abstract

Effective relay selection in non-orthogonal multiple access (NOMA) is an efficient way to attain a significant performance gain in terms of achieving a high system capacity, ergodic sum rate and a low outage probability. This become more promising when NOMA is treated under cooperation of more than one relay nodes. Relay selection performs well when the source node has an accurate and updated channel state information (CSI). As having perfect CSI is very difficult, therefore the relay selection with continuous time varying CSI is of paramount importance. This paper proposes a combined relay selection (CRS) scheme with time varying CSI which uses failure probability as an important criterion to improve the overall performance of cooperative NOMA system. The proposed approach is compared with most commonly used relay selection schemes: round robin relay selection (RRRS), opportunistic relay selection (ORS) and balanced criteria relay selection (BCRS) scheme. The simulation results show that proposed scheme outperforms the RRRS, BCRS and ORS in terms of ergodic sum rate, system capacity and outage probability.