Performance Analysis Of Relay Based Cooperative NOMA System

Due to the increase in massive device connectivity and increasing demands of future technologies, the Fifth-Generation (5G) networks are expected to support high spectral efficiency and low latency. In this regard, Non-Orthogonal Multiple Access (NOMA) technique has grabbed drastic attention from researchers and industry. Furthermore, to improve the performance of the NOMA system, we have incorporated the idea of cooperative communication. This paper considers a downlink NOMA system consisting of a Base Station (BS), two relays named R1 and R2, employed with Decode and Forward (DF) protocol, one far user, and one near user. In this work, an algorithm to investigate the Symbol Error Probability (SEP) performance of cooperative downlink NOMA system with Quadrature Phase Shift Keying (QPSK) modulation in the presence of the Rayleigh channel fading environment is developed. From the simulation results, it is observed that the SEP performance of the proposed NOMA system is significantly enhanced compared to that of the existing downlink NOMA system due to cooperation from the relay nodes. In addition to that, the SEP performance analysis has been made by varying the distance between the relays and BS resulting in increased SNR and reduced SEP.