Performance Analysis of DF Cooperative-NOMA System with QPSK-BPSK Scheme in the Presence of SIC Errors

Non-orthogonal multiple access (NOMA) is a promising radio access technique for 5th generation (5G) communication systems. In order to enhance the performance of NOMA based systems, a decode-and-forward (DF) cooperative NOMA system is analyzed in this paper. In particular, we present the performance analysis at the near and far user of DF cooperative downlink NOMA system in the presence of successive interference cancellation (SIC) errors over Rayleigh fading channels. A novel closed-form expression for the symbol error rate (SER) is derived for the considered cooperative-NOMA system. Also, we present the ergodic rate analysis, and it is observed that the ergodic rate for the NOMA based system is higher as compared to that of conventional orthogonal multiple access (OMA). Further, we analyze the impact of the power allocation coefficient on the NOMA system performance. The analytical results are verified with Monte-Carlo simulations to demonstrate accuracy.