Performance analysis of NOMA in a MIMO system over Rayleigh channels under imperfect SIC

Non-orthogonal multiple access (NOMA) is a superior technique for achieving massive-scale connectivity and high spectral efficiency requirements for beyond-5G (B5G) networks. This paper focuses on a performance analysis of the achievable capacity and bit error rate (BER) at far and near users of downlink NOMA in a multiple-input multiple-output (MIMO) system under imperfect successive interference cancellation (SIC) for different modulation schemes. Paired binary phase-shift keying–binary phase-shift keying (BPSK-PAIR) and quadrature phase-shift keying–quadrature phase-shift keying (QPSK-PAIR) are the modulation methods that are employed. Analytical expressions are developed and simulated using Gaussian Q-functions. The simulated findings show that the suggested MIMO system outperforms a NOMA system without MIMO at the expense of greater computational complexity than either a MIMO OMA system or the NOMA system without MIMO. The sum capacity obtained for the proposed system at a signal-to-noise ratio (SNR) of 25 dB is 11.93 bps/Hz, and the BERs at far and near users are 3.7 × 10−4 and 8.5 × 10−4, respectively.