BER performance analysis for downlink NOMA systems over cascaded Nakagami-m fading channels

In this study, the downlink non-orthogonal multiple access (NOMA) system in which successive interference cancellation (SIC) errors exist is discussed. The new closed-form expressions for the bit error rate (BER) performance analysis over cascaded Nakagami-m fading channels are analytically derived for near and far users. In addition, new mathematical equations are obtained for the asymptotic BER as well as the diversity order to analyze the system performance. The theoretical results precisely match the simulations in all cases, validating the effectiveness of the theoretical analysis. The results demonstrate that the system performance decreases as the degree of N cascading increases. As for a fixed degree of cascading, BER performance increases as the m parameter increases. Moreover, for the power allocation coefficient \(\alpha \) influences the SIC operation performed on the near user, it also substantially affects the BER performance. Monte Carlo simulations using \(10^{6}\) iterations are presented to validate the derived analytical results.