Integrated NOMA and RIS Systems in 6G: A Focus on Enhanced Performance with Generalized Fading Scenarios

The synergy between Non-Orthogonal Multiple Access (NOMA) and Reconfigurable Intelligent Surfaces (RIS) is anticipated to significantly boost spectrum and energy efficiency in the upcoming 6G networks. Hence, this work presents a downlink NOMA communication system, aided by two RISs to boost the transmit signals between a source and two users: a cell-center user and a cell-edge user. Direct connection between the source and the users is unavailable because of barriers or large distances, which is mitigated by improving the signal-to-noise ratio (SNR) at the users by the RISs’ reflection and optimization of the signal. The performance analysis is carried out by deriving analytical expressions for key performance metrics and validating them through Monte Carlo simulations. The numerical results obtained with respect to some key aspects like power allocation, fading severity, path loss, etc., show that the proposed framework is successful in lowering the outage probability (OP), and average bit error rate (ABER), and enhancing the ergodic capacity (EC) for both users. For example, compared to the existing models, the cell-center user achieves an above 96% improvement in OP and ABER and a 90.6% increased EC at 20 dB average SNR with similar remarkable gains for the cell-edge user.