RIS-Assisted Hybrid NOMA-OMA System with Imperfections in SIC and Phase Compensation

In this paper, we investigate the performance of reconfigurable intelligent surface (RIS)-assisted downlink nonorthogonal multiple access (NOMA) system while accounting for practical limitations, such as imperfect successive interference cancellation (SIC) and phase compensation errors. We derive achievable data rate expressions for NOMA users as functions of these imperfections and establish bounds on power allocation and the SIC imperfection factor to ensure that NOMA outperforms orthogonal multiple access (OMA) systems. Based on these bounds, we propose a hybrid NOMA/OMA scheduling algorithm that performs NOMA pairing and power allocation to maximize the sum rate. Through extensive numerical simulations, we demonstrate that the proposed hybrid scheduling algorithm achieves superior performance compared to existing benchmark algorithms.