Performance Analysis of RIS-Aided V2I NOMA Under i.n.i.d. Selective Fading With Imperfect SIC

Abstract

This work investigates the performance of Re-configurable intelligent surface (RIS)-assisted 6G vehicular-to-infrastructure non-orthogonal multiple access (NOMA) systems over independent but non-identically distributed (i.n.i.d.) cascaded Nakagami-m fading channels. Closed-form expressions for outage probability (OP), asymptotic OP, and diversity order are derived, where the Bessel function is employed for approximation, and upper and lower bounds on ergodic rates are obtained using Jensen's inequality. Monte Carlo simulations validate the analysis under practical impairments, including channel estimation errors (CEE) and successive interference cancellation (SIC) residual errors. Results indicate that increasing RIS elements from 16 to 64 improves OP by 10%. However, this gain diminishes as an increase in CEE, leading to error floors, with OP improvement reducing to just 1% at a CEE of 0.05. Additionally, SIC errors significantly impact the weak user, rendering it undecodable when SIC error reaches 0.45 for a target data of 1 b per channel use. © 2025 IEEE.