Performance Analysis of RIS-assisted 6G Vehicular Networks with NOMA under Diverse Channel Conditions

Abstract The evolution of vehicular networks towards sixth-generation (6G) applications necessitates meeting the stringent requirements of low latency, high spectrum efficiency, and ubiquitous connectivity. This paper proposes leveraging re-configurable intelligent surfaces (RISs) in tandem with non-orthogonal multiple access (NOMA) as a promising solution to address these demands. We investigate the performance of NOMA in RIS-assisted vehicular networks from both theoretical and practical perspectives under diverse channel conditions including line-of-sight (LOS) and non-line-of-sight (NLOS). Conventionally, the performance of vehicular networks has been evaluated by assuming that the channels between the BS, RIS, and vehicles are identically distributed, which is not realistic in practice. Therefore, this paper evaluates the outage probability , ergodic rate, and sum rate performance of RIS-enabled vehicular NOMA networks over independent but not identically distributed (i.n.i.d) Nakagami-m 1 fading channels. Analytical expressions for the cumulative distribution function of LOS and NLOS channels from the BS to the RIS and from the RIS to the vehicles are derived by taking into consideration the i.n.i.d channel characteristics. The obtained channel characteristics are then used to procure closed-form expressions for the outage probability and ergodic capacity as well as simplify the expressions of the outage probability and ergodic capacity for asymptotic analysis at a high signal-to-noise ratio. The presented analytical and simulation results demonstrate that incorporating RIS with a higher number of reflecting elements can significantly improve the outage and rate performance of vehicular networks.