On RIS-Assisted Angle Diversity Receiver for Downlink VLC-NOMA

Non-orthogonal multiple access (NOMA) is a recent technology proposed for wireless communication networks to improve overall system capacity. In visible light communication (VLC), the coverage footprint is small and confined, and any movement or change in the orientation of the VLC receiver may cause the signal to drop or be lost. This paper investigates the use of an optical reconfigurable intelligent surface (RIS) in downlink NOMA VLC systems equipped with an angle diversity receiver (ADR). To improve robustness against field of view (FoV) limitations, a truncated-pyramid ADR is combined with a modeled optical RIS. The considered scenario involves a multicell system in which inter-cell interference is present. We evaluate the proposed RIS-assisted ADR-NOMA framework using Monte-Carlo simulations in a two-access-point indoor environment. The results demonstrate that RIS-assisted ADR-NOMA offers a simple and effective solution for enhancing average user rates, improving fairness, and reducing the probability of zero gain caused by signals falling outside the FoV.