Capacity Analysis of RIS-assisted Visible Light Communication Systems with Hybrid NOMA

In this paper, we study reconfigurable intelligent surface (RIS) assisted visible light communication (VLC) systems, where the hybrid non-orthogonal multiple access (NOMA) technology is used to improve its performance. Specifically, sparse code multiple access (SCMA) and power-domain NOMA (PDNOMA) are jointly used to support more users in each light emitting diode (LED) lamp group. Meanwhile, the maximum capacity of the system under different RIS allocation schemes is studied. To maximize the communication capacity of the VLC system on the basis of meeting users' fairness, a two-step optimization scheme is used to optimize the power distribution ratio of the user group and RIS reflection unit respectively. Numerical results show that the hybrid NOMA and RIS techniques can significantly improve the communication capacity of VLC systems.