RIS-Based Beam Steering for Visible Light Communication: Channel Model and Optimization

The performance of visible light communication (VLC), as a key technology for next-generation wireless communication networks, can be significantly enhanced in terms of data rate, delay, and fairness, through the integration of optical reconfigurable intelligent surfaces (RISs). This paper introduces a novel channel model for a VLC system incorporating RIS-equipped transmitters, where the RIS is directly integrated with the VLC transmitter. This new design is shown to effectively provide beam steering (BS), enabling the concentration of optical power at desired directions with a typical 9.2dB power gain compared to a scenario without BS capability. To further illustrate the BS capability of the modeled RIS-equipped transmitter, a traffic-aware resource allocation scheme is formulated and efficiently solved using a tailored fractional programming (FP) approach with an affordable computation complexity. This approach allows to jointly optimize user association and power control by decoupling the interference interactions caused by BS. Simulation results reveal that BS-capable VLC through the proposed channel model and optimization scheme, can enhance data rate and fairness considerably while keeping delay within acceptable levels.