Joint Dimming and Data Transmission Optimization for Multi-User Visible Light Communication System

Visible light communication (VLC) is regarded as a promising technology for indoor communications due to its safety, availability, and efficiency. By deploying multiple light-emitting diodes (LEDs) at the transmitter, high data rate can be achieved. On the other hand, the dimming control is necessary in VLC systems to meet the lighting requirements, and puts an additional constraint to the system design. Thus, providing required communication quality while preserving the maximum dimming control capability becomes the baseline design philosophy for VLC systems. In this paper, we focus on multi-user multiple-input multiple-output VLC systems and propose a joint beamforming and direct current bias design. The proposed scheme can be formulated as an optimization problem and finds the minimum dimming level subject to the transmission rate requirement as well as the lighting constraints. Semi-definite program method and concave-convex procedure are exploited to solve the optimization problem efficiently. The impacts of locations of LEDs and users to the dimming control are also studied with numerical results.