Rate Maximization for Downlink Multiuser Visible Light Communications

We are interested in optimizing transmit beamforming for a visible light communication multiuser system such that the achievable sum rate is maximized. We first derive a closed-form sum rate expression via information-theoretic tools. Then, by further including light-emitting diode optical power constraints, we formulate the rate maximization problem in a mathematical optimization form. To address this difficult non-convex problem, we establish an iterative algorithm that exploits sequential parametric convex approximation. Compared with the existing zero-forcing beamforming strategies, the proposed approach does not restrict the co-channel interference to be zero, and thus achieves a higher sum rate, as is validated by simulations.