Max-Min Fairness and Sum-Rate Maximization of MU-VLC Local Networks

In this paper, we study multi-user multiple-input single-output (MU-MISO) visible light communications (VLC)for indoor broadcast systems. Multiple LED arrays are deployed as transmitters to serve multiple users simultaneously. In such broadcast systems, the main challenging issue is the presence of multi-user interference (MUI) among users. In order to completely cancel the MUI, the zero forcing (ZF) precoding technique which is originally designed for radio frequency (RF)communications, is adopted due to its low computational complexity. However, different from RF counterpart the VLC signal is inherently non-negative leading to the necessity of modifying the design of ZF precoding matrix. The paper investigates the maxmin fairness and the lower bound for the sum-rate maximization of all users in the room scale scenario taken into account the non-negativity signal constraint imposing on precoding matrix. Furthermore, numerical results show that relative user´s positions has a considerable impact on the system performance.