Abstract
With fairness consideration, optimal linear precoding designs for multi-color, multi-user visible light communication (VLC) systems are presented in this paper. Utilizing both the spatial and multi-color resources, the precoding designs are proposed to mitigate the impact of the multi-user interference (MUI) and the multi-color crosstalk. With the constraints of chromaticity, luminance, and signal range, the precoding designs are formulated to achieve the max-min fairness and the maximum sum-rate. Since the closed-form expression for the capacities is not available, the lower and upper bounds are chosen as the performance criterions. To make the optimization problems be easy to be solved by using standard optimization packages, the non-convex problems are cast into convex ones. Subsequently, algorithms are developed to find optimal solutions. Extensive simulation results indicate that the proposed precoding schemes outperform the conventional pseudo inverse method.
Highlights
Nowadays, visible light communication (VLC) technology using white light-emitting diodes (LEDs) has attracted tremendous attention in the world
Along with the rising and vigorous development of light-emitting diode (LED) lighting industry, VLC technology has been viewed as a potential solution to provide simultaneous indoor illumination and wireless data transmission due to its wide bandwidth and immunity to interference from electromagnetic sources [1,2,3,4,5,6]
A Cartesian coordinate system whose the origin is the center of the floor is used for specifying the positions of users and the LEDs
Summary
Visible light communication (VLC) technology using white light-emitting diodes (LEDs) has attracted tremendous attention in the world. To further increase the data rates, another method is multiple-input multiple-output (MIMO), which exploits the spatial multiplexing gain [19,20,21,22,23,24,25] In these studies, the VLC networks are Crystals 2018, 8, 404; doi:10.3390/cryst8110404 www.mdpi.com/journal/crystals. For VLC systems, both communication performance and lighting quality should be taken into consideration. Considering the real and non-negative signal constraint in VLC systems, some optimal precoding design with either mean square error (MSE) or zero-forcing (ZF) criterion have been reported [30,31,32,33,34,35]. Due to that each user is equipped with multi-color receivers, the system should be regarded as a MIMO system for each user This makes the channel matrix and the objective function of the optimal precoding design more complicated than other VLC systems.
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