Research On Light Resource Layout Of MIMO-VLC System

Recently, in an energy-deficient and environment-severe world, because of many advantages such as the high brightness, the low consumption of power, the long lifetime, the stable performance and so on, white LEDs are more and more widely used in the lighting of life and commerce. The indoor visible light communication(VLC) based on white LEDs can not only provide illumination, but also realize a steady and reliable data communication. However, the character of the low modulation bandwidth of white LEDs limits the system’s capacity and the data’s transmission rate in VLC systems. Combining with the technology of Multi-input Multi-output(MIMO), MIMO-VLC uses multi-antenna units in both transmission and receiving terminal, to establish the spatial parallel transmission channels of visible light, which can improve manyfold the communication quality and transmission rate in condition of the unchanged bandwidth and transmission power.When we study MIMO-VLC system, the first problem is the layout of the light resource. The reasonable layout not only is the necessary condition of system’s normal operation, but also can solve some practical problems with the minimum cost. For example, MIMO-VLC makes use of the signal’s multi-path transmission to improve the system’s capacity and transmission rate, but the diffuse reflection links will lead to the existence of the inter symbol interference(ISI) and the increase of the bit error rate. However, different layouts will present different distributions of reflection power. Now, how to choose the layout in which the influence of the reflection power distribution on the system performance is smallest has become a hot point of research.Because the working principle is different from VLC, the method and the key factors should be considered in designing MIMO-VLC layout of the light resource. In this paper, the system model of VLC is analyzed firstly. Secondly, the system model of MIMO-VLC considering the reflection link is analyzed and the key factors in designing layout are introduced:(1) The basic communication / lighting condition should be met;(2) Make the impact from reflection link as little as possible. Finally, the layout in which the system can communicate and light normally is designed, then using Genetic Algorithms(GA), the layout is optimized to make the influence of ISI on the system as smallest as possible and the simulation of BER in the receiving plane has been done.