Research And Design Of The Indoor Visible Light Communication System Based On LED

VLC(Visible Light Communication) as a new bandwidth of wireless communication technology, was born in2000, because of its high-speed modulation characteristics, no occupation of the radio spectrum resources, high safety and other unique advantages, its attention degree is more and more high, it has become a major research focus at home and abroad in mainstream equipment business, each university and research institutions, so it has a great development potential and its practical prospects in the future is quite worthy of our expectations.At present, the research on VLC is mainly divided into indoor and outdoor two areas, this paper focus on the design and implement of indoor VLC system based on white LED.This paper briefly discusses the background and significance and research status of VLC technology at home and abroad, then studies the source characteristics of white LED as the theoretical foundation of the design of LED drive circuit. After that, the article analyzes the characteristics of indoor radio channel, including the optical paths, link methods and channel impulse response of indoor communication system, then selects the most simple way of direct line of sight as the link of system. Through the analysis of relevant literature, understand the main influence factors that affect the system communication performance is the inter-symbol interference caused by multipath effect, thus the OFDM(Orthogonal Frequency Division Multiple) which has strong anti-multipath ability is introduced, then present its basic principles, finally, a set of indoor visible optical communication experiment system is designed. In this system, PC machine is used to send and receive data, modulation and demodulation module is realiazed through FPGA(Field Programmable Gate Array) based on the Quartus II11.0development environment, obviously, this method can bring more convenience and have better performance compared with the traditional hardware circuit realization way.The emphasis of this paper is the design work of the whole system, first of all, the LED drive circuit, preamplifier circuit and filter and the main amplifier circuit, in order to overcome the deformation of modulation signal may exist, a high-speed comparator is added between the modulation module and driving module to adjust the signal to standard square wave according to the reference level setting;secondly, the design of OFDM system which includes from each small module to the whole last two big modulation and demodulation module;at last, the whole system is built, through the comparison of the data that the PC sends and receives to judge whether the system could work normally, the realization of the experiment system can provide certain reference value for further optimization work.