The Research Of Wireless Optical Communication System Based On White LED

Visible light communication technology is an emerging wireless optical communication technology based on LED indoor lighting, which has been used to design indoor white LED wireless communication system bringing in advantages of short response time and high-speed modulation characteristics.White LED wireless communications system can be both used in lighting and communication, which not only save the energy but also reduce the duplication of investment, therefore, the white LED communication system has great significance and great development prospects, and it has been recognized as an emerging short-range high-speed wireless communication systems.This paper mainly discusses indoor visible light communication system based on white LED. Firstly, the physical characteristics of the white LED such as light-emitting principle and the basic structure, as well as the characteristics of radiation is deeply analysed; Secondly, base on the discussion of the photon emitted mechanism theory of white LED radiation pattern and reconciled with the characteristics of the integrated Gaussian and cosine functions, the general mathematical model of LED emitting is given, that is, an integrated model. The simulation results show that:assuming the same coefficients, integrated model has smaller root meam square and higher normalized correlation coefficient, while under the same accuracy requirements, the intergated model has less coefficients and simpler features. Thirdly, the indoor LED brightness distribution is studied and indoor LED light brightness distribution theory is given, the different link models of the LED visible light wireless communication channel are analysed, the transmitter circuit and receiving circuit which receives and demodulate the visible light signal is designed, then the multi-path effects and the turbulence of the communication system cased by background light noise is studied. Finally, visible light modulation technology is studied. The transmit power, transmission capacity and mistaken slot rate of the OOK modulation, pulse position modulation, pulse interval modulation is analysed.The OFDM with guard interval is simulated and the simulation results show that OFDM can inhibit the Multi-path effects and make great improvement of the system communication performance.