Research On Indoor Visual Light Communication Using MIMO-OFDM Technology

Currently using white LED light sources in wireless information transmission has become a hot research topic at home and abroad. Visible light communication(VLC) combines LED lighting and wireless communications, transmits information by high speed adjusting the brightness of LED,for the characteristics that white LED has short response time and high-speed modulation. Because of radiation safety, ultra wide band the universality of the LED, VLC technology will become solutions to indoor wireless high-speed communications.MIMO-OFDM combines OFDM with space-time coding technology, can effectively resist multipath effects, interference and noise suppression, can greatly improve the transmission rate and the channel capacity of wireless communication systems, also can achieve high-speed and reliable transmission of data.This paper studies the orthogonality of subcarriers, modem and transmission bit error rate performance of OFDM system. Through of detailed simulation comparison with the single-carrier transmission system, the OFDM system can also have a desirably low transmission error rate even in a large-scale fading channel. This paper also analyses the indoor visible light communication MIMO channel, a non-imaging optical MIMO wireless communications, and the other is an imaging MIMO communication, and gets that imaging optical wireless communication is more suitable for practical applications.By analyzing the driving characteristic of white LED and channel model of indoor visible light transmission, we proposed the use of MIMO-OFDM technology for indoor visible light communication system, to achieve high-speed and reliable transmission of information. By comparing MIMO-OFDM technology, PPM modulation and MIMO modulation under different SNR in simulation, we can get that MIMO-OFDM technology applied in visible light communication has lower error rate in the condition of the same transmission rate, and enables faster information transfer and lower bit error rate in the same symbol period to transmit information. In the MIMO signal detection, we analyzed ML detection algorithm, ZF and MMSE detection algorithm under different SNR. The maximum likelihood detection method has the smallest date error rate, and the smallest mean square error detection has smaller data error rate. However, with the increasing in the number of antennas and modulation order, the algorithm complexity of the maximum likelihood detection will dramatically increase.