Study On Parallel And Multiplexed OFDM Visible Light Communication Technology

Visible light communication(VLC)technology is an intriguing alternative for radio frequency wireless technology.This technology offers a huge,unregulated and unlicensed bandwidth,meanwhile provides both illumination and harmless communication.Indoor visible light communication will produce intersymbol interference(ISI)by experiencing multipath fading channel.And,transmitting terminal light emitting diode(LED)has the problem of limited modulation bandwidth.Therefore,by using orthogonal frequency division multiplexing(OFDM)in VLC system,the ISI caused by multipath effect will be solved effectively.Also,the bandwidth efficiency is able to be improved.Current research in VLC indicates that high-speed communication technology is the focus point.Therefore,by introducing multiple-input multiple-output(MIMO)and wavelength division multiplex(WDM)technology can increase data rate without the need for additional bandwidth expansion as well as providing improvement in channel robustness.According to this point,this paper mainly studies technology for parallel and multiplexed OFDM high-speed VLC communication.The main innovations of this paper can be described as follows:Firstly,this paper establishes channel impulse response model and MIMO channel model of visible light in typical office scenarios,and theoretical analysis the visible light channel characteristic in diffuse reflection.Meanwhile,summarizing the influence of multipath effect in VLC.Through above analysis provides theoretical basis for MIMO-OFDM system farther research.Secondly,this paper proposing a non-imaging MIMO-OFDM based VLC,and analyzed its bit-error-rate(BER)performance for different LED arrangements.Thus,giving one LED arrangement that suitable for MIMO-OFDM system.Thirdly,this paper proposes and realizes synchronization method and power compensation algorithm based on training sequences.At the same time presents an experimental hybrid OFDM-WDM VLC system,which used RGB LEDs for data transmission and illumination,respectively within an indoor environment.Completing offline experimental test,and the results show that the proposed system can increase VLC system 3-dB bandwidth and improve the VLC system transmission rate and transmission distance effectively.In addition,this article also introduces the advantages of visible light communication,The current development of visible light communication,the composition of visible light communication system,the application scenarios and future research trend.