Research On Indoor Visible Light MIMO Communication System Based On White LEDs

At present, the bandwidth of LED is only few megahertzs, which cannot meet the demand forlarge capacity and high data rate in visible light communication (VLC). The finite beam angle ofLED is between omnidirectional antenna and directive antenna，and is regarded as quasi-directionalantenna, which makes the coverage of LED limited. The multiple-input-multiple-output (MIMO)technology based on VLC employs LED array as transmitted antenna. It will effectively increasethe coverage of LED and broaden the link range, get a higher transmission rate without increaseingthe bandwidth or power. Furthermore, it can overcome the link interruption caused by human’swalking and shadow effect, and improve the spectrum efficiency.In this paper, the development status and technical feature of VLC and the characteristics ofdifferent MIMO detection algorithm in wireless communication are investigated. The channelcharacteristics and the influence of different detection algorithm of indoor visible light MIMOcommunication are researched with emphasis. The performances of MIMO dectetion algorithms areverified by the experimental MIMO system. The mian work is embodied in the following aspects:(1) The paper analyses the channel characteristics of indoor MIMO-VLC by Matlab, includingthe illuminance distribution, received power distribution, impulse response distribution，SNRdistribution and channel capacity distribution.(2) An indoor MIMO-VLC system is built. The different channel matrixes are used to achievethe ZF, MMSE and QR detection algorithms. The above-mentioned detection algorithms are used torealize parallel data transmission with2Mbit/s transmission data rate in every branch. TheMIMO-VLC demonstration system gets4times the transmission rata of SISO system. The paperalso experimentally analyzes the influence on performance of MIMO-VLC system exerted bydifferent channel matrix and detection algorithms.The paper verifies that the ZF, MMSE and QR detection algorithms multiplies the transmissionrate in VLC-MIMO system.