Research On Indoor Visible Light Wireless Communication System Based On MIMO-OFDM Technology

The visible light communication(VLC) utilizing the white LEDs is a new kind of wireless communication characterized by low cost, rich spectrum resources, no electromagnetic radiation, high safety and energy-saving,etc. In VLC system, white LEDs are used to provide simultaneous illumination and dara transmission. VLC occupies an important position and value in the future communication field. Indoor visible light wireless communication is an important aspect of visible light communication applications, with a huge market potential, it has attracted scholar’s attention both at home and abroad.Firstly, in this paper, the model of indoor optical wireless multiple-input-multiple-output(MIMO) system is established and simulation is implenmented. One of the key challenges in VLC system is the limited modulation bandwidth of sources, typically several MHz. However, as a room or coverage space would typically be illuminated by an array of LEDs there is the potential for parallel data transmission. Reasonably arranging the array of LEDs and using an optical MIMO technique can not only meet the illuminance of indoor lighting and avoid shadow area, but also achieve higher transmission rate and system capacity.Secondly, on the basis of simulation, an experimental demonstration of an indoor optical wireless MIMO system with a nonimaging receivere is proposed. The system setup consists of a 2×2 array of white LEDs with spacing 15 cm, and a 2×2 photodector array with spacing 10 cm. In order to detect the transmitted information, in this thesis, zero-forcing(ZF) detection and minimum-mean-square-error(MMSE) detection are utilized, analysed and compared, with bit-error rate(BER) operation at different vertical height, separating transmitter and receiver.As one of multicarrier modulation manners, orthogonal frequency division multiplexing(OFDM) achieves frequency multiplexing utilizing the orthogonality among sub-carriers. OFDM can reduce interface between subchannels in parallel with the improvement of transmission rate. In addition, it has a fairly strong anti-multipath progagation capability due to the addition of the guard interval and cyclic prefix(CP). Finally, the combination of MIMO and OFDM techniques is proposed to apply to VLC system,the simulation analysis of indoor visible light MIMO-OFDM system is conducted and the superiority in anti-interference ability and increasing data rate of MIMO-OFDM communication system is highlighted.