Research On VLC-MIMO System Based On SM And NOMA Technology

Visible light communications(VLC)refers to a wireless communication mode in which the information at the transmitting end is transmitted in the form of optical signal through LED after a series of modulation and coding,taking the visible light in the light wave band as the carrier.VLC not only realizes optical communication,but also meets the needs of indoor lighting.Therefore,in practical application,the light source usually adopts multiple LED arrays,combined with modulation and coding technique to optimize the quality of the communication system.Based on this,this dissertation studies the LED placement,space-time encoding,spatial modulation,non orthogonal multiple access and other technologies involved in visible light MIMO system.The specific research contents are as follows:Firstly,an indoor model of multi-array VLC system is established,and its LED placement and channel capacity are numerically calculated and simulated.Combined with Lambert radiation model and illumination international standard,the 4led array layout model suitable for MIMO system is designed,and the spatial diversity technology is introduced into MIMO system to build STBC-MIMO system,and simulated its reliability.Although STBC can effectively ensure the anti-interference ability of the system through spatial diversity,it can not eliminate the bit error caused by inter channel interference.Secondly,spatial modulation(SM)technology is introduced into MIMO system to resist inter channel interference,and SM-MIMO and GSM-MIMO system models are designed respectively.The transmitter adopts the random antenna selection technology and the receiver adopts maximum likelihood(ML)detection algorithm.Simulation results prove that SM and GSM technique can improve the spectral efficiency.GSM can use fewer transmitting devices to achieve the same information transmission rate as SM,so it can save system overhead,and the bit error performance of GSM is better than SM.Thirdly,for the sake of optimize the transmission rate of the system and increase the number of users,non-orthogonal-multiple-access(NOMA)technology is introduced into MIMO system.Based on the fixed power allocation algorithm,a visible MIMO system based on NOMA is designed to realize two-user communication.The precoding technology and signal detection technology in NOMA are used to ensure the reliable transmission of the system.Experiments prove that NOMA technology can improve the data rate of VLC-MIMO system.Although the BER capability of the system reduced slightly,it improves the user access of the system.Finally,this paper proposes a SM assisted MIMO-NOMA system,namely SM-MIMO-NOMA system,which can improve the effectiveness of the system and avoid inter user interference.The transmitter adopts antenna selection technology and fixed power allocation algorithm in turn,and the receiver uses the combination of ML detection algorithm and SIC for deciphering.Experiments prove that the system has excellent robustness,and reduce the bit error rate while ensuring the data transmission rate.The experiments prove that the SM assisted MIMO-NOMA system can take into account both the data transmission rate and the bit error rate.