Design And Experimental Study Of Performance Improvement Scheme In Wireless Optical MIMO System

Ultraviolet communication(UVC)uses solar-blind ultraviolet(UV)light as the signal carrier.UVC has the characteristics of small interference,good secrecy and non-line-of-sight communication.And UVC can be used in some special occasions that can not be used in visible light communication(VLC)and infrared communication.Therefored,UVC has great value of research.Multiple Input Multiple Output(MIMO)is a technology that uses multiple transceiver and multiple receiver arrays to achieve data transmission.Orthogonal space time block code(OSTBC)can reduce the influence of atmospheric chahhel environment on ultraviolet signal and increase the capacity of the system by increasing information redundancy.Supported by national natural science foundation of China,this paper mainly studies the reliability of ultraviolet MIMO communication systems.The mainly innovative work is as follows:(1)The ultraviolet Non-Line of Sight(NLOS)communication channel model based on MC method is built,then the UV channel test platform is built.And according to the test platform,the channel loss values of different distance and different elevation angle are measured.(2)In order to solve the problem of serious fasing of UV channel and high bit error rate,we propose an ultraviolet MIMO communication scheme based on OSTBC.By off-line experiment,the error code performance of the system under on-off keying(OOK)and binary pulse position modulation(2-PPM)mode are compared.The experimental results show that when the channel environment is poor,the 2-PPM mode is more suitable for ultraviolet MIMO communication scheme based on OSTBC than the OOK mode,which can better improve the BER performance of the system.(3)In order to keep the total power of each symbol constant and suitable for any Q-PPM(Q>2),an optimized scheme of pulse symmetrical position-orthogonal space-time block code(PSP-OSTBC)is proposed and applied with Q-PPM(Q>2)without the use of a complex decoding algorithm in an ultraviolet MIMO system.The performance of 1 X 1,2 X 1,2×2 PSP-OSTBC systems with 4-PPM are compared experimentally as the optimal tradeoff between modification and coding in practical application.The results suggest that the proposed scheme makes the system insensitive to the influence of path loss with a larger channel capacity,and a higher diversity gain.