Analysis Of The Parabolic-lens-based Receiver For Indoor MIMO VLC System

Visible light communication has received extensive attention because of its both lighting and communication.MIMO technology uses space multiplexing technology to increase the channel capacity and enhance the reliability of the optical communication system without increasing the spectrum resources.Compared with non-imaging systems,MIMO imaging system can effectively reduce the multipath effect,and has more advantages.On the basis of the receiving structure of hemispherical lens,in order to improve the performance of indoor visible light communication system,a parabolic-based lens is analyzed.The main research works are as follows:(1)We analyze a parabolic-based lens structure.By using ray-tracing method and imaging principle,the spot coordinate on focal plane is calculated.The general law of spot change is obtained with MATLAB,which provides a theoretical basis for simulation experiments.(2)By modifying the MIMO channel model,the optical intensity is obtained.In previous studies,the light source was assumed to be a point source and the incident light was parallel.In this paper,we take account of the light source divergence angle and light diffuse reflection.By using non-sequential mode in ZEMAX,the parabolic-lens-based receiver is moved in different directions in the interior,and the receiving position on the spot distribution is analyzed.(3)The receiving characteristics of the system are analyzed by channel gain matrix H.The channel gain matrix H is calculated by the optical intensity,and the parameters such as the SNR,the channel capacity and the spectral efficiency are derived by using the matrix theory.The relation between the signal-to-noise ratio and the receiver's off center distance,and the spectral efficiency versus SNR curve are obtained.Besides,the indoor receiving area is divided,and the practicability of the lens is analyzed.The results show that the parabolic-based lens has good focusing performance and is favorable for integration;It can effectively reduce the multipath effect and separate signals at any position in the room;The SNR of the detection quadrant is up to 36 dB,and the spectral efficiency is highest in the indoor center position.In addition,70% of the indoor area is of high-quality reception.Therefore,the parabolic-based lens has a good application prospect in MIMO visible light communication system.