Performance Analysis And Optimization Of IRS-aided VLC Systems

With the rapid development and application of mobile Internet and the Internet of things,the visible light communication(VLC)meets the increasing requirements of wireless network for spectrum and energy efficiencies.In the VLC system,the line-of-sight(Lo S)link between the transceiver is easily blocked.However,intelligent reflective surfaces(IRS)can effectively compensate this phenomenon,as well as improve the channel impulse response and system performance.There are two types of IRS in the VLC system: metasurfaces and mirrors.In comparison,mirrors are less complex,power-consuming,costly,and easier to deploy.However,the IRS in the current works is mostly used as a single fixed array.In addition,the position and the direction of the receiver are often fixed.Actually,different deployments of the IRS can affect the system and the direction and position of the receiver can be randomly changed.Therefore,this thesis will explore these issues.Firstly,the error performance of the single IRS-aided indoor VLC system is analyzed and the size and number of the reflected units are optimized.Specifically,the VLC system is modeled with the assistance of IRS considering of the blockage probability of the Lo S link.In the system,the channel gains of the Lo S link and NLo S link are derived with and without IRS.The theoretical expression of average bit error rate is also derived.Moreover,the optimization problems are established for the key parameters(the size and number of the units)of IRS,and the corresponding optimization schemes are given for the optimization problems.At the same time,the hardware implementation method of IRS in the VLC system is proposed.Finally,the results of the simulation experiment are carried out using the computer,and the simulation results show that the IRS with appropriate optimization can improve the performance of the indoor VLC system.Secondly,the achievable data rate of multiple IRS-aided indoor VLC systems is analyzed and the numbers of IRS and walls to deploy IRS are optimized.Specially,based on multiple IRS-aided indoor VLC system,the effects of different deployments of IRS are analyzed and the expression of the achievable data rate is given.Moreover,the corresponding optimization problems for the numbers of IRS and walls to deploy IRS are established.The particle swarm optimization algorithm is used to obtain the local optimal solution of the two variables.What’s more,the simulation experiment for different deployments is carried out by computer and the simulation results are analyzed.The simulation results show that the system with optimization is superior to the system without optimization,which show the validity of the algorithms.In addition,the more scattered the array deployment,the higher the achievable data rate of the system can be.Therefore,in the indoor VLC system,the appropriate optimization of the number of arrays and walls to deplay IRS can further improve the system performance.Finally,based on the rotating receiver,this thesis discusses the effects of its rotation angles on the achievable data rate in the IRS-aided indoor VLC system,and the rotation angles are optimized.Specially,the IRS-aided VLC system with a fixed transmitter and a rotating receiver is analyzed and the expression of the achievable data rate based on the angles of the receiver(the yaw angle,pitch angle and roll angle)is given.The simulation and comparison analysis are carried out for the optimization of different angles based on the sine-cosine algorithm.Lastly,the necessity of the joint optimization of the rotation angles of the receiver is verified by the numerical results.Consequently,in the IRS-aided indoor VLC system,optimizing rotation angles of the receiver can further improve the system performance.