Performance Analysis And Optimization Design Of High Speed Visible Light Communicaion System Based On HDMA

Visible Light Communication(VLC)has unique advantages in five major areas: broadband high-speed,ubiquitous coverage,securit y compatibility,integration and inclusiveness,and green energy conservation.It fits into multiple key dimensions of the sixth generation mobile communication(6G)technology,such as high energy efficiency,high reliability.It provides a new way of data communication and has a promising application development prospect of multiple fields,multiple scenarios,and multiple industries.However,visible light communication systems lack in-depth performance analysis in practical environments and do not fully utilize frequency band resources and do not fully utilize frequency band resources.Band gaps between different frequency bands waste spectrum resources,and channel capacity is far from reaching the Shannon limit.Therefore,based on existing research,this thesis further analyzes the performance of large capacity visible light communication systems,designs and optimizes a larger capacity VLC system to further improve the spectral efficiency of VLC.Main work of the thesis as follows.(1)In order to tackle the problem that the performance analysis of visible light communication systems based on power domain non orthogonal multiple access(PD-NOMA)is not thorough enough,the distribution function of the received signal and the noise of the system in the actual environments is analyzed,the calculation methods of noise and signal-to-noise ratio are summarized.The influence of ambient noise on the received signal-to-noise ratio to different reception radii and the comparative analysis of the system bit error rate(BER)with and without ambient light noise are analyzed.The theoretical BER formulas for multi-user PD-NOMA-VLC systems in different environments are also derived.The theoretical analysis and simulation results are consistent with numerical simulation.(2)In order to tackle the design issues of large capacity VLC systems;this thesis proposes a high-speed visible light communication system based on hybrid domain multiple access(HDMA).HDMA integrates multiple domain mixed signals such as power domain,code domain,and frequency domain for multiple access transmission,further improving communication capacity and spectral efficiency and proposed an adaptive encoding and decoding method to reduce system decoding complexity while also improving decoding accuracy;At the receiving and decoding end,the theoretical average BER expression for the two user groups of the system is derived.At the same time,the minimum power allocation ratio is derived to ensure that the dual user group signals do not overlap.The numerical simulation results show that the theoretical analysis done in this thesis is basically consistent with the simulation results.(3)In order to tackle the optimization design of high-speed visible light communication systems based on HDMA,this thesis analyzes and studies various modules of the reconfigurable intelligence surface(R IS)assisted HDMA based visible light communication system,proposes a system optimization model,considers the constraints on various VLC systems,and establishes optimization objectives.By optimizing the power allocation ratio and the R IS reflection unit,the system can meet the quality of service(Qo S)requirements while maximizing communication capacity;To solve the non-convex problem of optimization objectives,this thesis proposes a method based on resource allocation and RIS joint optimization,which converts the non-convex problem with a convex problem and solves it using the CVX optimization tool.S ystem simulation results show that the proposed VLC system has a significant improvement in communication capacity compared to traditional VLC systems.