Design And Implementation Of Faster-Than-Nyquist Visible Light Communication Signal Transmission System

The rapid development of technology such as big data,intelligent access,and the Internet of Things has led to an increase in data communication,which demands higher transmission speed and required bandwidth in systems.To improve spectral efficiency,modulation and multiplexing methods are used,and Visible Light Communication(VLC)has attracted attention due to its rich spectrum resources,excellent electromagnetic interference resistance,low communication cost,and reliable communication confidentiality.To further improve system transmission speed and spectral efficiency,Faster-Than-Nyquist(FTN)technology compresses the intervals between transmitted symbols to achieve the goal of sending multiple symbols in a single cycle.Although FTN technology introduces inter-symbol interference,the use of high-performance computing power can eliminate errors,making it increasingly valued.FTN transmission theory is mainly applied to optical fiber communication,and there is relatively little research in the field of atmospheric optical communication,and significant challenges exist in hardware circuit design and system implementation.Based on existing research on visible light communication,this paper introduces FTN transmission theory and designs an FTN-based visible light image transmission and display system using a Field-Programmable Gate Array(FPGA).The system’s performance is tested by building an actual hardware system.The research contents include:(1)Introduction of the research background and theoretical basis of visible light communication technology and FTN technology.The system model of FTN visible light signal transmission and commonly used modulation methods such as OOK,PPM,MPPM,and DPPM in optical communication are discussed.A detailed introduction is given to the types of core components in optical communication,such as semiconductor lasers and photodetectors,and the basic structure and design process of FPGA.(2)Analysis of the demand for introducing FTN technology in visible light communication systems and proposed a system scheme for visible light image transmission and display using FTN transmission method.The system can complete the function of front-end image acquisition,signal transmission through both electrical and optical signals,and image display.The hardware platform of the FTN visible light communication signal transmission system is built using FPGA and electrical components,and the system’s transmission speed,transmission distance,and reliability are tested to evaluate its advantages and disadvantages.(3)Using Quartus Ⅱ software,Verilog HDL hardware programming language is used to write programs for front-end image acquisition,data packaging,data transmission,direct digital synthesis,and data demodulation.Model Sim simulation software is used to simulate and verify the various parts of the program.The OV7725 image acquisition module is added to achieve real-time image transmission and display.Finally,the system is tested as a whole,combining the designed hardware circuit and software program.The test results show that the system can achieve stable transmission of 10 Mbps data at a transmission distance of 50 cm,and its spectral efficiency is 22% higher than that of the Nyquist system under the same conditions.