Performance Analysis Of Multi-carrier Visible Light Communication System

Visible light communication is an extremely attractive communication technology,which has gradually attracted widespread attention recently and has become a research hotspot.This communication technology does not require an authorized spectrum,can be used in radio frequency restricted areas,and it can provide relatively safe and confidential wireless communication.In VLC,LEDs are generally used for optical communication.The key condition is that it is relatively easy to perform amplitude modulation at a high enough frequency to achieve meaningful data transmission without interfering with the lighting function of the LED itself.In addition,in the visible light communication system,intensity modulation/direct detection technology is a relatively simple and low-cost communication implementation method.In visible light communication,OFDM technology is widely used because of its compelling advantages,such as high spectral efficiency and the signal's ability to resist inter-symbol crosstalk.However,if OFDM technology is applied to visible light communication systems,The OFDM transmission signal must meet the characteristics of a real positive signal.Based on the visible light communication system,the thesis proposes an enhanced OFDM/OQAM modulation scheme,and performs system performance analysis and simulation.Furthermore,a visible light communication hardware platform was designed and built,and the enhanced OFDM/OQAM and DCO-OFDM schemes were separately implemented offline and the ABO-OFDM scheme was implemented in hardware.The specific work is as follows:(1)The application of OFDM/OQAM technology in visible light communication needs to add a large DC offset,which results in low power efficiency of the OFDM/OQAM system.Therefore,the paper proposes an enhanced OFDM/OQAM scheme.In this scheme,half of the sub-carriers on the NORMAL branch carry useful data and the remaining half is reserved for carrying negative clipping noise,which will interfere with the information on the OFFSET branch and improve the system's performance.Power efficiency.On the OFFSET branch,all sub-carriers carry data information.In addition,a flexible power distribution method is also introduced into the system to further improve the system's bit error rate performance.The simulation results show that,compared with the PHO-OFDM scheme,the proposed EO-OFDM/OQAM scheme has better bit error rate performance at the same average bit rate,and the regeneration and elimination of interference noise is no longer required at the receiving end,reducing the complexity of system implementation.(2)Based on the visible light communication hardware platform,the VLC multi-carrier digital baseband communication system is designed and implemented in hardware.First,the visible light communication hardware platform is designed and the frequency response and noise characteristics of the visible light transceiver system are tested.Furthermore,using MALLAB,FPGA and mixed signal oscilloscope to verify the feasibility of using optical OFDM signal for transmission in the indoor visible light communication system through offline implementation.Secondly,based on the actual hardware conditions,for the ABO-OFDM system model,the basic parameters of the communication system,the physical layer data frame structure and the baseband implementation structure of the three parts of the digital baseband plan are designed,and the transmitter and receiver in the baseband system are involved.The obtained modules are analyzed,and FPGA implementation is carried out based on ISE software and Verilog hardware description language.Among them,the offline implementation results show that the VLC system can reach a gross rate of 9.8Mbps,a net rate of 7.127 Mbps,and a bit error rate of0.74405×10^-3 at a communication distance of 1.5 meters.This paper provides a certain reference for the research and application of multi-carrier technology in visible light communication.