Research On Automatic Alignment Technology Of Indoor Visible Light Communication Systems

Indoor white LED visible light communication technology can transmit data while providing lighting,which realizes deep coupling of lighting and communication.With the miniaturization of LED visible light communication equipment,mobility and portability become the future development trends.Automatic alignment has become an urgent problem in high-quality visible light communication,otherwise the application of portable visible light communication will be greatly limited.The problem of automatic alignment of indoor visible light communication downlink is studied in this paper,and the research scheme of indoor visible light communication automatic alignment system is proposed.Mainly research work is carried out as the following aspects:(1)The illumination distribution of a single LED lamp in a room with an indoor area of 5m×5m is modeled and simulated.The illumination distribution of white LED at different half power angles of 45 degrees and 60 degrees is analyzed.The whole structure of the downlink of the indoor visible light communication automatic alignment system is introduced in this paper,and the hardware circuit of the downlink is designed,including LED driving circuit,photoelectric receiving circuit,ethemet card module circuit,digital to analog conversion circuit and analog-to-digital conversion circuit.(2)The overall design of the system is given for the design requirements and design principles of the indoor visible light communication automatic alignment system.The tracking methods of white LED are introduced and compared,and the LED spot tracking method based on image processing is selected,the recognition and positioning algorithm of white LED is studied,achieve identification and precise positioning of white LEDs.(3)Based on STM32 microcontroller,the hardware and software of the system are designed to realize the tracking function of white LED,including serial communication circuit design,TFT LCD display circuit design,driver development of system control board and PID control algorithm design(4)The experiment platform of downlink communication and white LED tracking are built respectively,and the software debugging and hardware circuit welding and debugging.With DQPSK modulation technology,when the communication distance is 3m,the video signal transmission is stable,and the tracking device realizes the recognition,positioning and tracking functions of white LED are realized through the tracking device,and the tracking accuracy of the system is givenFinally,a white light LED visible light communication automatic alignment tracking system is built according to the system design scheme.The experimental results show that the system can automatically adjust the reception direction according to different positions,the function of automatic alignment of downlink communication is initially realized,which reduces the impact of alignment problems on the communication quality,and the peak-to-peak variation characteristics with alignment angle are measured,and the necessity of automatic alignment system is analyzed.