Design And Implementation Of Visible Light Communication Multiplexing System

In recent years,the research of visible light communication(VLC)technology is increasing,the transmission rate of VLC system is increasing,and the application scenarios are becoming more and more abundant.Unlike traditional radio frequency(RF)systems,VLC systems use low-cost,energy-efficient light emitting diodes(LEDs)to encode data into high-frequency light intensity changes that are hard to be detected by human eyes.Any device equipped with photoelectric detector(e.g.photodiodes)can recover data by monitoring the change of light intensity.Compared with traditional RF technology,VLC has not been applied to most industries due to the bottleneck of transmission rate,but this does not mean that low-rate VLC system has no application prospects.In many scenarios,such as multiple billboard displays and text data transmission under multiple types of users,the transmission rate of the system is not the first factor,while sending different content to multiple types of clients is more important.At present,VLC multiplexing technology is used in high-speed communication scenarios,and because of its expensive equipment and the complexity of the system,it is obviously not suitable to use in low-speed scenarios.Therefore,this paper proposes a new VLC multiplexing system in low-speed scenario,in which one sender can transmit text data for multiple clients without interference.The main work of this paper is as follows:1)This paper introduces the system structure and working principle of VLC,analyzes the core devices of the sending end and the receiving end of VLC system,including the emitting principle of LED at the sending end and the principle of photoelectric detector at the receiving end,and completes the selection of the core devices at the sending end and the receiving end of VLC multiplexing system.2)The VLC multiplexing experiment system solely based on pulse width modulation(PWM)is designed and constructed.The experiment of one to many character data transmission based on the system is completed.The experimental results show that the accuracy of the system is 99%at the total rate of 2.84kbps.3)Based on the pulse position modulate(PPM),pulse amplitude modulate(PAM),pulse width modulate(PWM)are designed and constructed.In the VLC multiplexing experiment system of PPM,PAM and PWM,the character data transmission experiment based on the system is completed,and the data frame error correction and detection of the system are designed.The test results show that under the conditions of three types of users,the total speed of the system reaches 3.87kbps,and the accuracy reaches 99%.