Design And Realization Of Visible Light Multi-user Voice Communication System In Coal Mine Working Face

Coal mine safety work is inseparable from the underground communication technology and how to achieve a stable information transmission is a key topic.For the special environment of underground,the use of visible light for information transmission becomes an option.On the one hand,it can save the cost by using the lighting system of the working face to realize the information transmission.In addition,it is good environment for visible light communication as the relatively closed environment of the underground,which can reduce the external light interface effectively.In connection with the complex and changing working environment of coal mine,the application of visible light communication technology in coal mine working face is put forward.This paper firstly introduces the overall structure of visible light communication system in coal mine working face,including module,structure and implementation scheme.The visible light communication between the LED base station and the mobile node is mainly studied and the hardware circuit implementation is highlighted.The general-purpose hardware circuit of visible light communication which mainly includes the LED driver circuit of the transmitter,the photodiode amplifier circuit of the receiver and the frequency domain equalization circuit which aims at improving the bandwidth of the system.For the part of LED driving circuit,in order to improve the output optical power of the LED,the Bias-Tee is designed to couple the DC signal and the digital AC signal.In addition,a switching regulator circuit to regulator the output voltage is described detailedly.For the part of the photodiode amplifier circuit,influence of the feedback resistance and the feedback capacitance on the circuit bandwidth is analysed by simulation.Finally,in order to meet the required amplification gain and bandwidth a secondary amplifier circuit is a good choice.This paper designs a visible light transmission system of the speed signal,which is on the basis of the general-purpose hardware circuit of visible light communication.This system is related to the coding and decoding of the voice signal.Finally,a multi-user implementation scheme of visible light communication is introduced.The scheme is based on the principle of time-division multiplexing and realizes transmitting two path voice signal simultaneously.In addition,a solution to improve the output optical power of the LED of the transmitter is proposed.