Design Of Wireless Positioning And Voice Communication Systems Based On Visible Light Under Mines

In recent years,the mine safety problem attracts people's attention.The existing mine communication system is vulnerable to electromagnetic interference,low anti-interference ability and poor security.This thesis based on the development of visible light communication,applying the visible light communication technology in coal mine,provides a new solution for under the mine communication.Visible light communication is the use of LED high-speed modulation characteristics to modulate the information to LED using the optical signal transmission,and realizes lighting and information transmission.Combined with the environmental characteristics of mine and the advantages of visible light communication technology,this thesis designs a wireless positioning and voice communication system based on visible light.Using the LED in mine roadway to send its own address information,miners and mine vehicles use the receiving device to identify the location information to achieve wireless positioning.It can be used to transmit voice signals to LED mine roadway,too.Miners use a communication device on the cap to receive the signal and restore the voice information,we can also use LED on the mine cap to send voice messages between the LED and the miners,and realize duplex voice communication.The system uses the existing LED in mine,without laying a large number of nodes,saving costs,green security,no electromagnetic interference and good security performance using visible light communication.This thesis mainly has the four aspects.First,the research status of visible light communication technology in China and abroad is discussed.Then the system composition,channel model and the modulation principle of the LED are analyzed.Second,the wireless positioning module based on visible light is designed,including transmitter and receiver circuit,positioning method,frame structure,multi light source time division multiplexing access mode and communication protocol.According to the characteristics of coal mine environment,this thesis proposes a method of locating the mine,based on the ID for coarse positioning algorithm,combined with multiple receiving points to realize the precise positioning algorithm,realizing mobile terminal positioning itself to use the LED of the vehicle and mine cap in tunnel.Third,the mine voice communication module based on visible light is designed including transmitter and receiver circuit,and the module can achieve the function of duplex voice communication.Fourth,based on the study of visible light communication system,in order to further improve the transmission rate,increase transmission distance and avoid the influence of multipath effect on the system.According to the OFDM signal peak to average ratio caused by the LED nonlinear distortion problem,the OFDM modulation technology applies to visible light communication system,this thesis proposes a novel nonlinear solution based on sigma-delta modulator.