Research On Wide Band Radio Wave Transmission Characteristic And The Modulation And Demodulation Project In Coal Mine Tunnel

Through the ray tracing method, the transmission characteristic of UHF wide band radio wave in coal mine tunnels is investigated by the Matlab software. The tunnels investigated are empty rectangular straight tunnel and empty rectangular branch tunnel. In the empty rectangular straight tunnel, the influence to the propagation loss and RMS time delay spread of the radio wave is investigated. The influence factors contain antenna polarization, the distance between the transmitter and receiver, the section size of the tunnel, rough of the tunnel wall, tilt of the tunnel wall and the relative dielectric constant. In the empty rectangular branch tunnel, the influence to the propagation loss and RMS time delay spread of the radio wave is also investigated. The influence factors contain antenna polarization, position of the branch tunnel, the section size of the tunnel, rough of the tunnel wall, tilt of the tunnel wall and the relative dielectric constant.Since the OFDM may decrease the ISI (InterSymbol Interference), OFDM is applied to improve the performance of wireless communication system in coal mine. The paper summarizes the range of the RMS time delay spread in the tunnels and designs part of the OFDM parameters.