Study Of Low Frequency Through-the-earth Communication Channel And Weak Signal Detection

Through-the-earth communication that supports communication between themining workers and the upon-ground officers plays a vital role in the miningindustry. However, the maintenance of wired through the earth communicationsystem is difficult. It is not efficient in people rescue when accident occurs.Therefore, it is necessary to investigate on the topic of wireless through-the-earthcommunication on the channel of ground. This paper mainly focuses on theweakness of received signal caused by the seriously fading through the channel, andproposes a series of solution.Firstly, this paper analyzes the composition of the earth and the subsequencefeatures as radio channel. Suppose that the earth heterogeneous, we derive thethree-layer earth model, transmission and reflection coefficients using analyticalmethod. We also substantiate that low-frequency signal is the key of robustness ofthrough-the-earth communication.Secondly, we propose the receive scheme of low-frequency elastic wave basedon the RAKE receiver technique. Considering the multi-path effect and the requestof SNR, we use time-diversity and max ratio combining to get extra gain. We alsosimulate the low frequency trough-the-earth communication system viamatlab/Simulink to show the BER curves and analyze the advantages anddisadvantages of the proposed scheme.Finally, a receive method using low-frequency wave based on matched filter isproposed to deal with the difficulty caused by the distance. Through the simulationvia matlab/Simulink we substantiate that the proposed method can accomplish thecommunication task effectively. The reliable frequency distance could reach1000meters.