| Coal resources are the precious wealth that nature endows mankind.The coal resources of our country have the characteristics of large amount and wide distribution.In the report on the work of the government at the March 2018 meeting of the people's Congress,which was referred to as environmental pollution,71% coal-fired power units have achieved ultra low emission to promote energy conservation and emission reduction in key industries,the proportion of clean energy consumption has been raised,and the proportion of coal was reduced by 8.1 percentage points.Although the proportion of coal has decreased,the fluctuation of coal consumption in the power industry is still small,and coal energy is still our country's dominant energy.The communication and liaison system in mining production can transmit information accurately and quickly by means of various means,which plays a crucial role in mining production and dispatching.In 2011,the StateAdministration of safety supervision and the State Coal Mine Safety Supervision Bureau jointly issued the notice on Issuing the "six systems" for coal mine underground safety and construction,and improving the basic norms(Trial Implementation),and the "six major systems" of safe havens include communication systems.The notice clearly points out that the communication and liaison system of the mine should be able to notify the personnel to evacuate and communicate with the safe haven in time during the disaster.At present,the communication in the mine is mainly realized by the traditional wired dispatching telephone system.In the event of a sudden accident,the wired communication equipment has been seriously damaged,resulting in paralysis of the system,unable to play the role of normal communication,and resulting in huge casualties and property losses.In order to make up for the shortage of wired communication,the research and development of the wireless communication system of the ground have come into being.However,due to the complexity of the channel and the shortage of channel resources,the theoretical research is very difficult,which is far less than the development of ground wireless communication.This paper analyzes the principle of wireless through-the-earth communication system,through-the-ground communication is greatly different from traditional communication.The channel in the ground communication is mainly composed of complex strata,so the transmission conditions are bad,and the signal will be greatly attenuated when it is propagated in the channel,andthese types of interference are not a single type.In order to reduce the impact of these problems,in addition to the compression of speech signals,the research team has studied the speech signal compression processing part,and also need to select the transmission mode of the signal,because the appropriate transmission mode can effectively improve the anti-interference ability of the signal,enable the speech signal to be effectively transmitted,and then be recognized by the receiving end,so as to serve for mine rescue and so on.In order to select the appropriate mode of signal transmission,firstly this paper analysis on the basic principle,characteristics and applications of transmission methods of digital signal and gets a more effective preliminary conclusion.Then the System View simulation software is used to build the system model,and the related parameters are set up to and get the results of bit error rate comparison of several digital modulation methods.Finally,this paper simulates the multipath effect in the ground penetrating channel,and propose that the 2FSK incoherent demodulation method can better satisfy the transmission requirement of the wireless through-the-ground communication system when the signal is regarded as the phase signal,which is a more effective and relatively ideal transmission mode. |
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