Study On Speech Compression Coding Based On CELP In Mine Wireless Through-the-earth Communication

The mine accidents occur in a high frequency in China. When mineaccident occurs, not timely rescue trapped workers would cause a great loss tothe society and family. Once natural disasters or production accidents happen,emergency alarm and mining personnel search and rescue is based on the goodcommunication system of the refuge chamber. But the ruptured or no power partof wired communication system cable and pipeline results that the search andrescue personnel can’t get in touch with the trapped workers in time and thendelay the rescue work. So the study on the mine wireless through-the-earthcommunication system is very important.This paper analysis on the channel of the mine wireless though-the-earthcommunication in this paper, and we know that the channel of thecommunication mode is composed of earth rock. When propagating through thechannel, electromagnetic wave will suffer from attenuation seriously. Theattenuation becomes the bottleneck of the voice transmission technologydevelopment in mine wireless though-the-earth communication. In order tosolve this problem, the communication system selects ultra low frequencyelectromagnetic wave. It is because of the selection of the ultra low frequencyelectromagnetic wave, the bandwidth of the communication channel reducesgreatly, and high rate speech signal can’t transmit in the channel. So enhances the importance of compression coding on speech signals, which means reducingthe signal transmission rate is extremely important in the communicationsystem.In order to establish a suitable voice compression encoding method for themine wireless though-the-earth communication in the case of the mineemergency rescue and disaster relief, this paper analyzes the influence ofelectromagnetic wave when propagating in channel and mine roadway. At thesame time, according to the requirements of mine emergency communication tospeech signal, this paper propose a coding rate low, the synthesized speechquality high, anti-interference ability requirements for coding scheme.According to this several requirements, this paper compares the performanceindexes of waveform coding, parameter coding and hybrid coding, and thenselects Code Excited Linear Prediction coding (CELP) as the compressionencoding method of mine wireless through-the-earth communication.In the premise of the understanding of speech compression coding theoryand technology foundation, this paper analyzes the principle and preparesalgorithm of each module of the CELP method, select algorithms to make thecoding method performance better, so as to determine the final coding scheme.The simulation results of this compression scheme by using MATLAB showthat by using this compression project， the voice frequency that can becompressed is250~3500Hz and the transmission rate can be compressed downto4.53kbit/s on the premise of subjectively identifiable and undistorted voice.The results achieve the purpose of speech signal compression in mine wirelessthrough-the-earth communication.