Research On Wireless Communication Attenuation Characteristics In Dangerous Region Of Coal Spontaneous Combustion

It is important to coal spontaneous combustion prevention and controlling that feature information extraction in dangerous region. The monitoring methods currently used have many defects. Wireless communication network is widely used in mine production because of its low cost, low power, highly scalable high coverage, configuration and flexible networking. But now it’s mainly used for environmental monitoring of the underground tunnel. There is few study in gob-side entry, enclosed areas and rock-coal mass. Wireless communication characteristics of these three areas are studied in this paper.This paper researched on wireless communication frequency and attenuation characteristics in dangerous region of coal spontaneous combustion. Wireless communication environment and transmission loss factors in of these three areas are analyzed, coal-rock mass belongs to the dissipative medium, the process of electromagnetic transfer mainly affected by coal-rock electrical parameters and communication frequency. Gob-side entry belongs to limited space, the process affected by the influence of coal-rock electrical parameters, laneway surface section size, roughness and electromagnetic interference. The attenuation models of wireless communication are established in coal-rock mass and gob-side entry. Through theory calculating, the communication frequency in coal-rock mass should no more than 1MHz when skin depth is 5 meters. The cut-off frequency in gob-side entry is 291 MHz. Considering electromagnetic interference, the optimizing frequency need no more than 500 MHz. Wireless communication characteristics of coal-rock mass and gob-side entry are simulated by MATLAB software, the quantitative relationship between attenuation coefficient and effective communication distance is obtained and fitted a quadratic function under different communication frequency.Choosing 2303 working face and the ground pile of coal in Longgu coal mine, we tested the transmission distance and attenuation characteristics of 169 MHZ, 500 MHZ, 780 MHZ, 900 MHZ, 2.4GHz, the theoretical calculation is verified by this means.