Research on 5G frequency band selection and antenna optimization setting in coal mine

Mine wireless communication and mine-used 5G mobile communication technology is one of the key technologies of coal mine intelligence.In order to improve wireless transmission distance and diffraction ability as well as stability and reliability of wireless communication system in underground coal mine, reduce base station consumption, networking cost and maintenance workload, the effect of mine-used 5G working frequency band and antenna position of base stations on wireless transmission loss and transmission distance is studied.The major conclusions are as follows: ① Wireless transmitting power in underground coal mine is limited by intrinsically safe explosion-proof, receiving sensitivity is limited by electromagnetic noise, and antenna gain is limited by intrinsically safe explosion-proof and tunnel space.Therefore, under the conditions of limited wireless transmitting power, receiving sensitivity and antenna gain in coal mine, it is necessary to increase wireless transmission distance and diffraction ability, improve stability and reliability of wireless communication system, and reduce base station consumption, networking cost and maintenance workload by optimizing wireless working frequency band and antenna location setting.② 700 MHz is recommended as mine-used 5G working frequency band. Compared with other 5G frequency bands such as 2.6 GHz, 3.5 GHz and 4.9 GHz, 700 MHz frequency band in underground coal mine has the advantages of low wireless transmission loss, long wireless transmission distance, strong diffraction ability, less base station consumption, low networking cost and maintenance workload and so on.③ Analysis method of transmission loss/position change rate is put forward, which is convenient to analyze the change of transmission loss caused by position change in different transversal areas of tunnel.④ The antennas of wireless base stations should be set close to tunnel side, not less than 0.01 m away from tunnel side, and the height of antennas should be about 2/5 of tunnel height.This is convenient for installation and maintenance, not only does not affect pedestrians and driving but also can satisfy the requirements of low transmission loss and long transmission distance. ⑤ In order to improve wireless transmission distance, wireless terminals used in underground coal mine, such as mobile phones, personnel positioning cards, portable wireless methane detection alarms, multi-functional wireless lamps, portable wireless cameras, portable wireless instruments and equipments, wearable wireless devices, vehicle positioning cards, vehicle wireless devices, wireless cameras, wireless sensors, Internet of things devices and so on, should be closer to the tunnel center as much as possible under the condition of not affecting normal use.