Analysis and testing of wireless transmission attenuation in coal mine underground and research on the optimal operating frequency band

The application of technologies such as 5G, UWB, ZigBee and WiFi6 in coal mine mobile communication, personnel and vehicle positioning, and wireless transmission has promoted coal mine safety production and intelligent construction. However, due to the limitations of electrical explosion-proof measures, the wireless transmission power underground in coal mines is not greater than 6 W, which restricts the wireless transmission distance in the mine, and increases the usage of base stations and system costs. It is not convenient for system use and maintenance. Under the condition that the wireless transmission power is limited by electrical explosion-proof measures, selecting a wireless operating frequency band with smaller transmission attenuation can effectively increase the wireless transmission distance, reduce the usage of base stations, and reduce system costs. In order to meet the needs of selecting and optimizing the working frequency band of wireless transmission in mines, wireless transmission tests in the 700 MHz to 6 GHz frequency band are conducted in the auxiliary transportation roadway and fully mechanized working face of the Sandaogou Coal Mine of the National Energy Group. The test results are analyzed and the optimal frequency band for wireless transmission in mines is proposed. ① The optimal operating frequency band for wireless transmission in auxiliary transportation roadways is 700 to 910 MHz. ② The optimal working frequency band for wireless transmission in fully mechanized working faces is 700 to 1 710 MHz. ③ The wireless transmission attenuation of the auxiliary transportation roadway is smaller than that of the fully mechanized working face. As the frequency increases, the difference in wireless transmission attenuation between the auxiliary transportation roadway and the fully mechanized working face decreases. ④ The optimal working frequency band for wireless transmission in mines is 700 to 1 710 MHz.