Radio propagation within coal mine longwall faces at 900 MHz

Measurements of radio-wave propagation at 900 MHz within two longwall faces of a coal mine are reported. Variations of received power with distance having distinct near and far regions separated by a breakpoint are observed. Values of propagation loss exponent and standard deviation before and after the breakpoint are derived for the two longwall faces of the coal mine. It is shown that propagation undergoes great attenuation.