Effect of Mining Machinery on MIMO–UWB Radiowave Propagation Within an Underground Gallery

In this paper, the characterization of a multiple-input–multiple-output (MIMO) ultrawideband (UWB) propagation channel is reported based on experimental analysis. The wireless channel is measured from 3- to 10-GHz frequency range for a 2 $,\times,$ 2 MIMO system in an underground mine. The UWB spectrum is divided into subbands (flat fading), and all results are averaged within the 7-GHz bandwidth. Two situations are distinguished and studied separately: the line of sight (LOS), i.e., gallery free of machinery and the non-line-of-sight (NLOS), i.e., machinery obstruction. It is demonstrated that measured $K$ -factors were higher than 1.2 dB and lower than 0.2 dB for LOS and NLOS, respectively. Moreover, the MIMO subchannels have maximum correlation coefficients of 0.69 and 0.65 for LOS and NLOS, respectively. Furthermore, path loss exponent is of $\alpha = 1.42$ for LOS, however, for NLOS, it is about 3.19. Hence, results suggest that mining machinery presence leads to shadowing and scattering that affect both the received power and time dispersion parameters experienced by the link. Consequently, such presence should be considered when assessing the performance of underground mine gallery wireless systems. The values of these parameters can be used for MIMO–UWB channel modeling.