Effect of antenna array properties on multiple-input-multiple-output system performance in an underground mine

There is no deployment strategy or capacity prediction available for wireless multiple-input-multiple-output (MIMO) communication systems inside underground mines. In such environments with low angular spread, the authors showed how antenna properties including antenna spacing, polarisation and height impact a 4 × 4-MIMO system performance. They used channel-frequency-response data near the 2.4 GHz obtained from measurements collected in a short underground mine, along with the recently developed multimode waveguide model. Several uniform-linear-array configurations were assessed for various propagation scenarios in the mine. They used the singular value, correlation coefficient and capacity analysis to compare their performance. Based on the results, they proposed an array orientation and element spacing, which provides sufficient spatial decorrelation among MIMO subchannels. The spatial decorrelation results are close to that of an i.i.d. Rayleigh channel and are not sensitive to different propagation scenarios. The authors´ study of the array height and element polarisation revealed that they mainly impact the subchannels´ power, which leads to offering different MIMO channel capacities. They also observed that in spite of geometrical dissimilarities between underground mines and large tunnels, some of their measurement results in the mine are similar to those of subway tunnels obtained by previous studies.