On the Performance Enhancement When Combining STBC and Channel Estimation Techniques in Underground MIMO Channels

One way to enhance the channel data rate in enclosed environments is by incorporating multiple-input-multiple-output (MIMO) systems. Very often, this comes at the cost of data reliability. Motivated by the proven efficiency of space-time block coding (STBC) technique in conventional MIMO systems in improving the communication quality, we propose to incorporate it in wireless underground MIMO communication system and investigate data reliability at the reception in terms of bit error rate (BER). For this purpose, an intensive channel measurement campaign was performed in a mine-laboratory in northern Canada to obtain the perfect channel state. As a second step, the underground MIMO channel is estimated by sending a pilot sequence and using minimum mean square error (MMSE) principle on the received pilots. The resulting MIMO channel estimate is used to evaluate the data part in the STBC block and perform a decision using the maximum likelihood (ML) detector. Moreover, both the channel and transmitted data estimates are given analytically, and the degradation of the BER performance of the system due to MMSE estimation errors is studied using Monte Carlo simulations.