Underground Mine Channel Research Articles

Achievable rate of hybrid precoding for hardware impaired MIMO underground mine channel

Hybrid precoding has become a well-accepted approach to enhance the achievable rate in the adverse millimetre-wave (mm-Wave) MIMO channels. Transceiver impairments are inherent to any practical communication system, yet they are generally omitted when investigating the performance of wireless systems. More particularly, for the case of mm-Wave underground channels, no study has been reported yet. To overcome this limitation, in this Letter, a new architecture encompassing hybrid precoded mm-Wave MIMO structure, in which the hardware impairments have been incorporated in the transceiver processing, is presented. Furthermore, the geometrical one ring model is applied on the underground mm-Wave measured channel in which the architecture is tested.

Time delay estimation for UWB non coherent receiver in indoor environment, from theory to practice

Extracting parameter estimates from noisy observations of an underlying signal is a common problem in many fields. Time delay estimation (TDE) is essential for many areas, such as localization, array processing, and radar. The performance of any estimator is often evaluated via the mean square error (MSE) that can then be compared to analytical MSE lower bounds. In this paper, we first analyze a maximum likelihood (ML) estimator based on the knowledge of noisy second order statistics of the channel. We investigate lower bounds for the time delay estimation error for ultra-wideband ranging systems operating in realistic multipath environments. Based on the Cramer-Rao lower bound (CRLB), we derive analytically a lower bound of the time delay estimation calculated using the Karhunen–Loève decomposition of the estimated channel autocorrelation matrix. Also, we investigate the practical implementation (based on energy detection) of the time delay estimator. In the second part of the paper, we have analyzed the time delay estimation performances with the energy maximization receiver. Simulations are evaluated using a simulated UWB underground mine channel. This can be considered as the first step for a global positioning system for use mining industry.

A highly sustainable multi-band orthogonal wavelet code division multiplexing UWB communication system for underground mine channel

The underground mine channel is highly hostile for communication. A sustainable communication system is required to be integrated as a multipurpose system capable of transferring all types of information such as data, voice and video on identical infrastructure. With its large bandwidth, the Ultra Wide Band (UWB) provides a promising solution to satisfy these requirements. The Multi-Band Orthogonal Frequency Division Multiplexing (MBOFDM) UWB system provides high resilience to Inter-Symbol Interference (ISI) caused by multipath fading channels. This study compares the performance of various existing multi-band UWB systems in the IEEE UWB channel and underground mine channel: MBOFDM, Multi-Band Orthogonal Frequency Code Division Multiplexing (MBOFCDM) and Multi-Band Orthogonal Wavelet Division Multiplexing (MBOWDM). Further, the application of 2D spreading to the MBOWDM UWB system is attempted, and as a result, the Multi-Band Orthogonal Wavelet Code Division Multiplexing (MBOWCDM) UWB system is proposed. The performance of the MBOWCDM system in the IEEE UWB channel and underground mine channel is investigated. The performance of the MBOWCDM UWB system is observed to be superior to those of other multi-band UWB systems. Moreover, the MBOWCDM UWB system supports a higher data rate with low complexity and lower overheads.

A Performance Study of Line-of-Sight Millimeter-Wave Underground Mine Channel

This letter studies the performance of the line-of-sight underground mine channel in the millimeter-wave band. Using a vector network analyzer (VNA) and three carefully chosen antennas, one omni and two horn antennas, we performed measurements at the 40- and 70-m levels in the CANMET mine located in Val-d'Or, QC, Canada. The performance of the channel is studied in terms of its path-loss exponent, shadowing, and capacity. Results prove that the path-loss exponent in an underground mine is smaller than the free-space value. The shadow fading fits very well with the normal distribution. A model of the capacity as a function of the distance between transmitter and receiver is investigated. Channel capacity depends on the multipath characteristics; the capacity found in the narrow environment (70 m) is higher than in the wider environment (40 m). The results also show that it is better to use omnidirectional antennas for a wireless communication system in the millimeter-wave band in an underground mine environment.