Wireless Body Area Networks for advanced underground mines applications

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Wireless communication technologies in mining environment will have a significant impact on mine operations in the coming decades. For instance, continuous monitoring of workers and equipment is a crucial safety item. However, when a disaster occurs, regrettably, it is still noticed that some of the fundamental problems have not been resolved yet. In fact, underground mine are known to be an environment into many fatal events might occur (e.g. Fires, toxic gases such as presence of Carbon Monoxide CO and Methane, oxygen concentration, etc.). The rescue process could be also highly risky without detecting environmental information with high accuracy. In order to fully exploit the benefit of wireless technologies in underground mines, a new type of wireless network emerges: Wireless Body Area Network (WBAN). **In this research program, we seek to exploit the promising features of WBAN with wearable antennas-sensors in the miners' protective clothing to provide information about the wearer's state of health and environment parameters in this harsh environment. These wearable antennas should meet bio-compatible and size limit requirements and need to be flexible for wear comfort and sufficiently robust to ensure a good communication link. However, several phenomenon like geothermal heat, mining machines, high temperature and humidity are present in this harsh environment where conventional substrate water/humidity absorption can lead to unacceptable antenna losses. Hence, new materials engineering and technologies must be identified properly to tackle simultaneously these challenges of performances. In the first part of this research program, we propose to develop a novel class of wearable fluidic antennas based on Polydimethylsiloxane (PDMS) elastomeric substrate that tolerate severe mechanical shock by flexing instead of breaking. The flexibility of PDMS substrate enables conforming to any shape and to fabricate multilayered structures by simple bonding techniques. These characteristics make them suitable for wearable antennas. On other hand, the conventional solid patch antennas, which uses a copper as a conductor, are poorly suited for flexible devices because it fatigues when bent repeatedly and undergoes irreversible plastic deformation. We aim to fully utilize the deformability of the PDMS substrate by replacing the solid metal components with a fluid metal, thus allowing significant stretchability and flexibility over conventional, solid antennas.**Actually, multipath and shadowing effects in this environment (underground mine) make the signal levels fluctuate severely while the miners move around. The quality of the link can be drastically improved using Multiple Input Multiple Output (MIMO) techniques to combine signals transmitted and/or received by multiple antennas. This MIMO system will be designed and built to overcome the lack in the link budget and the line of sight blockage limitations due to the miners and machinery present in this environment. In addition, the human body has a high dielectric constant with a high loss tangent and low conductivity at the microwave frequency band. Therefore, the gain and radiation efficiency of the antenna can be deteriorated when it is operated on the human body. The purpose of the second part of this research program is to evaluate the performance of underground WBAN-MIMO communication channel in terms of path loss, channel correlation, capacity, gain and average spectral efficiency in order to establish an appropriate radio communication system in underground mine.