Wireless Body Area Networks for advanced underground mines applications

矿山环境无线通信技术将在未来几十年对矿山作业产生重大影响。例如，对工人和设备的持续监控是一项至关重要的安全项目。然而，令人遗憾的是，当灾难发生时，人们仍然注意到一些根本问题尚未得到解决。事实上，众所周知，地下矿井是一个可能发生许多致命事件的环境（例如火灾，有毒气体如一氧化碳CO和甲烷的存在，氧气浓度等）。如果不能准确地探测到环境信息，救援过程也会非常危险。为了充分发挥无线技术在地下矿山中的优势，一种新型的无线网络应运而生：无线体域网络（WBAN）。**在本研究项目中，我们试图利用矿工防护服中的可穿戴天线传感器来开发无线宽带网络的有前途的特性，以提供有关佩戴者在恶劣环境下的健康状况和环境参数的信息。这些可穿戴天线应满足生物相容性和尺寸限制要求，并需要灵活的佩戴舒适性和足够的鲁棒性以确保良好的通信链路。然而，在这种恶劣的环境中存在地热，采矿机器，高温和高湿等现象，传统的基材水/湿度吸收会导致不可接受的天线损耗。因此，必须正确识别新材料工程和技术，以同时解决这些性能挑战。在本研究计划的第一部分中，我们提出了一种基于聚二甲基硅氧烷（PDMS）弹性体衬底的新型可穿戴流体天线，该天线通过弯曲而不是断裂来承受严重的机械冲击。PDMS基板的灵活性使其符合任何形状，并通过简单的粘合技术制造多层结构。这些特性使其适合用于可穿戴天线。另一方面，传统的固体贴片天线，使用铜作为导体，不适合柔性设备，因为它在反复弯曲时疲劳，并经历不可逆的塑性变形。我们的目标是通过用流体金属代替固体金属组件来充分利用PDMS基板的可变形性，从而使传统的固体天线具有显著的可拉伸性和灵活性。**实际上，在这种环境下（地下矿井），多径和阴影效应会使矿工移动时信号水平波动严重。使用多输入多输出（MIMO）技术来组合由多个天线发送和/或接收的信号，可以大大提高链路的质量。该MIMO系统的设计和制造将克服链路预算不足和由于这种环境中存在的矿工和机械造成的视线阻塞限制。此外，人体在微波频段具有高介电常数、高损耗正切和低电导率。因此，在人体操作时，天线的增益和辐射效率会下降。本研究计划第二部分的目的是从路径损耗、信道相关、容量、增益和平均频谱效率等方面评估井下WBAN-MIMO通信信道的性能，以便建立适合井下矿井的无线电通信系统。

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.