Wireless Body Area Networks for advanced underground mines applications

采矿环境中的无线通信技术将在未来几十年内对矿山运营产生重大影响。例如，对工人和设备的持续监测是一个至关重要的安全项目。然而，当灾难发生时，令人遗憾的是，人们仍然注意到一些根本问题尚未解决。事实上，已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）。如果不能高精度地检测环境信息，救援过程也可能是高风险的。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（WBAN）。 在这项研究计划中，我们试图利用WBAN的有前途的功能，在矿工的防护服可穿戴天线传感器提供有关穿戴者的健康状况和环境参数在这个恶劣的环境中的信息。这些可穿戴天线应满足生物兼容性和尺寸限制要求，并且需要具有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几种现象，如地热、采矿机、高温和高湿度，其中传统的基板水/湿度吸收可能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，以同时应对这些性能挑战。在这项研究计划的第一部分，我们建议开发一类新的可穿戴流体天线的基础上聚二甲基硅氧烷（PDMS）弹性体基板，容忍严重的机械冲击弯曲，而不是打破。PDMS基底的柔性使得能够符合任何形状，并通过简单的键合技术制造多层结构。这些特性使它们适合于可穿戴天线。另一方面，使用铜作为导体的传统固体贴片天线不适合于柔性设备，因为它在反复弯曲时疲劳并经历不可逆的塑性变形。我们的目标是充分利用PDMS基板的可变形性，用流体金属取代固体金属组件，从而使传统的固体天线具有显著的拉伸性和灵活性。 实际上，在这种环境（地下矿井）中的多径和阴影效应使信号水平在矿工走动时剧烈波动。通过使用多输入多输出（MIMO）技术来联合收割机组合由多个天线发射和/或接收的信号，可以显著地提高链路的质量。该MIMO系统的设计和构建将克服链路预算的不足以及由于矿工和机器在这种环境中存在而导致的视线阻塞限制。此外，人体具有高介电常数，在微波频段具有高损耗角正切和低电导率。因此，当天线作用在人体上时，天线的增益和辐射效率会恶化。本研究计划的第二部分的目的是为了建立一个合适的无线电通信系统在地下矿井中的地下WBAN-MIMO通信信道的性能进行评估的路径损耗，信道相关性，容量，增益和平均频谱效率。

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.