Advanced Tutorial on Wireless Communication and Electronic Tracking: Introduction

• Emergency communications
• Leaky feeder communications systems
• Medium frequency communications systems
• Through-the-earth communications systems
• Wireless node communications systems

In 2006, three major underground coal mine accidents in the United States claimed the lives of 19 miners and prompted lawmakers to pass the Mine Improvement and New Emergency Response Act (MINER Act) of 2006. One of the requirements of the MINER Act is to provide wireless two-way communications and location information between underground workers and surface personnel following an underground accident. At the time of the accidents in 2006, most coal mine communications systems consisted of either leaky feeder systems or pager phones. A few mines had electronic brass-in/brass-out systems or zone-based tracking, but location tracking throughout the entire mine was not a common practice. Since then, efforts to develop new radio communications and personnel tracking technology have resulted in many new systems on the market for underground mine applications, and new systems continue to be introduced. New communications technologies include radio node network systems, such as mesh and Wi-Fi; improved leaky feeder systems; low-frequency, through-the-earth systems ; medium frequency radios; and combinations of these technologies. New personnel electronic tracking technologies include radio frequency identification (RFID) and radio ranging techniques. Due to the increasing availability of new systems, the Mine Safety and Health Administration (MSHA) requires underground coal mines to have compliant communications and electronic tracking (CT) systems installed by June 15, 2011.

The new CT technology that is available may be unfamiliar to mining professionals who need to purchase, install, and use this technology. To provide a better understanding of CT technology, a two-part tutorial has been developed by the Office of Mine Safety and Health Research (OMSHR), a division of the National Institute for Occupational Safety and Health (NIOSH), which consists of an overview of the available technologies (Part 1) and advanced details on how available systems operate (Part 2). The reader should review the Tutorial on Wireless Communication and Electronic Tracking - Part 1: Technology Overview online before studying this document - Part 2: Advanced.

Readers of this tutorial are assumed to be associated with coal mining, and therefore familiar with coal mining operations and terminology, and to have a technical background in electronics and/or communications systems. This tutorial is meant for those who need detailed information to compare systems and whose job responsibilities require advanced knowledge. For example, the mine’s communications expert will need to understand how the underground environment influences the performance of CT systems, how different CT systems work, and their advantages and disadvantages.

This tutorial provides an advanced discussion of the available CT technologies and operating characteristics starting with general communications system performance considerations in Section 2.1. This is followed by descriptions of specific technologies used for both primary communications (daily use, high bandwidth) and secondary communications (emergency use, low bandwidth). A comparison of the available technologies is presented in Section 2.6. Chapter 3 provides details on the operation and performance of the available miner tracking systems.

A critical question related to CT technology is, "What happens after a major accident?" Chapter 4 discusses issues related to survivability and reliability. Chapter 5 discusses safety issues such as MSHA certification of electronics used in explosive atmospheres, safe battery designs, and concerns related to electromagnetic fields. Chapter 6 discusses considerations related to the mine operations center (MOC) on the surface. There are also two appendices; Appendix A provides CT systems engineering specifications, and Appendix B gives basic wireless CT theory including link budget analysis and electromagnetic interference (EMI). A list of technical references and standards are also included at the end of this tutorial for further information. The italicized words in the text of this document are hyperlinked directly to the Mine Communications and Tracking Glossary.