Ever since the United States passed the MINER Act of 2006 there has been much interest in reliable underground communication systems. In the harsh environment and changing topology of a mine, reliable communication is a high-stakes issue. Regular, above-the-ground techniques can't be applied in the underground environment. Transmitting radio signals over optical fiber is an excellent way to get the mines connected. This technology, called ROF for short is very reliable and provides enough bandwidth to handle multiple services. Optical fibers are readily available and are unaffected by the electromagnetic interference or radiation commonly emitted by mining equipment. However, there are many technical challenges need to be addressed. A typical underground communication system consists of three channels that are in cascade (1) the ROF link, (2) a special kind of coaxial cable called the 'leaky feeder' (3) the underground wireless channel. The biggest concern in ROF link is the nonlinear distortion at the RF-Optical modulators. Broadband RF amplifiers also create nonlinear distortion. The distortion is severe in the uplink. There are three signal-to-noise ratio's involved in this system. The resulting SNR is a weighted sum of these three and smaller than the smallest of them.

Once a reliable underground communication system is designed it can accommodate various sensors to enable tracking the miners, poisonous gases and even the status of equipment in mines. This will not only enable saving miners' life, it can also reduce the energy consumption by monitoring and controlling power hungry equipment such as huge exhaust fans in mines.

The tutorial will address the design issues of the underground communication systems. How appropriate sensing can be used improve the reliability of these networks and to track miners and other equipment.

Wisam Farjow is a Senior Engineering Manager in Mine Radio Systems Inc., Good wood Ontario. He has been involved in the design and development of underground communication systems for many years and many countries.

Xavier Fernando is an Associate Professor at Ryerson University. He is a member of IEEE COMSOC Education Board - Working Group in Wireless Communications. He leads Ryerson Communications Lab. He has co-authored more than eighty research articles and holds a patent 'An Optical Fiber-Based Wireless Scheme for Wideband Multimedia Access'. He has delivered invited talks worldwide in the area of ROF systems. He was a visiting scholar at the Institute of Advanced Telecommunications (IAT), UK in 2008. He is a co-author of WEBOK, the Wireless Engineering Body of Knowledge used for standard text to the wireless IEEE COMSOC Wireless Communication Engineering Technology program (WCET). He is the Chair of the IEEE Communications Society, Toronto Chapter. >

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