Using wireless underground sensor networks for mine and miner safety

Wireless sensor networks (WSNs) are a specific type of networks that link sensors and have the potential to greatly benefit monitoring of coal mine applications, underground mine safety and localization of miners. Such systems can monitor the underground environment in real-time, provide information about the localization of miners and production parameters thus enabling early warning. In this paper, the possibilities and limitations of using WSNs that can effectively operate in coal environments are investigated. In particular, the coal communication channel is modelled considering the propagation of electromagnetic (EM) waves in coal, the multipath effect and providing an evaluation about the bit error rate of the modelled channel depending on the coal type and depth. The propagation characteristics are investigated using a theoretical approach. More specifically, the paper sets the theoretical background for examining the path loss of EM waves propagating in coal in the MHz range and determines the incurred path loss. As a result the frequency window, which provides the best performance, has been determined in the 615 MHz band since compared to the 2.216 Ghz band it has a weaker dependence on both the molecular composition of the medium and the transmission distance in coal medium.