High resilience networks and microwave propagation in underground mines

Underground mining operations are an extremely hazardous and harsh environment to work within. Whilst overall safety has dramatically improved in modern-day underground mining, recent incidents such as the Sago mine disaster in West Virginia are a tragic reminder of this fact. Robust underground wireless communication and data transmission systems are a highly desirable medium in underground operations in terms of mobility, rapid deployment and ease of scalability, within a dynamic underground environment. However, subsurface radio propagation is of a highly complex nature and presents a challenging transmission medium within this type of environment. This paper examines the application of high-resilience wireless mesh network technology in underground mining. Various microwave transmission tests have been carried out, within the 2.4GHz ISM band, along with performance comparisons of various wireless technologies (WiFi, Bluetooth, Zigbee) underground. The collaborative research between Camborne School of Mines (CSM) and Mines Rescue Service Ltd (MRSL) is developing Zigbee/IEEE 802.15.4 related smart sensor mesh network applications in underground mines. Mesh wireless networks can significantly increase robustness and be over-designed to provide fail-safe redundancy. Potential applications include: voice, monitoring and control telemetry and active tracking of personnel and vehicles. High resilience wireless underground networking could also enhance both precautionary and reactive measures in safety and emergency situations; this has potential applications in mines other and sectors including public underground railway stations.