Mines and industrial sites are becoming increasingly more networked. Emerging safety requirements in the US and internationally, demand real-time wireless communications for voice and data. Process control and other operations are increasingly monitored by hand-held data devices and/or centralized IP video. These new networking applications create expectations of high performance over many wireless "hops" (node to node relays), with dependable support for video, voice, and data. 

With this increased focus on safety in underground coal mines, efforts are being made to reduce risks to miners in any way possible. "Longwall" mining differs from "Room & Pillar" mining in that the mine roof is expected to fall when operations are concluded in a particular area of the mine. For this reason, roof supports are not as extensive at the working mine face. This holds obvious danger to the miners operating at the mine face using the mining machines called "shearers".
  
One way to reduce this risk is to remove the miners from the immediate area in which the machines are being operated by as much as one mile. But to efficiently operate the shearer, the miner must still be able to see the coal face, a problem from a mile away. The obvious solution is to put full motion video cameras on both working ends of the shearer (the shearer operates both forward and backward). Because of the precision nature of the mining process, there cannot be any meaningful delay in the image from the video camera to the machine operator. This demands a very high performance network with minimal delay and jitter for the video connection. And because the area being mined is to be allowed to collapse when mining operations are complete, it is impractical to install any sort of permanent infrastructure, such as wired network.

A wireless video connection is the obvious solution, but it must deliver high performance over many "hops" (node-to-node connections). MeshDynamics equipment in production mine environments delivers outstanding video connectivity over many "hops", making remote mining machine operation practical and cost-effective. The MeshDynamics MD4000 has all of the characteristics to support the operation of precision heavy machinery from a distance, providing connectivity for high quality video over the multiple hops necessary to ensure that the miners are removed to a safe operating zone. (In some cases, it may be decided to operate the machine from the surface which requires even more hops.) High data rate wireless video surveillance has also been demonstrated with the MD4000 Mesh nodes. 

Successful "Longwall" Mining Pilot Demonstration

A recent successful demonstration of remote mining involved a Longwall shearer operated remotely. The MD4000 wireless mesh network offered high quality video of the working faces to the remote operators. Operators were able to observe the operation and performance of the machine, adjusting controls as necessary without exposing themselves to the dangers of the immediate area being mined. The MD4000 network provided a consistent throughput over fourteen hops with a 5.8 GHz backhaul, more than enough to support the two 15fps video cameras with PTZ controls. Delays through each MD4000 node are only 1-2 milliseconds, providing the real-time video necessary for successful remote operation.

Because of the dynamic nature of the typical Longwall mining operation, the mine itself is constantly being reconfigured. As the mine face moves forward, sections of the mine are allowed to collapse and new areas are opened. As part of this deployment, it was demonstrated the MD4000 network instantaneously and automatically adapts to the changing environments. MD4000 nodes may be redeployed to new areas of the mine as these are opened, joining the existing network to provide coverage for the video application. No complex network engineering is required.

With this network in place to provide remote operation of the Longwall shearer, it is also possible to extend the network to the surface and connect it to the PBX/phone system and other data and voice network. This could ease the maintenance and support of the mining machinery by allowing real-time phone support at the site of the operators and/or equipment as well as to allow access to on-line technical documentation from underground.

Successful "Room and Pillar" Mining Pilot Demonstration.  

In another successful demonstration, a working "room and pillar" mine required long distance connectivity for voice, location tracking, and video process monitoring. Because the headquarters and processing plant is some distance from the main entry to the mine, multiple hops were needed both outside and inside the mine, a total distance of 3½ miles. MeshDynamics MD4000 nodes are installed in a number of locations within the mine itself, secured to the roof or supporting timbers as appropriate for each location and powered by a battery back-up system.

Voice connectivity is provided from wireless WiFi Voice-over-IP (VoIP) handsets carried by individual miners to the PBX at the headquarters site, with PSTN (Public Switched Telephone Network) access via the PBX. Clear voice connections are provided at the furthest extent of the current installation, a total of 14 "hops".

A miner location and tracking system based on WiFi is also supported over the MeshDynamics wireless infrastructure. Along with the two-way voice communications, this helps to fulfill the MINER Act requirements. In addition, an IP-based video camera is being used to monitor remotely a key junction of the belt system that is crucial to mine productivity.

The mine operator is enjoying multiple benefits from the MeshDynamics installation. Besides fulfilling MINER ACT requirements, mine personnel may be more productive through better communications. Requests for supplies, tools, and other material may be made over the VoIP system, saving the time and inconvenience of multiple mantrip shuttles. The ability to remotely monitor the operation of key belt locations has also provided an increase in uptime and productivity.

Unique MeshDynamics Technology Benefits:
 
The key to these successful demonstrations is the ability to provide very high performance for high-quality video and voice over a large number of hops. While most WiFi mesh solutions would fail after a handful of hops, MeshDynamics' patented and patent-pending solutions begin by providing two backhaul radios to each node. To overcome the problems of congestion and contention one radio is used to create a link to its upstream (nearer the wired source or "root") node. Another radio creates a link downstream to the next neighbor node.

Thus, each node may be sending and receiving simultaneously to its upstream and downstream neighbors, unlike most competitive solutions, which must continually "turn around" between sending and receiving upstream and downstream. Because each link is managed independently, the available channels may be re-used across the network. This expands the available spectrum, increasing performance of the network 50 times or more compared to traditional mesh solutions, delivering the video performance necessary for efficient real-time remote observation and control of the mining machinery. [More]

MeshDynamics' third generation mesh networking software creates an RF-aware "radio robot" in each MD4000 node. This distributed dynamic radio intelligence constantly monitors the surrounding radio environment. The node locates adjacent nodes in the network as they are added. Based on this continual scanning of the environment, the MeshDynamics nodes form a network in an independent, but coordinated fashion, with relationships based on highest performance, interference rejection, and optimal re-use of channel assignments for maximal network bandwidth. In the remote mining environment, this continuously and automatically adapts the MD4000 network to the changing configuration of the mine and locations of the mining machinery.
 
MeshDynamics provides this networking power in a compact, robust enclosure requiring little room in the cramped underground environment. Low power draw and available battery power solutions permit use in harsh environments and provide back-up functionality in case of power failure or other incidents.  Our dynamic radio intelligence allows nodes to be installed and supported easily, without costly site surveys and pre-engineering.  MeshDynamics products also include intrinsically safe technologies for deployment in severe environments, as well as specialized support for voice-over-IP and other real-time networking requirements.

Related Links:

 Remote Control of "Longwall" Mining Machinery improves Safety and Productivity  Case Study, pilot network installed, 2007.
 Increased Safety, Communications, Control and Productivity in Underground coal mining. Case Study, pilot network installed, 2007.
 
MD4000 Configuration Options Overview of configuration options including 3.3VDC explosion proof enclosures.
Frequently asked Questions On Antenna selection, GPS, Mobility extensions, Hazard proof enclosures.
MeshDynamics ''Mines'' New Outdoor Wireless Enterprise Opportunity MeshDynamics Press Release, ACT partnership.