No. 547 December 2011 

Cost-Effective, Off-the-Shelf Wireless Links for Surface Integrated Mine 

Emergency Communications 

Objective 

To provide a reliable and timely method of establishing a 

secure, wireless surface network that includes voice, video, and 

control information and links: (1) a command center to remote 

surface communications sites, and (2) alternate surface 

connection points to the existing in-mine communications 

systems. With viable workarounds to address possible line-ofsight obstructions, this type of network would effectively 

provide integrated mine emergency communications, thereby 

facilitating successful and timely mine rescue operations. 

Background 

Immediately following mine emergency events, a critical 

need exists to provide effective, reliable, and secure 

communications among emergency management personnel 

(usually located at a command center, or CC), other surface first 

responders located at remote sites, and underground miners. 

Depending on the nature of the incident, normal 

communications between the surface and underground may be 

inoperative; however, underground communications may reach 

the surface at an alternate location, possibly far from the CC. 

Often, it is necessary to drill an emergency borehole at a remote 

site to reach trapped miners. A borehole camera may be inserted 

into the borehole to assess the conditions in the mine. Ideally, 

the CC would be the hub of a centralized communications 

system or network that could access and link all the 

communications devices, data sources, and control functions 

that might be separated by miles in rugged terrain. The wireless 

communications systems brought by emergency responders 

frequently do not work due to obstructions to the 

communications path. These systems often do not offer easily 

deployed workarounds to resolve obstruction-related problems. 

If a communications path can be established using the 

emergency responder’s system, a difficult challenge still exists 

to link various sources such as video and data to the CC and 

alternative sites. With the proposed integrated communications 

technology and trained personnel to overcome potential 

obstructions, an effective network could be put into successful 

operation with sufficient security to prevent unwanted intrusion. 

Approach 

During a mine emergency, a successful integrated 

communications system could use cost-effective, off-the-shelf 

wireless surface network equipment that can be quickly 

assembled onsite to provide the critical communications links 

for the mine rescue operation. The resulting network can be 

made secure so that only those directly involved in the rescue 

operation have access to information obtained from the system. 

The example in Figure 1 shows the configuration of an effective 

integrated communications system and illustrates how the 

recordings of a video camera at a borehole drilling operation can 

be displayed on a laptop computer located at a CC, possibly five 

or more miles from the borehole site. To test the effectiveness of 

such an integrated network, researchers at the National Institute 

for Occupational Safety and Health (NIOSH) built and tested a 

test network using off-the-shelf hardware components at 

NIOSH’s Pittsburgh research facility. Motorola CanopyTM 900 

MHz devices were used to provide the wireless link using a 

carrier frequency of 900 MHz, +/- 2 MHz. The Motorola 

CanopyTM system also integrated the voice, video, and control 

signals into the network. The Motorola CanopyTM system was 

chosen because of the ease with which the voice, video, and 

control information are integrated into the system and 

transmitted to remote sites over possibly multiple wireless links. 

The CanopyTM system can also be easily reconfigured by adding 

appropriate hardware modules and reconfiguring the software 

via a few programming procedures using a configuration laptop 

attached by cable to the device. 

Figure 1. Network configured to transmit video from a remote site 

subscriber module (SM) to the command center access point (AP). 
For this test, a Motorola CanopyTM Access Point Module 

(AP) with a directional antenna was located at a test site 

representing the CC. Two Motorola CanopyTM Subscriber 

Modules (SMs) with directional antennas were used to simulate 

radio sources that were remote from the CC. 

Test results showed that the AP was able to send voice, 

video, and control signals to each of the individual SMs. The AP 

was able to receive voice and video from each of the SMs. An 

Internet access point was extended from the CC to the SM 

locations. The effectiveness of the system depends on: (1) the 

terrain between the CC (location of the AP) and the remote 

locations (location of the SMs), (2) the degree of precision in 

orienting the directional antennas of the APs and SMs for 

maximum signal strength, and (3) the bandwidth requirements 

for the information channels. Figure 2 shows a Motorola 

CanopyTM Subscriber Module (SM) with a directional high-gain 

antenna. The antenna is approximately 3 feet in length and is 

mounted 6 feet above the ground. Not shown is the 

configuration laptop computer connected via cable to the SM 

used to initially configure the SM software. Once the SM is 

configured, the laptop is no longer needed. 

 

Figure 2. A CanopyTM Subscriber Module (SM) / Directional Antenna 

typically deployed at a remote site from the command center (CC). 

The wireless surface network test system was used to 

communicate over a distance of 1–5 miles over terrain similar to 

that found at remote mining sites. The range could be increased 

to up to 40 miles, if necessary, by using a repeater located on 

high land roughly half the distance between the transmitter and 

receiver. Although higher frequencies are sometimes used, 900 

MHz was chosen because communications at that frequency are 

less affected by foliage. A CanopyTM device has the capability 

of transmitting both locally generated information, such as video 

from a camera, and information from other legacy video sources 

using Internet Protocol (IP). When a webcam is used as the 

video capture device, it can be connected directly to the Canopy. 

Legacy video or voice has to be converted to IP using a 

conversion device (i.e., a video or voice server). Although there 

are other possible commercial manufacturers, one legacy video 

converter device is the Slingbox® by Sling Media, Inc. Laptop 

computers are used to transmit, receive, interpret, and distribute 

the transmitted information. Thus, the issue of incompatibility 

of signal sources such as voice, video, or control signals is 

handled by the CanopyTM device, the IP converting devices, and 

the laptops. The system can also extend Internet service to the 

remote sites (if desired) provided that Internet service is 

available at the CC. To enable Internet service, two wired or 

wireless routers are used—one at the CC and another at the 

remote surface site. 

Summary 

A surface network system using off-the-shelf components, 

consisting of two Motorola CanopyTM Subscriber Modules 

(SMs), one CanopyTM Access Module (AP), associated 

antennas, and legacy video converter, successfully established 

strategic communications links in a limited mine-simulated 

environment. When needed, the system could be expanded with 

additional hardware to establish a communications path over 

greater distances to link multiple communications devices and 

other monitor and control devices and their data to a CC. A 

person with experience in aiming antennas and configuring 

wireless local area networks would be capable of setting up a 

secure system in a timely manner, and also address issues 

relating to obstructions due to local topography and foliage. The 

CC would be the hub of a secure centralized communications 

system that could link all the communications devices, data 

sources, and control functions. In a situation where the normal 

communications between the surface and underground are 

interrupted and an alternative communications path to the 

surface is established, the technology provides a least-cost 

solution for connecting the alternative communications path to 

the CC. 

For More Information 

For more information on wireless links for integrated mine 

emergency communications, contact Frank Duda 

(FDuda@cdc.gov) or the Health Communications Coordinator 

(OMSHR@cdc.gov), NIOSH Office of Mine Safety and Health 

Research, P.O. Box 18070, Pittsburgh, PA 15236-0070. 

To receive NIOSH documents or for more information 

about occupational safety and health topics, contact: 1-800-

CDC-INFO (1-800-232-4636), 1-888-232-6348 (TTY), e-mail: 

cdcinfo@cdc.gov, or visit the NIOSH Web site at 

http://www.cdc.gov/niosh. 

Mention of any company name or product does not constitute 

endorsement by the National Institute for Occupational Safety 

and Health.

DHHS (NIOSH) Publication No. 2012–111