2
Not only do various sources of EMI such as electri-
cal equipment and machinery contribute, but geological
formations can also degrade communication quality in the
subterranean environment of coal mines. These formations,
including mineral deposits, rock types, and the structural
complexity of the mine layout, can cause signal reflec-
tion, refraction, and absorption, thereby complicating the
propagation of wireless signals and degrading communica-
tion effectiveness. As wireless communication technologies
become increasingly integral to the mining industry’s digital
transformation, understanding how these systems perform
and maintain reliability in the presence of EMI is essential.
This research paper aims to explore the performance
and reliability of wireless communication links subjected to
EMI in underground coal mines. By using a wireless proto-
type system that is used in an actual commercial product,
we investigate the impact of EMI on the communication
link. This study seeks to identify key factors that influence
the performance of wireless communication links, propose
potential mitigation strategies, and contribute to the devel-
opment of more robust communication solutions tailored
to the challenging conditions of underground mining.
Through this investigation, the paper will provide valuable
insights for engineers, miners, and technology developers
working to enhance wireless communication reliability in
challenging mining environments.
PROBLEM AND CHALLENGES
The study was initiated in response to a reported incident at
a coal mine in Pennsylvania which is suspected to have been
caused by EMI. The issue involved intermittent communi-
cation loss between a remote controller and a piece of heavy
machinery Considering the systems in place at a working
face, it is hypothesized that the issue might have been
caused by radio radio interference from an adjacentradio
communication system that is commonly used in under-
ground coal mines. NIOSH researchers conducted prelimi-
nary field tests at the mine to investigate this issue, with
the support from the machinery vendor’s technical repre-
sentatives. The result shows that the wireless link between
the remote controller and the machinery can be interfered
with by an in-band AM-modulated signal generated by a
benchtop signal generator. Additionally, low signal strength
caused by metallic objects blocking the line-of-sight propa-
gation path further degraded communication.
Several challenges arose in determining the root cause
of the communication interruption. First, capturing the
electromagnetic fingerprints in the actual working environ-
ment of the machinery required on-site testing. Second, lab
equipment such as spectrum analyzers and signal generators
are not intrinsically safe, meaning they are not allowed to
be used in the coal mine’s working area. Third, the intermit-
tent nature of the issue made it difficult to predict when the
problem would occur, necessitating long-term monitoring
and extensive data storage. Additionally, the machinery’s
communication system is proprietary, making it difficult
for NIOSH researchers to pinpoint which part of the sys-
tem triggers abnormal shutdowns due to communication
interruptions. Different functions have varying timeout
requirements. For functions that could lead to unintended
movement, timeouts are short, typically within tens of mil-
liseconds, while other functions allow for longer timeouts.
The goal of this study is to evaluate the performance of
wireless communication between two nodes in the presence
of interference from another wireless system operating in the
same ISM band but on an adjacent frequency channel. Key
performance indicators include bit error rate (BER), packet
error rate (PER), and the duration of communication inter-
ruptions. Due to the constraints mentioned, an emulated
communication system has been created which was then
tested in a safety research coal mine. This system simu-
lates the communication signals between the machinery
and the remote controller, including modulation schemes,
data transmission rates, and channel filter bandwidths. The
interference signal will be generated by a vector signal gen-
erator that outputs GFSK-modulated radio frequency (RF)
signals, similar to those used by the communication system
near the machinery involved in the communication link
dropout issue. The frequency spacing between the emu-
lated communication and interference signals is set to 600
kHz, representing the closest possible spacing between the
frequency channels of the actual communication system
and the machinery communication system. The objective
is to evaluate communication performance under varying
interference levels and human activity conditions.
TEST SETUP AND PROCEDURE
To simulate remote-control communication, two CC112x
evaluation boards from Texas Instruments were employed.
These boards closely resemble the CC1020 RF commu-
nication chips used in the machinery system. One board,
serving as the transmitter, mimics the handheld compo-
nent of the remote control, continuously transmitting sta-
tus data. The other board, acting as the receiver, represents
the component on the heavy machinery, receiving signals
from the transmitter. In the tests, the transmitter board
transmits predefined data packets continuously until the
user interrupts, and the receiver board checks the integ-
rity of received data packets, without sending back any
response. The receiver board then sends a report to a user
Not only do various sources of EMI such as electri-
cal equipment and machinery contribute, but geological
formations can also degrade communication quality in the
subterranean environment of coal mines. These formations,
including mineral deposits, rock types, and the structural
complexity of the mine layout, can cause signal reflec-
tion, refraction, and absorption, thereby complicating the
propagation of wireless signals and degrading communica-
tion effectiveness. As wireless communication technologies
become increasingly integral to the mining industry’s digital
transformation, understanding how these systems perform
and maintain reliability in the presence of EMI is essential.
This research paper aims to explore the performance
and reliability of wireless communication links subjected to
EMI in underground coal mines. By using a wireless proto-
type system that is used in an actual commercial product,
we investigate the impact of EMI on the communication
link. This study seeks to identify key factors that influence
the performance of wireless communication links, propose
potential mitigation strategies, and contribute to the devel-
opment of more robust communication solutions tailored
to the challenging conditions of underground mining.
Through this investigation, the paper will provide valuable
insights for engineers, miners, and technology developers
working to enhance wireless communication reliability in
challenging mining environments.
PROBLEM AND CHALLENGES
The study was initiated in response to a reported incident at
a coal mine in Pennsylvania which is suspected to have been
caused by EMI. The issue involved intermittent communi-
cation loss between a remote controller and a piece of heavy
machinery Considering the systems in place at a working
face, it is hypothesized that the issue might have been
caused by radio radio interference from an adjacentradio
communication system that is commonly used in under-
ground coal mines. NIOSH researchers conducted prelimi-
nary field tests at the mine to investigate this issue, with
the support from the machinery vendor’s technical repre-
sentatives. The result shows that the wireless link between
the remote controller and the machinery can be interfered
with by an in-band AM-modulated signal generated by a
benchtop signal generator. Additionally, low signal strength
caused by metallic objects blocking the line-of-sight propa-
gation path further degraded communication.
Several challenges arose in determining the root cause
of the communication interruption. First, capturing the
electromagnetic fingerprints in the actual working environ-
ment of the machinery required on-site testing. Second, lab
equipment such as spectrum analyzers and signal generators
are not intrinsically safe, meaning they are not allowed to
be used in the coal mine’s working area. Third, the intermit-
tent nature of the issue made it difficult to predict when the
problem would occur, necessitating long-term monitoring
and extensive data storage. Additionally, the machinery’s
communication system is proprietary, making it difficult
for NIOSH researchers to pinpoint which part of the sys-
tem triggers abnormal shutdowns due to communication
interruptions. Different functions have varying timeout
requirements. For functions that could lead to unintended
movement, timeouts are short, typically within tens of mil-
liseconds, while other functions allow for longer timeouts.
The goal of this study is to evaluate the performance of
wireless communication between two nodes in the presence
of interference from another wireless system operating in the
same ISM band but on an adjacent frequency channel. Key
performance indicators include bit error rate (BER), packet
error rate (PER), and the duration of communication inter-
ruptions. Due to the constraints mentioned, an emulated
communication system has been created which was then
tested in a safety research coal mine. This system simu-
lates the communication signals between the machinery
and the remote controller, including modulation schemes,
data transmission rates, and channel filter bandwidths. The
interference signal will be generated by a vector signal gen-
erator that outputs GFSK-modulated radio frequency (RF)
signals, similar to those used by the communication system
near the machinery involved in the communication link
dropout issue. The frequency spacing between the emu-
lated communication and interference signals is set to 600
kHz, representing the closest possible spacing between the
frequency channels of the actual communication system
and the machinery communication system. The objective
is to evaluate communication performance under varying
interference levels and human activity conditions.
TEST SETUP AND PROCEDURE
To simulate remote-control communication, two CC112x
evaluation boards from Texas Instruments were employed.
These boards closely resemble the CC1020 RF commu-
nication chips used in the machinery system. One board,
serving as the transmitter, mimics the handheld compo-
nent of the remote control, continuously transmitting sta-
tus data. The other board, acting as the receiver, represents
the component on the heavy machinery, receiving signals
from the transmitter. In the tests, the transmitter board
transmits predefined data packets continuously until the
user interrupts, and the receiver board checks the integ-
rity of received data packets, without sending back any
response. The receiver board then sends a report to a user