6
approximately –33 dBm, while the communication power
on the 915 MHz band is measured at around –60 dBm
at the measurement antenna. Since we can only modify
an internal parameter to adjust the packet rate, the packet
rate and throughput are calculated based on the number
of packets received over a specific period. Therefore, these
values are approximate. Each test is conducted for approxi-
mately 20 minutes. The results are displayed in Table 7.
Table 7. Impact of packet size on packet error rate and
interruption time
Throughput (bit per second) 11558 11582 11536
Packet Size (bytes) 16 32 64
Packet rate (pkt/s) 90.3 45.24 22.53
Bit error rate (‱) 9.2 8.3 9.0
Packet error rate (%)13 21.8 40.6
Max consecutive lost/
error packets
7 7 8
As shown in Table 7, all three test cases have similar
throughput, approximately 11.56 Kbps. The bit error rate
remains consistent across the tests, ranging from 8‱ to
9‱. This is expected as all the tests are under the same
interference power level and the same signal power. The
maximum number of consecutive lost or errored packets
is also similar across all tests, with a count of around 7.
Because each packet occupies half time with half packet
size, the communication interruption time is also halved.
From the data, we observed that the packet error rate
almost doubles as the packet size doubles, indicating a direct
relationship between packet size and error probability. Let
us assume the error probability of each bit in the packet is
random and independent. Then, the packet error rate can
be estimated from the bit error rate as follows:
PER (packet error rate) =packet_size (bytes) *8
*BER (bit error rate)
As illustrated in the Figure 7, the estimated packet
error rates closely match the recorded values, confirming
the validity of our assumption that each bit has an indepen-
dent error probability.
Figure 7. Impact of packet size on packet error rate
DISCUSSION
Wireless communication in underground mine environ-
ments faces numerous challenges due to interference from
other devices, physical obstructions, and signal degrada-
tion caused by human or equipment movement. Devices
operating in the unlicensed ISM band—such as the wire-
less communication system installed in the aforementioned
mine and the remote controller built into the machinery—
are particularly susceptible to these issues, as this frequency
spectrum is shared by a wide range of equipment, including
Wi-Fi routers, Bluetooth devices, and other communica-
tion systems.
However, several methods and technologies can miti-
gate these challenges. Our tests reveal that the majority
of error packets contain only one or two bit errors for
instance, as shown in Table 4, nearly 96% of bit errors are
confined to one or two bits within a packet. Implementing
error correction codes in the communication system would
be highly beneficial. By correcting up to two-bit errors, we
could significantly reduce the packet error rate and poten-
tially improve communication quality by up to 25 times.
This approach is particularly useful in mining environ-
ments where interference is frequent and unpredictable.
In addition to error correction codes, advanced tech-
niques like diversity communication, smaller packet
0
5
10
15
20
0 1 2 3
Interference power (μW)
With people movement in between
With no people present
Figure 5. Bit error rate vs. interference with or without
people movement
0
1
2
3
0 1 2 3
Interference power (μW)
With people movement in between
With no people present
Figure 6. Max communication interruption time vs.
interference power, with people movement in between and
with no people present
Bit
error
rate
(
)
Max
interruption
time
(s)
approximately –33 dBm, while the communication power
on the 915 MHz band is measured at around –60 dBm
at the measurement antenna. Since we can only modify
an internal parameter to adjust the packet rate, the packet
rate and throughput are calculated based on the number
of packets received over a specific period. Therefore, these
values are approximate. Each test is conducted for approxi-
mately 20 minutes. The results are displayed in Table 7.
Table 7. Impact of packet size on packet error rate and
interruption time
Throughput (bit per second) 11558 11582 11536
Packet Size (bytes) 16 32 64
Packet rate (pkt/s) 90.3 45.24 22.53
Bit error rate (‱) 9.2 8.3 9.0
Packet error rate (%)13 21.8 40.6
Max consecutive lost/
error packets
7 7 8
As shown in Table 7, all three test cases have similar
throughput, approximately 11.56 Kbps. The bit error rate
remains consistent across the tests, ranging from 8‱ to
9‱. This is expected as all the tests are under the same
interference power level and the same signal power. The
maximum number of consecutive lost or errored packets
is also similar across all tests, with a count of around 7.
Because each packet occupies half time with half packet
size, the communication interruption time is also halved.
From the data, we observed that the packet error rate
almost doubles as the packet size doubles, indicating a direct
relationship between packet size and error probability. Let
us assume the error probability of each bit in the packet is
random and independent. Then, the packet error rate can
be estimated from the bit error rate as follows:
PER (packet error rate) =packet_size (bytes) *8
*BER (bit error rate)
As illustrated in the Figure 7, the estimated packet
error rates closely match the recorded values, confirming
the validity of our assumption that each bit has an indepen-
dent error probability.
Figure 7. Impact of packet size on packet error rate
DISCUSSION
Wireless communication in underground mine environ-
ments faces numerous challenges due to interference from
other devices, physical obstructions, and signal degrada-
tion caused by human or equipment movement. Devices
operating in the unlicensed ISM band—such as the wire-
less communication system installed in the aforementioned
mine and the remote controller built into the machinery—
are particularly susceptible to these issues, as this frequency
spectrum is shared by a wide range of equipment, including
Wi-Fi routers, Bluetooth devices, and other communica-
tion systems.
However, several methods and technologies can miti-
gate these challenges. Our tests reveal that the majority
of error packets contain only one or two bit errors for
instance, as shown in Table 4, nearly 96% of bit errors are
confined to one or two bits within a packet. Implementing
error correction codes in the communication system would
be highly beneficial. By correcting up to two-bit errors, we
could significantly reduce the packet error rate and poten-
tially improve communication quality by up to 25 times.
This approach is particularly useful in mining environ-
ments where interference is frequent and unpredictable.
In addition to error correction codes, advanced tech-
niques like diversity communication, smaller packet
0
5
10
15
20
0 1 2 3
Interference power (μW)
With people movement in between
With no people present
Figure 5. Bit error rate vs. interference with or without
people movement
0
1
2
3
0 1 2 3
Interference power (μW)
With people movement in between
With no people present
Figure 6. Max communication interruption time vs.
interference power, with people movement in between and
with no people present
Bit
error
rate
(
)
Max
interruption
time
(s)