5
0.40 µW, the combined percentage of 1-bit and 2-bit errors
is approximately 99%. At 1.26 µW and 2.51 µW, this
combined percentage is above 96%. These results indicate
that, even as interference intensifies, most errors remain
relatively minor, typically involving only a small number of
bits. The lost or errored packet pattern is also summarized
in the following Table 5.
As interference power increases, there is a slight rise in
the average number of lost or errored packets. Additionally,
the maximum number of consecutive lost packets, which
reflects the interruption duration of the communication,
also increases with higher interference power, shown in
Figure 4. A larger number of consecutive lost packets indi-
cates a longer interruption time. If this interruption time
exceeds a certain threshold, it could cause the system to
mistakenly assume that the communication link is down,
potentially triggering a fail-safe mechanism in the system,
e.g., a machine to shut down operation.
Test 2: Assessment of the impact of human movement
in the tunnel on the communication quality
In this test, using the same settings as before, we introduced
movement by adding three people who randomly walked as
obstructions in the tunnel between the two communication
evaluation boards. Table 6 provides a comparison of the test
results with and without the presence of people movement.
The data illustrates the impact of people movement on
communication performance under varying interference
power levels. When there is no interference, people move-
ment alone causes bit errors in packets between the com-
munication boards. As interference power increases, the
presence of people movement exacerbates communication
issues as seen in Figure 5. The bit error rate nearly doubles,
and the packet error rate increases by approximately 5%
compared to tests conducted without people movement.
Additionally, the maximum number of consecutive lost or
errored packets rises substantially, shown in Figure 6. At
an interference power level of 2.51 µW, there are 59 con-
secutive lost or errored packets, which is about 2 seconds
of continuous communication disruption. This indicates
that people movement, combined with interference, can
severely impact communication reliability.
Test 3: Assessment of the impact of packet size on the
packet error rate and interruption time
In this test, we evaluated the impact of packet size on the
packet error rate within the tunnel environment. During
these tests, the interference power on the 914.4 MHz
band, measured at the measurement antenna, is set at
Table 5. Packet error pattern vs. interference
Interference
power (µW)
0 0.20 0.40 0.63 1.26 2.51
Bit error
rate(‱)
0 0 1.1 1.7 6.7 11.1
Packet loss/error
rate(%)
0 0.04 1.26 16.54 31.36 45.44
Average
consecutive
lost or errored
packets
0 1 1.15 1.19 1.38 1.83
Max consecutive
lost or errored
packets
0 2 6 5 7 16
Max
communication
interruption
time (s)
0.0 0.07 0.20 0.17 0.23 0.53
Table 6. Bit/packet error rate vs. people movement
Interference
power (µW)
0 v 0.40 0.63 1.26 2.51
With no people present
Bit error rate(‱) 0 0 1.1 1.7 6.7 11.1
Packet loss/error
rate(%)
0 0.04 1.26 16.54 31.36 45.44
Max consecutive
lost or error packets
0 2 6 5 7 16
With people movement in between
Bit error rate(‱) 0.04 2.05 5.86 7.02 12.3 18.4
Packet loss/error
rate(%)
0.02 6.5 15.1 20.5 35.9 50.7
Max consecutive
lost or error packets
1 10 26 13 38 59
0.0
0.1
0.2
0.3
0.4
0.5
0 1 2 3
Interference power (μW)
Figure 4. Max communication interruption time vs.
interference power
Max
interrruption
time
(s)
0.40 µW, the combined percentage of 1-bit and 2-bit errors
is approximately 99%. At 1.26 µW and 2.51 µW, this
combined percentage is above 96%. These results indicate
that, even as interference intensifies, most errors remain
relatively minor, typically involving only a small number of
bits. The lost or errored packet pattern is also summarized
in the following Table 5.
As interference power increases, there is a slight rise in
the average number of lost or errored packets. Additionally,
the maximum number of consecutive lost packets, which
reflects the interruption duration of the communication,
also increases with higher interference power, shown in
Figure 4. A larger number of consecutive lost packets indi-
cates a longer interruption time. If this interruption time
exceeds a certain threshold, it could cause the system to
mistakenly assume that the communication link is down,
potentially triggering a fail-safe mechanism in the system,
e.g., a machine to shut down operation.
Test 2: Assessment of the impact of human movement
in the tunnel on the communication quality
In this test, using the same settings as before, we introduced
movement by adding three people who randomly walked as
obstructions in the tunnel between the two communication
evaluation boards. Table 6 provides a comparison of the test
results with and without the presence of people movement.
The data illustrates the impact of people movement on
communication performance under varying interference
power levels. When there is no interference, people move-
ment alone causes bit errors in packets between the com-
munication boards. As interference power increases, the
presence of people movement exacerbates communication
issues as seen in Figure 5. The bit error rate nearly doubles,
and the packet error rate increases by approximately 5%
compared to tests conducted without people movement.
Additionally, the maximum number of consecutive lost or
errored packets rises substantially, shown in Figure 6. At
an interference power level of 2.51 µW, there are 59 con-
secutive lost or errored packets, which is about 2 seconds
of continuous communication disruption. This indicates
that people movement, combined with interference, can
severely impact communication reliability.
Test 3: Assessment of the impact of packet size on the
packet error rate and interruption time
In this test, we evaluated the impact of packet size on the
packet error rate within the tunnel environment. During
these tests, the interference power on the 914.4 MHz
band, measured at the measurement antenna, is set at
Table 5. Packet error pattern vs. interference
Interference
power (µW)
0 0.20 0.40 0.63 1.26 2.51
Bit error
rate(‱)
0 0 1.1 1.7 6.7 11.1
Packet loss/error
rate(%)
0 0.04 1.26 16.54 31.36 45.44
Average
consecutive
lost or errored
packets
0 1 1.15 1.19 1.38 1.83
Max consecutive
lost or errored
packets
0 2 6 5 7 16
Max
communication
interruption
time (s)
0.0 0.07 0.20 0.17 0.23 0.53
Table 6. Bit/packet error rate vs. people movement
Interference
power (µW)
0 v 0.40 0.63 1.26 2.51
With no people present
Bit error rate(‱) 0 0 1.1 1.7 6.7 11.1
Packet loss/error
rate(%)
0 0.04 1.26 16.54 31.36 45.44
Max consecutive
lost or error packets
0 2 6 5 7 16
With people movement in between
Bit error rate(‱) 0.04 2.05 5.86 7.02 12.3 18.4
Packet loss/error
rate(%)
0.02 6.5 15.1 20.5 35.9 50.7
Max consecutive
lost or error packets
1 10 26 13 38 59
0.0
0.1
0.2
0.3
0.4
0.5
0 1 2 3
Interference power (μW)
Figure 4. Max communication interruption time vs.
interference power
Max
interrruption
time
(s)