sends a beacon message every 0.4 seconds with par-
ticular transmission power. The receiver node mea-
sures the RSSI for each beacon message the receiver
also gets the values of humidity and temperature val-
ues through the DHT11 sensor, recording RSSI, hu-
midity, and temperature and sending them through a
UART communication to the computer where the data
is saved in a CSV file to be later analyzed. During the
experience, two different scenarios were launched,
the first was wired communication, where the sender
and the receiver are connected through an SMA cable
using a step attenuator in between to variate the atten-
uation of the signal from 0 to 80dB where the receiver
was placed in the climatic test chamber. The second
experience was wireless, using the radio communica-
tion between the two nodes at different input power
levels.
To test the temperature impacts, the same setup
is followed in the climatic test chamber CTC256 for
both wired and wireless communication, the humidity
is off and the variation of temperature was in [-10..40]
°C range. The variation of temperature was by 5 °C
scales, and for each scale of temperature 100 samples
are taken to be analyzed in the next step. For the hu-
midity impacts, the temperature was fixed at 30 °C.
The humidity varies in the [40..90]RH % range. The
variation of humidity was by 10RH % and in every
scale of humidity, up to 100 samples are recorded to
be analyzed later.
The wired connection didn’t show a variation of
RSSI that could be adopted later in OMNET++. The
reason for this link quality stability is that the signal
is well protected with the cable and the factor of at-
tenuation is very low. To ensure that both temperature
and humidity had no effect on the RSSI in wired com-
munication the correlation has been calculated and
shown in the results below:
• Corr(RSSI,humidity) = -0.028
• Corr(RSSI,temperatur)= -0.017
The correlation is considered too low (close to the
zero value) as a consequence of the stable value of the
RSSI even the changes applied on temperature and
humidity.
The second setup is to implement a wireless con-
nection between the sender and the receiver, which
were placed at the edges of the climatic test cham-
ber. After getting the dimension of the climatic cham-
ber(width, height, and depth) CTC256, the distance
between the two nodes could be calculated using the
Euclidian distance:
Distance =
p
0.642
2
+ 0.672
2
+ 0.62
2
= 1.1m (2)
In this case, the attenuator has no place so the idea
is to control the output transmission power from the
CC1101 ship through sending different values to the
PATABLE register. the output transmission power
was -10dBm, -20dBm and -30dBm. In the beginning,
the humidity was off, the temperature was at 25 °C,
the output power was programmed at -10dBm, the
spectrum analyzer shows that there were 8dBm losses
due to the transmitter, the received signal strength was
at -71dBm.
Losses = −71 + 10 + 8 = 53dB. (3)
The conclusion of the 50dB losses that are coming
from reflections of the metallic climatic chamber. The
same distance will be kept for the whole measure-
ments setup inside the testing chamber.
3.3 RSSI Data Measurement’s
Discussion
After saving data, the idea was to format it using mul-
tiple methods and search for a suitable correlation. In
each case, the simple moving average had the highest
value of correlation. So the simple moving average is
manipulated in each level of transmission power ap-
plying the linear regression and calculating the slope
and the intercept. the window of the simple moving
average was equal to 20. The reason behind choosing
a window of 20 is that we took 100 samples for each
scale of humidity and temperature, in some scales the
RSSI varies up to 6dBm, so centralizing the data was
a better choice to align it to a definite behavior, if we
close the window to 100 so we are closer to the mean
of the data which is not a base form in data analysis
that depends on a high number of sets if less than 20
so we are going in a path of decreasing the correlation
and decentralizing the set of data. This step made the
implementation easier since the simulator is depend-
ing on the close behavior of the CC1101 ship but not
the exact way of working.
Fig. 2 shows the impact of Humidity on the RSSI
using -10dBm transmission power. The correlation
was -0.92. the slope and the intercept were calculated
after applying the linear regression, those variable are
showed in the equation below:
RSSI = RSSI0 − 0.2234 ∗ H (4)
were:
• RSSI0 = -53.8565 in dBm.
• H is the humidity in RH%
Fig. 3 shows the impact of Temperature on the
RSSI using -10dBm transmission power. But as
shown in the graph there’s some fluctuation around
-5°C. That was the effect of the relative humidity in
the climatic chamber and that’s when showed the role
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