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2016 ITU Kaleidoscope Academic Conference
5. GROUND TRUTH EVALUATION
As argued in the paper that there are no propagation mod-
els clearly known to perform better in regions of the devel-
oping world that can be used in geo-location databases, the
first step that countries in these regions should take is to per-
form extensive spectral measurements and compare values
of the path losses obtained from the measurements against
those estimated by propagation models suggested for use in
geo-location databases. Therefore, the authors did a limited
physical evaluation of the approaches by conducting spec-
tral measurements and comparing values of the path losses
obtained from the measurements against those estimated by
some common propagation models. The experiments were
conducted in the city of Cape Town in South Africa. This
section gives a detailed discussion of how the whole process
was carried out.
5.1. Propagation models examined Figure 3: Measurement sites relative to BS transmitter
Five propagation models were examined and compared with
values from measurement data; Longley-Rice (Irregular Ter- a Nagoya NA-773 wide band telescopic antenna with verti-
rain Model), Hata for urban areas, Egli, Ericsson 9999 and cal polarization, which has wide band measurement capabil-
Free Space Path Loss (FSPL). ity. The RF Explorer was connected to an Android phone
installed with an android code that starts to measure spec-
5.2. TV transmitter used trum immediately after the RF Explorer is connected using
an On-The-Go (OTG) cable. At each site, spectrum monitor-
An analog terrestrial television (ATT) transmitter of one of ing was done for 8 hours from 08:00 in the morning to 16:00
the public TV broadcasters in South Africa called South in the afternoon.
Africa Broadcasting Corporation 2 (SABC2), located on
00
0
◦
00
0
◦
latitude 33 52 31 S and longitude 18 35 44 E, was used
5.5. Results
as a base station (BS) transmitter. Its transmission param-
eters obtained from the Terrestrial Broadcasting Frequency
The 3-hour measurements at each measurement location in
Plan 2013 document by the Independent Communications
channel 22 from which the BS transmitter was broadcasting
of South Africa (ICASA) [10] are: UHF channel = 22, fre-
were averaged and the mean value was taken as the received
quency = 479.25 MHz, Effective Radiated Power (ERP) = 2
signal power R x . As a starting point of our analysis, we de-
KW = 63.01 dBm, antenna polarisation = vertical.
cided to confirm the square law dependence of power loss
with distance first. We used the average value of the mea-
5.3. Measurements points sured power at the closest point to the BS transmitter (SITE
1) and estimate from there the power received at longer dis-
Twelve locations located at different distances from the BS tances along the same approximate radial by using the Friis
transmitter site were identified where measurements were transmission equation [12] (equation 1).
done. Tables 1 shows the geographical positioning system
(GPS) coordinates of the sites and their distances away from Pr(d) = Pr(d o ) + 20 ∗ log(d o /d) (1)
the BS transmitter. The table also shows values of the height
above avarage terrain (HAAT) of the sites calculated using where Pr(d) is the received power at distance d in
GLOBE 1 km Base Elevation database [11] with the number the same radial where d o is calculated, Pr(d o ) is the
◦
of evenly spaced radials equal to 360 in each case. Figure 3 received power at a close-in-reference-distance d o .
shows the measurement points relative to the BS transmitter
generated using google maps. In that way, we were able to compare the measurements with
those values obtained using equation 1. As Table 2 shows,
there is reasonable agreement between the measured and cal-
5.4. Spectrum measurements setup
culated values. This confirm that the square law dependence
Outdoor spectrum measurements in the UHF ATT frequency of power loss with distance is adequate.
band were done at the locations using a hand-held RF Ex- The accuracy of an Effective Isotropic Radiated Power
plorer model WSUB1G, which has a measurement frequency (EIRP) of a transmitter, the gain and return loss of a receiv-
range of 240 MHz to 960 MHz. The model was fitted with ing antenna determines the real path loss. In this experiment,
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