Abstract
TV white space (TVWS) refers
to the unused UHF and VHF spectrum owned by primary users, such as TV (DVB-T2)
broadcasters in a certain location. The protection of primary users'
interference from white space devices has been the major implementation issue.
Protection ratio setting is commonly used to limit the amount of transmission
power that white space devices can permit. In the present study, the simulation
and experiment for the proposed protection ratio values are compared.
Simulation using Monte Carlo has been conducted. Field measurements were implemented
to see whether the protection ratio value could be used to assist the
government in implementing TVWS. The outcomes showed that the simulation-based
protection ratio was 1 dB greater than the field test result. The results
indicate that the simulation model can be used as a reference for the
government to estimate the value of the protection ratio and facilitate better
efficient implementation.
Keywords: Index Terms�TVWS;
Protection Ratio; DVB-T2; Field Measurement
Received: 2022-01-20; Accepted:
2022-02-05; Published: 2022-02-20
Introduction
White space refers to the unused
frequency spectrum in the wireless spectrum. In 2011, the
Federal Communications Commission (FCC) and the Electronic Communications
Committee (ECC) have opened up the opportunity to use white space channels (Third Memorandum Opinion and Order,
in the Matter of Unlicensed Operation in the TV Broadcast Bands, Additional
Spectrum for Unlicensed Devices below 900 MHz and in the 3 GHz Band, 2012). Both
agencies have published a TV White Space (TVWS)
framework using different approaches, primarily to protect primary users, i.e.,
Digital Television Terrestrial (DTT) broadcasters. The TVWS framework is
tailored to the environment. However, no framework is the same across countries
that implement TVWS (TRAAC, 2014). Owing to the
interference problem, authorities in many countries argue about whether to
allow the TV channels or other bands for secondary purposes (Foo, 2017; Freyens & Loney, 2013;
Nekovee, Irnich, & Karlsson, 2012). Therefore, the FCC and ECC use the protection ratio value to protect
the primary users of Digital Television Terrestrial (DTT). In this study, we
consider DVB-T2 as the DTT standard Note, in which the protection ratio is referred
as the ratio of the primary system's field strength and the secondary system's
field strength in the receiver (ITU-R, 2007; Planning Criteria,
Including Protection Ratios, for Digital Terrestrial Television Services in the
VHF/UHF Bands, 2017; Planning Criteria, Including Protection Ratios, for
Second Generation of Digital Terrestrial Television Broadcasting Systems in the
VHF/UHF Bands, 2015). The protection ratio maintains a minimum carrier-to-interference (C/I)
ratio. The European Telecommunications Standards Institute (Union, 2012) provides the minimum desired signal-to-noise ratio (C/N) that a
DVB-T2 system can tolerate, revealing that the C/I value will be equivalent to
C/N with the absence of an intruder. With or without an interferer, if the
ratio of the signal intensity (C) to the unwanted signal (N + I) is less than a
specified threshold, the receiver can receive better information. On the other
hand, the C/I value is measured at the receiver input based on the antenna gain
and cable loss. In practice, the field strength is used to calculate the
transmitter coverage area. The propagation model, transmitting antenna gain,
and noise have effects on the value of the field strength. The magnitude of the
field strength at the receiver level varies, which depends on the location (Lessy Sutiyono Aji, Witjaksono,
Wibisono, & Gunawan, n.d.). Therefore, the
protection ratio must accommodate these variations.
A study (L
S Aji, Juwono, Wibisono, & Gunawan, 2018) uses Monte Carlo simulation to
propose a new protection ratio calculation against White Space Device (WSD). The
study (L
S Aji et al., 2018)
complements the value of the protection ratio, where the FCC proposes a more
specific DTT system, namely DVB-T2. However, this
approach (L
S Aji et al., 2018)
lacks field measurement. As a result, the present study reports field
measurements to compare the simulation findings of the protection ratio value
with the real conditions. In this analysis, we use a case study of DTT TVRI
Patuk Jogjakarta's coverage region in Indonesia. DVB-T2 64 QAM is the digital
TV standard used in Jogjakarta. The white space device used in the case is the
GWS 3000, which has a 5 MHz bandwidth (FCC,
2018; Inc., 2013).
The
measurement method is adopted based on the recommendation by the International
Telecommunication Union (ITU) (ITU-R,
2016, 2018; ITU, 2011; Planning Criteria, Including Protection Ratios, for
Digital Terrestrial Television Services in the VHF/UHF Bands, 2017). During the field
measurement, we found that the bandwidth of the GWS 3000 equipment differed from
the ITU guidelines. As a result, a significant discrepancy is noted
between the simulation and the field measurements. After adjusting the WSD bandwidth
in the GWS 3000 device stimulation, the results of the Monte Carlo simulation computation
showed that the protection ratio value was 1 dB higher than the protection
ratio value acquired from the field experiments.
The rest of
the paper is structured as follows: �Section II revisits protection ration
matters, including the DVB-T2 and WSD standards. Section III discusses the
methodologies used in modeling and carrying out the field measurements. Section
IV presents the results and analysis. Finally, Section V concludes the paper.
A. Protection Ratio
To preserve a specified minimum C/I value, the protection ratio is defined as the
ratio of the primary user's (DTT) field strength value to the secondary user's
(WSD) field strength value, as measured at the receiver. C/I is defined as the ratio of the
intended signal strength to the interferer signal strength at the receiver
input (Achtzehn, Riihij�rvi, & M�h�nen,
2014). The protection ratio varies depending on the DTT system. As a
result, determining the DTT system becomes critical in providing protection
requirements. To correctly receive information, the distinction between DTT
systems is critical to evaluate the minimal C/N value required by DTT
recipients. The discrepancy in the C/N value will influence the device's
sensitivity level, thereby impacting the protection ratio value as computed on
the DTT receiver's sensitivity level. Table I shows the DVB-T2 and WSD/IEEE
802.22 WRAN specifications. The IEEE 802.22 was chosen to represent the white
space in outdoor conditions.
Tabel I�
Specifications Of Dvb-T2 (ITU-R,
2014; Union, 2012)
And Wsd/Ieee 802.22 (IEEE,
2011)
|
Specification
|
DVB-T2
|
IEEE 802.22/ WSD
|
|
Modulation
|
64 QAM
|
64 QAM
|
|
Noise Floor
|
-129.16 dBm
|
-105.071 dBm
|
|
Sensitivity
|
-109.63 dBm
|
-67.067 dBm
|
|
Freq. Range
|
610 � 634 MHz
|
610 � 634 MHz
|
|
Transmitter
Height
|
40 Meters
|
40 Meters
|
|
Receiver Height
|
10 Meters
|
10 Meters
|
|
Power
|
60 dBm
|
Varying
|
|
C/N
|
18.89 (19.53 dB)
|
(18.3 dB)
|
Method
A. The calculation of Protection Ratio by
simulation
Path
loss PL(d) at a given location is randomly distributed owing to
the shadowing effect at many measurement locations (Ribeiro
et al., 2012).
A statistical approach is appropriate for this case, using the Monte Carlo
method, which relies on repeated random sampling to obtain values that represent
uncertain conditions (L
S Aji et al., 2018; Gunawan, Saraswati, & Aji, 2019; Oberle, 2015).
This
present study uses the same simulation applied by (L
S Aji et al., 2018)
to find the value of the protection ratio as follows (see Fig. 1):
1)
The DTT transmits power (PDTT) is set to 60 dBm
(1000 watts).
2)
The distance between the DTT transmitter and the
victim link receiver (VLR) is set to one kilometer.
3)
The white space transmitter is one kilometer
away from the VLR.
4)
The heights of the DTT transmitter and the WSD transmitter
height are set to hDTT = hWSD = 40 m.
5)
The height of the VLR antenna is 10 meters.
6)
The WSD transmit power is adjusted such that the
interference probability is less than 5%.
Furthermore,
the aforementioned scenario in the VLR implies that the DTT and WSD transmitter
field strength levels are the same. As a result, the ratio of �PDTT�
to PWSD at the transmitter is identical to the EDTT
to EWSD ratio at the receiver.
Fig.
8 shows the calculation procedures of the maximum transmitted power of a white
space transmitter. The maximum transmitted power of white space is the amount
of maximum transmit power that shows the maximum probability value of
interference to be 5% (Cheng,
Wang, Yun, & Lee, 2014; I.-K. Cho, Lee, & Park, 2013; I. Cho, Lee,
& Park, 2012; Mathe, Freitas, Farias, & Costa, 2014). In other words, with a
significance value (p) of 5%, the minimum value of the probability of
non-interference (PoI) is 95%. By using equation (1), the value of the
protection ratio is obtained and summarized in Table 4.
Figure 8
Maximum WSD transmit power on
DVB-T2 64 QAM system
Table
IV shows the protection ratio values based on the simulation result. The stated
value is rounded up from the actual value of the simulation results (ITU-R, 2016). The symbol ∆f =
{0, � 1, and � 2} represent the co-channel, the first adjacent channel, and the
second adjacent channel.
Table 4
The Protection Ratio Values Based on
Simulation
|
∆ f
|
64 QAM
|
|
0
|
25
|
|
�1
|
−28
|
|
�2
|
−28
|
B. The Protection Ratio
Values based on Field Measurement
For each
signal, the power value received by the measuring equipment is calculated based
on the measurement findings. When the DTT reception was disturbed, the
protection ratio value was calculated by subtracting the received DTT power
from the WSD received power. Table V gives a recapitulation of the measurement
findings.
Table 5
The Protection Ratio Values Based on
Field Measurement
|
No
|
White
Space Transmitter Coordinate
|
Receive
Power DTT (dBm)
|
Receive
Power WS (dBm)
|
PR
(dB)
|
|
Latitude
|
Longitude
|
|
1
|
7�48'19.28"S
|
110�23'32.74"E
|
-112,85
|
-83,57
|
29,28
|
|
2
|
7�47'10.54"S
|
110�22'37.66"E
|
-105,10
|
-76,59
|
28,51
|
For
location 2, the protection ratio measurement was 29.28 dB for sites 1 and 28.51
dB. The protection ratio was 29.05 dB when an average of the two values was
approximated. When the white space operated on the same channel as the
principal user/co-channel, the protection ratio was calculated. The measurement
results could not be acquired for the activities of neighboring channels since
the WSD GWS 3000 device had a maximum power of 20 dBm, and no interference had
been identified for the primary user. Although the point of failure for
neighboring channels had not been identified, it was demonstrated that TVWS
operations on adjacent channels had significant potential.
As
listed in Table V, the protection ratio value based on simulations is 25 dB for
WSD operations on a co-channel. As determined from field measurements, the
amount of protection ratio is 29 dB, leading to differences of 4 dB. From the
result, the simulation assumes that the FCC requirement for WSD bandwidth is 1
MHz (FCC,
2012).
When the WSD bandwidth in the field measurement is 5 MHz, the usable bandwidth
is 3 MHz based on the GWS 3000 tool requirements, as illustrated in Fig. 9. The
change in bandwidth produces a difference in the iRSS quantity at the receiver
side, resulting in a greater protection ratio. If the simulation uses the same
bandwidth as the GWS 3000 device, the maximum WSD transmitted power value is 30
dBm, according to (1). Thus, the protection ratio is 60 dBm � 30 dBm = 30 dB
for a DTT transmit power of 60 dBm. Based on these findings, a 1 dB discrepancy
is still noted between the measurement and simulation results. This is because
the simulation value of 1 dB is added as an erosion margin for the device and
other variations (Beek et al., 2012).
|
|
 |
Figure 9
White Space Emission at a maximum
power of WSD transmitter
Based
on the findings of these field measurements, it is reasonable to conclude that
the value of the protection ratio based on the Monte Carlo simulation and the
field measurements results are insignificantly different. Alternatively, the
simulation-based protection ratio value can be implemented in the field.
Moreover, the greatest value of the 5% interference can match the real field
circumstances. However, the demonstrated protection ratio is only for
co-channels. Since the GWS 3000 device has a maximum transmit power of 100 mW,
it cannot cause interference to adjacent channels. Furthermore, the number of
test points is restricted to two. In the future, more points are required to
enhance data quality and present findings that represent varied circumstances
in the field.
Conclusions
The
simulation results are compared with the field measurement results of the TVRI
Patuk service area, Jogjakarta. The outcomes showed that the WSD channel width
based on the FCC recommendations was different from the WSD channel width of
the GWS 3000 device. After adjustment, it was found that the protection ratio
value based on the simulation was 30 dB, whereas the protection ratio value
from the field measurements was 29 dB, revealing a difference of 1 dB. This
indicates that the Monte Carlo is quite close to the results of field
measurements. The government can use the results to define the protection
values. Using simulation only, the government can still obtain valid results
without field measurements. However, it is necessary to add points to enrich
the data to obtain results that can represent various conditions in the field.
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|
Copyright holder:
Lessy
Sutiyono Aji (2022)
|
|
First publication
right:
Syntax Literate: Jurnal Ilmiah
Indonesia
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This article is
licensed under:
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