=Paper=
{{Paper
|id=Vol-2544/shortpaper2
|storemode=property
|title=Spectrum Survey and Coexistence Studies in the TV, WLAN, ISM and Radar Bands for Wireless Broadband Services
|pdfUrl=https://ceur-ws.org/Vol-2544/shortpaper2.pdf
|volume=Vol-2544
|authors=Nasir Faruk,Adebowale Q. Ramon,Segun I. Popoola,Abdulkareem A. Oloyede,Lukman A Olawoyin,Nazmat T. Surajudeen-Bakinde,Abubakar Abdulkarim,Yinusa A. Adediran
|dblpUrl=https://dblp.org/rec/conf/irehi/FarukRPOOSAA18
}}
==Spectrum Survey and Coexistence Studies in the TV, WLAN, ISM and Radar Bands for Wireless Broadband Services==
https://ceur-ws.org/Vol-2544/shortpaper2.pdf
Spectrum Survey and Coexistence Studies
in the TV, WLAN, ISM and Radar Bands
for Wireless Broadband Services
Nasir Faruk, Adebowale.Q. Ramon, Segun I. Popoola, Abdulkareem. A.
Oloyede, Lukman A Olawoyin, Nazmat. T. Surajudeen-Bakinde,
Abubakar Abdulkarim and Yinusa A. Adediran
faruk.n@unilorin.edu.ng
Abstract- The proliferation of smartphones usage necessitates the increase of mobile
data traffic volumes. Thus, Mobile Network Operators (MNOs) have to expand their
network infrastructure in terms of coverage and capacity. However, the limited attributes
of the electromagnetic spectrum, endlessly, pose challenges in meeting these demands.
Recently, the International Telecommunication Union (ITU) identified TV (694-790
MHz), L-band (1.427-1.518 GHz) and lower part of C-band (3.4 -3.6 GHz) for possible
mobile broadband services. In this paper, a comprehensive spectrum survey in the
recommended bands is provided. Spectrum occupancy measurements were conducted at
the dense urban areas of University of Ilorin, Kwara state, Nigeria. Energy Detection
(ED) technique and Duty Cycle (DC) model were used for measurement evaluation
analysis. Findings from this work revealed that Radar L band is fairly occupied with duty
cycle of 17.19%. The C band is completely free and unoccupied by neither fixed satellite
nor radar systems as only about 1% of the spectrum is presumably occupied. The
occupancies in the Television (TV) and Industrial, Scientific and Medical (ISM) and
Wireless Local Area Networks (WLAN), bands are 9.54% and 15.09% respectively.
Findings show that huge amount of bandwidth is available for wireless broadband in the
2.4 GHz and C bands but not in the proposed TV and L bands.
Keywords: Spectrum Occupancy; Telecommunication Infrastructure; Radar
band; TV band; Interference Studies
1. MOTIVATION
Global traffic of the mobile data is projected to increase by 57% from 2014 to
2019 [1]. This is driven by the increased in higher acceptance of data intensive
devices such as smartphones. However, one of the major challenges that come
with the explosive growth is that users also expect seamless mobile data
connectivity, irrespective of their locations. In a progressively relaxed market,
this has indulged the MNOs to expand their network infrastructure so as to meet
customers’ loyalty and remain competitive. The limited electromagnetic
spectrum, endlessly pose serious challenges both from the regulatory and service
providers’ point of views. From the regulators’ perspectives, the key desirable
objective is ensuring flexibility in the spectrum usage and providing maximum
interference protection to the licensed users. However, there is dichotomy
between the spectrum usage and its allocation [2]. To this end, the craving for
unlimited services with frequency spectral conservation, have prompted the
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regulators with no other option than to find a sophisticated technique to
efficiently manage the spectrum resources. Unfortunately, connectivity in
question is not limited to the provision of voice communications alone but also
includes data transmission. With the recent advances in ICT, wireless
telecommunications have transformed from leisure to necessity.
Telecommunication has dominated all facets (education, health, business, etc.)
of daily human life, making it the key to attaining the Sustainable Development
Goals (SDGs). The Nigeria’s population has increased to 182 million people as
at 2016 population census with an annual growth rate of 3.5% according to the
National Population Commission (NPC) [3]. The total number of GSM
subscriptions has also exponentially increased from just over two million
registered subscribers in 2002 to about 173 million in the end of 2018. Fig 1
shows the Nigeria subscriber data from the Nigerian Communications
Commission (NCC) database [4]. The broadband penetration currently stood at
35.40% of both fixed and mobile service [4], a number considered low, aside the
prevalent digital divide. The NCC has however released 30 MHz in the 2.3 GHz
band, in the way, 2 X 70 MHz in the 2.6 GHz band in 2013 and 2016
respectively [5] [6]. This effort was to make more spectral spaces available for
broadband internet penetration. Similarly, the ITU, during the World Radio-
communication Conference (WRC-15) in 2015 [7], concluded its deliberations
that revised the international treaty and the Radio Regulations, with the
objective of making more spectral spaces available for mobile broadband
services. The WRC-15 acknowledged 694-790 MHz frequency band, some
frequency bands in the L-band (1427-1518 MHz) and the lower part of the C-
band (3.4 -3.6 GHz) for mobile broadband used [8]. However, it was clearly
mandated that the usage of these bands in the regions must not originate
interference to other services. As such, studies related to the spectrum
identification in these bands and coexistence with other services was included in
the agenda for the WRC in 2019. Member states, particularly in Region 1, were
encouraged to provide justification of using these bands. Therefore, in this
paper, we provided a comprehensive spectrum survey in the recommended 694-
790 MHz, L and C bands.
Fig 1: Nigeria Subscriber Data (Data Source, NCC: [4])
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2. THE SUB 800 MHz (694-790) FREQUENCY BAND
In the last WRC-15 meeting, a major decision was taken to enhance the capacity
in the 694-790 MHz band for mobile broadband services in ITU Region-1
(Africa, the Central Asia Middle East, and Europe,). Also, a worldwide
coordinated solution was proposed for the enactment of the digital dividend.
Decision made to assign 694-790 MHz band to mobile services and signifies
same with International Mobile Telecommunication (IMT) in ITU Region-1 was
concluded by the WRC-07 [9]. The said band was allocated to ITU Region-2
(The Americas) and Region-3 (Asia-Pacific). Protection right has been given to
aeronautical radio navigation systems as well as to the television broadcasting
that operates in this frequency band by allocating guard bands. Nevertheless,
research on interference and coexistence studies within the band is still
paramount.
3. THE ITU PROPOSAL OF RADAR BANDS
The ITU, at the WRC-15 in 2015 [10], proposed the revision of the international
treaty and Radio Regulations by allocating Radar (3.4 -3.6 GHz) which forms
the lower part of C-band and L-band (1427-1518 MHz) for mobile broadband
usage [8]. Conventionally, radar bands are used for several purposes, including
surveillance for defense and security, air traffic control, severe weather tracking,
geophysical monitoring of Earth resources from space, and automotive safety.
Standard radar types and their corresponding frequency of transmission are
provided in [11]. Radar operation on some bands is either primary or secondary.
Studies in [12][13] revealed that service such as 4G LTE produces out-of-band
(OOB) emissions from secondary sources also compete for the radar band. This
could significantly degrade radar system performance and subsequent decrease
the maximum detection range. It is therefore; very clear that secondary operation
on this band could be very challenging.
4. METHOD OF DATA COLLECTION
The set up used for the spectrum occupancy campaign comprises of an Omni
directional antenna, a Global Positioning System (GPS), the Agilent Module
N9342C spectrum analyzer with frequency range of 100 KHz to 7 GHz ad 32
GB storage device. The campaign were carried out at outdoor at the densely
populated areas of the University of Ilorin, Kwara State, Nigeria (4o38'47''E
8o27'49''N). Spectrum utilization is evaluated based on the duty cycle (DC).
Table 2 provides detailed information about the service bands that are covered in
this study. Fig 2 provides the measurement framework.
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Fig. 2. Spectrum Occupancy Measurement Set-up
Table 2: Service Bands Considered
Service Bands Frequency Bandwidth
range (MHz)
(MHz)
TV Band 694-790 96
L Band 1427-1518 91
C-band 3400 -3600 200
WLAN, ISM T2300-2500 200
The spectrum usage data collected were stored in matrix form. In order to
process the collected information, the received signal powers element were
presented in the form of P (ti, fi) (in dBm), in which fi represents the frequency
and ti the time slot. Three steps were involved in the spectrum occupancy
measurement evaluation process namely: inputting campaign data; append
detection threshold; and computation of average duty cycle. The matrix, Y, of
the datasets with the elements P (t i , f j ) defined by Equation (1).
P(t1 , f1 ) . . . P(t1 , f j )
. . . . .
(1)
Y ( n) . . . . .
. .. .. . .
P (t , f ) . . . P (ti , f j )
i 1
where y(n) is a matrix of received power at each point n. An energy detection
(ED) [14] sensing technique was used as a sensing approach. A hypothesis is
proposed such that the signal, {H1} is present, if and only if the threshold λ is
less that the power detected. It is suggested as noise If it is not greater than the
threshold, {H0}. The threshold could either be set directly or estimated via Noise
Floor (NF), which is the mean of the noise values. Despite the fact that the
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uncertainty about NF could be significant and also as a time dependent variant,
it should be updated regularly. Mean measured noise of 5dB was used as the
optimum in this study as suggested in [15-20].
5. Duty Cycle Model
The duty cycle was attained using the binary hypothesis as shown in Equation
(2), the position of frequency band at a given location over period of time, x can
be defined as an indicator function 1D(x) : P ti , f j {0, 1} defined in [20]:
0, if Pti , f j j
D ti , f j
1, if Pti , f j j
(2)
Then, the duty cycle can be obtained by Equation (3).
ti , f j
1 Nt
j (3)
N t i 1
where j represents the duty cycle and t , f is a sample of power, when
i j
P ti , f j j . j is determined for each frequency band.
6. RESULTS AND DISCUSSION
The measurement set-up in Fig. 2 was used to carry out the spectrum survey
using the service bands in Table 2. Fifty (50) sample frames were collected for
each band. Each frame has 461 time slots. The data frames were processed and
duty cycle computed. Fig 3 show the Spectrogram for Radar L and C bands;
Sub 800 MHz , WLAN and ISM bands.
In Fig 3 (a), a strong carrier was observed at 1.5 GHz frequency and other weak
carriers spread within the band. The band is fairly occupied with weak signal
between 1.42- 1.50 GHz and is 17.19% occupied (see Table 3). In Fig 3 (b)
there was no indication of strong carrier signal within the band as the received
signal strength measured varies between -101 dBm to -100 dBm. This may be
considered to be noise. The 3.4-3.6 GHz band may be completely free as only
about 1% of the spectrum is presumably occupied. It is apparently unoccupied
by neither fixed satellite nor radar systems. Therefore, about 200 MHz
bandwidth can be exploited for secondary transmission. The trace observed on
the spectrogram is a background noise since there is no detectable strong carrier
in the band. Fig 3 (c) shows the spectrogram and trace of the signals for sub 800
MHz band. The frequency under investigation spans from 694 to 790 MHz,
covering a total bandwidth of 96 MHz. The frequencies of two major services
were allocated within this band. These include the Personal Mobile Radio
(PMR) that offers trunk radio services in the frequency range of 960-1429 MHz
and the TV band 4 operating between 606-870 MHz. A total of seven carrier
signals were seen, one of which is a wideband transmission. About 15.09% of
the spectrum is occupied, freeing 81.5 MHz bandwidth. While, in Fig 4 (d)
considerable activities were noticed on the WLAN and ISM bands. Spikes of
carrier signals with varying degree of power levels were observed. About 9.54%
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of the spectrum is occupied and the activities on this band were mostly the
WLAN access points within the study location.
(a) (b)
(c) (d)
Fig 3. Spectrogram (a) Radar L band (b) Radar C band (c) Sub 800 MHz TV
band (d) WLAN and ISM band.
TABLE 3: AVERAGE DUTY CYCLE
S/N Start Stop Average
Frequency Frequency Duty Cycle
(GHz) (GHz) (%)
1 3.49 3.70 1.08
2 1.43 1.52 17.19
3 2.30 2.50 9.54
4 0.694 0.790 15.09
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7. CONCLUSION
In order to justify the availability of TV, WLAN, ISM and radar bands for
mobile broadband service deployment in Nigeria, an extensive spectrum survey
and coexistence studies were conducted in these bands to facilitate decision
making at the forthcoming WRC. Spectrum occupancy measurements were
conducted at the dense urban areas of University of Ilorin, Kwara state, Nigeria.
Availability of spectrum in each of the bands under study was detected based on
Energy Detection (ED) technique and spectrum occupancy measurement was
quantified using the duty cycle. The analysis of the measurements collected
showed that Radar L band is fairly occupied with duty cycle of 17.19%. In
contrast, C band is found to be unoccupied (only about 1% of the spectrum is
presumably occupied) by neither the fixed satellite nor the radar systems.
15.09% of the TV band is occupied while the WLAN and ISM has 9.54% of
being occupied. Therefore, a huge amount of bandwidth is available for the use
of Long Term Evolution (LTE) wireless broadband in the 2.4 GHz and C bands
but not in the TV and L bands. Hence, the spectrum campaign has proved the
feasibility of reusing these bands for the deployment of broadband internet
services in Nigeria.
ACKNOWLEDGMENT
This research was piloted under the umbrellas of the Communication and
Networking Research Group (CNRG) of the University of Ilorin, Ilorin, Nigeria.
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