gbenga-ilori ph.d. thesis
TRANSCRIPT
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DEVELOPMENT OF VHF AND UHF SPECTRUM OPTIMIZATIONFOR DIGITAL SERVICES IN SELECTED STATES OF NIGERIA
BY
GBENGA-ILORI, ABIODUN OMOWUNMI
(00/68GJ001)
A Thesis
Submitted to the Department of Electrical Engineering,University of Ilorin
In Partial Fulfillment of the RequirementsFor the Award of
Doctor of Philosophy
Degree in Electrical Engineering
2010.
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CERTIFICATION
Development of VHF and UHF Spectrum Optimization for Digital Services inSelected States of Nigeria, (Gbenga-Ilori Abiodun Omowunmi, B.Sc. Electricaland Electronics Engineering (U.I. 1997), M.Eng. Communications Engineering(FUTA 2000)).
This is to certify that this thesis has been read and approved as meeting therequirements of the Department of Electrical Engineering, University of Ilorin forthe award of Doctor of Philosophy degree in Electrical Engineering.
Professor T. S Ibiyemi DateSupervisor
Dr Y.A. Adediran DateChief Examiner
External Examiner DateProf. U.G. Danbatta
------------------------------------------ ---------------------------Internal Examiners DateDr. A.A. Ayeni
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DEDICATION
Dedicated to God Almighty for His guidance through life and for His Words thatmade me know that achievement is not just aiming but hitting my target.
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ACKNOWLEDGEMENTS
I give thanks and glory to the Almighty God for giving me the grace to start and complete this
work. I would like to also specially thank my supervisor, Professor T.S. Ibiyemi who besides
guiding me on the winding path to a Ph.D. thesis, also has provided encouragement and drive for
the completion of the work. Professor Ibiyemi’s broad knowledge of engineering is as rich and
varied as anyone I have ever known and working with him has proved to be consistently
challenging and exciting. I also owe a debt of gratitude to Dr. S.A. Aliu and Dr. A.J. Falade for
their support during the period of this research work.
Next, I would like to acknowledge friends and colleagues at the Institut fur Rundfunktechnik
(IRT), Germany for being a great source of help and inspiration during my six-month research
visit. I will like to specially thank Dr. Roland Brugger for his encouragement, advice and
friendship. I also thank Mrs. Philip for her help on all administrative matters during my stay
there.
I would like to appreciate friends and colleagues at the University of Lagos. First, I would like to
acknowledge the Dean of Engineering, Professor M.A. Salau, and the head of department,
Electrical and Electronics Engineering department, Professor F.N. Okafor, for their support to
my research work. I would especially like to mention Engr. M.A.K. Adelabu, Engr. (Mrs.) A.
Abdulsalam, Engr. Adeola Balogun, Engr. (Mrs.) F. Olobaniyi, Engr. Oluseyi and Engr.
Adetona. Other friends worth mentioning are Engr. Segun Afolabi and Engr. Obiseye Obiyemi. I
consider all of you good friends.
Writing a thesis is a demanding task and this thesis could not have been written without the
support and understanding of my family. I especially want to appreciate my husband, Gbenga,
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for believing in me. I do not think I would have been able to complete this work without your
support. You are really the best. I also want to express my love and appreciation to my children:
Ibukunoluwa, Oreoluwa, and Boluwatife for being patient and understanding, especially when
the research work led to a temporary separation from them. My parents, Chief and Mrs. J. Ola
Idowu, have also been wonderful throughout the period of this research. I hope you all know
how much I value your support and I thank you for it.
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ABSTRACT
The key objective of this research is to address the problem of optimal use of the VHF and UHFspectrum in order to accommodate new digital communication services in Nigeria. The use ofVHF and UHF frequency bands for communication services is highly attractive for digitalcommunication services. However, the challenge is the less than optimal use of these frequencybands by analogue television. This inefficiency has led to the development of digital televisiontechnology. With the aid of the compression technique employed in digital broadcasting, morethan one television programme can be transmitted using only one analogue television channel.
The objective was achieved by first determining the present usage of the VHF and UHFspectrum by analogue television broadcasting services in Nigeria by using an appropriatedeterministic propagation model known as the IRT propagation model. This propagation modelhas been tested suitable for the Nigerian environment by comparing field strength from threedifferent propagation models with those obtained from a field strength survey conducted atdifferent locations in some States in Nigeria. The results from the comparison showed that theIRT propagation model produced field strength closest to measured values within the selectedstates. The states selected are the Yoruba-speaking states comprising of the south-western statesas well as Kogi and Kwara states. The choice of the states is for network planning feasibilitysince local content is important in broadcasting and all these Yoruba-speaking viewers can be puton the same digital multiplex.
The IRT model was later used to determine the present analogue television coverage and futuredigital television coverage in the selected states. The coverage result was used to assess the levelof co-existence of present analogue and future digital television during simulcast period and alsoto determine the digital television coverage possible after switch-off of analogue television.Results show that digital television coverage of 62% is possible for the selected states during thesimulcast period. After switch-off of analogue television, digital television was predicted toachieve up to 95.3% coverage. The result of the digital television coverage was used to estimatespectrum use by future digital television services by determining the number of programmes thatcould be accommodated in a multiplex. This was used to estimate the spectrum utilizationefficiency. Results show that a total VHF and UHF spectrum saving of 74.8% could be achievedin the selected states after transition to digital. This means that more spectrum can be madeavailable for new digital services. The analysis of the data used in this work was done at theInstitut fur Rundfunktechnik (IRT), Germany. The outcome of this research has produced fourarticles published in International Journals and Conference Proceedings.
The research concludes that the spectrum released from the transition from analogue to digitaltelevision, digital dividend, would meet the growing demand for the VHF and UHF spectrum inNigeria. Recommendations with regards to the use of digital dividend are made in a way thatallows the country bridge the present digital divide and help improve the social and economicneeds of the Nigerian citizens.
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TABLE OF CONTENTS
TITLE PAGE i
CERTIFICATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRACT vi
TABLE OF CONTENT vii
LIST OF FIGURES xii
LIST OF TABLES xv
GLOSSARY OF TERMS xvi
CHAPTER 1: INTRODUCTION 1
1.1 Background to Study 1
1.2 Research Problem 4
1.3 Research Objectives 6
1.4 Justification for the Research 7
1.5 Outline of the Report 8
1.6 Research Scope and Justification 9
1.7 Operational Definition of Terms 10
1.8 Summary 11
CHAPTER 2: RADIO PROPAGATION PREDICTIONS 12
2.1 Introduction 12
2.2 Radio Wave Propagation in Free Space 12
2.3 Radio Wave Propagation in the VHF and UHF Bands 14
2.3.1 Reflection 14
2.3.2 Diffraction 15
2.3.2.1 Multiple Diffraction Losses 19
2.3.2.2 Rounded Obstacle Losses 21
2.3.3 Scattering 22
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2.3.4 Atmospheric Attenuation 24
2.4 Propagation Models for Irregular Terrain 24
2.4.1 Semi-Empirical Models 25
2.4.1.1 Okumura Model 26
2.4.1.2 Hata Model 27
2.4.1.3 ITU-R/P Recommendations 28
2.4.2 Deterministic Models 29
2.4.2.1 Longley-Rice Model 29
2.4.2.2 TIREM Model 30
2.5 GIS in Radio Propagation Studies 30
2.5.1 Data Format for GIS 31
2.5.2 Geographic Data Sources 32
2.6 Chapter Summary 32
CHAPTER 3: COMPARISON OF FIELD STRENGTH MEASUREMENTS AND
PREDICTION MODELS 33
3.1 Introduction 33
3.2 Measurement Program 33
3.2.1 Measurement Experiment Setup 35
3.2.2 Measurement Procedure 37
3.3 Prediction Models and Methods 38
3.3.1 ITU-R P.1546(3) 40
3.3.2 IRT Prediction Method 43
3.3.3 Modified ITM Method 45
3.3.4 FRANSY 48
3.3.5 Data 49
3.3.5.1 Terrain Data 49
3.3.5.2 Land Cover Data 50
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3.3.5.3 GIS Data 51
3.3.6 Field Strength Prediction Result 53
3.4 Comparison of Measured and Predicted Field Strength 53
3.5 Summary 77
CHAPTER 4: TELEVISION COVERAGE PLANNING 78
4.1 Introduction 78
4.2 Television Coverage Analysis 79
4.3 Analogue Television Coverage in Selected States 83
4.3.1 Analogue Television Coverage Results 84
4.4 Predicted Digital Television Coverage in Selected States 87
4.4.1 Assumptions and Proposals made in Digital Television Network planning 88
4.4.2 Digital Television Coverage during the Simulcast Period 90
4.4.2.1 Digital Television (Simulcast) Results 92
4.4.3 Digital Television Coverage after Analogue Television Switch-off 93
4.4.3.1 Digital Television (Switch-Off) Results 95
4.5 Summary 96
CHAPTER 5: ESTIMATION OF DIGITAL DIVIDEND 97
5.1 Introduction 97
5.2 Television Spectrum Efficiency 97
5.3 Current Analogue Television Spectrum Use in Nigeria 99
5.3.1 Analogue Television Spectrum Utilization Efficiency 101
5.4 Predicted Digital Television Spectrum Utilization Efficiency 102
5.5 Possible Future Spectrum Savings in Nigeria 103
5.5.1 Improving Digital Television Spectrum Efficiency 105
5.6 Estimating Future Spectrum Savings 107
5.7 Summary 111
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CHAPTER 6:USE OF DIGITAL DIVIDEND 113
6.1 Introduction 113
6.2 Potential Services for the Use of Digital Dividend 114
6.3 Technical Preconditions for the Use of Released Spectrum 117
6.4 Approaches for Analyzing Areas of Application 118
6.4.1 Economic Evaluation 118
6.4.1.1 More SDTV Programmes 118
6.4.1.2 HDTV Programmes 118
6.4.1.3 Mobile Television 119
6.4.1.4 Fixed Wireless Access (FWA) for Fixed Reception 119
6.4.1.5 Mobile Broadband and Telephony 119
6.4.1.6 Summary of Revenue Potential 120
6.4.2 Social Evaluation 120
6.4.2.1 Education 121
6.4.2.2 Democracy 122
6.4.2.3 Promotion of Culture 122
6.4.2.4 Belonging to a Community 123
6.4.2.5 Access and Inclusion 123
6.4.2.6 Quality of Life 124
6.4.3 Summary of Social Evaluation 124
6.5 Proposed VHF and UHF Digital Dividend Spectrum Use 125
6.6 Summary 126
CHAPTER 7: CONCLUSION AND RECOMMENDATIONS 128
7.1 Conclusion 128
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7.2 Project Outcome 129
7.3 Recommendations 130
7.3.1. Recommendations to Government and Policy Makers 131
Appendix A: Transmitter Parameters from Nigerian Broadcasting Commission 133
Appendix B: Standard Deviation in Excel 135
Appendix C: GE 06 Data (Analogue and Digital Television) 137
Appendix D: Publications 152
References 202
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LIST OF FIGURES
Figure 1.1: Radio Frequency Spectrum 1
Figure 2.1 Plane-Earth Reference Model 14
Figure 2.2: Fresnel Zone 16
Figure 2.3 (a): Diffraction loss with positive h 17
Figure 2.3 (b): Diffraction loss with negative h 17
Figure 2.4: Bullington – Multiple Knife-edge approximation 19
Figure 2.5: Epstein-Peterson – Multiple Knife-Edge 20
Figure 2.6: Deygout - Multiple Knife-Edge Approximation 21
Figure 2.7: Diffraction by a rounded obstacle 21
Figure 2.8: Effect of vegetation 23
Figure 3.1 Locations of Field Strength Measurements 34
Figure 3.2 Actual Television Field Strength Measurement setup 35
Figure 3.3 Block Diagram for Measurement Experiment set-up 38
Figure 3.4: Deygout’s Construction 44
Figure 3.5: Modified Deygout Construction 44
Figure 3.6: Terrain Profile Separated by ∆ 47
Figure 3.7: Digitization Process 52
Figure 3.8: UBS 56
Figure 3.9: SILVERBIRD 56
Figure 3.10: NTA Channel 10 Lagos 56
Figure 3.11: NTA Channel 5 Lagos 57
Figure 3.12: MITV 57
Figure 3.13: MINAJ 57
Figure 3.14: LTV 58
Figure 3.15: Galaxy 58
Figure 3.16: DBN 58
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Figure 3.17: Channels Television 59
Figure 3.18: AIT 59
Figure 3.19: Kwara State Television 59
Figure 3.20: Kwara State Television – Ilorin city and environs 60
Figure 3.21: NTA Patigi 60
Figure 3.22: NTA Ilorin 60
Figure 3.23: NTA Ilorin – Ilorin City and Environs 61
Figure 3.24: NTA Oshogbo 61
Figure 3.25: NTA Oshogbo - Oshogbo and environs 61
Figure 3.26: OSBC 62
Figure 3.27: OSBC – Oshogbo and environs 62
Figure 3.28: NTA Ile-Ife 62
Figure 3.29: NTA Akure 63
Figure 3.30: NTA Akure – Akure City 63
Figure 3.31: NTA Okitipupa 63
Figure 3.32: OSRC 64
Figure 3.33: OSRC – Akure 64
Figure 3.34: NTA Channel 12 Abeokuta 64
Figure 3.35: NTA Channel 12 Abeokuta – Abeokuta 65
Figure 3.36: NTA Ijebu-Ode 65
Figure 3.37: NTA Imeko 65
Figure 3.38: OGTV 66
Figure 3.39: OGTV – Abeokuta 66
Figure 3.40: BCOS 66
Figure 3.41: Galaxy, Ibadan 67
Figure 3.42: NTA Ibadan 67
Figure 3.43: NTA Ogbomosho 67
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Figure 3.44: NTA Ogbomosho – Ogbomosho 68
Figure 3.45: NTA Oyo 68
Figure 3.46: NTA Saki 68
Figure 3.47: Broadcasting Service of Ekiti 69
Figure 3.48: Broadcasting Service of Ekiti – Ado-Ekiti 69
Figure 3.49: NTA Ado-Ekiti 69
Figure 3.50: NTA Ado-Ekiti – Ado-Ekiti city 70
Figure 3.51: KSTV 70
Figure 3.52: KSTV – Lokoja 70
Figure 3.53: NTA Kaaba 71
Figure 3.54: NTA Lokoja 71
Figure 3.55: NTA Lokoja – Lokoja city 71
Figure 3.56: Prediction Errors for all the considered states 72
Figure 3.57: Prediction Errors for the Urban/Suburban Areas 73
Figure 3.58: Prediction Errors for the Rural Areas 74
Figure 3.59: Clutter Effect Lagos-ROUTE 1 76
Figure 3.60: Clutter Effect Lagos -ROUTE 2 76
Figure 3.61: Clutter Effect Oshogbo-ROUTE 1 76
Figure 3.62: Clutter Effect Oshogbo -ROUTE 2 77
Figure 4.1: Analogue Television Interference-Limited Coverage .
Map for Selected States 85
Figure 4.2: Digital Television (Simulcast) Interference-Limited Coverage Map
for Selected States 91
Figure 4.3: Digital Television (Switch-off) Interference-Limited Coverage Map
for Selected States 94
Figure 5.1: Present number of analogue terrestrial television stations in Nigeria 100
Figure 5.2: Gain of statistical multiplexing 107
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LIST OF TABLES
Table 3.1: Comparison of Measured and Predicted Field Strength 54
Table 3.2: Result for Urban and Suburban Areas 73
Table 3.3: Result for Rural Areas 74
Table 4.1: Minimum Field Strength for Analogue Television Planning 80
Table 4.2: Minimum Field Strength for Digital Television Planning 81
Table 4.3: Result of Spectrum Used by Each State with Analogue Television 86
Table 4.4: Digital Television Protection Ratio 87
Table 4.5: Result of Spectrum Used by Each State with Digital Television (Simulcast) 92
Table 4.6: Result of Spectrum Used by Each State with Digital Television (Switch-Off) 95
Table 5.1: Analogue Television Spectrum Utilization Efficiency 101
Table 5.2: Predicted Digital Television Spectrum Utilization Efficiency 102
Table 5.3: Number of Programs with Fixed Reception in the Present 109
Table 5.4: Number of Programs with Fixed Reception in the future 110
Table 6.1: Television Spectrum in Selected States 114
Table 6.2: Compatibility Level of Services Competing for Digital Dividend 117
Table 6.3: Revenue Potential 120
Table 6.4: Summary of Social Evaluation 125
Table 6.5: Proposed Use of Digital Dividend 126
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GLOSSARY OF TERMS
ATV Analogue Television
BBC British Broadcasting Corporation
DEM Digital Elevation Model
DTV Digital Television
DVB-H Digital Video Broadcasting – Handheld
DVB-T Digital Video Broadcasting – Terrestrial
FWA Fixed Wireless Access
GE 06 Geneva 2006
GIS Geographic Information System
GPRS General Packet Radio Service
GPS Global Positioning System
GSM Global System for Mobile Communications
HDTV High Definition Television
ICT Information Communication Technology
IRT Institut für Rundfunktechnik
ITM Irregular Terrain Model
ITU-R International Telecommunication Union – Radio communication Sector
MBMS Multimedia Broadcast Multicast Service
MFN Multi Frequency Network
MPEG Moving Picture Expert Group
NTA Nigerian Television Authority
PR Protection Ratio
QAM Quadrature Amplitude Modulation
SAR Synthetic Aperture Radar
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SDTV Standard Definition Television
SFN Single Frequency Network
SRTM Shuttle Radar Topography Mission
TIREM Terrain Integrated Rough Earth Model
UMTS Universal Mobile Telecommunication System
USB Universal Serial Bus
WiMAX Worldwide Interoperability for Microwave Access
3G Third Generations
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CHAPTER 1
INTRODUCTION
1.1 BACKGROUND TO THE STUDY
The desire to have reliable means of communication anywhere and at anytime has led to new
innovations in digital communication technologies. Some of these new digital technologies
include mobile television and enhanced mobile phone services, digital television, wireless
broadband, security and surveillance, environmental monitoring, and distance learning. All of
these require the use of part of the electromagnetic spectrum for communication purposes.
These new developments in digital communication technologies have increased the pressure
on the part of electromagnetic spectrum known as radio frequency spectrum.
The electromagnetic spectrum is the range of all possible frequencies of electromagnetic
radiation. The electromagnetic spectrum is divided into sections based on wavelength and it
extends from frequencies used for electric power at the long wavelength to frequencies for
gamma radiation at the short wavelength, [1]. The frequency ranging from 3 Hz to 300 GHz
is generally referred to as the radio frequency spectrum, [2]. This part of the spectrum is
further divided into frequency bands as shown in figure 1.1 below.
VLF LF MF HF VHF UHF SHF EHF
3 30 300 3 30 300 3 30
300
kHz MHz GHz
Figure 1.1: Radio Frequency Spectrum.
2
Most communication technologies use the radio spectrum however, the Ultra High Frequency
(UHF) is particularly attractive to newer technologies because lower frequencies are very
prone to interference and higher frequencies have problems of limited signal range because of
the difficulty signals have in penetrating buildings. For these reasons, the UHF band is highly
competitive. The radio spectrum is a natural resource which can be reused and can only
accommodate a limited number of simultaneous users. This competition can lead to
congestion of the band and this can result in harmful interference that can degrade signals or
interrupt communication services if the spectrum is left unplanned.
Before the existence of the new digital services, the Very High Frequency (VHF) and Ultra
High Frequency (UHF) bands were primarily used for terrestrial analogue television
broadcasting services. The agreed bandwidth of an analogue television channel is 8MHz in
the VHF and UHF frequency bands III, IV and V. There have been questions on how much
spectrum is actually needed by television broadcasting services and how much has been
allocated in the past when there was no competition for the UHF spectrum. Some spectrum
managers are of the opinion that analogue television services has been allocated more
spectrum than needed and that with careful optimization and re-planning of the frequency
bands, some spectrum can be released for new services, [4].
Asides the issue of spectrum resource allocation, analogue television’s use of the spectrum is
inefficient compared to newer terrestrial digital television technology. Digital television is
the sending and receiving of moving images and sound by discrete (digital) signals, in
contrast to the analogue signals used by analogue television, [5]. Due to compression
technology employed in digital television broadcasting, signals can be compressed to allow
more information to be aired using less spectrum space compared to analogue television. The
use of less spectrum means that some spectrum can be freed up and made available to new
digital services.
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The efficient use of the spectrum by digital television has led to the worldwide campaign on
transition from analogue to digital television broadcasting television by spectrum regulators.
In Nigeria, a set date of 17th June, 2012 has been given by the Federal Government for the
transition to digital television, [6]. The transition to digital in Nigeria, as in most countries,
would not be a sudden switch off of analogue television but there would likely be a period of
simulcast when analogue and new digital television services would co-exist. Many countries
that have commenced digital television broadcasting services started with a period of
simulcast transmission of both types of signals. The length of the simulcast period is
dependent on a number of factors. Cost, to both broadcasters and viewers, is a major
determinant of the length of the simulcast period. In order to receive terrestrial digital
television, viewers need either a digital television set or convert signals. The cost of digital
television set or the set-up box will not encourage entire and immediate switch over to digital
television especially for a developing country like Nigeria.
For the reasons above, there is the need to optimize the use of spectrum by present analogue
television services and estimate to the amount of spectrum that can be released for new
digital services during simulcast transmission of both signals and also after switchover to
digital. The freed-up spectrum is referred to as the ‘digital dividend’ and it is defined as the
spectrum over and above the frequencies which are required to support existing analogue
broadcasting services in a fully digital environment, [7].
The size of digital dividend has been estimated in some developed countries, [7], and there is
also the need to assess or predict the size of this future digital dividend in Nigeria too. This
will help administrators and regulators to use and manage the released spectrum efficiently
since there are many competing services for its use. Also, there is need to estimating the size
of this future digital dividend ahead of time because if the VHF and UHF bands are not
available on time for these new digital services, other spectrum would have to be used and
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changing spectrum to these bands at a later date will introduce extra cost and reduce overall
cost benefit from the transition, [8]. For example, benefits from the release of digital dividend
in 2012 is estimated to add $325 million to New Zealand economy but if delayed till 2015
will add only $230 million to the economy, [9].
A major importance of the digital dividend for developing countries like Nigeria is that it will
help bridge the existing digital divide. This divide can be defined as the differences due to
geography, race, economic status, gender and physical ability in the access to information
through Internet, and other information technologies and services, as well as in the skills
knowledge and abilities to use them, [10]. Services lining up for the use of the freed-up
spectrum includes; mobile television, more digital television services, High Definition
Television (HDTV), broadband wireless applications, emergency and public safety services,
and communications technologies for medical professionals and educational institutions.
1.2 RESEARCH PROBLEM
The problem addressed in this thesis is to determine how the VHF and UHF spectrum can be
optimally used in order to accommodate anticipated new digital communication services in
Nigeria. The thesis focuses on the transition from analogue television to digital television as a
way of optimizing the use of the television spectrum in the VHF and UHF frequency bands.
It is believed that since digital television will use less spectrum space than analogue
television broadcasting services for equivalent programme content, some spectrum space can
be freed-up for new digital services after the transition. The work done in this thesis is
restricted to some selected states in Nigeria. The states selected are all the south-western
states as well as Kogi and Kwara states. Our objective here is network planning for these
selected states with the possibility of putting all these states on the same digital multiplex.
In order to solve this problem, the following research questions have to be answered;
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(i) What is the present usage of the VHF and UHF spectrum by current analogue
television services in the selected states of Nigeria?
(ii) What propagation model is suitable for the determination of broadcast coverage in
Nigeria?
(iii) How can the present VHF and UHF spectrum use by analogue television in the
selected states be optimized?
(iv)What level of co-existence is possible between analogue television and digital
television during the simulcast period?
(v) What amount of VHF and UHF spectrum can be freed-up in the selected states due
to transition from analogue to digital television?
(vi) What form of VHF and UHF re-planning is needed to accommodate new digital
services in the selected states?
In summary, at the end of this research work, the following contributions would be made.
Firstly, the present level of utilization of the VHF and UHF spectrum by the analogue
television services would be determined for the selected states of Nigeria. This would help to
assess any inefficiency in the usage of these spectrum bands by analogue television services.
Secondly, the level of co-existence between analogue television and future digital television
during the simulcast period would be determined for these states. This is because during the
simulcast period, analogue television services are susceptible to interference from digital
television services. Thirdly, the research work predicts the coverage and spectrum use of
future digital television services in the selected states using an appropriate propagation
model. The research work will also determines the amount of spectrum that can be freed-up
for new digital services in the VHF and UHF frequency bands in these states of Nigeria.
Finally, the research work will evaluate some of the digital services competing for the use of
this digital dividend and place priorities on some of them depending on factors bothering on
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technical issues, economic benefits to the nation and also social benefits to the citizens of the
country.
1.3 RESEARCH OBJECTIVES
The purpose of this thesis is to optimise the use of the present analogue television spectrum
within the VHF and UHF frequency spectrum for the accommodation of new digital services
in some selected states of Nigeria by:
a) Determining present usage of the VHF/UHF spectrum by analogue television services
using an appropriate propagation model;
b) Determining the level of co-existence of present Analogue television and future Digital
television during the simulcast period;
c) Forecasting the coverage and spectrum use of future Digital television services using an
appropriate propagation model;
d) Determining the spectrum that can be freed up (digital dividend) for new applications in
the VHF and UHF frequency bands
e) Proposing a plan for the use of the freed-up spectrum in a way that allows the co-existence
of digital services and benefit the citizens of Nigeria.
1.4 JUSTIFICATION FOR THE RESEARCH
The VHF and UHF frequency spectrum in Nigeria has been primarily used by analogue
broadcast services before the advent of digital technologies. The VHF band is between 30 –
300MHz and the analogue television broadcast services makes use of band III within the
VHF band which is between 174 – 230MHz. The UHF band is between 300MHz – 3GHz and
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the analogue television broadcast services makes use of band IV and V which is between 470
– 960MHz. [11].
The VHF and especially the UHF bands are highly attractive to new digital services because
lower frequencies are affected more by atmospheric noise and interference from electrical
equipment. Higher frequencies are also affected more by attenuation. However, in order to
encourage these new technological innovations and development, suitable spectrum must be
made available.
It is a known fact that the transition from analogue television to digital television would mean
the release of a substantial quantity of the present analogue television spectrum in the VHF
and UHF frequency bands. However, there is the need to assess the exact amount of spectrum
that can be released through this transition in Nigeria. This is needed to be able to investigate
the various kinds of areas of use for this spectrum. For technical reasons, certain systems are
able to co-exist a lot better than others with planned digital television networks, [12]. It is
therefore important to identify services that can co-exist with digital television services and
examine how the freed-up spectrum can be used by these services.
The freed-up spectrum can also be translated into monetary terms. Unfortunately, the cost
benefit is reduced with the delay in time. If these new digital services are temporarily
assigned to other frequency bands, there would be cost incurred in relocating to the freed-up
television spectrum later and so the overall cost benefit is reduced. With the transition date
from analogue to digital television in Nigeria set for 2012, there would be the need to predict
the amount of freed-up spectrum and plan for its use ahead of time in order to get the most
benefit in terms of cost.
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The provision of appropriate spectrum to accommodate these new digital services is
especially of importance to Nigeria, and Africa as a whole. This is because it will help bridge
the digital divide and more people can have access to these new technologies.
1.5 OUTLINE OF THE REPORT
This section gives a short introduction of each of the chapters in the thesis.
In chapter 2, a survey of the literature in the area of radio wave propagation models for
broadcast services, field strength and coverage prediction methods for broadcast services has
been done. Classification of propagation models into two main classes; semi-empirical and
deterministic models was also done. A brief overview of geographic data formats and sources
has also been given because of their usefulness in computations done in deterministic models.
In chapter 3, the methodologies used in this thesis for the television field strength survey
conducted are discussed. The method of data collection is also discussed. This chapter also
compares the measured television field strength with predicted television field strength using
three different propagation models based on both semi-empirical and deterministic models.
The propagation models are the ITU-R 1546(3), modified ITM method, and IRT method. The
purpose of the comparison is to determine the model that yields the acceptable closest to
measurements taken in Nigeria. This will ensure that an accurate model is used for the field
strength and coverage prediction for both analogue and television broadcast services within
the country. Results from the comparison shows that the IRT model is closest to field strength
from the survey.
Chapter 4 discusses method of television coverage prediction used. In this section, analogue
television coverage prediction results from our simulations are presented. The simulations
discussed in this chapter also predict future digital coverage in the selected states for both
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simulcast and switch-off stages. In chapter 5, the method used in assessing possible future
freed-up spectrum from the television spectrum in the VHF and UHF bands are discussed.
The chapter estimates the amount of spectrum that can possibly be released for new digital
services in the selected states of Nigeria.
Chapter 6 gives a proposal on the possible use of the television freed-up spectrum. It
highlights some digital services competing for the freed-up spectrum and suggests that four
of these services should be given higher considerations for the use of this digital dividend.
This decision is based on three considerations; technical, economic benefit and social benefit.
Lastly chapter 7 presents a summary of the work done. It also gives a conclusion as well as
suggestions for future work.
1.6 RESEARCH SCOPE AND JUSTIFICATION
The VHF and UHF spectrum optimization work done in this thesis is limited to seven states
within Nigeria. The states are Lagos, Ogun, Oyo, Osun, Ondo, Ekiti, Kogi, and Kwara. The
reasons for the choice of states in this thesis are as follows;
- Firstly, the seven states speak the same language; Yoruba. It is therefore easier to put
them on the same network because the local content can be same within the network.
Local content is important in broadcast network planning. About 60% of Nigerians
are illiterate, [13], and therefore rely on information communicated in their local
languages.
- Secondly, the transition to digital television would likely be in stages in Nigeria as
done in most countries that have implemented digital television. The work assumes
that the south-west region of the country has a higher possibility of starting digital
television upon commencement because of the number of analogue television
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channels present in this region. Lagos state alone has 11.6% of the total television
stations in the country.
- Thirdly, due to the density of the analogue television network in the selected states, it
is believed that the states will yield the most of television spectrum in the VHF and
UHF bands for new digital services in Nigeria.
- Fourthly, the first analogue television broadcasting in Nigeria started in 1957 in the
then Western region now known as South West of Nigeria.
1.7 OPERATIONAL DEFINITION OF TERMS
1. Simulcast period: This is the period of simultaneous transmission of the same
television program in both an analogue and a digital version using two different
channels or frequencies
2. Switch-off phase: At the end of the digital television transition period, analogue
transmission will cease and current analog channels will be used solely for digital
television. This phase is referred to as the switch-off phase.
3. Transition: Conversion from analogue television broadcasting to digital television
broadcasting.
4. Co-existence: The sharing of the same spectrum bands by communications services
without the risks of harmful interference.
5. Local content: Broadcast of television programmes that reflect a sense of local or
national identity, character and cultural diversity.
1.8 SUMMARY
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This chapter laid foundations for the report. It introduced the research problem and issues.
Thereafter, the research was justified, the limitations were given, the report was outlined and
definitions were presented. On these foundations, the report can proceed with a detailed
description of the research.