ABSTRACT
This research investigated the effects of greater ground conductivity and increased
foliage on mobile networks. The wet season is known to be characterised by greater
ground conductivity and increased foliage due to the increased moisture content.
Global System for Mobile Communications (GSM) signal strength measurements of
two networks were taken during the dry season at particular points and these
measurements were repeated during the rainy season. These data were then processed
to determine the relationship between the signal strength and ground conductivity and
foliage. To ensure greater accuracy of results, two networks (Airtel and MTN) were
evaluated. Furthermore, signal strength measurements were conducted in rural areas
around Kaduna. The results obtained were compared with those of Kaduna Metropolis.
GSM signals were discovered to suffer greater losses during the rainy season due to
increased foliage and greater ground conductivity. Losses of between 5 dBm and 10
dBm were observed in rural/suburban areas while the losses observed in the
metropolis were between 0dB and 4 dBm. These losses, though not significant in
urban areas, were quite significant in the rural/suburban areas. An inverse
relationship was also established between increased foliage/greater ground
conductivity and GSM signal strength within a particular environment. Finally, the
results obtained were compared with the Wiessberger and Iternational
Telecommunication Union (ITU) models and reasonable agreement with these foliage
models was observed.
TABLE OF CONTENTS
Title Page
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgements v
Abstract vi
Table of Contents vii
List of Figures x
List of Tables xii
List of Abbreviations xiv
CHAPTER ONE – GENERAL INTRODUCTION 1
1.0 Introduction 1
1.1 Problem Definition 1
1.2 Thesis Objectives 2
1.3 Motivation 2
1.4 Scope of Work 3
1.5 Thesis Outline 3
CHAPTER TWO – LITERATURE REVIEW AND THEORETICAL
BACKGROUND 4
2.0 Introduction 4
2.1 Literature Review 4
2.2 Basic Theory of Mobile Radio Propagation 6
2.2.1 Diffraction 6
2.2.2 Reflection 7
viii
2.2.3 Scattering 7
2.3 Propagation Losses in the Mobile Environment 7
2.3.1 Free Path Loss 7
2.3.2 Foliage Loss 9
2.4 Foliage Models 9
2.4.1 Weissberger’s Model 10
2.4.2 Early ITU Vegetation Model 10
2.4.3 Updated ITU Vegetation Model 11
2.4.3.1 Terrestrial Path with One Terminal in Woodland 12
2.4.3.2 Single Vegetative Obstruction 12
CHAPTER THREE – METHODOLOGY 13
3.0 Introduction 13
3.1 Research Steps 13
3.2 Choice of Experiment Sites 14
3.2.1 Kaduna Metropolis 14
3.2.2 Suburban/Rural Areas 14
3.3 Description of the Measurement Environments 15
3.3.1 Kaduna Metropolis 15
3.3.2 Suburban/Rural Areas 15
3.4 Measurement Equipment and Parameters 17
3.5 Measurement Procedure 18
3.5.1 Wet Season Measurements 18
3.5.2 Dry Season Measurements 18
CHAPTER FOUR – DATA PRESENTATION ANALYSIS AND RESULTS 19
4.0 Introduction 19
4.1 Wet Season Measurements 19
4.2 Dry Season Measurements 23
4.3 Comparison of Wet and Dry Earth Measurements 27
4.4 Difference in Signal Strengths between Wet and Dry Earth 32
ix
4.5 Comparison of Results with Foliage Model 37
4.5.1 Comparison of Results with Weissberger’s Model 37
4.5.2 Comparison of Results with ITU Model 38
CHAPTER FIVE – CONCLUSION AND RECOMMENDATION 40
5.0 Introduction 40
5.1 Summary of Results 40
5.2 Significance of Results and Application 41
5.3 Limitations/Problems Encountered 42
5.4 Conclusion 42
5.5 Recommendation for Further Work 43
REFERENCES 44
APPENDIX A Technical Features of the Sagem OT 290 Phone 47
APPENDIX B Graphical Representations of Wet Season Measurements 49
APPENDIX C Graphical Representations of Dry Season Measurements 53
x
CHAPTER ONE
INTRODUCTION
1.0 BACKGROUND INFORMATION
Since the introduction of GSM into Nigeria in August 2001 mobile telecommunications
industry has grown tremendously. This growth made it possible for urban as well as rural
dwellers to gain access to mobile phones. However, this growth came with attendant
problems. Some of which include poor signal reception at various points, dropped calls, and
congestion. GSM service providers in Nigeria have thus been trying to evolve methods of
tackling these problems. Some of these problems are not peculiar to any specific region
whereas others are. For instance, the vegetation cover in the area where these networks are
deployed could pose specific problems to the operators and thus solutions peculiar to these
environments need be sought. Nigeria as a country has a varied vegetation which ranges
from thick vegetation in the South to the savannah grassland in the middle belt to the semidesert
or Sahel savannah regions of the extreme North.
The middle belt region of Nigeria experiences between 4 to 6 months (between April and
October) of rainy season every year. The increased earth moisture content during this period
gives rise to greater ground conductivity and increased foliage. This condition is likely to
affect GSM signal strength. For GSM operators to ensure all year round quality service
delivery, the relationship or effects of greater ground conductivity and increased foliage on
signal strength needs to be understood particularly in the specific region where such networks
are deployed.
1.1 PROBLEM DEFINITION
The optimal performance of wireless communication systems depends to a large extent on
signal strength. Various propagation losses are experienced by wireless networks within the
wireless channel. Some of these losses include: free space losses, foliage losses and losses
due to refraction and scattering. This research focuses on losses due to increased foliage and
ground conductivity.
2
1.2 THESIS OBJECTIVES
Various researches have been conducted with a view to ensuring optimization of mobile
networks. These researches focussed on traffic analysis, congestion and path loss with
distance. With the ever increasing demand for quality service delivery in the Nigerian mobile
communication industry newer approaches have to be sought to ensure network optimization.
For a more comprehensive understanding of wireless channel the effect of greater ground
conductivity and increased foliage on GSM signals in Nigeria needs to be studied. This
research will thus seek to address the following:
a. Is there a relationship between greater ground conductivity/increased foliage
and GSM signal strength?
b. Does greater ground conductivity/increased foliage have a significant effect on
GSM signal strength?
c. What is the difference in the propagation characteristics between urban and
rural networks?
d. Does seasonal variation affect mobile networks propagation characteristics?
1.3 MOTIVATION
Nigeria’s GSM industry is one of the fastest growing and largest GSM industry in Africa.
The focus of GSM operators is gradually shifting from providing coverage to providing
quality service. The euphoria of owning a phone set is gradually giving way to complaints of
dropped calls and congestion (Ireti, 2005). The extensive period of rainy season in Nigeria
and its attendant effects on signal strength is a critical factor that must be considered in
planning and ensuring quality of service by any operator.
3
1.4 SCOPE OF WORK
This research is conducted in Kaduna Metropolis and environs. This region lies in the
savannah grassland area of Nigeria. Furthermore, GSM 900 signals of two
telecommunications networks, Mobile Telecommunications Network (MTN) and Airtel, were
considered. The base station transmitting frequency of MTN is from 950 – 955 MHz , while
that of Airtel is from 955 -960 MHz (NCC, 2010). Thus this work is limited to investigating
the effects of greater ground conductivity and increased foliage on GSM 900 signals in a
typical savannah grassland terrain.
1.5 THESIS OUTLINE
This work presents the results of an investigation on the effect of seasonal variation on GSM
propagation characteristics. Chapter one gives a general introduction to the subject and
outlines the research objectives, statement of the problem and the motivation for this work. In
chapter two, a review of relevant literature is made as well as a theoretical background to the
research. In chapter three the methodology used in this work is presented while chapter four
contains the results obtained and the analysis. Interpretation of the results was also presented
in chapter four. Finally, chapter five highlights the limitations and problems encountered
during the research. It ends with conclusions and recommendations for further work.
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