ABSTRACT
In this thesis, electromagnetic (EM) wave measurements at microwave frequency (10.7 GHz)
were conducted in a foliage environment under the influence of artificially created wind and rain
in order to investigate their combined effects on a short-range foliage radio-wave propagation
channel. The obtained data was normalized to its mean to extract the temporal fading
components due to the created weather-induced variations. A well-developed software program
(by Mathwave Technologies) called “EasyFit 5.5 professional” was then used to characterize and
model these variations through the commonly known probability distribution functions
associated with radio wave propagation channels. After successful modeling and
characterization, the temporal fading components were found to be Rician distributed, and the
Rician K-factor decreases as the strength of wind or rain increases. This reduction in the K-factor
indicates an increase in the variability of the channel when wind speed or rain intensity increases.
TABLE OF CONTENTS
TITLE PAGE………………………………………………………………………………………i
DECLARATION………………………………………………………………………………….ii
CERTIFICATION………………………………………………………………………………..iii
DEDICATION……………………………………………………………………………………iv
ACKNOWLEDGEMENTS……………………………………………………………………….v
TABLE OF CONTENTS………………………………………………………………………..vii
LIST OF FIGURES………………………………………………………………………………xi
LIST OF TABLES………………………………………………………………………………xiii
LIST OF SYMBOLS…………………………………………………………………………….xv
LIST OF ABBREVIATIONS………………………………………………………………….xvii
ABSTRACT…………………………………………………………………………………..xviii
CHAPTER ONE: INTRODUCTION
1.1 Background Information………………………………………………………………………1
1.2 Aim and Objectives……………………………………………………………………………2
1.3 Scope of the study …………………………………………………………………………….3
1.4 Motivation and Significance of the Study…………………………………………………….3
1.5 Methodology…………………………………………………………………………………4
1.6 Thesis outline……. ………………………………………………………………………….5
CHAPTER TWO: LITERATURE REVIEW AND THEORETICAL BACKGROUND
2.1 Introduction……………………………………………………………………………………6
2.2 Literature Review ……………………………………………………………………………..6
2.3 Comparison of the Literature in Relation to the thesis ……………………………………….7
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2.4 Theory of Attenuation due to Vegetation (foliage environment) ……………………………..8
2.5 Dynamic Effects …………………………………………………………………………….11
2.6 Attenuations due to rain ………………………………………………………………………13
2.6.1 Rain scatter…………………………………………………………………………………15
2.6.2 Why Rain Scatters Radio waves……………………………………………………………15
2.6.3 Essential Features of Rain Scatter………………………………………………………….16
CHAPTER THREE: METHODOLOGY
3.1 Introduction…………………………………………………………………………………..18
3.2 Experiment site………………………………………………………………………………18
3.3 Creation of the artificial rain…………………………………………………………………18
3.4 Creation of the artificial wind………………………………………………………………..21
3.5 Representation of the weather conditions (rain and wind) of Katsina metropolis……………25
3.6 EM wave measurement in the foliage channel under the influence of wind and rain……….25
3.6.1 EM wave measurement under ‘no rain and no wind’ condition……………………………26
3.6.2 EM wave measurement under ‘no rain and slight wind’ condition………………………..28
3.6.3 EM wave measurement under ‘no rain and strong wind’ condition………………………..30
3.6.4 EM wave measurement under ‘light rain and no wind’ condition………………………….31
3.6.5 EM wave measurement under ‘light rain and slight wind’ condition………………………33
3.6.6 EM wave measurement under ‘light rain and strong wind condition………………………34
3.6.7 EM wave measurement under ‘heavy rain and no wind’ condition………………………..36
3.6.8 EM wave measurement under ‘heavy rain and slight wind’ condition……………………37
3.6.9 EM wave measurement under ‘heavy rain and strong wind’ condition……………………39
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CHAPTER FOUR: RESULTS ANALYSIS
4.1 Introduction…………………………………………………………………………………..41
4.2 Normal distribution…………………………………………………………………………..41
4.3 Rician distribution……………………………………………………………………………43
4.4 Rayleigh distribution…………………………………………………………………………44
4.5 Nakagami distribution……………………………………………………………………….45
4.6 Introduction to “EasyFit 5.5”…………………………………………………………………46
4.6.1 Key Features……………………………………………………………………………….46
4.7 Additional Power attenuation imposed by different weather phenomena…………….……..51
4.8 Modeling and characterization of the temporal variations…………………………………..49
4.9 Results analysis of different weather phenomena……………………………………………51
4.10 Characterization of the temporal variations………………….……………………………..61
CHAPTER FIVE: SUMMARY, CONCLUSION AND RECOMMENDATIONS
5.1Introduction……………………………………………………………………………………63
5.2 Summary …………………………………………………………………………………….63
5.3 Conclusion …………………………………………………………………………………..64
5.4 Limitations……………………………………………………………………………………65
5.5 Recommendations for further work…………………….……………………………………65
Reference………………………………………………………………………………………..67
Appendix A ………………………………………………………………………………………69
Appendix B………………………………………………………………………………………72
Appendix C………………………………………………………………………………………73
Appendix D………………………………………………………………………………………74
CHAPTER ONE
INTRODUCTION
1.1 Background Information
A foliage radio-wave propagation channel refers to the space between transmitter and receiver
embedded with trees or shrubs which may or may not attenuate the propagating waves,
depending on many factors such as water content and size of tree leaves, tree trunks diameters,
frequency of the waves etc. While microwave propagation refers to the technology of
transmitting information or power by the use of radio waves whose wavelengths are
conveniently measured in small numbers of centimeters. This part of radio spectrum ranges
across frequency of roughly 1.0 GHz to 30 GHz. This corresponds to 30.0cm to 1.0cm (Natasha,
2011).
Near-ground foliage radio-wave propagations are of interest for the emerging military
applications, such as battle field sensor networks and for wireless communication between
dismounted soldiers. In order to guarantee link availability and provide targeted quality-ofservice
to all the soldiers concerned, a thorough understanding of the temporal variations in the
wireless channel is essential. Besides that, knowledge concerning channel time characteristics is
also required to design effective fade mitigation schemes (Joshi, et al, 2005).
Wind/rain-induced tree movement is one of the main factors which contribute to temporal
variations in foliated fixed wireless links (Chua, et al, 2010). The influence of this factor on the
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variability of a short-range, short-height foliage radio-wave propagation channel (in the Savanna
region of Northern Nigeria) is investigated and presented in the following chapters of this thesis.
1.2 Aim and Objectives of the Thesis Work
The aim of this thesis work is to determine the additional power attenuations, statistically model
and characterize the temporal variations caused by wind and rain on a short-range, short-height
foliage radio-wave propagation channel.
The objectives of this investigation are as follows:
-To create the required rain (artificially).
-To determine the relationship between rain intensity and rotations of the stop cock of water
sprinkler (i.e. to calibrate the valve or faucet which controls the rate of water flow and hence the
rain intensity).
-To create the required wind (artificially).
-To determine the relationship between wind speeds and currents into the fan (i.e. to calibrate the
current transformer which controls the current flow into the fan and hence the wind speed).
-To group each weather condition into three and combine them to form nine combinations so that
the resulting weather model represents that of Katsina metropolis where the investigation was
conducted.
-To apply the created weather conditions (at different ranges of rain intensities and wind speeds)
on the short-height foliage environment in which the microwave transmitter and receiver are
situated.
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-To carry out EM wave measurements in the foliage channel under the influence of these applied
weather conditions.
-Finally, to carry out statistical analysis of the results.
1.3 Scope of the Study
It is viable to make theoretical computations of temporal changes imposed on the channel due to
the effects of rain and wind. Unfortunately, there is still no mathematical model (in the open
literature) that represents signal loss in vegetation under the combined influence of wind and rain
(Meng et al, 2007). The closest is a Radiative Energy Transfer Theory (RET) model which
represents just the power loss in vegetations without the combined influence of rain and wind.
This investigation is concerned with the experimental determination of the dynamic effects
caused by artificially created wind and rain on the foliage radio-wave propagation channel and
the statistical analysis of the signal variations by comparing the experimental results with the
four theoretical models which are usually used for modeling radio-wave propagation channels.
Namely, Gaussian, Rician, Rayleigh and Nakagami distribution models (Meng et al, 2007).
1.4 Motivation and Significance of the Study
The significance of the study cannot be over emphasized because near ground communication is
extensively used both for scientific and military applications. These two applications require a
detailed understanding of the foliage propagation channel in order to establish a good
communication link through a well-defined link budget and a good design of the fade margin
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(Jim, et al, 1998). Signal variations caused by the influence of wind and rain on a foliage
channel, if not taken into consideration during design process, can affect the reliability of modern
communication systems when implemented for use within such environments
1.5 Methodology
In this work, the methods used to carry out the investigation are experimental. Three different
sets of experiments were conducted in order to obtain the required data. They are:
1) Determination of the relationship between wind speed in m/s and current into the fan in
amperes. This is achieved using an electric fan, an anemometer (air velocity meter), and an
analogue ammeter for current measurement.
2) Determination of the relationship between angles of rotation (in degrees) of stopcock (i.e.
valve for controlling water flow) and rain intensity in mm/h, using a water pumping machine,
high pressure hose pipes, water sprinkler with stopcock, a rain gauge and a digital electronic
timer.
3) EM wave measurements in the foliage channel under the influence of the created wind and/or
rain at different wind speeds and/or rain intensities. This was achieved using a microwave
transmitter (10.7GHz), a microwave receiver (10.7GHz), a digital voltmeter with data-hold
facility and a digital storage oscilloscope (DSO).
After collecting the required data, Microsoft Excel was used for data normalization. Finally, a
well-authored software program by Mathwave Technologies named EasyFit 5.5 professional was
then used for statistical analysis of the results.
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1.6 Thesis Outline
The thesis report is organized into five chapters. Chapter one is the introduction which paves the
way for the entire contents of the report. Chapter two is the literature review and theoretical
background of the study. Chapter three is methodology which gives the full details of the
measurements set-up together with pictorial and schematic illustrations. The obtained raw data
under each weather phenomenon as well as the plotted waveforms are also presented in this
chapter. Chapter four is results analysis which includes determination of the imposed
attenuations on the channel, data normalization, modeling and characterization. It also introduces
the four probability distribution functions associated with radio-wave propagation channels and
the software used for the analysis. Finally, chapter five gives concise summary, conclusion and
recommendations for further work.
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