rain attenuation prediction on earth- to-satellite
TRANSCRIPT
RAIN ATTENUATION PREDICTION ON EARTH-
TO-SATELLITE MICROWAVE LINK IN LIBYA AS A
CASE STUDY
BY
ASMA ALI HUSSEIN BUDALAL
A dissertation submitted in fulfillment of the requirement for
the degree of Master of Science (Communication
Engineering)
Kulliyyah of Engineering
International Islamic University Malaysia
FEBRUARY 2017
i
ABSTRACT
Earth-to-satellite microwave links are revolutionary communication systems that
supports high-speed data rate. It can accommodate a large number of users with
increased spectral efficiency and high throughput. However, performances of those
links operating in Ku, Ka, and V-bands are degraded by the environment and strongly
attenuated by rain. Rain attenuation is the most significant consideration and challenge
for higher frequency bands. Hence, it is essential for the satellite link designer to take
into account rain fade margin accurately before system implementation. Rain rate is
the main measured parameter to predict of rain attenuation. Rainfall statistical data
measured and recorded in Libya with 3-hours integration time for the period of 30
years are collected. The prediction methods require one minute integration time rain
intensity. Therefore, collected data were analysed and processed to convert into one –
minute rain rate cumulative distribution in Libya. Several prediction models for
conversion of one –minute rain rate have been utilized by considering different
climatic conditions. A suitable prediction model is recommended to predict one-
minute rain rate distribution for microwave link design in Libyan environment.
Chieko and Yoshio is recommended in the calculation of one-minute rain rate
cumulative distribution under Libyan climatic conditions. The model proposed by
International Telecommunication Union-Radio wave Propagation (ITU-R) is used to
predict and investigate rain fade based on converted 1-minute rain rate data. C, Ku-
band downlink at 4-12 GHz rain fading is not a considerable factor in Libya. The
further result shows a fade marginal difference of about 15 dB between Ku- and Ka-
band frequencies for 99.99% availability of time in coastal regions. As well as the
results obtained at V-band downlink shows that 99.99% availability is possible in all
the southern part stations in Libya. It is observed that the ITU-R model seems to under
estimate the rain attenuation in northeast and northwest in Libyan costal line. Rain
fade predicted at five locations are used for performance analysis in terms of link
spectral efficiency and throughput. Taking into account of rain fade margin at
different outage probabilities. Findings will enable the earth-to-space link designer to
determine the optimum transmitting power to mitigate rain fade. Results and analysis
of this research will be a very useful resource to design highly reliable earth-to-
satellite communication links in Libya.
ii
خلاصة البحث
نطاقات تردديه التي تدعم اللاسلكيةظمه الساتلايت ثوره علميه في تقنيه الاتصالات أن باستخدامتصالات الادثت أح مثل ولكن هذه الاشارات ذات الترددات العاليه . الخدمات جوده وتحسين الاتصال قنواتوسرعه سعة لزيادةعاليه
Ku, V, Ka, والتشتت بسبب عوامل الطبيعه في الغلاف الجوي اثناء انتشارها.ولعل تعاني من التشويه والتوهينتصالات الساتلايت إانظمه فمن الضروري جدا لمصممي .هم هذه العوامل المؤثرهأمطار احد لأالتوهين بسبب ا
في وصلات الساتلايتبدقه متناهيه قبل تنفيد ثير الامطار أت حساب الفقد بسببباستخدام وصلات المايركويف لنماذج المعمول بها في حساب التوهين لاهم المدخلات منمعدل المطر المقاس بالمليمتر / الساعه يعتبر .الدراسه منطقه
في عام 03 لفتره مطار لأطول اله حصائيهإبيانات . في هذا البحث تم تجميع مطار لأبسبب ا اشارات الساتلايتفي وهذا فتره طويله جدا لايمكن التعامل .ساعات -0مقاسه كل 0313الى 1891ليبيا منطقه الدراسه من سنه
لايتعدى والتي تعتمد بشكل اساسي على معدل امطار مقدار الاضمحلال والتوهين لقياس الاتصالات لغرض معها معدل الامطار بالنسبه للدقيقه الواحده غير مقاس ويصعب وبما ان . minute rain rate-1الدقيقه الواحده
المتعارف عليها من قبل بعض الباحثين تم الاعتماد علي بعض نماذج التحويل من هناتحديده في مختلف مناطق العالم نماذج لتغيير 6ختبارإوبالفعل قد تم .الواحدالى الدقيقه تغيير معدل الامطار في منطقه الدراسهلالمهتمين بهذا المجال
ومقارنتها مع القيمه المحسوبه لتوزيع معدل كميه الامطار من مليمتر الي مليمتر في الساعه بفارق زمني دقيقه واحده .ومن النتائج المتحصل عليها تبين ان .في ليبيا القيم المقاسه في مناطق جغرافيه مختلفه تحويل مطار المتحصل عليها منلأا
Chieko and Yoshio .باستخدام نموذج القيم المحتمله للتوهين تم حسابمن انسب النماذج للأستخدام في ليبيا outageوحساب احتماليه الخروج عن الخدمه ITU-RPتصالات موجة الانتشار الراديولأتحاد الدولي للأا
probabilities .حساب كفاءه الطيف عن طريق الساتلايت داء وصلات أتحليل تم وختاما عند ترددات مختلفهوحساب C,Ku,Ka,V المقترحةلمختلف مدى الترددات link spectral efficiency (bps/Hz) الترددي
GHz 12-4لترددات اتأثير لتوهين الامطار هناك ليس اظهرت النتائج ان .throughput Mbps الإنتاجية منطقه في الغربيلاشارات في الجزء الشمالي الشرقي والشمالي ا. وعند ترددات اعلى تسبب الامطار توهين في ليبيا
في المناطق الساحليه عند Ku- Ka-band بين fade marginal فرق dB 15 وهناك الدراسه 99.99% availability.كذلكV-band downlink يعمل في المناطق الجنوبيه فقط عند انيمكن
تعد مصدر مهم يمكن الرجوع إليه لرسم خرائط توزيع معدلات الامطار ث نتائج تحليل هذا البح . 99.99%التخطيط لتنفيذ و التصميم عن rain fade margin التوهين الامطار هامش وتحديد ،ليبيافي ج عنهااتوالتوهين الن
لتحديد قوة outage probabilitiesوحساب ستقباللإارسال والإوحساب تكلفه الوصلات وتصميم محطات ا .ليبيا في Kuعند استخدام مدى ترددات اعلى من الإرسال المثلى
iii
APPROVAL PAGE
I certify that I have supervised and read this study and that in my opinion, it conforms
to acceptable standards of scholarly presentation and is fully adequate, in scope and
quality, as a dissertation for the degree of Master of Master of Science
(Communication Engineering)
…………………………………..
Md. Rafiqul Islam
Supervisor
…………………………………..
Mohamed Hadi Habaebi
Co-Supervisor
I certify that I have read this study and that in my opinion it conforms to acceptable
standards of scholarly presentation and is fully adequate, in scope and quality, as a
dissertation for the degree of Master of Science (Communication Engineering)
…………………………………..
Internal Examiner
…………………………………..
Internal Examiner
This dissertation was submitted to the Department of Electrical And Computer
Engineering and is accepted as a fulfilment of the requirement for the degree of
Master of Science (Communication Engineering)
………………………………….
Anis Nurashikin Novdin.
Head, Department of Electrical and
Computer Engineering
This dissertation was submitted to the Kulliyyah of Engineering and is accepted as a
fulfilment of the requirement for the degree of Master of Science (Communication
Engineering)
…………………………………..
Erry Yulian Triblas.
Dean, Kulliyyah of Engineering
iv
DECLARATION
I hereby declare that this dissertation is the result of my own investigations, except
where otherwise stated. I also declare that it has not been previously or concurrently
submitted as a whole for any other degrees at IIUM or other institutions.
Asma Ali Hussein Budalal
Signature ........................................................... Date .........................................
v
INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA
DECLARATION OF COPYRIGHT AND AFFIRMATION OF FAIR
USE OF UNPUBLISHED RESEARCH
RAIN ATTENUATION PREDICTION ON EARTH-TO-SATELLITE
MICROWAVE LINK IN LIBYA AS A CASE STUDY
I declare that the copyright holders of this dissertation are jointly owned by the student
and IIUM.
Copyright © 2017 Asma Ali Hussein Budalal and International Islamic University Malaysia. All rights
reserved.
No part of this unpublished research may be reproduced, stored in a retrieval system,
or transmitted, in any form or by any means, electronic, mechanical, photocopying,
recording or otherwise without prior written permission of the copyright holder
except as provided below
1. Any material contained in or derived from this unpublished research may
be used by others in their writing with due acknowledgement.
2. IIUM or its library will have the right to make and transmit copies (print
or electronic) for institutional and academic purposes.
3. The IIUM library will have the right to make, store in a retrieved system
and supply copies of this unpublished research if requested by other
universities and research libraries.
By signing this form, I acknowledged that I have read and understand the IIUM
Intellectual Property Right and Commercialization policy.
Affirmed by Asma Ali Hussein Budalal
……..…………………….. ………………………..
Signature Date
vi
ACKNOWLEDGEMENTS
In the name of Allah, the most gracious and most merciful,
All praise is due to Allah (s w t) with the help of Allah the thesis would have reached
this stage. I would like to express my most sincere appreciation and gratitude to
Professor. Md. Rafiqul Islam for his advice, guidance, suggestions, critical comments
and supervision during the period of my study. He has added beneficial experience to
my life.
Additionally, I wish to express my appreciation and thanks to Libyan National
Meteorological Center (LNMC) for providing data used in rain fade estimation
Special thanks to Dr. Khalid Elfadli who provided their time, effort and support for
this project.
I wish to express my deep gratitude to my parents. To my mother Hameeda for her
endless support, love and patience.
Finally, special acknowledgment to my dear husband Abd Kareem, thank you for your
support and patience to accomplish this goal. I will be forever grateful to you.
vii
TABLE OF CONTENTS
Abstract .................................................................................................................... i
Abstract in Arabic .................................................................................................... ii
Approval Page .......................................................................................................... iii
Declaration ............................................................................................................... iv
Copyright Page......................................................................................................... v
Acknowledgements .................................................................................................. vi
Table of Contents ..................................................................................................... vii
List of Tables ........................................................................................................... ix
List of Figures .......................................................................................................... xi
List of Symbols ........................................................................................................ xiii
List of Abbreviations ............................................................................................... xv
CHAPTER ONE: INTRODUCTION .................................................................. 1
1.1 General Overview ................................................................................... 1
1.2 Problem Statement And Its Significance ................................................ 5
1.3 Purpose Of The Study............................................................................. 5
1.4 Research Objectives ............................................................................... 6
1.5 Research Scope ....................................................................................... 6
1.6 Rechearch Methodology ......................................................................... 7
1.7 Organization Of The Dissertation ........................................................... 8
CHAPTER TWO: LITERATURE REVIEW ..................................................... 11
2.1 Introduction ............................................................................................ 11
2.2 The Need Of Long Duration Rainfall Statistics ..................................... 11
2.3 Importance Of One- Minute Rain Rate Integration Time ...................... 11
2.4 Rain Rate Data ........................................................................................ 12
2.4.1 ITU-R Model ................................................................................ 12
2.4.2 Global Crane Model (Crane, 1996) .............................................. 13
2.4.3 Moupfouma Model ....................................................................... 13
2.4.4 Chebil’s Model .............................................................................. 14
2.4.5 Rice–Holmberg Model .................................................................. 15
2.4.6 Chieko Ito And Yoshio Hosoya .................................................... 16
2.5 Rain Attenuation Prediction ................................................................... 17
2.5.1 Rain Attenuation Prediction Measurements Methods .................. 17
2.5.2 Prediction Of Rain Attenuation .................................................... 18
2.5.3 Specific Attenuation Of Rain ....................................................... 19
2.6 Rain Attenuation Prediction Models ...................................................... 11
2.6.1 The ITU-R Model ......................................................................... 11
2.6.2 Crane’s Model ............................................................................... 24
2.6.3 Ajayi Model .................................................................................. 25
viii
2.6.4 Dissanayake- Allnutt Model ......................................................... 25
2.7 Satellite Links Budget Design ................................................................ 25
2.8 Link Performance And Availability ....................................................... 27
2.9 Link Margin ............................................................................................ 29
2.10 Link Budget Importance ....................................................................... 29
2.11 Summary ............................................................................................... 11
CHAPTER THEE: RAIN RATE DISTRIBUTION IN LIBYA ....................... 32
3.1 Introduction ............................................................................................ 32
3.1.1 Rainfall Patterns ............................................................................ 32
3.2 Data Collection And Data Processing .................................................... 33
3.3 Rain Rate Conversion ............................................................................. 37
3.4 Converted Rain Rate ............................................................................... 41
3.5 Type and the Characteristic of Intensity in Libya According to
Range of Rainfall Rate R .............................................................................. 43
3.6 Summary ................................................................................................. 43
CHAPTER FOUR .................................................................................................. 45
RAIN ATTENUATION PREDICTION AND ITS EFFECTS .......................... 45
4.1 Introduction ............................................................................................ 45
4.2 Rain Attenuation Analysis ...................................................................... 45
4.2.1 Effects Of Polarization .................................................................. 50
4.2.2 Effects Of Frequency Band ........................................................... 52
4.2.3 Effects Of Percentage Of Time Of The Year ................................ 55
4.3 Comparison With ITU-R Predicted Attenuation .................................... 56
4.4 Satellite Communication Link Design ................................................... 61
4.4.1 Rain Effects On Uplink And Downlink ........................................ 61
4.5 Performance Analysisi Of Satellite To Earth Microwave Link ............. 62
4.6 Summary ................................................................................................. 67
CHAPTER FIVE: CONCLUSION AND RECOMMENDATION ................... 69
5.1 Conclusion .............................................................................................. 69
5.2 Recommendation And Futre Work......................................................... 72
REFERENCES ....................................................................................................... 73
LIST OF PUBLICATIONS .................................................................................. 77
ix
LIST OF TABLES
Table No. Page No.
2.1 Articles in term of findings and limitations 30
3.1 Locations of 20 meteorological stations from which rainfall
data are collected
35
3.2 Measured Precipitation Data from 20 Meteorological
Stations
35
3.3 Measured Precipitation Data of 5 Selected Sites in Libya.
With 100% Availability of Rainfall Data during the Time
Period from 1981-2010
38
3.4 Comparison of converted 1- Min Rain Rate at 0.01% of
time in a year, Predicted by 6 Models at 5 Locations using
measured Data
40
3.5 Predicted One- Minute Rain Rate based on Chieko and
Yoshio Model for 20 Metrological Stations in Libya using
rainfall data from January 1981, to December 2010
41
3.6 Range of Rain Intensity R in Function of the Type and the
Characteristic of Intensity (Gustavo -2015)
43
4.1 Local Geometry Parameters For Five Stations in Libya. 46
4.2 Frequency-Dependent Regression Coefficients for
Estimating Specific Rain Attenuation
47
4.3 Estimated Rain Fades A0.01 (dB) for C, Ku, Ka, V-band
Downlink Frequency at Horizontal Polarization
50
4.4 Rain fades A0.01% (dB) for Uplink and Downlink frequency
in Tripoli
53
4.5 Calculated Rain Fades A0.01% (dB) for C, Ku, Ka, V-band
Downlink at Different Polarization for Benina and Tripoli
airport stations
54
4.6 Rain Fades A0.01 (dB) at Tripoli and Benina based on
Measured R0.01 For Downlink Frequency Bands at
Different % of Time of the Year
55
x
4.7 Comparison of Rain Attenuation A0.01% (dB) Based on
ITU-R Recommended and Measured R0.01% at Different
Percentage of the Time of the Year in Tripoli
56
4.8 Comparison of Rain Attenuation, A0.01% (dB) at Shahat 57
4.9 Estimated Rain Fades Ap (dB) at Different Percentages of
Time for Down link frequency bands at Horizontal
Polarization for the Maximum R0.01
58
4.10 Spectral Efficiency and Throughput in Satellite- to- Earth
Microwave Links working at Tripoli
64
4.11 Spectral Efficiency and Throughput in Satellite- to- Earth
Microwave Links working at Shahat (Maximum R0.01)
65
4.12 Spectral Efficiency and Throughput in Satellite- to- Earth
Microwave Links working in Sebha (Minimum Measured
R0.01).
65
xi
LIST OF FIGURES
Figure No Page No.
1.1 Rain Attenuation at Microwaves and Millimetre- Wave
Frequencies
3
1.2 A small portion of the satellite path is affected by rain which may vary with elevation angles
4
2.1 Explain Rain Rate And Losses Vary Along The Path
18
2.2 Schematic presentation of an Earth–Space path
22
2.3 Example CCDF curve for rain rate 27
2.4 a
Performance Threshold Link’s Performance Above Target
28
2.4b
Availability Threshold Link Is Not Available Due To Bad
Performance
34
3.1
Locations of national weather network stations-Libya.
Source
34
3.2 a
Cumulative Distribution Of Maximum Rain Rate
Variation At Shahat
38
3.2 b
Rain Rate Variation At Sebha In South Of Libya
38
3.2 c
Rain Rate Variation At Tripoli
39
3.2 d
Rain Rate Variation At Benina
39
3.2 e
Cumulative Distribution Graph Of Rain Rate Variation Of
Tripoli Airport
39
4.1
Rain Attenuation For C, Ku, Ka, V-Band Downlink At
Horizontal Polarization Using Minimum Measured Value
Of R 0.01
51
4.2
Rain Attenuation For C, Ku, Ka, And V-Band Downlink
At Horizontal Polarization Using Maximum Measured
Value Of R0.01%
51
4.3
Variation Of Rain Attenuation For C, Ku, Ka, And V-
Band Downlink At Horizontal Polarization In Tripoli At
Different Percentage Of Time Of The Year
54
xii
4.4
Comparative Of Rain Attenuation For Horizontal
Polarization In Tripoli At V Downlink Frequencies Band
57
4.5
Comparison Of Rain Attenuation For Horizontal
Polarization In Maximum At V Downlink Frequencies
Band
58
4.6
Comparative Plot Of Rain Attenuation For Horizontal
Polarization In Sebha At V- Downlink Frequencies Band.
59
4.7
Comparison of Rain Attenuation For Horizontal
Polarization In 5 Different Locations At V- Downlink
Frequencies Band
60
4.8
The relation between spectrum efficiency and SNR
63
xiii
LIST OF SYMBOLS
A Attenuation level in dB
A0.01 Attenuation exceed for 0.01% of the time in dB
d Path length
D Drop diameter
D0 Drop mean diameter
La Atmospheric losses
σ ζ Standard deviation of the conditional fade slope
Δh Altitude relative to the rain height in meters
γR Specific attenuation of rain in dB/km
E Expected value
f Frequency in Hz
Re Effective radius of the Earth (8 500 km)
hs Height above mean sea level of the earth station (km)
hR. Rain height as given in Recommendation ITU-R P.839
Ls Slant-path length, in km
LG Horizontal projection of the slant-path length in km
LE The effective path length through rain in Km
φ Altitude of the earth station
Θ Elevation angle (degrees)
r 0.01 Horizontal reduction factor for 0.01% of time
v0.01 Vertical adjustment factor, for 0.01% of time
β The thunderstorm ratio
k and α Frequency and polarization dependent coefficients
N(D) Drop size distribution
xiv
N0 Drop concentration at D = 0
Pr Received power
Pt Transmitted power
R Rain rate in mm/hr
R0.01% Rain rate exceeded for 0.01% of the time in mm/hr
R0.001% Rain rate exceeded for 0.001% of the time in mm/hr
T Number of hours in the year
Z Altitude
xv
LIST OF ABBREVIATIONS
ITU-R International Telecommunication Union- Radio Sector
DSD Drop Size Distribution
CD Cumulative Distribution
PDF Probability density function
CDF Cumulative Distribution Function
LNMC Libyan National Meteorological Center
BER Bit Error Rate
SNR Signal to Noise Ratio
FM Fade Margin
BW Band Width
FSPL Free Space Path Loss
EiRP Effective Radiated Power
1
CHAPTER ONE
INTRODUCTION
1.1 GENERAL OVERVIEW
Future satellite communication systems acutely require the use of higher frequency
bands in order to achieve larger bandwidths (Siles, Gustavo, et al, 2015). These bands
offer many advantages to satellite communication services and applications, in terms
of spectrum availability, reduced interference potential and minimized equipment size
(Owolawi,.2009 &Sujimol, et al,. 2015). However, rain attenuation is an important
challenge that limits the use of frequency above the 10 GHz and above in tropical and
sub-tropical regions. Atmospheric hydrometer affects the characteristic of the satellite
signals (Badron, et al. 2015). It causes considerable reduction in the density of an
electromagnetic wave as it propagates through the rain (Kamruzzaman et al, 2014).
Rain is therefore, directly responsible for link outages and causes link performance
degradation. Rain attenuates the signal, disturbs the polarization and increases system
temperature (Panchal& Joshi, 2016). In order to avoid these ramifications, an accurate
prediction of rain attenuation is of utmost significance while designing a reliable
microwave link at higher frequencies. The prediction methods require rain intensity at
one-minute integration time. In this study, one-minute integration time rain-rate
cumulative distribution (CD) has been derived from the total monthly rainfall
measured at 20 different meteorological stations in Libya over a span of 30 years.
Both converted as well as ITU-R proposed rain rates have been used to predict rain
fades at C, Ku, Ka and V-bands with Vertical, Horizontal and Circular polarized
2
waves for five stations in Libya. The performance of links has also been analyzed with
and without rains.
The Rainfall rate R (mm/h) is the most significant parameter to predict rain
attenuation in radio waves propagation. Rain fade is directly responsible for link
outages at Ku, Ka and future V-bands. Variations of rain fade with microwave
frequencies and rain intensities are shown in Fig. 1.1. The quality of services for
wireless communication depends strongly on it, especially at higher frequencies.
Signal attenuates because of absorption of the energy or by scattering of the energy
through raindrops. Attenuation depends on the frequency, wavelength of the signal
shape and size of raindrops as well as the effective path and rain rate (Siles, Gustavo
et al, 2015) as shown in Fig 1.2.
It is mentioned that in Tamosiunas, (2006) absorption causes attenuation more
than scattering if the wavelength is small compared to the drop size. On the other
hand, the attenuation caused by scattering is larger than absorption if the wavelength
is large compared to drop size. As well as rain attenuation higher at lower elevation
angle as the effective path passes the rain layer will be longer.
3
Figure 1.1 Rain attenuation at microwaves and millimetre- wave frequencies (E-Band
Technology, 2011)
Satellite link’s reliability depends mostly on convective rain. (Abdulrahman, et
al., 2015). In ŞEN & Eljadid, (1999) represents a Mediterranean climate region such
as Libya, whereas the temperate rain is mostly stratiform and widespread. Rain‐Rate
which vary in time and space randomly. Therefore the statistics of, Rain‐Rate and
related propagation effects are of major attention (Karagianni, et al., 2016). Hence, the
conditions of the electromagnetic wave propagation absolutely different in Libya
because of rain intensities vary significantly over large areas in the country. Thus,
rainfall rate cumulative distribution was derived in this work using long-term
statistical data. The highest and the lowest prediction of rain rate in the study of
interested locations are considered and analyzed.
4
Figure 1.2 A portion of the satellite path is affected by rain which varies with
elevation angles and rain characteristics
Satellite signals propagate long distance and decades exponentially as a
function of distance. As rain is not in the constant rate it fluctuates when the signals
propagate for the longer rainfall duration.
This dissertation aims at highlighting the importance of rain rate distribution and one-
minute rain rate data collection. Rain rate prediction models proposed by ITU-R,
Crane and Moupfouma have also been elaborated here. Additionally, to elucidate the
subject for better understanding, few prediction models, which convert rainfall data
from hourly/daily/ annual rainfall to rain rate with 1-minute integration time have
been presented in this dissertation. Apart from these, this dissertation also includes
conversion models proposed by Chebil, Rice Holmberg, Chieko Ito and Yoshio
Hosoya. Finally rain attenuation prediction proposed by ITU-R has been elaborated
step-by-step.
The following rainfall data has been collected from 20 meteorological stations
in Libya over a span of 30 years. This rainfall statistical data has been subsequently
recorded with 3-hours integration time and then eventually analyzed to be converted
Earth-station
Satellite
5
into one–minute rain rate cumulative distribution in Libya. Six conversion models
Chebil, modified-Chebil, Rice-Holmberg, Chieko and Yoshio, Crane global model,
and ITU-R have also been used in the process.
1.2 PROBLEM STATEMENT AND ITS SIGNIFICANCE
Rain attenuation is the most significant consideration to design an earth-to-satellite
links at higher frequencies. The consequences of this rain attenuation are degradation
of microwave link performance and increase link outage probability. The Problem
statement of this study is stated in the following points:
1. The lack of satellite propagation impairments studies in Libya and
consequently feasibility of future Ka and V-bands applications has not been
investigated thoroughly integration time is very long to assess the fluctuation
of rain attenuation.
2. No measurement for 1- minute rain rate in Libya is available in order to predict
rain fade on earth-to-satellite path operating at higher frequencies.
3. Suitable conversion model is required to convert annual and seasonal rainfall
data with longer integration time measured by meteorological department of
Libya for 30 years at more than 20 locations to 1-minute data.
1.3 PURPOSE OF THE STUDY
The purpose of this study is to help earth-to-space link designers for fixed satellite
communication services at Ku, Ka and V-bands for 20 stations in Libya by investigating
the effect of rain on microwave links. In order to predict the largest additional losses on
6
the free space that link will experience in the given reliability threshold of the satellite
links.
1.4 RESEARCH OBJECTIVES
The study is aimed to achieve the following objectives:
1. To convert available measured long term monthly rainfall data, collected from
different meteorological stations in Libya into one- minute integration time rain
rate
2. To predict rain attenuation in different frequency bands with different
polarizations and percentages of time of the year.
3. To analysis estimated rain fade margins and evaluate the earth-to satellite link
performances at different locations in Libya.
1.5 RESEARCH SCOPE
In this research only the rain attenuation prediction over Libya is considered. Monthly
rainfall data measured and recorded with 3- hours’ integration time in the Libyan
National Meteorological Center (LNMC) have been collected and processed. Data
were available at 20 stations in Libya over the 30 years-period from 1981 to 2010. In
this study, monthly total in (mm) are used from daily rainfall data. Since most of daily
rainfall records are zeros in arid regions. In addition to the 30 years commutative
rainfall data, the other parameters which are average annual total rainfall M (mm/yr),
the highest monthly precipitation Mm (mm/month), the average number of rainy days
in a year are utilized to estimate ratio of maximum monthly rainfall to the total
average rainfall accumulation (β). Predicted attenuation using ITU-R-618P-11 is used
7
to evaluate system performance for 0.01% exceedance attenuation value which gives
the 99.99% availability on a radio link .To elaborate attenuation variation
characteristics frequencies of C, Ku, Ka and V bands with different polarizations, and
various percentage of times are considered. ARABSAT-5A satellite located at 30.5E◦
would be used for reference. Predicted values of rain fade margin would be utilized to
analyses of satellite to earth microwave link performance.
1.6 RECHEARCH METHODOLOGY
In respect of the objectives outlined above, the following approaches are used in the
present study:
Step 1. Collecting and processing of rainfall data from Libyan nation metrological
center.
Step 2. Processing of rainfall data for 20 stations
Step 3. Conversion of long- term rainfall statistical data into 1-minute rain rate using
Matlab 7.0, which can be called in Microsoft Excel as a function. The parameters used
are:
Annual rainfall accumulation M in mm
Number of rainy days
Thunderstorm ratio β
Percentage of time unavailability Pin %.
Step 4. Selection of suitable conversion model ITU-R, Crane, Chebil, Rice-Holmberg
and Chieko-Yoshio models are investigated with 3 hourly measured data from 5
locations .Suitable conversion model is recommended for Libya.
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Step 5. Conversion of 30 years measurement for 20 locations to 1-minute rain rate
using recommended conversion model.
Step 6. Prediction of rain attenuation at C, Ku, Ka and V-bands with horizontal,
vertical and circular polarization for 0.01% outages. MATLAB program has been
written for conversion
Step 7. Performance is analyzed based on link efficiency in bps/Hz and throughput in
Mbps. Performance parameters:
7 dB SNR
BER = 10-6 at clear air condition
Particular reliability to evaluate earth –to satellite microwave link in different
cities in Libya
1.7 ORGANIZATION OF THE DISSERTATION
This thesis presents five chapters. The first chapter provides an overall background of
the thesis, including research motivations, problem statement, research objectives,
research scope, and research methodology. The second chapter considers literature
review of the previous works done in the area. Strength and limits of each work are
critically reviewed in order to evaluate the performance of rain rate and rain
attenuation prediction models by considering the weather peculiarity in the study area
of interest. The research methodology procedure of this work is described in chapter
three. This chapter will describe data analysis and processing. The method of how to
convert the raw long term rainfall data to rain rate mm/h. Then the capability of some
working model of converting of annual rainfall data into 1-minute rain rate is
highlighted in this chapter.