LOCAL MULTIPOINT DISTRIBUTION SERVICES ARCHITECTURE BASED
ON RAIN PROFILE EXTRACTED FROM METEOROLOGICAL RADAR
KUSAY FAISAL A. AL-TABATABAIE
UNIVERSITI TEKNOLOGI MALAYSIA
i
LOCAL MULTIPOINT DISTRIBUTION SERVICES ARCHITECTURE BASED
ON RAIN PROFILE EXTRACTED FROM METEOROLOGICAL RADAR
KUSAY FAISAL A. AL-TABATABAIE
A thesis submitted in fulfilment of the
requirements for the award of the degree of
Doctor of Philosophy (Electrical Engineering)
Faculty of Electrical Engineering
Universiti Teknologi Malaysia
MARCH 2013
iii
Dedicated to my parents, brothers, wife and our beloved children Huda and
Abdullah
iv
ACKNOWLEDGEMENT
Praise to Allah, the Most Gracious and Most Merciful, Who has created the
mankind with knowledge, wisdom and power.
I would like to take this opportunity to express my deepest gratitude to a
number of people who supported me in their helpful comments and enlightening
suggestions.
First of all, my supervisor, Assoc. Prof. Dr. Jafri Din, always gave me the
courage and support to carry out my research in Malaysia (abroad for me) as well as
the full technical and mental supports. I wish to express my gratitude to my co-
supervisor, Dr. Nor Hisham Bin HJ Khamis for helpful comments during my
research and careful reviews of this thesis.
Special thanks are dedicated to my friends Ali Mohammed Qasim who
offered invaluable programming assistance and supports, and Lam Hong Yiw who
share with me some ideas and suggestions to ease my work.
I owe special thanks to Asmaa Gheyath Salih, my lovely wife for her patience
and understanding. And I also would like to thank my parents for continuous sponsor
support and encouragement.
Last but not least, I would like to express my most sincere gratitude to all
those who have helped me directly or indirectly to complete this work.
v
ABSTRACT
The growing demand for high-speed Broadband Wireless Access (BWA)
applications has motivated the use of millimetre waves operation in Ka band, point-
to-multipoint fixed cellular with a large bandwidth of 0.5–1.55 GHz. This service is
also known as Local Multipoint Distribution Service (LMDS). It has the advantages
of rapid installation, scalability, high capacity, ease of deployment and low initial
infrastructure costs; and could be an attractive alternative to other broadband access
technologies. However, the service is limited up to 8 km of coverage area due to line
of sight constraints. Co-channel interference and rain attenuation are major limitation
factors to system performance. This study is conducted to analyse LMDS
performance based on local rain cell profile. The long-term cumulative rainfall rate
was obtained from weather radar data. This data is compared with ITU-R
recommendation and data from rain gauge network. The influence of rain length
distribution probability to different rain rate thresholds had been studied from the
database for an area size of 25 km2. The target is to design LMDS that reaches up to
5 km of cell size service with good availability. Four architectures of fixed BWA
were investigated in terms of a carrier to interference ratio (C/I) using three types of
modulations which are QPSK, 16-QAM and 64-QAM. The rain cell profile results
shows that higher rain rates experience shorter rain length. The rain rates at 0.01
percentage of time for radar data in UTM is 106.25 mm/hr and rain length was less
than 0.46 km. Besides, during low rain rate events, the LMDS service coverage has
better performance than clear sky. This is due to fact that the low rain rates present
low attenuation to the desired signal but causes high attenuation to interfering base
station signals, resulting in better C/I performance. During heavy precipitation, the
effective service coverage area will reach to less than 2 km using QPSK in
conventional architecture at 99.99% availability. In addition, the co-channel
interference can be reduced by using certain design-rule for various architectures.
Moreover, it was observed that by decreasing LMDS cell size, the service coverage
performance would improve. Two methods had been proposed to improve the
performance. One is to use different architectures namely conventional with 4
frequency reuse, simplex ring relaying and dual ring relaying. The second method is
to reduce the LMDS service size, i.e. to determine appropriate cell size which offers
99.99% availability. It showed that, for conventional architecture, 3 km cell size was
sufficient to reach the required availability based on local climate. In addition, 5 km
service cell size for 99.98% availability can be achieved by using dual ring
architecture. All the information are important to present BWA network architectures
for Malaysian environment based on rain intensity distribution extracted from radar
data.
vi
ABSTRAK
Permintaan yang semakin meningkat untuk aplikasi yong menggunakan Akses
Jalur Lebar Wayarles (BWA) berkelajuan tinggi telah mendorong penggunaan
gelombang milimeter beroperasi pada jalur Ka, iaitu selular talian tetap titik ke pelbagai
titik dengan lebar jalur yang besar. Perkhidmatan ini juga dikenali sebagai Servis
Pemancaran Pelbagai Titik Tempatan (LMDS) yang mempunyai pemasangan yang
pantas, kebolehan untuk diskala, berkapasiti tinggi, kemudahan penempatan dan kos
infrastruktur awal yang rendah dan boleh menjadi satu alternatif menarik kepada
teknologi akses jalur lebar lain. Tetapi, perkhidmatan ini terhad sehingga 8 km dari
kawasan liputan kerana kekangan garis sesaluran penglihatan. Gangguan saluran
bersebelahan dan gangguan hujan adalah faktor utama yang menghadkan prestasi sistem.
Maka, kajian telah dijalankan untuk menganalisa prestasi LMDS berdasarkan profil sel
hujan tempatan. Kadar kumulatif hujan jangka panjang telah diperoleh daripada data
radar cuaca. Data ini dibandingkan dengan syor ITU-R dan data dari rangkaian tolok
hujan. Pengaruh taburan kebarangkalian panjang hujan ke atas kadar hujan yang berbeza
telah dikaji dari pangkalan data bagi saiz kawasan seluas 25 km2. Sasaran adalah untuk
mereka bentuk perkhidmatan LMDS yang mencapai sehingga 5 km dengan ketersediaan
baik. Empat seni bina BWA tetap telah dilakukan berdasarkan nisbah pembawa kepada
gangguan (C/I) menggunakan tiga jenis modulasi QPSK, 16-QAM dan 64-QAM. Sel
hujan profil hasil kajian menunjukkan kadar tinggi hujan mempunyai saiz hujan pendek.
Kadar hujan pada 0.01 peratus masa untuk data radar UTM adalah 106.25 mm/jam dan
saiz hujan untuk kadar ini adalah kurang daripada 0.46 km. Tambahan pula, semasa
kadar hujan rendah, liputan perkhidmatan adalah lebih baik berbanding keadaan tanpa
hujan. Ini kerana kadar hujan yang rendah memberi kesan minimum kepada isyarat yang
diingini tetapi menyebabkan rosotan yang besar kepada isyarat gangguan dari stesen asas
yang memberikan prestasi yang C/I lebih baik. Semasa hujan lebat, kawasan liputan
perkhidmatan berkesan akan menjadi kurang dari 2 km menggunakan QPSK dalam seni
bina konvensional pada ketersediaan 99.99%. Sehubungan itu, gangguan saluran
bersebelahan boleh dikurangkan dengan menggunakan peraturan reka bentuk tertentu
untuk pelbagai seni bina. Tambahan pula, dengan mengurangkan LMDS saiz sel prestasi
liputan perkhidmatan akan bertambah baik. Dua kaedah telah dicadangkan untuk
meningkatkan prestasi. Satu adalah dengan menggunakan seni bina yang berbeza iaitu
konvensional dengan 4 frekuensi guna semula, geganti gelung simpleks dan geganti
gelung duaan. Kaedah kedua adalah mengurangkan saiz perkhidmatan LMDS, iaitu
dengan menentukan saiz sel yang sesuai yang menawarkan ketersediaan 99.99%.
Didapati bahawa bagi senibina konvensional, 3 km adalah saiz sel yang sesuai untuk
mencapai ketersediaan yang diperlukan berdasarkan iklim tempatan. Di samping itu, saiz
sel perkhidmatan 5 km pada ketersediaan 99.98% boleh dicapai dengan menggunakan
seni bina gelung duaan. Semua maklumat ini adalah penting untuk seni bina rangkaian
BWA mengikut iklim Malaysia berdasarkan pengagihan keamatan hujan yang diekstrak
daripada data radar.
vii
TABLE OF CONTENTS
CHAPTER TITLE PAGE
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vi
LIST OF TABLES x
LIST OF FIGURES xii
LIST OF SYMBOLS xvii
LIST OF ABBREVIATION xviii
LIST OF APPENDICES xix
1 INTRODUCTION 1
1.1 Introduction 1
1.2 Problem statement 3
1.3 Research objectives 5
1.4 Scope of work 5
1.5 Contributions to knowledge 6
1.6 Structure of the study work 7
2 LITERATURE REVIEW 8
2.1 Introduction 8
2.2 Meteorological radar overview 9
2.3 Regression coefficient for radar reflectivity 12
2.4 Radar rainfall rate conversion 13
viii
2.5 Rain attenuation equation 14
2.6 Characteristics of wireless radio propagation 17
2.7 LMDS layout configuration 18
2.7.1 System deployment 19
2.7.2 Frequency reuse 20
2.7.3 Dual polarizations 21
2.7.4 LMDS cell planning 22
2.7.5 Co-channel interference 23
2.7.6 Inter-cell interference 25
2.7.7 Systems interference protection Criterion 27
2.8 Link budget 28
2.9 LMDS cellular architectures 29
2.9.1 Relaying protocol 31
2.10 Dynamic bandwidth allocation (DBA) 33
2.11 Effects of rain cell over LMDS system 37
2.12 LMDS cell coverage efficiency 38
2.13 Previous LMDS results 39
2.14 Summary 43
3 METHODOLOGY 44
3.1 Introduction 44
3.2 Filtering and decoding radar data 46
3.3 Permanent echo verification and data availability 47
3.3.1 Radar echo test 47
3.3.1 Data availability 48
3.4 Rain rate inferred from radar data 49
3.5 Determination of rain length along radar azimuths 51
3.6 Rain attenuation extracted from radar data 56
3.7 LMDS applied architecture
3.7.2 Conventional with 4 frequency reuse
architecture 62
3.7.3 Simplex ring relay architecture 63
3.7.4 Dual ring relay architecture 63
60
3.7.1 Conventional architecture 61
ix
3.8 LMDS antenna specification 64
3.9 Obtain C/I in LMDS system 66
3.10 Summary 66
4 RAIN INTENSITY PROFILE AND RAIN
ATTENUATION DISTRIBUTION EXTRACTED
FROM WEATHER RADAR DATA 67
4.1 Introduction 67
4.2 Rain intensity 68
4.3 rain length in study area 75
4.4 Specific rain attenuation 78
4.5 Rain attenuation for terrestrial path length 79
4.6 Summary 83
5 EVALUATION OF LMDS ARCHITECTURES 84
5.1 Introduction 84
5.2 C/I for different LMDS architectures in clear sky 85
5.3 Precipitation effects on different LMDS
architectures 89
5.4 LMDS architectures coverage 94
5.5 Optimum LMDS cell size for different
architectures 98
5.6 Summary 104
6 CONCLUSIONS AND FUTURE WORK 106
6.1 Conclusions 106
6.2 Future work 108
REFERENCES 110
Appendices A - J 120-158
x
LIST OF TABLES
TABLE NO. TITLE PAGE
2.1 Kluang Radar Specifications 11
2.2 Modulation methods (Ahamed, 2009) 34
2.3 modulation scheme efficiency and required carrier to
noise ratio (Lee et al., 1998) 35
2.4 The minimum required carrier to interference ratio for
LMDS (Lee et al., 1998) 37
3.1 The sixteen characters that define absolute levels 46
3.2 The forty-nine characters that define the deviation
encoding 46
3.3 The UTM selected point locations from radar data 50
3.4 Radar signal strength thresholds and the corresponding
rain rates using MP relation 50
3.5 The number of hypothetical links for every azimuth 57
3.6 LMDS parameters link budget calculations for selected
antenna (Lee et al., 1998; Chu and Chen, 2005) 65
4.1 One year CDF radar rain events data located at UTM
area 70
4.2 The CDF rainfall rates for all Rain Gauge Stations
RGN- UTM (Khamis, 2005) 73
4.3 CDF of rain length along radar azimuths from radar data 75
4.4 Rain length for 0.01% of time for different rain rates 77
4.5 CDF of one year radar specific rain attenuation
distribution (Dec 2006 – Nov 2007) for 28 GHz using
ITU-R P.838-3 regression coefficients 78
xi
4.6 Equivalent time percentage to the selected core values 81
5.1 Optimum cell sizes for each conducted LMDS
architectures 104
xii
LIST OF FIGURES
FIGURE NO. TITLE PAGE
2.1 Radar Simplified Block Diagram 10
2.2 Thunderstorm line viewed in (dBZ) on a PPI
scan 12
2.3 Scattering and absorbing caused by raindrops in
high frequency (Ishimaru, 1997) 17
2.4 RF band arrangement based on MCMC licence 20
2.5 Cell with different reuse factors 21
2.6 Twelve-sector cell using alternating polarity
method (Roman, 1999) 22
2.7 Typical cell planning in LMDS (Chen and Chu,
2007) 23
2.8 Illustration of (a) inter-cell and (b) intra-cell CCI 24
2.9 Dual polarization with frequency plan of (a) 1
Frequency, 2 polarization 90o sectors, and (b) 2
Frequency, 2 polarization 90o sectors 25
2.10 Inter-cell Interference in LMDS 27
2.11 Interference protection criterion 27
2.12 Relaying protocol 31
2.13 Relay-assisted transmission model 32
2.14 Effective of ICI on LMDS using ring relay
Model 33
2.15 Description criteria for slow adaptive
modulation systems BER= 10-2 35
2.16 Dynamic modulation scheme for LMDS 36
2.17 C/I Contour curves (Lee et al., 1998) 39
xiii
2.18 Desire signal for 6-km cell-size terminal in clear
days (Chu and Chen, 2005) 40
2.19 Desire signal for 6-km cell-size terminal in rainy
days (Chu and Chen, 2005) 41
2.20 Total downstream CIR(x, y) sector distribution
over a sector of a TDMA-based LMDS system
operating in Athens, Greece, at 25 GHz under
the specification AIP = 0.001%, cell radius
D = 3 km (Panagopoulos et al., 2007) 42
2.21 Upstream CIR(x, y) sector distribution for the
same LMDS system as in Fig. 4 under the
specification AIP = 0.001%. Interference
originates from a diagonal IS 42
3.1 Flowchart of the research methodology 45
3.2 UTM location inside the study sector from
Kluang radar station 49
3.3 Radar view of the selected locations at
UTM- Skudai 50
3.4 Radar view of the chosen sector 52
3.5 Rain length distributions at single PPI scan 52
3.6 Separating cores level from radar data 53
3.7 Core level path length per azimuth 54
3.8 Rain path length distribution for each level 55
3.9 The adopted method for obtaining rain rate to
every 1 km range 56
3.10 Convert from levels to equivalent rain rate for
study area 58
3.11 Attenuation analysis 59
3.12 Co-Channel interference of Conventional
architecture for LMDS 61
3.13 The high-level interference edges in a
Conventional scheme 61
3.14 LMDS cell planning with 4 frequency reuse
(Chen and Chu, 2007) 62
xiv
3.15 Simplex ring relay 63
3.16 Dual ring relay 65
4.1 Monthly CDF occurrences of rain rate from
radar data at B-C 69
4.2 Rain rate at three different locations in UTM
using ITU-R P.837-6 70
4.3 One year CDF Radar rain rate at UTM area 71
4.4 The locations of rain rate study at UTM-
Skudai campus 72
4.5 Comparison of CDF rain rate obtained from
radar data with UTM-RGN at E01 and ITUR
837-6 at B-C 73
4.6 CDF rain rate obtained from radar data
compared with UTM RGN along with
Singaporean RGN and ITUR 837-6 at BC 74
4.7 CDF of rain length probability corresponding
to different core intensity 76
4.8 Specific attenuation from Radar data compare
with ITUR data at 28 GHz for horizontal
polarization 79
4.9 CDF of rain attenuation from radar data at
different path lengths at 28 GHz for horizontal
polarization 80
4.10 The horizontal rain attenuation at 28 GHz to
different time percentage based on ITUR530-14
and radar versus different path lengths 82
5.1 Clear sky CIR contour of Conventional
architecture scheme 85
5.2 Clear sky CIR Contour of Conventional with 4
frequency reuse architecture 86
5.3 Clear sky CIR Contour of Simplex relay
architecture 87
5.4 Clear sky CIR Contour of Dual relay architecture 87
xv
5.5 Clear sky CIR worst case scenario for different
LMDS architectures 88
5.6 CIR based on extracted radar data information
at different path lengths from terminal stations
using conventional architecture scheme 89
5.7 CIR based on extracted radar data and ITUR
database at different path lengths from terminal
stations using conventional architecture scheme 90
5.8 CIR based on extracted radar data information at
different path lengths from terminal stations using
conventional with 4 frequency reuse architecture 91
5.9 CIR based on extracted radar data and ITUR
database at different path lengths from terminal
stations using conventional with 4 frequency
reuse architecture 92
5.10 CIR based on extracted radar data information
at different path lengths from terminal stations
using simplex ring relay architecture scheme 93
5.11 CIR base on extracted radar data information at
different path lengths from terminal stations
using dual ring relay architecture scheme 94
5.12 Proposed dynamic modulation scheme
distribution for LMDS 95
5.13 LMDS architectures coverage ratio for QPSK
modulation 96
5.14 LMDS architectures coverage ratio for 16-QAM
modulation 96
5.15 LMDS architectures coverage ratio for 64-QAM
modulation 97
5.16 The CIR of 4 km LMDS cell size planning
terminal station at different rain rates 98
5.17 The CIR of 3 km LMDS cell size planning
xvi
terminal station at different rain situation 99
5.18 The CIR of 2 km LMDS cell size planning
terminal station at different rain situation 100
5.19 The CIR of 4 km conventional with 4 frequency
reuse architecture cell size planning terminal
station at different rain rates 101
5.20 The CIR of 4.5 km simplex ring relay
architecture cell size planning terminal station at
different rain rates 102
5.21 The CIR of 4.8 km dual ring relay architecture
cell size planning terminal station at different
rain rates 103
xvii
LIST OF SYMBOLS
A - Rain Attenuation
ACI - Adjacent channel interference
AIP - Acceptance interference probability
Ar0.01 - Attenuation at 0.01 of time
BS - Base Station
C - Area coverage
CCI - co-channel interference
C/I - Carrier to Interference ratio
CIR - Carrier to Interference ratio
C/N - Carrier to noise ratio
CNR - Carrier to noise ratio
dB - Decibel unit
Fr - Frequency reuse
HS - Hub Station
I/N - Interference to Noise Ratio
ICI - Inter-cell Interference
ISI - Inter-symbol interference
km - Kilometer
PL - Path Loss
R - Rain Rate
Rth - Rain Rate threshold
R0.01 - Rain Rate at 0.01 percentage of time
RF - Radio Frequency
γs - Specific Attenuation
TS - Terminal Station
xviii
LIST OF ABBREVIATIONS
BWA - Broadband wireless access
CDF - Cumulative Distribution Function
CPE - Customer Premise Equipment
DBA - Dynamic Bandwidth Allocation
EIRP - Effective Isotropic Radiating Power
FBWA - Fixed broadband wireless access
FCC - Federal Communications Commission
FSL - Free Space Path Loss
GHz - Giga hertz
LAN - Local Area Network
LMDS - Local Multipoint Distribution Services
LOS - Line of sight
MCMC- Malaysian Communications and Multimedia Commission
mm/hr - Millimetre per hour
PDF - Probability Density Function
ITU-R - International Telecommunication Union - Radio communications
IEEE Std - International of Electrical and Electronic Engineering Standard
P-MP - Point to Multipoint Fixed Service
P-P - Point to Point Fixed Service
PPI - Plan Position Indicator
QAM - Quadrature Amplitude Modulation
QPSK - Quadrature Phase Shift Keying
RHI - Range Height Indicator
Z - Radar Reflectivity Factor
xix
LIST OF APPENDICES
APPENDIX TITLE PAGE
A List if author's related publications 120
B Radar measurement and calibration 122
C Radar range height indicator 123
D Filtering and decoding radar data 126
E Permanent echo chick 130
F Rain rate flow charts 132
G LMDS antenna aspects 136
H LMDS performance 144
I Rainfall and rain attenuation analysis 147
J Coverage performance in each architecture to
different modulation 155
1
CHAPTER 1
INTRODUCTION
1.1 Introduction
There is a growing interest of using broadband wireless access (BWA)
service, because it provides reliable transmission of information such as data and
video (Ahamed, 2009). BWA utilizes large bandwidth and has low error rates for
acceptable performance service to consumers, as compare to copper telephone wires
or coax cable (Agne and Telenor, 2000).
However, attenuation due to rain is a major limitation for terrestrial and slant
path links especially at shorter wavelengths. The rain attenuation might cause
temporary loss of signal therefore it is an important parameter in the design of
telecommunication systems which relies on wavelengths above 1 GHz (Crane,
1996).
Reliable estimates of rain attenuation can be obtained through measurements
taken from radar data (Adhikari et al., 2011; Akuon and Afullo, 2011; Yeo et al.,
2
2012). Direct measurements like rain gauge or microwave link are not convenient for
use, because of infrastructure and time constrain (Olsen, 1982; Seed et al., 1990;
Lahaie et al., 1993). In addition, it is sometimes complicated to transfer the outcomes
to other sites. Thus, there is growing interest in using indirect measurement
techniques such as radar data.
Radar (Radio detection and ranging) utilizes electromagnetic waves to
“remote-sense” the location, determine velocity, and determine characteristic of
targets. The primary reason for utilizing radar is the ability of this instrument to
detect with great spatial detail of precipitation over large area in real time and with
single installation. Radar data can be used principally to evaluate the propagation
impairments through simulations (Battan, 1973), which is due to hydrometeors for
any length of ground paths, any kind and complexity of radio system and for any
frequency. However, the shortcoming is the radar reflectivity (Z), that is fundamental
measurement for the meteorological target which can not be directly used, its
conversion to rain intensity and depends mostly on Drop Size Distribution (DSD)
(Capsoni and Caboni, 2003).
With rapid growth of information technology (Murdock et al., 2012), there is
a trend of using local Multipoint Distribution Service (LMDS) applications and
evolution (Ahamed, 2009; Panagopoulos et al., 2007; Dimitris et al., 2011). This has
led to the utilization and exploitations of high wavelengths band such as Ka band
(20/30 GHz) and above. The spectrum at Ka band is essential for BWA services.
This is so; due to relatively unused spectrum with essentially no congestion problem,
that provides greater bandwidths, and ability of frequency reuse comparing with
lower band frequency.
3
There are two kinds of interference in LMDS; first type is interference from
other communication systems known as "inter-system interference" such as
interference from other Ka-band communication systems (Bose et al., 2001). This
can be solved with proper licensing of spectrum band. The second interference is
known as "intra-system interference". This is essentially interference produced by the
system itself, including adjacent channel interference (ACI) and co-channel
interference (CCI). ACI could be resulted from signals which are adjacent within the
frequency for that desired signal. CCI is the major concern in LMDS cellular
architecture; the biggest problem is the consequence of interference of a single cell
on others throughout heavy rain because of frequency reuse (Hakegard, 2000).
Similarly, CCI sometimes happens due to crosstalk from two different radio
transmitters using the same frequency which is unquestionably the worst issue in the
coexistence. This study is devoted to CCI effect only.
A modified rain models (ITU-R P.837-6, 2012; ITU-R P.530-14, 2012)
according to local radar data measurements was used to identify the rain rate and rain
attenuation distribution. In this work, the performance of LMDS has been evaluated
in terms of carrier-to-interference ratio C/I under different rain conditions. Rain
attenuation and inter cell interference (ICI) play a very important factor in LMDS
planning techniques.
1.2 Problem statement
Wireless telecommunication world is very competitive; in view of that, power
budget and fade margin requirements need to be studied extensively in designing
Local Multipoint Distribution Service (LMDS). In any engineering discipline, pre-
implementation analysis is very much required for reliability. Predictions of reliable
4
local rain attenuation and path loss are necessary for service availability and quality
of service. Previous researchers demonstrated that rain is the principal reason for
system outage and service unavailability (Baldotra and Hudiara, 2004; Chu and
Chen, 2005). The knowledge of rain attenuation at the frequency of operation is
extremely required for design of reliable terrestrial and earth space communication
link at particular location.
Different LMDS architectures are proposed in this study. The performance
was based on local rain cell profile which indicates that, each architecture has its own
coverage limitations. For that, it is necessary to analyze and estimate the optimum
distance for LMDS during heavy rain. Base on this analysis changing the service cell
size coverage or system architecture is required to improve the link reliability.
LMDS systems could offer high order modulation schemes such as 64-QAM
which possess greater bandwidth efficiency (Lee et al., 1998). However, due to high
interference in Multicell LMDS, 64-QAM is useful for limited coverage area, where
it requires high data rate transfer close from the base station site (Ranjan Bose,
2004). Therefore, it is necessary to increase the coverage range area by switching to
a lower modulation plan like 16-QAM and QPSK. Furthermore, careful cell planning
and antenna placement are required to enhance the coverage area with maximum
scheme time available and reduce the interference.
The proposed architectures for LMDS in this study includes: simplex and
dual ring relay, which have already been applied in satellite but not performed yet in
LMDS.
5
1.3 Research objectives
The problem discussed earlier was the main challenge and focus in this
research work. The objectives of this research could be divided into the followings:
i. To estimate rain rate, and rain attenuation distribution for different path
lengths by employing radar data obtained from Malaysian Meteorological
Department.
ii. To determine the optimum required separation distance for LMDS cell in
Malaysia, to ensure system reliability.
iii. To propose LMDS architectures based on local rain profile, which leads to
higher LMDS availability.
1.4 Scope of work
In order to achieve the objectives, the research scope is as follows:
i. In this work, meteorological radar data has been utilized. The collected data
from Kluang meteorological radar station which is located with latitude
2.020o and longitude 103.320o in Johor, Malaysia. This radar concerns the
southern part of peninsular Malaysia. However, only data for the area which
concerns was UTM-Skudai and Johor Bahru was considered in this study.
ii. Duration of data collection lasted one year data (November 2006 – December
2007). The study focused on terrestrial path; because of that, only 0.5o plan
position indicator (PPI) scan elevation angle was considered. The available
6
range bin sizes were 500 m, 1000 m, and 2000 m. However, in order to obtain
more detail cell profiling, the 500 meter range bin resolution was selected.
iii. It is common to apply conventional architecture in LMDS (Chu and Chen,
2005; Panagopoulos et al., 2007; Charilas et al., 2011). For this work four
LMDS architectures had been investigated namely; conventional,
conventional with 4 frequency reuse, simplex ring relay and dual ring relay.
iv. In order to evaluate the performance of different LMDS architectures, the C/I
of each architecture is considered.
1.5 Contributions to knowledge
Through this thesis, there are number of contributions present in FBWA field.
These contributions are summarized as follows:
i. Significant study based on local weather radar data has been performed to
obtain rain intensity profiling and rain attenuation. The results were
comparable with ITU-R model and rain gauge network, which validate the
use of radar data for this study.
ii. Four different LMDS architectures scenarios namely; conventional,
conventional with 4 frequency reuse, simplex ring relay and dual ring relay
architectures had been presented, and evaluated in terms of C/I ratio.
iii. The optimum LMDS cell size for different architectures in Malaysia had been
identified. It had been obtained that, the proposed architectures offer larger
coverage area than conventional and conventional with 4 frequency reuse
architectures.
7
1.6 Structure of the study work
This thesis is divided into six chapters. The first chapter is the introduction,
problem statement, research objectives, scope of work, along with the layout of the
thesis. The second chapter contains the literature review, on meteorological radar,
rain attenuation, LMDS configuration, and contains LMDS performance results from
previous studies. The third chapter describes the procedure used to evaluating rain
profile, the proposed LMDS architecture, and performance evaluations. The fourth
chapter includes the results analysis for local rain rate and rain attenuation which will
be used in chapter five. The fifth chapter essentially uncovers the optimum
separation distance suitable for LMDS cells by employing local rain profile. It
analyzes different scenarios to determine the LMDS performance. The last chapter
presents the overall conclusions, the key contributions factors of the project and
recommendations for future work.
110
REFERENCES
Agne, N. and Telenor R&D (2000). LMDS Systems and their Application. IEEE
Communications Magazine. 38, 150-154.
Adhikari, A., Das, S. and Maitra, A. (2011). Improving rain attenuation estimation:
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