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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