SITE DIVERSITY AGAINST RAIN FADING IN LMDS SYSTEMS
ZAID AHMED SHAMSAN ABDO
A thesis submitted in partially fulfillment of the
requirements for the award of the degree of
Master of Engineering
(M Eng. Electrical-Electronics and Telecommunications)
Faculty of Electrical Engineering
Universiti Technologi Malaysia
MAY 2007
PSZ 19:16 (Pind. 1/97)
UNIVERSITI TEKNOLOGI MALAYSIA
BORANG PENGESAHAN STATUS TESIS *
JUDUL:
SITE DIVERSITY AGAINST RAIN FADING IN LMDS SYSTEMS
SESIPENGAJIAN: 2006/2007
ZAID AHMED SHAMSAN ABDO
Saya
mengaku membenarkan tesis (PSM / Sarjana / Doktor Falsafah)* ini disimpan di Perpustakaan
Universiti Teknologi Malaysia dengan syarat-syarat kegunaan seperti berikut:
1.
2.
3.
4.
Tesis adalah hakmilik Universiti Teknologi Malaysia.
Perpustakaan Universiti Teknologi Malaysia dibenarkan membuat salinan untuk tujuan
pengajian sahaja.
Perpustakaan dibenarkan membuat salinan tesis ini sebagai bahan pertukaran antara
institusi pengajian tinggi.
** Silatandakan(V)
SULIT
(Mengandungi maklumat yang berdarjah keselamatan
atau kepentingan Malaysia seperti yang termaktub di
dalam AKTA RAHSIA RASMI 1972)
TERHAD
(Mengandungi maklumat TERHAD yang telah
ditentukan oleh organisasi/badan di mana penyelidikan
dijalankan)
TIDAK TERHAD
Disahkan oleh
(TANDATANGAN PENULIS)
Alamat Tetap:
Faculty of Engineering,
Taiz University,
Taiz, Republic of Yemen
Tarikh: MAY 2007
(TANDATANGAN PENYELIA)
PM DR. JAFRI BIN DIN
Nama Penyelia
Tarikh: MAY 2007
CATATAN * Potong yang tidak berkenaan.
** Jika tesis ini SULIT atau TERHAD, sila lampirkan surat daripada pihak
berkuasa/organisasi berkenaan dengan menyatakan sekali sebab dan tempoh
tesis ini perlu dikelaskan sebagai SULIT dan TERHAD.
♦ Tesis dimaksudkan sebagai tesis bagi Ijazah Doktor Falsafah dan Sarjana
secara penyelidikan, atau disertai bagi pengajian secara kerja kursus dan
penyelidikan, atau Laporan Projek Sarjana Muda (PSM).
“I hereby declare that I have read the contents of this project and in my opinion it is
qualified in the aspects of scopes and quality for the purpose of the Master of
Engineering (Electrical-Electronics and Telecommunications).”
Signature : ………………………..…………
Supervisor : PM Dr. JAFRI BIN DIN
Date
MAY 2007
: …………………………………..
ii “I hereby declare that this thesis entitled ”Site Diversity Against Rain Fading In LMDS
Systems” is the result of my research except for works that have been clearly cited in the
references”.
Signature
: ………………………..…………
Name
: Zaid Ahmed Shamsan Abdo
Date
MAY 2007
: …………………………………..
iii To my beloved parents, to my beloved wife, to our sons Osamah and
Mohammad, and to our daughters Sumaih and Shadha.
iv ACKNOWLEDGEMENT
In the name of Allah, the Most gracious, the Most Merciful. Firstly, all
commendation to Allah for the incredible gift bestowed upon me and for give me the
determination to pursue with this study and enable me to prepare this thesis.
I deeply appreciate the inspirations and guideline that I have received from
my supervisor PM Dr. Jafri Bin Din for his personal kindness, skill, patience,
valuable advice and encouragement.
I would like to thank all of my family and all my friends for their moral
support on me for completing this work.
v ABSTRACT
Local Multipoint Distribution Service (LMDS) is a new terrestrial fixed radio
technology for broadband communication applicable that can be used to provide digital
two-way voice, data, Internet, and video services or other digital services requiring
high capacity traffic channels. LMDS is a point to multipoint wireless system operating
at frequencies above 20 GHz, the most serious impairment at these frequencies is rain
fading. In the system point of view a moving rain cell over the LMDS service area will
not only attenuate the desired signal but also the interferer. Many techniques could be
used to overcome rain fading. Applying Site Diversity as a possible solution to reduce
the effect of rain is necessary, because a rain-cell degrades the system performance at
a part of the service area but the rain can improve the carrier signal conditions
elsewhere depending on the locations of the Base Station, Terminal Station and the
rain-cell. The rain attenuation of different locations in Malaysia region in a given
LMDS is calculated and the effects of a moving rain cell over an LMDS system are
analyzed, different situations of interference according to the position of the rain-cell
over the service area of LMDS are elaborated. The site diversity is implemented based
on the ITU-R Recommendations to enhancement LMDS. The location dependent C/I
in the LMDS service area under rainy conditions with and without site diversity
technique is calculated and simulated. Different cell sizes of LMDS with and without
site diversity are considered in this project for significant analyses and discussions. It is
found that site diversity has high ability to improve the performance level of all LMDS
service area specially under rainy conditions.
vi ABSTRAK
Local Multipoint Distribution Service (LMDS) adalah suatu teknologi baru
daripada radio bumi yang ditetapkan untuk komunikasi jalur lebar yang dapat
digunakan untuk menyediakan jalur digital suara dua hala, data, Internet, dan
perkhidmatan video atau perkhidmatan digital lainnya yang memerlukan saluran trafik
berpasitas tinggi. LMDS adalah suatu sistem titik ke banyak titik dari media tanpa
wayar yang beroperasi pada frekuensi di atas 20 GHz, kebanyakan pelemahan
rangkaian pada frekuensi ini adalah pemudaran oleh hujan. Jika dilihat dari prespektif
system LMDS, sel hujan yang bergerak melepasi kawasan perkhidmatan LMDS bukan
sahaja melemahkan isyarat yang diterima, tetapi turut mengganggunya. Banyak cara
dapat digunakan untuk mengatasi masalah pemudaran hujan. Teknik kepelbagaian
lawan dapat digunakan sebagai kemungkinan mengurangi kesan hujan. Sel hujan akan
melemahkan prestasi perkhidmatan pada sebahagian kawasan liputan tetapi akan
meningkatkan prestasi perkhidmatan bergantung kepada kedudukan stesen tapak,
stesen terminal dan sel hujan. Pelemahan hujan pada beberapa lokasi LDMS di
Malaysia telah ditentukan dengan mengambilkira kesan pergerakan sel hujan melepasi
kawasan LDMS. Perbezaan situasi gangguan disebabkan oleh perbezaan kedudukan
sel hujan telah dilaporkan.
Prestasi LDMS dinilai berdasarkan pengalaman
perlaksanaan perkhidmatan LDMS. Teknik kepelbagaian laluan dilaksanakan
berdasarkan rekomendasi ITU-R. Lokasi bersandar C/I dalam perkhidmatan LDMS
ketika hujan dengan dan tanpa teknik kepelbagaian lawan dihitung dan disimulasikan.
Perbezaan saiz sel LMDS diambilkira dalam perbincangan dan analisa kajian. Ini
didapati bahawa teknik kepelbagaian lawan mempunyai keupayaan yang tinggi bagi
mempertingkatkan tahap prestasi semua kawasan perkhidmatan LMDS terutamanya
pada waktu hujan.
vii TABLE OF CONTENTS
CHAPTER
TITLE
PAGE
DECLARATION
ii
DEDICATION
iii
ACKNOWLEDGEMENTS
iv
ABSTRACT
v
ABSTRAK
vi
TABLE OF CONTENTS
vii
LIST OF FIGURES
xi
LIST OF TABLES
xiv
LIST OF ABBREVIATIONS
xv
LIST OF APPENDICES
xvii
1.
INTRODUCTION
1
1.1
Background
1
1.2
Objective of the Project:
3
1.3
Scope of the Project
3
1.4
Methodology of the Project
3
1.5
Thesis Outline
4
2.
LOCAL MULTIPOINT DISTRIBUTION SERVICE
AND RAIN FADING
6
2.1 Introduction
6
2.2
Basic Principles
8
viii 2.2.1
of LMDS
Advantages/Disadvantages
10
2.2.2
Applications and Service Performance
13
2.2.3 Frequency Band and Spectrum Allocation
13
2.3
Wireless Links and Access Options
15
2.3.1 TDMA or FDMA Selection
17
2.4
Cell planning 17
2.5
Link Budget Calculation
19
2.6
Dynamic Bandwidth Allocation
20
2.7
C/I and Inter-Cellular Interference
21
2.8
The Rain Fading
23
2.8.1
Introduction
23
2.8.2 Rain Effects
24
2.8.3 Rain Attenuation Equation
25
2.8.4
27
2.9
Rain-Cell over LMDS System
Effects of Rain Fading on the Efficiency of the
Ka-Band LMDS System
28
2.9.1
Interference Analysis of the Boundary Subscriber
29
2.9.2
Channel Capacity in Rain Fading
30
2.9.3
Bit Error Rate
31
2.9.4
Cell-Coverage Effect
32
SITE DIVERSITY TECHNIQUE
33
3.
3.1
Introduction
33
3.2
Site Diversity
34
3.3
Diversity Gain and Diversity Improvement Concepts
36
3.3.1
Cell-Site Diversity Performance
36
3.3.2
Cell-Site Diversity Performance Measures
38
3.4
Influenced Factors
40
ix 4.
PROJECT METHODOLOGY
42
4.1
4.2
4.3
Introduction 42
Establishing of LMDS Network
43
Calculation of Rain Attenuation
45
4.3.1 Specific Rain Attenuation
46
4.3.2
46
Effective Path Length
4.3.3 Rain Attenuation
47
4.4
Rain Cell Movement within LMDS
47
4.5
Site Diversity Implementation
47
5.
RESULTS AND ANALYSIS
49
5.1
Introduction
49
5.2
LMDS Configuration
50
5.3
LMDS Frequencies and Parameters
51
5.4
Rain Attenuation Data and Calculations
52
5.4.1
52
5.4.2 Effective Path Length Calculation
53
5.4.3
Rain Attenuation Calculation
54
5.4.3.1 Rain Attenuation at 24 GHz
54
5.4.3.2 Rain Attenuation at 26 GHz
56
5.4.3.3
Specific Rain Attenuation Calculation
Comparison between Rain Rates Attenuation at
Different Frequencies
58
Terminal Station Situation Possibilities
60
5.5.1
61
5.5.2 The Four Cases and Rain Cell Movement Effects over
5.5
All LMDS Service Area with Rain and without Rain
LMDS
63
x 5.5.2.1
Effect of Rain Movement on the Received
Signal at 24 GHz
5.5.2.2
5.6
Maximum Coverage & Different Sector Size
5.7
Coverage at 24 GHz
Coverage at 26 GHz
67
69
Site Diversity Implementation and Calculations
72
5.7.1
LMDS with Site Diversity
73
5.7.1.1
Site Diversity Calculations at 24 GHz
73
5.7.1.2
Site Diversity Calculations at 26 GHz
75
5.7.1.3 Overall Average C/I values of LMDS with and
without Site Diversity
67
5.6.2 Relationship between Sector Size and Maximum
5.8
65
5.6.1 Relationship between Sector Size and Maximum
Effect of Rain Movement on the Received
Signal at 26 GHz 63
Site Diversity with Different Cell Sizes of LMDS
77
79
6.
CONCLUSION AND FUTURE WORK
84
6.1 Summary
84
6.2 Conclusion
85
6.3 Future Work
86
REFERENCES
Appendices A - H
87
91- 104
xi LIST OF FIGURES
FIGURE No.
TITLE
PAGE
2.1
Illustration of an LMDS network
8
2.2
The operation of LMDS for broadcast and interactive services
9
2.3
Multipath propagation and LMDS systems
10
2.4
LMDS band allocation
14
2.5
FDMA access
15
2.6
TDMA access
15
2.7
Frequency plan for an LMDS service
18
2.8
Inter-Cellular Interference
22
3.1
Typical scenario of cell-site diversity
33
3.2
Diversity gain and diversity improvement concepts
36
3.3
Geometrical configuration of a cell-site diversity scheme
37
3.4
Single and joint annual exceedance probability of rain
attenuation for typical diversity LMDS system
40
4.1
LMDS area structure
43
4.2
The supposed scenario of LMDS
45
4.3
Site diversity implementation
48
5.1
The supposed scenario of LMDS without site diversity
50
5.2
Rain attenuation vs. path length at 24 GHz and 96 mm/h
5.3
(Jelebu)
55
Rain attenuation vs. path length at 24 GHz and 125 mm/h
5.4
(Johor Bahru)
55
Rain attenuation vs. path length at 24 GHz and 145 mm/h
(Taiping)
56
xii 5.5
Rain attenuation vs. path length at 26 GHz and 96 mm/h (Jelebu)
5.6
Rain attenuation vs. path length at 26 GHz and 125 mm/h
57
(Johor Bahru)
57
5.7
Rain attenuation vs. path length at 26 GHz and 145 mm/h (Taiping)
58
5.8
Rain attenuation vs. rain rates at 24 GHz
58
5.9
Rain attenuation vs. rain rates at 26 GHz
59
5.10
All LMDS with rain and without rain at 24 GHz
62
5.11
All LMDS with rain and without rain at 26 GHz
62
5.12
The four cases under 24 GHz and 96 mm/h conditions
63
5.13
The four cases under 24 GHz and 125 mm/h conditions
64
5.14
The four cases under 24 GHz and 145 mm/h conditions
64
5.15
The four cases under 26 GHz and 96 mm/h conditions
65
5.16
The four cases under 26 GHz and 125 mm/h conditions
65
5.17
The four cases under 26 GHz and 145 mm/h conditions
66
5.18
Maximum coverage vs. different sector size of worst case at
24 GHz and 96 mm/h
5.19
68
Maximum coverage vs. different sector size of worst case at
24 GHz and 125 mm/h
5.20
68
Maximum coverage vs. different sector size of worst case at
24 GHz and 145 mm/h
5.21
69
Maximum coverage vs. different sector size of worst case at
26 GHz and 96 mm/h
5.22
69
Maximum coverage vs. different sector size of worst case at
26 GHz and 125 mm/h
5.23
70
Maximum coverage vs. different sector size of worst case at
26 GHz and 145 mm/h
70
5.24
Implementation of site diversity
72
5.25
LMDS with and without site diversity at 24 GHz and 96 mm/h
73
5.26
LMDS with and without site diversity at 24 GHz and 125 mm/h
74
LMDS with and without site diversity at 24 GHz and 145 mm/h
74
5.27
xiii 5.28
at 26 GHz and 96 mm/h
LMDS with and without site diversity
75
5.29
at 26 GHz and 125 mm/h
LMDS with and without site diversity
76
5.30
LMDS with and without site diversity at 26 GHz and 145 mm/h
76
5.31
Site diversity vs. different sector sizes of worst case at 24GHz
and 96 mm/h
80
5.32
Site diversity vs. different sector sizes of worst case at 24GHz
and 125 mm/h
5.33
5.34
5.35
5.36
Site diversity vs. different sector sizes of worst case at 24GHz
and 145 mm/h
81
Site diversity vs. different sector sizes of worst case at 26GHz
and 96 mm/h
81
Site diversity vs. different sector sizes of worst case at 26GHz
and 125 mm/h
82
Site diversity vs. different sector sizes of worst case at 26GHz
and 145 mm/h
80
82
xiv LIST OF TABLES
TABLE NO.
TITLE
PAGE
2.1
Capacity comparison of available access technologies
11
2.2
LMDS Advantages/Disadvantages
12
2.3
Parameters and formulas for LMDS
19
2.4
Key parameter of some modulation scheme
21
2.5
An example of calculation of rain attenuation
27
2.6
Relationship between reversed distance dR, rain rate RR and
cell size
5.1
29
The distance between terminal station and the effective
base stations
51
5.2
Parameters, formulas for LMDS (26GHz)
51
5.3
Parameters, formulas for LMDS (24GHz)
52
5.4
Specific rain attenuation
53
5.5
Effective path length value of effective signals
54
5.6
Rain attenuation at corner of LMDS cell
60
5.7
Maximum coverage during worst case without using site
diversity
5.8
Average C/I (dB) of LMDS service area at d= 4.2456 km
(24 GHz)
5.9
71
77
Average C/I (dB) of LMDS service area at d= 4.2456 km
(26 GHz)
78
5.10
Average C/I (dB) of LMDS service area at d= 2 km (24 GHz)
78
5.11
Average C/I (dB) of LMDS service area at d= 2 km (26 GHz)
79
xv LIST OF ABBREVIATIONS
ADSL/VDSL -
Asynchronous/Very High– Rate Digital Subscriber Line
ATM
-
Asynchronous transfer mode
BER
-
Bit Error Rate
BS
-
Base Station
BSC
-
Base Station Controller
BTS
-
Base Station Transceiver
BWA
-
Broadband wireless access
C/B
-
Channel Capacity
CDF
-
Cumulative Distribution Function.
CDMA
-
Code Division Multiple Access.
C/I
-
Carrier to Interference ratio
CPE
-
Customer Premise Equipment
DBA
-
Dynamic Bandwidth Allocation
FCC
-
Federal Communications Commission
FDMA
-
Frequency Division Multiple Access.
FEC
-
Forward error correction
FTTH
-
Fiber-to-the-home.
HFC
-
Hybrid Fiber Coax
HS
-
Hub Station
ISI
-
Inter-symbol Interference
ITU-R
-
International Telecommunication Union Radio-Broadcasting
LAN
-
Local Area Network
LMCS
-
Local Multipoint Communication Systems
xvi LMDS
-
Local Multipoint Distribution Services.
LOS
-
Line of sight.
MCMC
-
Malaysian Communications and Multimedia Commission
MSS
-
Mobile Satellite Service
NOC
-
Network Operations Center
PDF
-
Probability Density Function
PONs
-
Passive Optical Networks
PSTN
-
Public Switch Telephone Networks
QAM
-
Quadrature Amplitude Modulation
QPSK
-
Quadrature Phase Shift Keying
SD
-
Site Diversity
SDBS
-
Site Diversity Base Station
S/I
-
Signal-to-Interference Ratio.
SNR
-
Signal to noise ratio
SRSP
-
Standard Radio System Plan
TDMA
-
Time Division Multiple Access.
TS
-
Terminal Station
WAN
-
Wide Area Network
xvii LIST OF APPENDICES
APPENDIX
TITLE
PAGE
Appendix A
Part of the ITU-R Specific Attenuation Parameters
91
Appendix B
LMDS Frequencies of Malaysia
92
Appendix C
MATLAB Program for Rain Attenuation
93
Appendix D
MATLAB Program for ALL LMDS with and
Without Rain
Appendix E
MATLAB Program for Possibilities Scenarios of
LMDS Area
Appendix F
100
MATLAB Program for the Worst Case Scenario
by Using Site Diversity
Appendix H
97 MATLAB Program for the Worst Case Scenario
and Different LMDS Cell Sizes
Appendix G
95 102
MATLAB Program for the Worst Case Scenario
and Different LMDS Cell Sizes by Using Site
Diversity Technique
104 CHAPTER 1
INTRODUCTION
1.1
Background
There is a growing interest in providing broad-band services through local
access networks to individual users. Millimetric-wave radio solutions are considered
as the optimal delivery systems for these services. They are termed as broad-band
wireless access (BWA) systems or local multipoint distributed services LMDS.
(Panagopoulos et al., 2002).
The new broadband networks and services are developed continuously to
serve the different demands, e.g., Internet, mobile Internet, broadcasting, telephony,
e-commerce, Video on Demand, etc. Point-to-multipoint wireless system could be a
promising solution to connect the users to the backbone network instead of
broadband wired networks because of its cost efficiency, easy and fast installation,
and re-configurability; however due to the time and location variable channel
conditions the system should apply fade mitigation techniques to reach the quality of
service requirements. (Sinka and Bito, 2003).
The Ka (20/30 GHz) and V (40/50 GHz) frequency bands are becoming increasingly
attractive for user oriented future commercial satellite services, due to their large
available bandwidths. However, they suffer more from rain fades in comparison to
the almost congested Ku (12/14 GHz) band. Therefore, prediction models for annual
rain attenuation, such as the ones developed by several research groups over the past
2
three decades are required to provide guidance in the course of balancing availability
requirements and cost. (Panagopoulos et al., 2002).
To combat rain attenuation, several fade mitigation techniques have been
developed such as diversity protection schemes, power control and adaptive
processing techniques. Among these techniques, the most efficient is site diversity
(SD). SD takes advantage of the spatial characteristics of the rainfall medium by
using two earth stations to exploit the fact that the probability of attenuation due to
rain occurring simultaneously on the alternative Earth-space paths is significantly
less than the relevant probability occurring on either individual path. (Panagopoulos
et al., 2002).
Though the cost effectiveness of SD remains questionable, the interest on SD
has been renewed, due to the significant reduction of ground terminal antennas and
other hardware sizes. Nowadays, terminals can be installed in customers’ premises
and the use of public terrestrial networks to carry out signaling seems possible.
(Panagopoulos et al., 2002).
A rain-cell degrades the system performance at a part of the service area but
the rain can improve the carrier-to-interference ratio C/I conditions elsewhere
depending on the locations of the Base Station, Terminal Station and the rain-cell.
Interference fluctuation is a very important thing in LMDS network planning
procedures, which needs countermeasure techniques to avoid degradation of the
quality of service. (Sinka et al., 2002).
From the pervious paragraphs, it is clarified that the problem statement of this
project indicates that the high availability of LMDS can not be obtained under rain
effects, so site diversity should be suggested as one effective means to overcome rain
fading.
3
1.1 Objective of the Project:
The main objective of this project is to study the effects of site diversity in
LMDS under rainy conditions in Malaysia.
1.2 Scope of the Project
The scope of this project includes:
•
To analyze the effects of a moving rain cell over an LMDS system
•
This study includes calculation of Rain Attenuation in a given LMDS system.
1.3 Methodology of The Project
To carry out this project, the following methodology is designed as the following
steps:
•
Establishing of LMDS Network:
By determining
- Frequency used and sectorisation
- Structure of system (BS & TS)
- Distance or cell size
•
Calculation of Rain Attenuation based ITU-R Model by using Rainfall rate of
different locations over Malaysia in order to cover all Malaysia region
weather and therefore the study can be generalized to include the regions that
have the same climate (tropical climate weather).
4
•
Analyzing of Rain cell Movement within LMDS, this is done by taking all
possibilities or terminal station situations over LMDS area and effect of
Interference signals.
•
Site Diversity Implementation, this step is done according to the previous
studies related to LMDS system.
1.5
Thesis Outline
The layout of this report is as follows, chapter one includes a brief general
background of LMDS system and rain attenuation. The objective of this project is
clearly stated. The research scope and methodology are presented.
Chapter two is the first chapter of the literature review, presents the Local
Multipoint Distribution Service Systems and its specifications and components as
will as rain fading and its effects on the signal, also this chapter includes steps to
calculate rain attenuation.
Chapter three shows the concept of Site Diversity system and expressions
which are used to describe the performance of the site diversity. This chapter
explains brief details about how to implement site diversity in LMDS system during
rainy conditions and some parameters to express site diversity.
Chapter four represents the methodology of this project, including the
details of how to establish LMDS, rain attenuation calculation, effects of rain over
LMDS area and site diversity implementation are presented.
Chapter five presents the whole results of this work and discussions of these
results as well as some of analyses. The results include specific rain attenuation, rain
attenuation and different LMDS cell sizes with and without site diversity.
Comparisons and simulations of these results are also presented.
5
Chapter six contains summary, conclusion and the recommendations or future
work which are presented based on the obtained results.
CHAPTER 2
LOCAL MULTIPOINT DISTRIBUTION SERVICE AND RAIN FADING
2.1
Introduction
LMDS is a broadband wireless point-to-multipoint communication system operating
above 20 GHz (depending on country of licensing) that can be used to provide digital
two-way voice, data, Internet, and video services.
The acronym LMDS is derived from the following:
• L (local) denotes that propagation characteristics of signal in this frequency range
limit the potential coverage area of a single cell site; ongoing field trials conducted in
metropolitan centers place the range of an LMDS transmitter at up to 5 miles.
• M (multipoint) indicates that signals are transmitted in a point-to-multipoint or
broadcast method; the wireless return path, from subscriber to the base station, is a
point-to-point transmission.
• D (distribution) refers to the distribution of signals, which may consist of
simultaneous voice, data, Internet and video traffic.
7
• S (service) implies the subscriber nature of the relationship between the operator
and the customer; the service offered through an LMDS network is entirely
dependent on the operator’s choice of business. (The international Engineering
Consortium (IEC)).
LMDS, or sometimes called LMCS (Local Multipoint Communications
Systems), offers an exciting new alternative to traditional means of providing voice,
data or video service to consumers over copper telephone wires or coax cable. This
use of fixed wireless technology eliminates the expensive task of installing
communication lines to each user, and can also be deployed in a relatively short
amount of time. With multi-service (Multipoint) capabilities and large bandwidth
capacity, LMDS addresses the present and future needs of the customer. Hence, this
technology is considered as one of the most prominent solutions to the "Last Mile
Problem” of extending communication to homes and businesses.
The last mile problem extends from the interface between the large network
backbones made up of high-speed fiber optic cables (Gbps capacity) with that of the
“local loop” transition copper cables (kbps modem lines) connected to homes and
local businesses. In order to resolve this restriction in capacity, broadband wireless
networks capable of handling capacities ranging into hundreds of Mbps, such as
LMDS, was developed. There are four main components in the basic architecture of
an LMDS system: network operations center (NOC), fiber-based infrastructure, base
station, and customer premise equipment (CPE). The following Figure 2.1 provides a
pictorial illustration of this network.
8
Figure 2.1: Illustration of an LMDS network [IEC]
The NOC is the control center of the LMDS service provider, which monitors
the performance of the network. At the base station, the connection and conversion
from wireless to the fiber-based infrastructure is established. This includes
connections to Internet and public switch telephone networks (PSTN). The Customer
Premise Equipment (CPE) is the customer’s interface with the subscribed network.
As demonstrated in the figure, this interface can be shared with many users or a
single user.
2.2 Basic Principles
LMDS are combined high-capacity radio-based communications and
broadcast systems with interactivity operated at millimeter frequencies. Early
systems, however, were mainly used for analog TV distribution, and it all started
with Cellular Vision and then it is proposed a system for TV distribution in a main
central. (Agne and Telenor, 2000).
Digital television opened for a combined transport of data representing TV
programs, data, and communication. The possibility of implementing a full-service
9
broadband access network by rebuilding a broadcast network into an interactive
network by functionally adding a communications channel for the return was a
reality that coincided almost perfectly with the growth of the Internet and data
services. Broadband interactivity arrived with digitalization. Interactive LMDS has a
point-to-multipoint downlink and a point-to-point uplink, as illustrated in the
following Figure 2.2.
The transmitter site should be on top of a tall building or on a high pole
overlooking the service area. The transmitter covers a sector typically 60–90° wide.
Full coverage thus requires 4-6 transmitters. The streams transmitted contain 34-38
Mb/s of data addressed to everybody (typical TV) in the coverage zone, subgroups or
individuals (typical communication, Internet). The capacity of the point to point
return channels is determined by the needs of the individual user.
Figure 2.2: The operation of LMDS for broadcast and interactive services.
Operation of LMDS in an area will normally require a cluster of cells with
separate base stations for co-located transmitter/receiver sites. One of the base station
sites will serve as coordination center for the franchise area and connect the LMDS
cells to external networks. Intercell networking may be implemented using fiber or
short hop radio relay connections. Co-location with mobile base stations allows for
infrastructure sharing. (Agne and Telenor, 2000).
10
2.2.1 Advantages/Disadvantages of LMDS
As described earlier, LMDS provides a wireless alternative to other wired and
wireless applications such as DSL, fiber, coax, or satellite. The different technologies
contributing to broadband access networking all have clear advantages and
drawbacks.
LMDS is essentially a line-of-sight technology. However, some research
shows that due to the high frequency and short wavelength, LMDS may be able to
take advantage of reflections from buildings to achieve coverage in some areas that
are not in the direct line of sight from a transmitter as it is shown in Figure 2.3.
(Blake, 2001).
Figure 2.3: Multipath propagation and LMDS systems
Illustrated in Table 2.1, is the capacity comparison of several access
technologies to each remote.
11
Table 2.1: Capacity comparison of available access technologies
Type
Uplink Data Rate
Downlink Data Rate
Max Range
(km)
Analog Modem
14.4 ~ 56 Kbps
14.4 ~ 56 Kbps
<6 ~ 7
ISDN
128 Kbps
128 Kbps
N/A
ADSL
64 Kbps ~ 1.5 Mbps
1.5 ~ 9 Mbps
2~6
VDSL
>10Mbps
13 Mbps
1
25 Mbps
Cable Modems
500 Kbps ~ 3 Mbps
30 Mbps (shared)
N/A
Satellite, DVB- RCS
2 Mbps
36 Mbps (shared)
Not limited
LMDS
0 ~ 8 Mbps typical
45 Mbps (shared)
5
25.8 Mbps possible
The advantages of the LMDS over the competitive access technologies such
as Hybrid Fiber Coax (HFC) and Passive Optical Networks (PONs) are as follows:
• Low entry and deployment cost.
• Ease and speed of deployment: deployment of cable and fiber systems is difficult in
certain areas where installing in-ground infrastructure is undesirable. LMDS can
provide similar access bandwidths and a two way capability without trenching streets
and yards.
• Faster realization of revenues as a result of rapid deployment.
• Quick response to growing market.
• Bandwidth on demand: Any or all the bandwidth is available to all subscribers
within the range of the hub. LMDS provides a wireless alternative to fiber, coax, and
asynchronous/very high– rate digital subscriber line (ADSL/VDSL) and offers a high
capacity locally compared with other radio solutions like interactive satellite systems.
Despite the above mentioned advantages, there are few disadvantages as well
which can be stated as follows:
12
• Because of the nature of frequency reuse there is always the possibility of
interference.
• In the frequency range of 20 GHz and above the wavelength is of the order of
millimeter. This poses the problem of coverage. With such a small size of
wavelength, tree buildings, terrain and even rain drops cause a high attenuation.
Propagation characteristics of millimeter waves require that transmission
should be line of sight; this means small coverage cells. Consequently we have a
larger number of cells for a given area and therefore an increased number of base
stations (BS) and distribution infrastructure. These advantages and disadvantages are
summarized in Table 2.2.
Table 2.2: LMDS Advantages/Disadvantages
LMDS Advantages
• Low entry and deployment cost
LMDS Disadvantages
• Operating in millimeter wavelengths
requiring line-of-sight to transmitter
• Ease and speed of deployment
• Attenuation effects due to rain, foliage,
and obstructions
• Point-to-Multipoint access-
• New, un-established, lack of standards
Provides a solution to the Last Mile
Problem
• Provides high capacity (broadband)
• Equipment is still in its early
service
development stage- equipment cost remains
quite high
• Scalability- Ability to grow-out
footprint coverage with demand
13
2.2.2 Applications and Service Performance
LMDS is wireless terrestrial bi-directional communication systems that are
intended to provide broadband services to home and business subscribers within
covered service areas. The targeted services range from one-way video distribution
and voice telephony to fully interactive switched broadband multimedia applications.
Some of these applications are as follows:
• Video on demand application
• Broadband Internet access
• Interactive multimedia
• Home office
• Distance education
• Voice and Video Telephony
• Entertainment TV
• Interactive video games
• Home shopping
The required service performance for LMCS can be summarized (Salem Salamah,
2000) as follows:
• Call set up < 10 sec.
• Isochronous cell loss rate < 10 −3 , asynchronous cell loss rate < 10 −4
• Maximum delay < 50 ms.
2.2.3 Frequency Band and Spectrum Allocation
Regulatory agencies such as the U.S. Federal Communications Commission
(FCC) are authorizing point-to-multipoint radio systems to operate over a block of
spectrum and throughout a large geographical area. FCC has proposed two separate
licenses, one license for a bandwidth of 1150 MHz, which includes the spectrum
from 27.5 to 28.35 GHz, 29.1 to 29.25 GHz and 31.075 to 31.225 GHz. This
spectrum is referred as Block A. The second license, referred as Block B, includes
the spectrum from 31 to 31.075 GHz and 31.225 to 31.3 GHz, a total of 150 MHz
14
(Douglas, 1997). Industry Canada granted two blocks of 500 MHz in the 27.35 to
28.35 GHz ranges. Additional spectrum from 25.35 to 27.35 GHz has been
designated for LMCS future use. Frequency bands in USA are shown in the
following Figure 2.4.
Figure 2.4: LMDS band allocation in USA [FCC]
The segment beginning at 29.1 GHz is shared with the mobile satellite service
(MSS) and has several restrictions. The restrictions (IEEE802.org/16) include:
1. Subscriber stations may not transmit.
2. LMDS hub antennas are restricted as to upper elevation gain.
3. The aggregate radiated power per square kilometer is restricted.
4. In some cases coordination is required with MSS earth stations.
These restrictions limit the distance between hub and subscriber sites and
increase system design and administration cost. Licensing and deployment in Europe
now indicate that there will be systems in different frequency bands from 24 GHz up
to 43.5GHz. The frequency band 24.5-26.6 GHz with sub-bands of 56 MHz has been
opened for point-to-multipoint applications in many European countries. These
bands may then be used for LMDS.
15
2.3 Wireless Links and Access Options
Wireless system designs are built around three primary access methodologies:
TDMA, FDMA, and CDMA. These access methods apply to the connection from the
customer-premises site to the base station, referred to as the upstream direction.
Currently, most system operators and standards activities address the TDMA and
FDMA approaches. In the downstream direction, from base station to customer
premises, most companies supply Time Division Multiplexed (TDM) streams either
to a specific user site (point-to-point connectivity) or multiple user sites (a point-tomultipoint system design). Figure 2.5 illustrates an FDMA scheme in which multiple
customer sites share the downstream connection. Separate frequency allocations are
used from each customer site to the base station.
Figure 2.5: FDMA access
Figure 2.6 illustrates a TDMA scheme in which multiple customer sites share both
the downstream and upstream channel.
Figure 2.6: TDMA access
16
With FDMA and TDMA access links, whether downstream or upstream,
there are a number of factors that affect their efficiency and usage. For FDMA links,
the customer premises site is allocated bandwidth which is either constant over time
or which slowly varies over time. For TDMA links, the customer premises is
allocated bandwidth designed to respond to data bursts from the customer site. These
two access methods will probably provide the majority of access links for LMDS
systems over the next few years. The choice between these access links is directly
related to the system operator business case, service strategy, and target market.
Large customer premises may require a wireless DS–3 or multiple
unstructured DS–1 connections. A customer might purchase the use of this wireless
connection with the understanding that the bandwidth is available 24 hours a day. In
this case, FDMA access links make sense, because the user is paying for and
receiving dedicated bandwidth over the wireless access system as well as over the
network infrastructure. Typically, the FDMA links terminate in a dedicated FDMA
demodulator circuit within the base station.
The other extreme customer case could be customer premises sites that
require a single 10BaseT port for Internet access. These users have very low
upstream data requirements (acknowledgment packets and data requests are the
primary traffic) but may have fairly large downstream data requirements. In this
case, TDMA access makes sense, allowing multiple low–data rate users to share a
single channel. In addition, the base station terminates the TDMA access link in a
single modem, allowing multiple customers to share the single modem at the base
station.
Most system operators will have a service mix and target market that lies
between these two cases. The choice of TDMA and/or FDMA access methods within
the system becomes an issue both for the system designer and the system operator.
As a final example, suppose a system operator wishes to serve a six-story
office building containing 20 employees per floor. This offers a total POTS line
count of 120. Each office currently uses various mixtures of frame relay, DS–1, fax
lines, and modem lines. Some offices wish to connect their in-office Ethernet local-
17
area network (LAN) to the wide-area network (WAN) using routers. The system
operator knows that only a percentage of the offices will switch to a wireless service
provider.
2.3.1 TDMA or FDMA Selection
How does a system operator decide when to use TDMA and when to use
FDMA? First, it is necessary to estimate the peak and average expected traffic data
rate from all of the potential or estimated offices. Second, it is important to determine
which traffic may be multiplexed and traffic-shaped to smooth out the traffic
burstiness. If the resulting burstiness is smooth enough, the upstream traffic
requirements can be handled effectively using FDMA techniques. Alternately, if
burstiness persists within the traffic stream, TDMA may be a better choice.
2.4 Cell Planning
Overall system architecture is cellular. And although LMDS systems can be
based on hexagonal cell patterns which are commonly used in mobile radio systems,
rectangular cell patterns have become very popular in LMDS network design.
A cell consists of one hub station and a multitude of terminal stations (TS).
One cell is sectorized with 4 sectors whose width is 90 degree. Cellular planning
aims at using as munch as possible channel bandwidth in each sector to maximize
link capacity (Lee and Chung, 1998). With a simple quadrature phase-shift keying
(QPSK) modulation, a 28-MHz channel is sufficient to transmit a useful data rate of
16x2 Mbit/s. The total bit rate per cell is then 64x2 Mbit/s and can be used to serve
for example 64 business customers with a 2 Mbit/s leased line each. This example is
only to give an idea of the cell capacity. In practice, the number of subscribers per
cell may be several hundreds or several thousands, and such a large number of users
are accommodated by dynamically sharing the available resources between them.
18
Assuming 1000 subscribers, the 64x2 Mbit/s cell capacity gives a bit rate of 128
kbit/s if all users are simultaneously active and the total capacity is evenly shared
between them. (Hikmet, 2000).
Figure 2.7 shows frequency plan for LMDS services. "A, B" means
horizontal polarization and "a, b" means vertical polarization. It enables 2x frequency
re-use and higher capacity. In this figure, bold line denotes cell boundary. Within one
cell, adjacent sectors use orthogonal polarization or different frequency bands to
minimize inter-cellular interference. (Lee et al., 1998).
In a fixed radio access system, cell planning aims at using as much as
possible of the channel bandwidth in each sector to maximize link capacity. Intercellular interference between different cells in addition to noise reduces the
achievable bandwidth efficiency. To minimize interference, frequency decoupling,
polarization decoupling and space decoupling method are used. Considering this
interference, C/I of received signal at terminal can be calculated. C/I contour curves
divide the cell into some partial areas appropriate for different modulation schemes.
Figure 2.7: Frequency plan for an LMDS service
19
2.5 Link Budget Calculation
To get link budget, many factors must be considered. Especially, above
2OGHz, rain attenuation affects critically the received signal intensity at terminal
station (TS). Table 2.3 lists all the parameters to be considered and contains the
comments and link budget formulae. If a TS is located on the cell boundary, 5 km
apart from Hub station (HS) or Base Station (BS), the CNR (Carrier-to-Noise Ratio)
is equal to 20.76(dB) shown at the bottom row. If TS is located within a cell, the
CNR depends on only the distance (r) between HS and TS. From Table 2.3, the
general formula for link budget has the following form:
CNR(dB)= 60.24 – 20Log r - 5.1 r
(2.1)
Where r (km): distance between HS and TS.
Equation (2.1) shows that CNR of-received signal at terminal station
decreases as the distance between hub station and terminal station increases.
Table 2.3: Parameters and formulas for LMDS
Parameter
Units
Formula
Transmit Power into antenna
dBW
Transmit Antenna Gain
dBi
Gt = Gant
Receiver Antenna Gain
dBi
Gr = Gant
Frequency
GHz
f : Transmit Frequency
Path Length
km
d : from base station to terminal station
Field Margin
dB
Lfm : Antenna Mis-Alignment
Free-Space Loss
dB
Lfs = 92.45 + 20 * log(f) + 20 * log(d)
Atmospheric Loss
dB
Latm = d * 0.1 dB/km
Excess Path Loss
dB
Lexcess = d * -5.0 dB/km (due to rain)
Ptx : Transmit power per carrier
20
Total Path Loss
dB
Effective Bandwidth
MHz
Receiver Noise Figure
dB
Equipartition Law
dBW/MHz
System Loss
dB
Receive Signal Level
dBW
Thermal Noise Power
Spectral Density
Carrier-to-Noise Ratio
Ltot = Lfm + Latm + Lfs + Lexcess
Brf : Receiver Noise Bandwidth
NF : Effective Noise Figure
10*log(k*To), k=1.38*10-23 J/ K, To=290K
Lsys = Gt + Gr - Ltot
RSL = Ptx + Lsys
dBW/MHz No = 10 * log(K * To) + NF
dB
C/N = RSL – No – 10 * log (Brf)
2.6 Dynamic Bandwidth Allocation
The basic idea of Dynamic Bandwidth Allocation (DBA) is, that in case of
changing traffic or data rate, the dual modem functionality allows for setting up a
new carrier with new transmission parameters like new data rate, modulation,
coding, carrier frequency, power level etc., while for a short time, until the new
carrier is fully setup and synchronized, the existing carrier is still in operation. In this
paper, focused on the modulation scheme of DBA, dynamic modulation scheme will
be applied to LMDS for better bandwidth efficiency. Each modulation scheme has
different key parameters, i.e. code rate, CNR and spectrum efficiency, etc. Higher
order modulation scheme has higher bandwidth efficiency but also needs higher
(CNR)th, in order to guarantee a specific BER.
Table 2.4 shows key parameters of modulation scheme needed for system
threshold (BER = 10 −6 ).According to the table, QAM has higher spectrum efficiency
than that of QPSK. But, it also needs higher (CNR)th.
21
Table 2.4: Key parameters of some modulation scheme
Note: * roll-off = 0.3
Modulation
Spectrum Efficiency
Channel Coding
CNRth (dB)
QPSK
7/8
12.3
1.75
16QAM
(RS 204,188)
19.2
3.69
46QAM
(RS 204,188)
25.5
5.53
Scheme
(bps/Hz)*
2.7 C/I and Inter-Cellular Interference
This section, for C/I terminal calculation. As shown in Figure 2.8, TS1 and
TS2 are placed on the sector l horizontal and vertical axis, respectively. And, TS3 is
placed on the diagonal axis of the same sector. Its frequency band is "a". The
terminal antenna is omnidirectional. It is aimed at the sector antenna located at the
center of cell. And, the beamwidth of the terminal antenna is very small. (3dB
beamwidth = 8 degrees).
The terminal antenna of TS1 heads westward along the horizontal axis. TS1
receives interference from sector 2 which reuses the same frequency band. The high
directivity of terminal antenna enables interferences from other sectors which reuse
frequency band "a" to be insignificant, therefore Sector 2 is the only interfering
sector. TS1 is only decoupled by additional free space attenuation. Therefore, the C/I
of TS1 can be calculated by following equation.
C
⎛ r1 ⎞
= 20 Log ⎜ ⎟
I
⎝ r2 ⎠
(2.2)
22
Where r2: distance from sector2 antenna
r1: distance from sector1 antenna
If there are infinite chain of interfering cells in horizontal axial direction, C/I
would decrease a little. In the same way, TS2 and TS3 receive interference from
Sector4 and Sector3 respectively. C/I of TS3 and TS4 can be also calculated using
equation (2). If TS1, TS2 and TS3 are moved by about 25 degree away form the
sector axis, its own sharp pattern will provide additional decoupling. Except a small
region around sector axis, C/I of terminal station can be calculated by link budget.
Using above results including link budget calculation, C/I of terminal which is
located arbitrarily within a sector.
.
Figure 2.8: Inter-Cellular Interference
Generally C/I tends to increase if TS comes closer to HS, because in that case
there is a surplus of power of the wanted signal compared to all interfering signal and
there exists less attenuation. Therefore, the appropriate modulation scheme can be
23
assigned to partial areas in a cell or certain terminal stations to maximize spectrum
efficiency (Lee et al., 1998).
2.8 The Rain Fading
There are two of the most common causes of rain fading and weakening are
listed below:
1. Absorption – Part or all of the energy generated when a radio wave strikes a rain
droplet. The droplet is converted to heat energy and absorbed by the droplet.
2. Scattering – A non-uniform transmission medium (the raindrops in the
atmosphere) causes energy to be dispersed from its initial travel direction.
Scattering can be caused by either refraction or diffraction:
• Refraction: The refractive index of the water droplets encountered by the
radio wave.
• Diffraction: The travel direction of the radio wave also changes as it
propagates around the obstacle in its path (a water droplet).
These different reactions ultimately have the same effect – they cause any
system to lose some of its normal signal level.
2.8.1 Introduction
The demand for ultrawide bandwidths for high-speed, high quality, and
multimedia transmission is driving the use of the higher radio frequency spectrum.
However, attenuation and fading due to rain has long been recognized as a major
limitation to reliable communication systems operating at higher frequencies. A
bandwidth over 1 GHz has been allocated by the Federal Communications
Commission (FCC) to LMDS to provide throughputs as fast as 1.5 Gb/s downstream
24
and upstream rates as high as 200 Mb/s. In fact, LMDS system can be deployed in a
short period of time involving both the transport layers and the service layers.
However, fading due to rain restricts the path length of a radio
communication system limits the use of higher frequencies for LOS microwave links
and affects the performance of wireless communication In past studies, both the
theoretical and experimental analyzes show that rain fading is highly dependent on
the rain rate and drop-size distribution (Chu et al., 2005).
It is apparent that, due to different climatic regions and geolocations, and,
thus, different rainfall conditions, such global models may not be applicable under
specific conditions or for a particular application such as the Ka-band LMDS system.
Thus, local parameters, obtained from measurements in local areas, are important to
tune the empirical parameters to optimize the models that can best describe the local
events. In a tropical region, such as in Malaysia, a scattered rain rate distribution and
signal attenuation may lead to model predictions being overestimated or
underestimated.
2.8.2 Rain Effects
Signal attenuation during normal propagation conditions is proportional to the
square of the distance, and what truly limits the cell coverage is rain fading which
further attenuates the transmitted signal by several dB or several tens of dB per km.
Due to this phenomenon and to the limited power that can be generated at low cost at
millimeter-wave frequencies, the cell radius in LMDS networks is in the range of 2
to 5 km depending on the climatic zone, the available transmit power, and the
required availability objectives ( Hikmet, 2000).
The effects of rain can generally be neglected for wireless applications
operating at frequencies less than 10GHz. However, attenuation due to rainfall is one
of the principal factors affecting path loss at LMDS frequencies. The Exceedance is a
performance metric of the radio link relative to rain attenuation. An Exceedance of
25
0.01% characterizes the link being unavailable for 0.01% of the time (52.56
minutes/year) and available for 99.99% of the time. The radio link must be designed
to overcome the rain attenuation, therefore meeting the exceedance metric. The unit
of the measured rain is in terms of mm/hr. For LMDS frequencies, long periods of
light rain effect the link availability much less than severe rainfall that lasts for 10-20
minutes.
The equation and steps taken for calculating rain attenuation based on the
International Telecommunications Union (ITU) model (ITU-R, P.530-11, 2005) are
as follows:
2.8.3
Rain Attenuation Equation based ITU-R Model:
Step1: Calculate of the “specific attenuation” equation (2.3)
AdB = k R α
(2.3)
The coefficients k and α are frequency and polarization dependent and are
calculated using equation (2.4) and (2.5). The appropriate frequency and antenna
polarization (horizontal, vertical, circular) for the coefficients need to be selected
when finding the values for k and α as seen in Table 3.4. The rain rate (R) needs to
be chosen for the appropriate exceedance; in this case it is started with 0.01%, and
the desired geographical region.
k = [k H + kV + (k H − kV ) cos 2 θ cos 2τ ] / 2
α = [k H α H + kV α V + (k H α H − kV α V ) cos 2 θ cos 2τ ] / 2k
Where (θ: path elevation angle, τ: polarization tilt angle)
(2.4)
(2.5)
26
Step2: Determine the path averaging factor (r) equation (2.6)
r=
1
1+ d
(2.6)
do
Determine what the path length of the radio link (d) and enter it into equation
(2.6). Then find do via equation (2.7, 2.8).
d 0 = 35e −0.015 R0.01 ; R0.01 ≤ 100mm / hr
(2.7)
d 0 = 35e −0.015×100 ; R0.01 ≥ 100mm / hr
(2.8)
Step3: Now find the attenuation for a 0.01% exceedance equation (2.9).
A0.01 = AdB / Km × d × r
(2.9)
Step4: Attenuation for other exceedance percentages can be calculated by using
equation (2.10)
AP / A0.01 = 0.12 × P − (0.546+ 0.043Log10 P )
(2.10)
An example of the calculation from above is presented in the following Table
2.5 showing the specific attenuation and the various exceedance rates based on a
vertically polarized antenna. (k=0.14, α=1.015).
27
Table 2.5: An example of calculation of rain attenuation
Percent
Percent
Minutes/Year
Rain Rate
Attenuation
Outage
Available
Unavailable
(mm/hr)
(dB/km)
1%
99.000%
5256 min.
1.5
0.211
0.1%
99.9%
525.6 min.
12
1.743
0.05%
99.95%
262.8 min.
25
3.673
0.01%
99.99%
52.56 min.
42
6.219
0.005%
99.995%
26.28 min.
80
11.960
0.0001%
99.999%
5.256 min.
100
15.001
2.8.4 Rain-Cell over LMDS System
The effect of a moving rain-cell over an LMDS system that includes C/I
conditions on the downlink directions were investigated. A moving rain-cell causes
different attenuation in different links that is changing continuously because of the
motion of the raincell and time-variance in rain intensity. From the C/I point of view
different situations can be determined according to the position of the rain-cell over
the service area of the LMDS system. For example the following (Sinka et al., 2002)
cases can be occurred:
A. High attenuation on the desired signal, low attenuation on the interferer:
Rain-cloud is located between the Base Station (BS) and the desired
Terminal Station (TS). In this case the carrier has high attenuation, while the
interferer has small rain-attenuation value. So the C/I have been degraded radically.
28
B. Low attenuation on the desired signal, high attenuation on the interferer:
It is no raining over the investigated connection therefore the carrier is not
attenuated. The rain-cell is located over the area, from where the dominant
interfering signals are received. In these cases the C/I will be higher.
C. Nearly the same attenuation on both the desired signal and the interferer:
In this situation very low variance of the C/I can be obtained independently
from the rain intensity. This situation can be occurred even in non-raining or at heavy
rain events.
To investigate the different effects of rain-cell positions at each time and
location in the LMDS service area the desired signal and the interference levels
should be calculated. This can be made in two steps. First calculating the C/I map for
the non-rain case, second calculating the rain-attenuation map of the service area for
each time and position of the raincell. The time-dependent C/I maps can be easily
derived by subtracting the rain attenuation map from the static C/I map of non-rain
cases. Finally the effects of the listed three fluctuation situations in the C/I values can
be easily obtained.
2.9 Effects of Rain Fading on the Efficiency of the Ka-Band LMDS System:
This point explains effects of rain fading on the efficiency of the Ka band
LMDS system which include the interference analysis of the boundary subscriber,
channel Capacity in rain fading, Bit Error Rate (BER) and cell coverage effect as
follow.
29
2.9.1 Interference Analysis of the Boundary Subscriber
The signal-to-interference (S/I) ratio performance in a lesser rain rate is better
than that for clear days. To evaluate more closely the impact of rain rate on S/I at
various distance from hub to terminal. In general, when the rain rate increases, S/I is
also increased. This is easily interpreted due to the fact the interference from adjacent
cells is blocked by rain. It occurs when the interference is greatly attenuated by rain;
that is, the interference is insignificant. Note that when the distance between the CPE
and the BTS is very short with a low rain rate, the effect of the rain is not so obvious;
therefore, the S/I values near the local hub are very close at different rain rates.
The trend is reversed, however, for when rain rate and distance go beyond
some points. The reverse rate is a function of cell size. For example, for a cell size of
3 km, the reverse point occurs at a rain rate of 37 mm/h and becomes pronounced at
50 mm/h, at which S/I drops at distance of 1.7 km. By analyses, it can be finding that
there is a clear reverse trend when the rain rate increases for the same cell size. Also
it can be defined two parameters, the reverse rain rate and the reverse distance, to
quantity this phenomenon, as given in Table 2.6 Generally, it can be seen that the
larger the cell size, the larger the distance, but the smaller the reverse rain rate.
Table 2.6: Relationship between reversed distance dR, rain rate RR and cell size
Reserved Rain Rate RR
Reserved Distance dR
(mm/h)
(km)
2km
52
1.9
3km
36
2.8
4km
27
3.8
5km
21
4.85
6km
17
5.7
Cell Size
30
2.9.2 Channel Capacity in Rain Fading
Channel-capacity analysis is an important factor for evaluating the operation
efficiency of the LMDS system in rain environment. The channel capacity, as defined by Shannon, is a good measure of the merit of any communication system,
since it gives the maximum rate of transmission signal over the channel. If the
channel is subject to fading, its capacity varies with the changes in the propagation
medium, meaning that the channel capacity inherits the one-way stochastic properties
of the fading process.
For continuous channels with additive white Gaussian noise (AWGN), the
capacity is given by Shannon’s expression
S⎞
⎛
C = B log 2 ⎜1 + ⎟ b/s
⎝ N⎠
(2.17)
Where B is the channel bandwidth in hertz and S/N is the signal-to-noise
power ratio for the channel. In order to make the analysis independent of the actual
bandwidth of the channel, the previous equation can be written as
C
S⎞
⎛
= log 2 ⎜1 + ⎟ bps/Hz
B
⎝ N⎠
(2.18)
Where the term C/B represents the channel capacity. If, due to propagation
fading, the term S/N is random, with an arbitrary but known distribution depending
on the type and characteristics of the fading process considered, the channel capacity
is also random. It is this random variability of the channel capacity that imposes
performance degradation on the system that utilizes this channel. Therefore, one may
wish to determine the Probability Density Function (PDF) and Cumulative
Distribution Function (CDF) of the channel capacity knowing those of S/N or,
equivalently, those of the fading process.
31
Using the standard transformation of random variables, the PDF of C/B can
be written in terms of S/N. In the presence of rain attenuation, the received signal-tonoise power level is given by
S ⎛S⎞
= ⎜ ⎟ − A (dBW)
N ⎝ N ⎠ο
(2.19)
Where (S/N)o is the signal-to-noise power level (in decibels) for clear
conditions and A is the total equivalent rain attenuation for the link.
2.9.3 Bit Error Rate ( BER)
Another measure of the LMDS performance is the BER. For a given
modulation scheme, the system’s BER is a function of SNR, which in the presence of
fading also is a random variable. It is possible to determine the CDF for the BER
performance under rain attenuation fading and turns out to give the probability that is
below the nominal value of BER.
The analysis of BER under rain fading at various service ranges is in order.
We first consider the case of no presence of interference. Increasing the distance, the
higher CDF of BER results, but tends to be saturated. A significant jump is observed
for the case from 1 to 2 km. When the interference is presented, we can do the
similar analysis under the same operation conditions, so It is seen that BER becomes
substantial larger, as expected. It may be concluded that it is not the rain attenuation
to affect the LMDS link interruption in a cellular environment, but the intercell
interference. Indeed, rain itself contributes blocking of intercell interference.
32
2.9.4 Cell Coverage Effect
It is interesting to see how the system performance is affected when the
service range is changed. To do so, we vary the cell size from 5 to 1 km and again
analyze the system’s efficiency. It is clearly seen that different cell sizes leads similar
behaviors when the CPE path lengths are at the cell boundary.
In summary, in cellular network environment, as the cell coverage radius
reduces, the BTS effective service range will be correspondingly compressed,
indicating that the cellular interference is even more serious than rain.
CHAPTER 3
SITE DIVERSITY TECHNIQUE
3.1
Introduction
Motivated by recent interest in North America and Europe in the use of
millimeter-wave radio frequencies to provide wireless access to broadband services,
embodied in a system generally termed Local Multipoint Distribution System
(LMDS), research activities have been initiated worldwide to study the propagation
characteristics of millimetric radio waves. One of the natural phenomena that
significantly influence the performance of communication systems operating in the
cited band, but the study of which has not yet been sufficiently thorough, is rain
attenuation. This is particularly true when the influence of rain is put into the context
of point-to-multipoint, fixed cellular radio networks, in which spatial statistics of rain
attenuation are as important as single-point temporal statistics.
Figure 3.1: Typical scenario of cell-site diversity.
34
At high rainfall intensities, the occurrence of which is of special interest in
systems requiring high- reliability links, the horizontal structure of rain is highly
variable. It is frequently observed that during a shower, high intensity rain is
localized in a very small area surrounded by a region of more uniform, low intensity
rain. Hence, in a cellular system under rain with very localized storms, there is a
potential that a subscriber terminal receiving a heavily attenuated signal from one
hub can obtain less attenuated, acceptable reception from another hub. This makes
cell-site diversity appear as a very promising method for improving link reliability
and area coverage. Such a scenario can be roughly sketched as in Figure 3.1 for cells
with overlapping areas.
When the link between a subscriber terminal (ST) and Hub 1, which is the
closest and hence the default hub for ST, experiences a performance drop due to a
high-intensity shower, there remains a possibility that Hub 2 or 3 can take over the
service delivery. Which of the two hubs is selected to receive the handover depends
on which hub location results in better signal reception at ST. This is all assuming
that the receiver and antenna technology used at the subscriber site allows these links
to be monitored simultaneously and continually, and the antenna main beam to be
rotated, either electrically or physically, to execute the handover. In principle, it is
akin to a macro diversity scheme employed in mobile cellular systems to combat
shadowing effects, taking the advantage of the fact that the effects of obstruction
losses around links that connect a mobile terminal to different base stations are only
partially correlated.
3.2 Site Diversity
In the cellular mobile networks handover mechanism is used between mobile
station and base stations to keep the received signal level above the predetermined
signal level value. However intense rain shower may cause a deep fade on the
microwave link between base station transceiver (BTS) and base station controller
(BSC) and cause an outage on the feeder Link. Site diversity method can be applied
to prevent this event. It use of the fact that intense rain cells usually have quite
35
limited horizontal dimensions, therefore the probability of two or more neighboring
feeder links having simultaneous deep fade is rather small. The degree of
improvement afforded by this technique depends on the extent to which the signals in
the diversity branches of the system are uncorrelated. This method useless with short
links because the rain cell may cover these links at all. The attenuation D(t) time
function of theoretical diversity link minimizes the link attenuation of the diversity
branches:
D(t ) = min i =1, N {ai (t )}
(3.1)
Where ai (t ) is the rain attenuation function of the i th link of the diversity
branches.
Two expressions are used to describe the performance of the site diversity.
The diversity improvement factor ID for fade depth A is defined by:
I D ( A) = min i =1, N {Pi ( A)} PD ( A)
(3.2)
Where PD ( A) and Pi ( A) are complement cumulative distribution function of
the attenuation measured on the theoretical diversity kink and the i th link of the
diversity branches, respectively. The diversity gain is the difference between the
unprotected A and diversity attenuation Ad values for the same time percentage:
G(P( A) = Pd ( Ad )) = A − Ad
(3.3)
In particular, the gain for two links aligned in approximately opposite
directions with respect to the hub was discovered in our study to be relatively
insensitive to their angular separation. Thus a separation of, say, 110° between the
two branches of a diversity system is adequate to yield a near maximum diversity
gain. It was consequently considered that the half-sinusoid model of gain variation
with angular separation could be improved by modifying the sinusoidal shape to
accommodate for this insensitivity.
36
3.3 Diversity Gain and Diversity Improvement Concepts
It is useful (Enjamio et al., 2002) to recall the concept of diversity gain. This
was introduced and characterized by Hodge in order to measure the advantage
introduced by employing space diversity configuration. The diversity gain (G) is the
difference between the path attenuations associated with the single terminal and a
diversity of modes of operation for a given percentage of time. Diversity
improvement (I) is the ratio between the percentage of time associated with the
single terminal attenuation and the percentage of time associated with the joint
terminal distribution, both at the same value of attenuation. Figure 3.2 illustrates both
concepts to measure diversity performance.
Figure 3.2: Diversity gain and diversity improvement concepts.
3.3.1 Cell-Site Diversity Performance
Figure 3.2 depicts the cell-site diversity configuration upon which the
following analysis is based. The configuration consists of a fixed user (denoted by U)
receiving the signals intended to him from the hub station (denoted by S1) at a
37
distance of L1 kilometers. When the quality of link US1 deteriorates due to rain
attenuation, it is possible to also receive the signal from a second hub station S2 via
the alternative path US2 and to choose the best signal using an appropriate criterion
(signal selection, signal switching, and signal combining). The length of path US2 is
°
°
denoted by L2 while θ ( 0 ≤ θ ≤ 360 ) is the angular separation between US1 and
US2.
Figure 3.3: Geometrical configuration of a cell-site diversity scheme
The configuration in Figure 3.3 consists of a fixed user U and two hub
stations S1 and S2. The lengths of the two converging paths US1 and US2 are denoted
by L1 and L2, while their angular separation is denoted by θ .
The objective of the analysis is to evaluate the availability percentage of
diversity schemes located in heavy rain climatic regions, that is, the time percentage
within a year during which the diversity configuration is capable of servicing its
users. The outage probability is directly associated with the probability of rain
attenuation exceeding simultaneously certain thresholds on both the alternative paths.
This joint exceedance probability is expressed as:
38
P1,2 = P[ AS1 ≥ χ S 1 , AS2 ≥ χ S 2 ]
(3.4)
Where AS1, AS2 are the rain induced attenuations on the single paths US1 and
US2, respectively, and χ S 1 , χ S 2 (all expressed in dB) are the corresponding rain
attenuation thresholds. In case the two path lengths and the equipment in both hub
stations are identical, χ S 1 = χ S 2 , yielding a balanced cell-site diversity system, After
calculating P1,2, one can determine the minutes within a year during which the
diversity system is available to its users
Tavail = 525600 × (1 − P1, 2 )
min/year
(3.5)
This approach is analogous to the calculation of the annual availability time
of site diversity systems in earth-space communications.
3.3.2 Cell-Site Diversity Performance Measures
To evaluate the improvement offered by a diversity system, the cell –site
diversity gain (CSDG) parameter is commonly used as a performance measure.
CSDG is defined as the difference in dB between the attenuation ASi on either one of
the two hub-to-user paths (i=1, 2) and the joint attenuation AD after diversity is
employed for the same exceedance probability level P%
CSDGi (P%) = ASi (P%) − AD (P%)
i=1, 2
(3.6)
Besides CSDG, another performance measure of diversity systems less
frequently used is cell-site diversity improvement (CSDI), defined as the ratio of the
single link to the joint exceedance probability, for the same attenuation value As1,
that is:
39
CSDI i ( ASi ) =
PSi ( ASi )
PD ( ASi )
i=1, 2
(3.7)
However, in most cases reliability reasons impose the use of CSDG as a
figure of merit due to the statistical implications of using CSDI (e.g. in the case of
experiments with different durations).
To elaborate on the calculation of CSDG and CSDI, Figure 3.4 presents an
implementation of the proposed model in terms of the outage probability for various
attenuation thresholds. The three curves correspond to a single hub system without
diversity (dotted line) and to diversity schemes with alternative paths separated by
600 and 150°. From Figure 3.4 and for a 99.9% system availability, the
corresponding rain induced attenuation is As (0.1%) =20.35dB for the single hub
system, while AD(0.1%)=16.80dB and AD(0.1%)=15.47dB for 0 equal to 60° and
150°, respectively.
Thus, the corresponding diversity gains turn out to be CSDG (60°) = 3.55 dB
and CSDG (150°) = 5.O6 dB. On the other hand, the corresponding diversity
improvement factors are CSDI(60°)=1.4 and CSDI(150°)= 1.7, taking into account
that Psi(15dB)=0.17%, while for the selected θ =60° and θ =150° values the
respective exceedance probabilities are PD (l5dB)=0.12% and PD (l5dB)=0.10%.
Figure 3.4 clarifies single and joint annual exeedance probability of rain
attenuation for typical diversity LMDS system
for θ =60°, 150°.
and
the calculation is carried out
40
Figure 3.4: Single and joint annual exceedance probability of rain attenuation for
typical diversity LMDS system.
3.4 Influenced Factors
Two major factors (Zvanovec and Pechac, 2004) influence the site diversity
performance. The first is a correlation between two links as a result of spatial
variation of rain rate. The correlation is generally given by angular separation
between the links. The second factor involves difference in the link path lengths
strongly influencing the path loss. If a terminal station can be connected to more than
two hubs (BS) in a dense network various rules for a diversity hub selection can be
employed. A nearest hub is assigned as a “main” link to each terminal station. Then
the diversity link is selected using different algorithms when more hubs were
available:
(a) No diversity link (terminal station without the site diversity).
41
(b) Distance: diversity link selected based on distance, terminal station can be
connected to two nearest hubs.
(c) Angle): diversity link is selected based on the maximal angular separation.
(d) Gain or average C/I: diversity link is chosen based on the best gain or average C/I
ratio. Always the best diversity link is selected in each time step.
CHAPTER 4
PROJECT METHODOLOGY
4.1 Introduction
The purpose of this project as it was described in chapter one, is to study the
effects of site diversity in LMDS under rainy conditions in Malaysia. It is important
to study and identify all the objectives to carry out the study.
To achieve the objectives, there are some steps that have been fulfilled to
ensure the continuous and logical build us of defining and justifying this project. The
steps include establishment LMDS Network by determining frequencies used,
sectorisation, structure of system (BS & TS) and distance of terminal station or cell
size. The second step is directed to calculate rain attenuation based ITU-R Model of
different areas in Malaysia having different rain rates as an effort to cover Malaysia
weather. Thirdly rain cell Movement within LMDS is analysed to find rain impacts
on these systems. Site diversity was implemented to estimate the availability at the
receiver during rain condition. Different cell sizes were considered to analyse and
select the best size of LMDS cell during different heavy rain rates to avoid worst
cases or an outage on the feeder link and get maximum coverage of LMDS service
area.
43
4.2 Establishing of LMDS Network
As it was mentioned in a previous part in this work, LMDS is a system to
deliver the service to fixed customers in area does not exceed 5 kilo meters and LOS
is considered between terminal station and base station which their connection is
point to multipoint from base station to terminal station and point to point from
terminal station to base station. The overall architecture of this system is cellular as
following Figure 4.1:
Figure 4.1: LMDS area structure
A cell in LMDS area has a regular size and consists of four sectors, all four
sectors are covered by one base station of 90° antenna type. This means that the
investigated system contains 9 Base Stations configuration with four 90° sectors per
cell operating at different carrier frequencies (f1, f2, f2 and f4) as shown on Figure
4.1. The BFWA or LMDS cell has size of 6 × 6 kms, therefore a sector has a size of
3 × 3 kms realizing an 18 × 18 kms BFWA coverage area model in our calculations.
According to previous studies of LMDS system, a given LMDS parameters
were considered, these parameters include transmitted power, received power, gain
44
of transmitter, gain of receiver and additional to maximum distance between
transmitter and receiver. The frequency used of these systems in Malaysia is found
from Standard Radio System Plan which is supported by Malaysian Communications
and Multimedia Commission (MCMC).
As well as the other parameters are taken into account which include
atmosphere attenuation, fade margin or antenna miss-alignment and free space loss.
To achieve the purpose of our work, the worst case is chosen where the
terminal station was putted at the corner of sector ( farthest point ) of LMDS area in
order to show the major effects of rain over service area, as it known the longer path
length has higher attenuation loss specially during rain.
Most of the project calculations are computed in term of carrier to
interference ratio C/I ratio as a measure performance of LMDS system starting by the
power received equation in free space and applying the horizontal and vertical
frequencies to extract the effect of both of them. Different cell sizes are introduced in
worst case which causes an outage in the link.
The following Figure 4.2 shows the supposed scenario in the calculations that
are applied, in which as it is clear that the terminal station is putted at the left bottom
sector of the service area and receive the desired signal (C) (it is shown in white
color line) from the base station BS while there are three interference signals (I1, I2
and I3) (they are shown in black color lines) coming from the adjacent stations which
are marked BS1, BS2 and BS3. Desired signal and interference signals have the same
frequency, polarization and sectorization.
45
Figure 4.2: The supposed scenario of LMDS
4.3 Calculation of Rain Attenuation
Rain attenuation is calculated by applying ITU-R model on rain rate of
Malaysia region .different rain rates of different areas over Malaysia were chosen for
the sake of extension the study to cover the whole country. These areas are Jelebu
(96 mm/h), Johor Bahru (125 mm/h) and Taiping (145 mm/h), they represent highest,
middle and lowest rain rate for exceedance of 0.01 of a year. The frequencies used
are 24 GHz and 26 GHz as the lowest frequencies in LMDS spectrum which are
reserved of Malaysia.
Indication to previous Figure 4.2 that represents the assumed scenario, it can
be seen that there are six cases and scenarios could occur over LMDS service area
during rain and without rain.
46
4.3.1 Specific Rain Attenuation
Specific rain attenuation is the fundamental and main quantity for rain
attenuation calculations of terrestrial path it is calculated as a rain attenuation per unit
distance (dB/km) at exceedance of R
0.01.
The other factors the specific rain
attenuation based on are k and α coefficients which depend on frequency and
polarization.
4.3.2 Effective Path Length
As rain is not uniformly distributed with distance, exact path length can not
be considered as equal to the simple actual distance, d, between transmitting and
receiving points. ITU-R P.530 recommendation proposes a model for the calculation
of the effective path length. According to this model, actual path length, d, is to be
corrected by the factor, r, which is indirectly dependent on the rainfall rate. As it was
mentioned in chapter two for the formula of deff, the effective path length calculation
is carried out where the effective path length equals
d
eff
=d×
d
eff
1
d
1+
− 0.015 × R
⎛
0.01 ⎞⎟
⎜ 35 × e
⎟
⎜
⎠
⎝
=d×
1
d
1+
7.81
in case R
≤ 100 mm / hr (4.1)
0.01
in case R
≥ 100 mm / hr (4.2)
0.01
47
4.3.3 Rain Attenuation
It is applied by depending on the specific rain attenuation which is multiplied
by the effective path length for each rain rate and the certain frequency that is
predetermined. The calculation at the beginning is carried out for cell size of 6 × 6
kms (i.e. 3 × 3 kms sector size ) after that it is calculated for step size of 1 × 1 km
(i.e. 0.5 × 0.5 km sector size ).
4.4 Rain Cell Movement within LMDS
A moving rain-cell causes different attenuation in different links that is
changing continuously because of the motion of the rain cell and time-variance in
rain intensity, different scenarios of rain position are analyzed in term of average C/I
ratio and its effects on availability of service over targeted area.
This project’s goal is to study effects of a moving rain-cell over an LMDS
system, C/I conditions on the downlink direction are investigated for each link of
scenario according to different cell sizes and all cases that have a probability to be
occurred. Matlab program is done to verify and simulate the results.
4.5 Site Diversity Implementation
Site diversity temporarily gives the opportunity to the TSs for switching to
other BS than its original one reaching better C/I level during the rain period. Site
diversity technique needs an algorithm to switch the desired signal from the original
base station covered by rain to the nearest rain free base station and in case of
measured C/I at the receiver under a predefined C/I threshold (this threshold is based
on the type of modulation and the required BER) the TS tries to find a BS from the
nearest BSs with better C/I (not covered by rain). The switchover is made for the BS
48
with the highest C/I. The C/I threshold detection process must have hysteresis for
optimal performance in order to avoid tilting between BSs around the C/I threshold.
The following Figure 4.3 shows the procedure which is done to implement
site diversity to switch the desired signal to the nearest base station especially in
worst case when the original station suffer from high rain attenuation. As it is clear
the dashed lines represent the desired signal (C) coming from the either two base
stations SDBS instead of the previous operation that was in Figure 4.2 where the
desired signal (C) was coming from original base station BS (white color line).
Figure 4.3: Site diversity implementation
The calculations are executed in terms of C/I to find the site diversity effect
on LMDS system during rain. All results have been done by Matlab program to
simulate these effects and seeing the difference before and after using site diversity.
CHAPTER 5
RESULTS AND ANALYSIS
5.1 Introduction
This part of the thesis represents the results of calculations which are carried
out by Matlab program of a given LMDS system parameters and the rain rates of
three different locations in Malaysia region. These locations are Jelebu, Johor Bahru
and Taiping. LMDS parameters and rain attenuation calculation are presented
including to vertical and horizontal polarization frequencies. Overall scenarios of
rain movements during our system for different cell sizes are also represented,
discussed and commented also the discussions include the effects of using different
cell size. Site diversity calculation is clarified to show the advantages of using this
technique in fixed wireless systems especially during rainy conditions. Most of
results are figured to enhance the study and present a good analyses and clear vision.
Some comparisons are carried out and obtained to confirm the results and extend the
discussions and analyses for the study covers many aspects of LMDS system, rain
fading and site diversity.
50
5.2 LMDS Configuration
As it is mentioned in the methodology, the service area of supposed LMDS
was established by determination the cell size which it is 6 × 6 kms and the
considered scenario according to (Sinka and Bito, 2003); so the distance between the
desired base station and terminal station which was putted at the left lower bottom
corner of LMDS area or the path length of (C) is 4.2426 kms, while the three
interference signals are coming from different adjacent base stations and different
distances where I1 has a distance of 21.2132 kms and the others two interference
signals (I2 and I3) have the same distance of 15.2970 kms. Also a line-of-sight
(LOS) was established between the BSs and TS.
Figure 5.1: The supposed scenario of LMDS without site diversity
Therefore the path length of desired signal and interference signals can be
summarized in the following Table 5.1.
51
Table 5.1: The distance between terminal station and the effective base stations
The Base Station
The Path Length ( km)
Desired signal (C)
4.2426
Interference signal (I1)
21.2132
Interference signal (I2)
15.2970
Interference signal (I3)
15.2970
5.3 LMDS Frequencies and Parameters
Malaysian Communications and Multimedia Commission has regulated the
frequency bands or LMDS 24.25 GHz to 27.00 GHz, 27.00 GHz to 29.50GHz and
31.00 GHz to 31.30 GHz for Local Multipoint Communication Systems (LMCS) or
LMDS in Malaysia. In this work 24 GHz and 26 GHz were used. Indicating to (Lee
et al., 1998), the LMDS parameters were considered to investigate this work, these
parameters are included in the following Tables 5.2 and 5.3:
Table 5.2: Parameters, formulas for LMDS (26 GHz).
Parameter
Transmit Power into
antenna
Units
dBW
Formula
Value
Ptx : Transmit power per carrier
2.0
Transmit Antenna Gain
dBi
Gt = Gant
18.0
Receiver Antenna Gain
dBi
Gr = Gant
38.0
Frequency
GHz
f : Transmit Frequency
26.0
Path Length
km
d : from base station to terminal station
4.2426
Field Margin
dB
Lfm : Antenna Mis-Alignment
1.0
Free-Space Loss
dB
Lfs = 92.45 + 20 * log(f) + 20 * log(d)
133.3
Atmospheric Loss
dB
Latm = d * 0.1 dB/km
0.42426
52
Table 5.3: Parameters, formulas for LMDS (24 GHz).
Parameter
Transmit Power into
antenna
Units
dBW
Formula
Value
Ptx : Transmit power per carrier
2.0
Transmit Antenna Gain
dBi
Gt = Gant
18.0
Receiver Antenna Gain
dBi
Gr = Gant
38.0
Frequency
GHz
f : Transmit Frequency
24.0
Path Length
km
d : from base station to terminal station
Field Margin
dB
Lfm : Antenna Mis-Alignment
Free-Space Loss
dB
Lfs = 92.45 + 20 * log(f) + 20 * log(d)
Atmospheric Loss
dB
Latm = d * 0.1 dB/km
4.2426
1.0
132.6
0.42426
5.4 Rain Attenuation Data and Calculations
Rain attenuation was calculated for each rain rate at R 0.01, Jelebu (96 mm/h),
Johor Bahru (125 mm/h) and Taiping (145 mm/h) and both of two frequencies 24
GHz and 26 GHz were used. Every frequency (24GHz and 26GHz) were chosen
from SRSP belonging to MCMC as shown in Appendix B and according to ITU-R
P.530 recommendation the coefficients k and α has been used as shown in Appendix
A.
5.4.1 Specific Rain Attenuation Calculation
According to ITU_R model which was used, specific rain attenuation is the
first step to obtain rain attenuation, the specific rain attenuation was calculated for
both of horizontal and vertical polarizations for each frequency. Specific rain
attenuation values are shown in the following Table 5.4.
53
Table 5.4: Specific rain attenuation
Specific Rain Attenuation
(dB/km)
Rain Rate
Horizontal Polarization
Vertical Polarization
(R0.01)
24 GHz
26GHz
24 GHz
26 GHz
96 mm/h (Jelebu)
14.3254
15.6969
11.0310
12.3014
125 mm/h(Johor Bahru)
18.7027
20.3762
14.1979
15.7745
145 mm/h (Taiping)
21.7276
23.5957
16.3626
18.1418
As it can be seen from the Table 5.4, a high rain rate leads to high specific
attenuation as in Taiping location while Jelebu location has the lowest specific rain
attenuation because it has the lowest rain rate, also it is clear that vertical polarization
has lowest attenuation compare to horizontal attenuation this is because of rain drops
face smaller area of electrical field in the vertical polarization than that of horizontal
polarization.
By comparison of the lower frequency 24 GHz to higher frequency 26 GHz,
it is clearly that specific attenuation has high values at higher frequency than the
other frequency.
5.4.2 Effective Path Length Calculation
Effective path length was calculated for every link of the targeted system and
all scenarios using all rain rates. All calculations were done for three interference
signals (I1, I2 and I3) as well as the desired signal (C) as it is mentioned in ITU_R
recommendations. Reduction factor was multiplied by the actual distance between
the transmitter and receiver, it was found that the reduction factor decreases as path
length increases.
54
The following Table 5.5 shows the values were obtained depending on the
previous given data of distance between terminal station and all effective base
stations (BS, BS1, BS2 and BS3) and rain rates.
Table 5.5: Effective path length value of effective signals
The Path to Terminal Station
Effective Path Length (km)
96 mm/h
125 mm/h
145 mm/h
Desired Base Station (BS)
2.8067
2.7492
2.7492
Interference Base Station ( BS1)
5.9619
5.7084
5.7084
Interference Base Station ( BS2)
5.3774
5.1703
5.1703
Interference Base Station ( BS3)
5.3774
5.1703
5.1703
5.4.3 Rain Attenuation Calculation
Depending on specific rain attenuation and effective path length, rain
attenuation was obtained for each rain rate and frequency which were considered in
this work. Rain attenuation was calculated along every point of link between desired
base station and terminal station and links between terminal station and all
interference base stations for both horizontal and vertical polarization frequencies to
extract the difference between them and its effect on the performance of system.
5.4.3.1 Rain Attenuation at 24 GHz
The following Figures 5.2 to 5.4 show the rain attenuation effects on the
desired signal related to the distance between desired base station (at zero point on
horizontal axis) and terminal station which can be putted at any point along the link
up to the maximum distance of 4.2426 kms. All the following figures are for 24 GHz
and the different rain rates.
55
60
50
Rain Attenuation (dB)
40
H-pol.
30
V-pol.
20
10
0
0
0.5
1
1.5
2
2.5
3
3.5
Distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.2: Rain attenuation vs. path length at 24 GHz and 96 mm/h (Jelebu)
60
50
Rain Attenuation (dB)
H-pol.
40
V-pol.
30
20
10
0
0
0.5
1
1.5
2
2.5
3
3.5
Distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.3: Rain attenuation vs. path length at 24 GHz and 125 mm/h (Johor Bahru)
56
60
50
H-pol.
Rain Attenuation (dB)
40
V-pol.
30
20
10
0
0
0.5
1
1.5
2
2.5
3
3.5
Distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.4: Rain attenuation vs. path length at 24 GHz and 145 mm/h (Taiping)
From the above graphs it can be seen that horizontal polarization frequency
suffers from significant high attenuation than that of vertical polarization this is due
to electrical field of the transmitted signal in case of horizontal polarization is
horizontal therefore rain affects on a large area of the transmitted signal.
5.4.3.2 Rain Attenuation at 26 GHz
Also the three Figures below from 5.5 to 5.7 clarify effects of polarization at
26 GHz. It can be noted that vertical polarization suffers from attenuation less than
horizontal polarization. By comparing
the attenuation at 24 and 26 GHz it can be
seen that at 26 GHz the signal attenuation is greater than that of the other frequency.
57
70
60
Rain Attenuation (dB)
50
H-pol.
40
V-pol.
30
20
10
0
0
0.5
1
1.5
2
2.5
3
3.5
Distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.5: Rain attenuation vs. path length at 26 GHz and 96 mm/h (Jelebu)
70
60
Rain Attenuation (dB)
50
H-pol.
40
V-pol
30
20
10
0
0
0.5
1
1.5
2
2.5
3
3.5
Distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.6: Rain attenuation vs. path length at 26 GHz and 125 mm/h (Johor Bahru)
58
70
60
H-plo.
Rain Attenuation (dB)
50
V-pol.
40
30
20
10
0
0
0.5
1
1.5
2
2.5
3
3.5
Distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.7: Rain attenuation vs. path length at 26 GHz and 145 mm/h (Taiping)
5.4.3.3 Comparison between Rain Rates Attenuation at Different Frequencies
70
60
145 mm/h
Rain Attenuation (dB)
50
125 mm/h
40
96 mm/h
30
20
10
0
0
0.5
1
1.5
2
2.5
3
3.5
Distance between Terminal Station & Desired Base Station (km)
4
Figure 5.8: Rain attenuation vs. rain rates at 24 GHz
4.5
59
70
60
145 mm/h
Rain Attenuation (dB)
50
125 mm/h
40
96 mm/h
30
20
10
0
0
0.5
1
1.5
2
2.5
3
3.5
Distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.9: Rain attenuation vs. rain rates at 26 GHz
It is noted from the last two figures that the signal attenuation increases with
increasing frequency also it is observed that the signal attenuation increases with
increasing rain rate and in the following Table 5.6 there is a summary of the rain
attenuation values were obtained by Matlab program at the corner of LMDS cell i.e.
at distance of 4.2426 kms. It can be observed that the attenuation at 96 mm/h is the
lowest value of 34.5260 dB by using 24 GHz vertical polarization frequency while
the highest value is 64.8679 dB at 145 mm/h by using 26 GHz horizontal
polarization frequency.
60
Table 5.6: Rain attenuation at corner of LMDS cell
Rain Attenuation (dB) ( d = 4.2426 km)
Rain Rate
Horizontal Polarization
Vertical Polarization
24 GHz
26 GHz
24 GHz
26 GHz
96 mm/h (Jelebu)
40.2068
44.0561
30.9605
34.5260
125 mm/h (Johor Bahru)
51.4162
56.0170
39.0319
43.3662
145 mm/h (Taiping)
59.7323
64.8679
44.9829
49.8744
(R0.01)
From the former Figures 5.2 to 5.9 and Table 5.6, it can be observed that rain
attenuation could be increased by the following factors:
a) High rain rate.
b) High frequency.
c) Using horizontal polarization frequency.
d) Longer path length.
5.5 Terminal Station Situation Possibilities
According to the assumed LMDS system and indicating to Figure 5.1, there
are six cases and scenarios can be occurred of terminal station at any time. These
scenarios can be listed them down into two scenarios:
The first four cases, the effective signals have different situations in relation
to rain movement over LMDS service area as follow:
a) Case1: desired signal (C) & Interference signal (I1) are in rain while (I2 & I3)
are without rain (THE WORST CASE).
61
b) Case2: desired signal (C) & Interference signals (I1& I2) are in rain while I3
is without rain.
c) Case3: desired signal (C) & Interference signal (I1) are without rain while (I2
& I3) are in rain.
d) Case4: desired signal (C) & Interference signals (I1& I2) are without rain
while (I3) is in rain.
However, in the other two cases the effective signals has uniform situation in
relation to rain these two cases can be listed as follow:
e) All LMDS service area is with rain and
f) All LMDS service area is without rain.
According to (Sinka and Bito, 2003) and (Panagopoulos, 2006) the overall
performance of the LMDS system is measured by average C/I. Average C/I was
calculated for all rain rates (96, 125 & 145 mm/h) at 24 GHz and 26 GHz for all
scenarios which may be happen in LMDS service area to compare the effects of site
diversity in rain. The comparisons between the scenarios have been simulated by
Matlab program attached in Appendices D and E.
5.5.1 All LMDS Service Area with and without Rain
The Figures 5.10 and 5.11 show situation of targeted terminal station in
LMDS cell at every point in the link in term of average C/I values.
62
160
Average Carrier to Interference Ratio C/I (dB)
140
120
100
with rain
80
60
40
without rain
20
11
0
0
0.5
1
1.5
2
2.5
3
3.5
Distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.10: All LMDS with rain and without rain at 24 GHz and 125 mm/h
In order to compare the two cases - all LMDS with rain and without rain- rain
rate of 125 mm/h was chosen for both the horizontal frequencies 24 GHz and 26
GHz.
160
Average Carrier to Interference Ratio C/I (dB)
140
120
with rain
100
80
60
40
without rain
20
11
0
0
0.5
1
1.5
2
2.5
3
3.5
Distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.11: All LMDS with rain and without rain at 26 GHz and 125 mm/h
63
From the above comparisons of two different situations of terminal station in
LMDS service area it is clearly that when all LMDS is under rain it produces higher
average C/I values than that of LMDS without rain at every point of the link of both
frequencies. This is as mentioned before because that the interference signals from
adjacent cells are blocked by rain.
5.5.2 The Four Cases and Rain Cell Movement Effects over LMDS
The different situations or cases that can be occurred depending on the
supposed scenarios were represented by four cases, case1 to case4 which were
calculated and simulated. Case1 represents the worst case in which the rain cell
covers significant part of the desired signal (C) and interference signal (I1) paths
while the other interference signals (I2 and I3) paths mostly are outside the rainy
area.
5.5.2.1 Effect of Rain Movement on the Received Signal at 24 GHz
180
Average Carrier to Interference Ratio C/I (dB)
160
140
120
100
case3
80
60
case4
40
case2
20
11
case1
0
-20
0
0.5
1
1.5
2
2.5
3
3.5
Distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.12: The four cases under 24 GHz and 96 mm/h conditions
64
180
Average Carrier to Interference Ratio C/I (dB)
160
140
120
100
case3
80
case4
60
40
case2
case1
20
11
0
-20
0
0.5
1
1.5
2
2.5
3
3.5
Distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.13: The four cases under 24 GHz and 125 mm/h conditions
180
Average Carrier to Interference Ratio C/I (dB)
160
140
120
case3
100
80
case4
60
40
case2
20
11
case1
0
-20
0
0.5
1
1.5
2
2.5
3
3.5
Distance between Terminal Station & Desired Base Station (km)
4
Figure 5.14: The four cases under 24 GHz and 145mm/h conditions
4.5
65
5.5.2.2 Effect of Rain Movement on the Received Signal at 26 GHz
180
Average Carrier to Interference Ratio C/I (dB)
160
140
120
100
case3
80
60
case4
150
case2
20
11
case1
0
-20
0
0.5
1
1.5
2
2.5
3
3.5
Distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.15: The four cases under 26 GHz and 96 mm/h conditions
180
Average Carrier to Interference Ratio C/I (dB)
160
140
120
case3
100
80
case4
60
40
case1
20
11
case2
0
20-
0
0.5
1
1.5
2
2.5
3
3.5
Distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.16: The four cases under 26 GHz and 125 mm/h conditions
66
180
Average Carrier to Interference Ratio C/I (dB)
160
140
120
case3
100
80
case4
60
40
case2
20
11
case1
0
-20
0
0.5
1
1.5
2
2.5
3
3.5
Distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.17: The four cases under 26 GHz and 145 mm/h conditions.
As it is shown from the previous Figures from 5.12 to 5.17, it can be extract
the following notes:
a) High attenuation on the desired signal (C), low attenuation on the interference
signals (I):
This represents case (1) and case (2) so that rain-cloud was located between
the desired Base Station (BS) and the Terminal Station (TS) therefore the rain cell
covers the significant part of the desired signal (C) path as well as interference signal
(I1) while the interference signals (I2) and /or (I3) paths either mostly suffer of very
low intensity rain or are outside the rainy area. In this case the carrier has high
attenuation, while the interferer has small rain-attenuation value. So in these cases
the C/I have been degraded radically.
b) Low attenuation on the desired signal(C), high attenuation on the interference
signals (I):
This represents case (3) and case (4) so that it is no raining over the
investigated connection therefore the carrier (C) is not attenuated as well as
67
interference signal (I1). The rain-cell is located over the area where dominant
interfering signals (I2) and / or (I3) suffer from rain attenuation. In these cases the
C/I will be higher.
From the above figures also can be seen that the worst case is case(1) because
of the values of C/I are degraded under 11 dB as a threshold value specially when the
path length is more than 2.5 km which mean that outage of link will occur at the area
around the corner of served cell. The other cases will not suffer from outage because
the C/I values are greater than C/I threshold value. So to get a high performance of
case1, it must be used a technique to overcome this problem.
5.6 Maximum Coverage & Different Sector Size
As a result of worst case it needs to be overcome and because of the
calculations which were already calculated for 6×6 kms have shown no coverage at
cell corner at the different rain rates and frequencies. Different sector sizes were
considered for every 0.5 km step starting from 0.5×0.5 km, 1×1km, 1.5×1.5 kms
until 3×3 kms. The results were graphed for both frequencies 24 and 26 GHz.
5.6.1 Relationship between Sector Size and Maximum Coverage at 24 GHz
Figure 5.18 shows average C/I of worst case for different sector sizes of
LMDS at 96 mm/h, this graph explains the maximum distance of every sector size
equals (sector size × 2) and the average C/I value at each point on this distance. For
example, sector size of 3×3 kms has maximum path length (the point at corner of
sector) of 3× 2
4.2426 kms and the average C/I value is 1.6509 dB which means
there is no coverage at the corner point as the graph shows but the average can be
available at distance lower than 3 kms from the desired base station (at the zero point
68
120
Average Carrier to Interference Ratio C/I (dB)
100
80
60
40
2.5km
20
3km
11
0.75km
0.5km
0
-20
0
0.5
1km
1.5km
2km
1
1.5
2
2.5
3
3.5
Maximum distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.18: Maximum coverage vs. different sector size of worst case at
24 GHz and 96 mm/h
on the horizontal axis). The following Figures 5.19 and 5.20 also show the values at
125 and 145 mm/h.
120
Average Carrier to Interference Ratio C/I (dB)
100
80
60
40
20
0.5km
11
0.75km
1km
1.5km
0
2km
2.5km
3km
-20
0
0.5
1
1.5
2
2.5
3
3.5
Maximum distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.19: Maximum coverage vs. different sector size of worst case at
24 GHz and 125 mm/h
69
120
Average Carrier to Interference Ratio C/I (dB)
100
80
60
40
20
0.5km
11
0.75km
1km
1.5km
2km
0
-20
3km
2.5km
0
0.5
1
1.5
2
2.5
3
3.5
Maximum distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.20: Maximum coverage vs. different sector size of worst case at
24 GHz and 145 mm/h
5.6.2 Relationship between Sector Size and Maximum Coverage at 26 GHz
120
Average Carrier to Interference Ratio C/I (dB)
100
80
60
40
20
0.5km
11
1km
1.5km
2km
2.5km
0
-20
0
0.5
1
1.5
2
2.5
3
3.5
Maximum distance between Terminal Station & Desired Base Station (km)
3km
4
4.5
Figure 5.21: Maximum coverage vs. different sector size of worst case at
26 GHz and 96 mm/h.
70
120
Average Carrier to Interference Ratio C/I (dB)
100
80
60
40
20
11
0.5km
1km
0
2km
1.5km
2.5km
3km
-20
0
0.5
1
1.5
2
2.5
3
3.5
Maximum distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.22: Maximum coverage vs. different sector size of worst case at
26 GHz and 125 mm/h.
120
Average Carrier to Interference Ratio C/I (dB)
100
80
60
40
20
11
0.5km
1km
0
1.5km
2km
2.5km
-20
0
0.5
3km
1
1.5
2
2.5
3
3.5
Maximum distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.23: Maximum coverage vs. different sector size of worst case at
26 GHz and 145 mm/h.
71
From the previous Figures 5.18 to 5.23 the availability of LMDS system in
worst case can be observed that it is not obtainable at the corner of sectors have cell
sizes of (6×6, 5×5, and 4×4) kms at 96 mm/h where the average C/I values are less
than 11 dB as a practical value of digital systems. However, at the rain rates of 125
and 145mm/h it can be observed that the availability at the corner of sectors which
have cell size of (6×6, 5×5, 4×4 and 3×3) kms is not provide.
Depending on the former notes and figures, LMDS system can achieve a
maximum coverage even during worst case without using site diversity if sector sizes
are decreased as the next Table 5.7.
Table 5.7: Maximum coverage during worst case without using site diversity
Maximum coverage (100 %) without Site Diversity for both of 24 GHz & 26
GHz, C/I = 11dB
Rain Rate
Maximum Sector Size (km)
Maximum distance
(R0.01)
To avoid worst case
between TS & BS
96 mm/h (Jelebu)
1.5×1.5
2.12 km
1×1
1.41 km
1×1
1.41 km
125 mm/h (Johor
Bahru)
145 mm/h (Taiping)
It is clearly that the maximum distance between the base station and terminal
station of Malaysia region is slightly more than 1 km for rain rates of 125 and 145
mm/h and 2 kms for rain rate of 96 mm/h.
72
5.7 Site Diversity Implementation and Calculations
Site diversity was applied when the C/I reaches the critical value caused by
rain, this is done by making a switch-over to one of the nearest “rain free” neighbor
SDBS. As it is noted from the figure below when the LMDS area suffer from rain
specially the worst case (case1) the average C/I reaches the critical value, therefore
the connection to terminal station or the desired signal (C) from BS will reload to the
available SDBS1 or SDBS2 or that one provides greater C/I whereas BS will be
switched off. The distance from the SDBS1 and SDBS2 are equal as it is drawn in
dashed lines in Figure 5.24 and the interference signals still effect on the terminal
station.
According to the Figure 5.24 the distance of new desired base station or site
diversity base station (SDBS1 or SDBS2) to terminal station TS has changed to
become 9.4868 kms while all interference signals distance did not change.
Figure 5.24: Implementation of site diversity
73
The power received from SDBS was calculated depending on the new
distance without rain attenuation and C/I for every link also calculated to obtain
average C/I value at terminal station for every rain rate and the two frequencies 24
and 26 GHz. Matlab program was used to simulate the results were obtained by
calculations to provide a clear vision of site diversity advantages against worst case
over LMDS without site diversity.
5.7.1 LMDS with Site Diversity
The same LMDS parameters and formulas mentioned formerly were applied
to obtain site diversity improvement against worst case which causes outage on the
feeder link. In order to compare between LMDS before using site diversity technique
and LMDS after using site diversity technique the graphs below were obtained.
5.7.1.1 Site Diversity Calculations at 24GHz
120
Average Carrier to Interference Ratio C/I (dB)
100
80
60
with Site Diversity
40
20
without Site Diversity
11
0
-20
0
0.5
1
1.5
2
2.5
3
3.5
Distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.25: LMDS with and without site diversity at 24 GHz and 96 mm/h
74
120
Average Carrier to Interference Ratio C/I (dB)
100
80
60
with Site Diversity
40
without Site Diversity
20
11
0
-20
0
0.5
1
1.5
2
2.5
3
3.5
Distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.26: LMDS with and without site diversity at 24 GHz and 125 mm/h
120
Average Carrier to Interference Ratio C/I (dB)
100
80
with Site Diversity
60
40
without Site Diversity
20
11
0
-20
0
0.5
1
1.5
2
2.5
3
3.5
Distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.27: LMDS with and without site diversity at 24 GHz and 145 mm/h
From the Figures 5.25 to 5.27 the using of site diversity as a technique to
combat rain fading and prevent an outage on the feeder link has proved a high
75
performance and high stability. Where as it is shown in the figures were obtained
LMDS without site diversity has a low values of average C/I of 1.6509 dB for 96
mm/h and go under zero (negative values ) during 125 and 145 mm/h rain rates of 2.4417 dB and -5.0021 dB respectively at the corner of cell.
However, by using site diversity the average C/I were obtained have stable
and high values of 34.3435 dB, 41.4604 dB and 47.2160 dB at every point on the
link for 96, 125 and 145 mm/h respectively. Also it can be seen that as rain rate is
high the C/I is high during site diversity exploiting.
5.7.1.2 Site Diversity Calculations at 26 GHz
120
Average Carrier to Interference Ratio C/I (dB)
100
80
60
with Site Diversity
40
without Site Diversity
20
11
0
-20
0
0.5
1
1.5
2
2.5
3
3.5
Distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.28: LMDS with and without site diversity at 26 GHz and 96 mm/h
76
120
Average Carrier to Interference Ratio C/I (dB)
100
80
with Site Diversity
60
40
without site Diversity
20
11
0
-20
0
0.5
1
1.5
2
2.5
3
3.5
Distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.29: LMDS with and without site diversity at 26 GHz and 125 mm/h
120
Average Carrier to Interference Ratio C/I (dB)
100
80
with Site Diversity
60
40
without Site Diversity
20
11
0
-20
0
0.5
1
1.5
2
2.5
3
3.5
Distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.30: LMDS with and without site diversity at 26 GHz and 145 mm/h
Depending on the Figures from 5.28 to 5.30 site diversity at a the other
frequency (26 GHz) also has proved a high performance to avoid an outage on the
link by getting values of C/I more higher than 11 dB (practical value of digital
77
systems) at any point on the link. The values at the corner of LMDS cell are 36.9984
dB, 44.3818 dB and 50.3187 dB for 96, 125 and 145 mm/h respectively.
5.7.1.3 Overall Average C/I Values of LMDS with and without Site Diversity
The overall average C/I values in dB of LMDS with rain and without rain
before and after using site diversity were calculated in worst case at corner point
(4.2456 kms) and a distance of 2 kms from the original desired station. These values
can be summarized in the following Tables from 5.8 to 5.11.
Table 5.8: Average C/I (dB) of LMDS service area at (24 GHz) and
d= 4.2456 kms
AVERAGE C/I (dB) of the LMDS Service Area in WORST CASE
(Downlink) (f =24 GHz) at the corner( d= 4.2456 kms)
Rain Rate
Without
With rain, without
With Rain, and
Gain
(R0.01)
Rain
Site Diversity
with Site Diversity
Improvement
13.3887
1.6509
34.3435
32.6926
13.3887
-2.4417
41.4604
43.9021
13.3887
-5.0021
47.2160
52.2181
96 mm/h
(Jelebu)
125 mm/h
(Johor Bahru)
145 mm/h
(Taiping)
78
Table 5.9: Average C/I (dB) of LMDS service area at (26 GHz) and
d= 4.2456 kms
AVERAGE C/I (dB) of the LMDS Service Area in WORST CASE
(Downlink) (f =26 GHz) at the corner( d= 4.2456 kms)
Rain Rate
Without
With Rain, without
With Rain, and
Gain
(R0.01)
Rain
Site Diversity
with Site Diversity
Improvement
13.3887
0.5271
37.0691
36.5420
13.3887
-3.8582
44.6446
48.5028
13.3887
-6.5833
50.7704
57.3537
96 mm/h
(Jelebu)
125 mm/h
(Johor Bahru)
145 mm/h
(Taiping)
When Ts is in the mid-distance between the BS and the corner of the sector
(approximately at d=2 kms from the BS):
Table 5.10: Average C/I (dB) of LMDS service area at (24 GHz) and
d=2 kms
AVERAGE C/I (dB) of the LMDS Service Area in WORST CASE
(Downlink) (f =24 GHz) at ( d= 2 kms) from the desired BS
Rain Rate
Without
With Rain, without
With Rain, and
Gain
(R0.01)
Rain
Site Diversity
with Site Diversity
Improvement
18.8977
23.3677
34.3605
10.9928
18.8977
23.6074
41.2957
17.6883
18.8977
24.3691
46.8739
22.5048
96 mm/h
(Jelebu)
125 mm/h
(Johor Bahru)
145 mm/h
(Taiping)
79
Table 5.11: Average C/I (dB) of LMDS service area at (26 GHz) and
d=2 kms
AVERAGE C/I (dB) of the LMDS Service Area in WORST CASE
(Downlink) (f =26 GHz) at ( d= 2 kms) from the desired BS
Rain Rate
Without
(R0.01)
Rain
96 mm/h
(Jelebu)
125 mm/h
(Johor Bahru)
145 mm/h
(Taiping)
With Rain, without
Site Diversity
With Rain, and
Gain
with Site Diversity
Improvement
18.8977
23.7956
36.9984
13.2028
18.8977
24.0288
44.3818
20.3530
18.8977
24.8395
50.3187
25.4729
Site diversity improvement can be obtained by comparison of the second and
third column of Tables from 5.7 to 5.10, it can be seen from these tables that average
C/I is higher with site diversity.
5.8 Site Diversity with Different Cell Sizes of LMDS
Different cell size were considered to observe the site diversity effects and its
relation with cell size, it is found than site diversity is not suitable of small cell size
because the rain cell may cover these links at all furthermore average C/I by using
site diversity has higher value for large cell size than that of small cell size as the
Figures 5.31 to 5.36 below.
80
36
3 km
34
Average Carrier to Interference Ratio C/I (dB)
2.5 km
32
2 km
30
28
1.5 km
26
1 km
24
22
20
18
16
0.5 km
0
0.5
1
1.5
2
2.5
3
3.5
Maximum distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.31: Site diversity vs. different sector sizes of worst case
at 24 GHz and 96 mm/h
45
Average Carrier to Interference Ratio C/I (dB)
3 km
40
2.5 km
2 km
35
1.5 km
30
1km
25
0.5 km
20
0
0.5
1
1.5
2
2.5
3
3.5
Maximum distance between Terminal Station & Desired Base Station (km)
4
Figure 5.32: Site diversity vs. different sector sizes of worst case
at 24 GHz and 125 mm/h
4.5
81
50
Average Carrier to Interference Ratio C/I (dB)
3km
2.5 km
45
2 km
40
1.5 km
35
1km
30
25
0.5 km
20
0
0.5
1
1.5
2
2.5
3
3.5
Maximum distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.33: Site diversity vs. different sector sizes of worst case
at 24 GHz and 145 mm/h
38
3 km
Average Carrier to Interference Ratio C/I (dB)
36
2.5 km
34
2 km
32
1.5 km
30
28
26
1 km
24
22
20
18
0.5 km
0
0.5
1
1.5
2
2.5
3
3.5
Maximum distance between Terminal Station & Desired Base Station (km)
4
Figure 5.34: Site diversity vs. different sector sizes of worst case
at 26GHz and 96mm/h
4.5
82
45
3 km
Average Carrier to Interference Ratio C/I (dB)
2.5 km
40
2 km
1.5 km
35
1 km
30
25
0.5 km
20
0
0.5
1
1.5
2
2.5
3
3.5
Maximum distance between Terminal Station & Desired Base Station (km)
4
4.5
Figure 5.35: Site diversity vs. different sector sizes of worst case
at 26GHz and 125mm/h
55
3 km
Average Carrier to Interference Ratio C/I (dB)
50
2.5 km
2 km
45
1.5 km
40
1km
35
30
25
20
0.5 km
0
0.5
1
1.5
2
2.5
3
3.5
Maximum distance between Terminal Station & Desired Base Station (km)
4
Figure 5.36: Site diversity vs. different sector sizes of worst case
at 26GHz and 145mm/h
4.5
83
These graphs are proved that site diversity is an excellent technique to avoid
rain fading and weakness of the signal during rain with different cell sizes, it can be
noticed that average C/I of worst case of horizontal polarization frequency has high
values for large cell sizes, high rain rates and high frequency while it is low for small
cell sizes, low rain rate and low frequency. All average C/I values are significantly
higher than the minimum practical value of C/I (11 dB) as the Figures from 5.31 to
5.36 show.
CHAPTER 6
CONCLUSION AND FUTURE WORK
6.1 Summary
This study was carried out for studying and knowing the effects of site
diversity in LMDS system under rainy conditions in Malaysia. LMDS system is
considered as a system to remove the bottlenecks between advanced communication
networks (like optical) and the home and office. Furthermore this system provides
high capacity (broadband) service. However these systems suffer from high rain
attenuation due to that it use frequencies above 20 GHz. There are number of the
aspects were discussed and analysis in this project.
LMDS has been explained as a system and its components addition to the
advantages and disadvantages, the capacity and applications of this system and
frequency bands were also described in chapter two. Cell planning, the formulas and
equations of LMDS system were presented as well as some aspects related to this
system.
Rain fading effects and its causes were elaborated in brief details especially
of high frequencies which are specified to LMDS, the steps to calculate rain
attenuation based ITU-R were explained. Interference and effects of movement of
rain cell over LMDS cells were presented depending of previous researches.
85
Site diversity has been explained by describing its parameters, diversity gain
and Improvement factor concepts additional to how to implement site diversity and
the influence factors and the ways to apply site diversity were described.
6.2 Conclusion
•
It can be stated from overall results were obtained from this project that, high
rain intensity, horizontal polarization, higher frequencies and longer path
length lead to high attenuation and degrade the system performance very
significantly in locations of BFWA area.
•
There is no significant different between 125 and 145 mm/h rain rates in term
of Avg. C/I when desired signal suffer from rain.
•
Higher C/I value of all LMDS area during rain is obtained than LMDS area
without rain; because rain contributes blocking of cells interference.
•
Maximum coverage (100 %) during worst case can be obtained without site
diversity by reducing cell size for maximum distance (TS to BS) of 2.12 km
(cell size= 3×3 km2 ) in R0.01=96 mm/h and for maximum distance of 1.41 km
(cell size = 2 ×2 km2 ) in R0.01=125 & 145 mm/h.
•
Preventing the highest degradation of performance level in the LMDS area
can be applied by using site diversity. When the C/I value reaches the critical
threshold caused by rain the TS can make a switch-over to the nearest rainfree SDBS.
•
Site diversity is capable to improve the performance level even at LMDS
corner area or worst case.
86
6.3 Future Work
The objective was achieved within the scope of this project. There are few
recommendations which might be helpful in the future work as given below,
•
Applying LMDS system in Malaysia region by using different Rain
profiles models and studying movement effects of rain cell along LMDS.
•
It is recommended to repeat the study at frequencies lower than 10 GHz
(approx. 5 GHz) i.e. trying to develop an LMDS operating in bands lower
than 10 GHz to avoid Rain attenuation effects which are not significant
for these bands.
•
It should be taken into account the multipath and non line of sight effects
in future studies to obtain approximate practically results.
REFERENCES
Agne Nordbotten, Telenor R&D (2000). LMDS Systems and their
Application. IEEE Communications Magazine June 2000.
Arapoglou, P. D. M., Kartsakli, E., Chatzarakis, G. E. and Cottis, P. G.
(2004). Cell-Site Diversity Performance of LMDS Systems Operating in
Heavy Rain Climatic Regions. International Journal of Infrared and
Millimeter Waves, 2004 – Springer.
Arapoglou, P. D. M., Panagopoulos, A. D., Kanellopoulos, J.D. and Cottis,
P.G. (2005). Intercell radio interference studies in CDMA based LMDS
network. IEEE Trans. Antennas Propag. vol. 53, no. 8, Aug. 2005.
Athanasios, D. Panagopoulos, Pantelis-Daniel M. Arapoglou, John D.
Kanellopoulos, and Panayotis G. Cottis. (2005). Long-Term Rain Attenuation
Probability and Site Diversity Gain Prediction Formulas. IEEE Transactions
on Antennas and Propagation, vol. 53, no. 7, July 2005.
Blake, R. (2001). Wireless Communication Technology. Wadsworth Inc.
Chu, C. and Chen, K. S. (2005). Effects of Rain Fading on the Efficiency of
the Ka-Band LMDS System in the Taiwan Area. IEEE Transactions on
Vehicular Technology, Vol. 54, NO. 1, January 2005.
88
Douglas A. Gary (1997). A Broadband Wireless Access System at 28 GHz.
IEEE, Wireless Communications Conference, Aug11-13, pp.1-7.
Enjamio, C., Vilar, E. and Fontán, F. P. (2002). Spatial Distribution of
Rainfall Rate: Benefits of the Site Diversity as a Dynamic Fade Mitigation
Technique. COST 280 PM3009 1st International Workshop 2002.
Falconer, D. D. and DeCruyenaere, J. P. (2003). Coverage Enhancement
Methods for LMDS. IEEE Communications Magazine, vol. 41, no. 7, pp. 8692, July.
Heder, B., Singliar, R., and Bito, J. (2005). Site Diversity Examination based
on Rain Attenuation Measurement. 47th International Symposium ELMAR,
08-10 June 2005, Zadar, Croatia.
Hendrantoro, G., Bultitude, R. J. C. and Falconer, D. D. (2002). Use of CellSite Diversity in Millimeter-Wave Fixed Cellular Systems to Combat the
Effects of Rain Attenuation. IEEE JSAC, vol. 20, no. 3, Apr. 2002, pp. 602-14.
Hikmet Sari. (2000). “Trends and Challenges in Broadband Wireless Access.
0-7803-6684, IEEE, 2000.
ITU-R Recommendations (2005). Propagation data and prediction methods
required for the design of terrestrial line-of-sight systems. P.530-11.
ITU-R Recommendations (2005). Specific attenuation model for rain for
use in prediction methods. P.838-3.
Lee, C., Chung, B. and Lee, S. (1998). Dynamic Modulation Scheme In
Consideration of Cell Interference for LMDS. International Conference on
Communication Technology, ICCT'98 October 22-24, Beijing China, 1998.
89
Michael D. Lei. (2001). Factors Affecting Deployment Strategies for an
LMDS System in a Rural Commercial Environment. M.Eng. Thesis, Faculty
of the Virginia Polytechnic Institute and State University.
Panagopoulos, A. D. and Kanellopoulos, J. D. (2002). Cell-site diversity
performance of millimeter-wave fixed cellular systems operating at
frequencies above 20 GHz. IEEE Antennas Wirel. Propag. Lett., vol. 1, pp.
183-185.
Panagopoulos, A. D, Liolis, K. P. and Cottis, P. G. (2006). Cell-Site Diversity
Against Co-Channel Interference in LMDS Networks. Wireless Personal
Communications 39: 183–198, Springer.
Salem Salamah (2000). Transmit power control in fixed broadband wireless
systems”, M.Eng. Thesis, Carleton University Aug. 2000.
Sinka, C., Bito, J. (2003). Site diversity against rain fading in LMDS systems.
IEEE Microw. Wireless Comp. Lett., vol 13, no. 8, pp. 317-319, August
2003.
Sinka, C., Lakatos, B., Bitó, J. (2002). The Effects of Moving Rain Cell Over
LMDS Systems. COST Action 280, PM3027, 1st
International Workshop
July 2002.
Standard Radio System Plan. (2003). Requirements for Local Multipoint
Communications Service (LMCS) Operating in the Frequency Bands From
24.25 GHz to 27.0 GHz, 27.0 GHz to 29.5 GHz and 31.00 GHz to 31.3 GHz.
Malaysia Communications and Multimedia Commission (MCMC SRSP)509, Issue 3.
The International Engineering Consortium (IEC). (2005). Local Multipoint
Distribution
Service
(www.iec.org.14/9/2006).
(LMDS).
web
proforum
tutorials,
90
Zvanovec S., Pechac P. (2004). Site Diversity Time-Space Simulations for
LMDS. 0-7803-8521-7/04 IEEE.
91 APPENDIX A
Part of the ITU-R Specific Attenuation Parameters
92 APPENDIX B
Frequency Bands allocated for LMCS or (LMDS)
93 APPEENDEX C
The Rain Attenuation Program
% this code is for calculating rain attenuation in both cases Horizontal
and %Vertical.
% f=26;
%frequency in GHz
% kh=0.1724;
% kv=0.1669;
% alfa_h=0.9884;
% alfa_v=0.9421;
%R=125;
% Johor Bahru rain rate in mm/h
%R=145;
%Taiping rain rate in mm/h
R=96;
%Jelebu rain rate in mm/h
f=24;
%frequency in GHz
kh=0.1425;
kv=0.1404;
alfa_h=1.0101;
alfa_v=0.9561;
size=3;
%size of the cell is (size*size)
w=(size*sqrt(2));
% the point at the corner of sector
for j=0.0001:0.005:w,
d=j;
d1=((size*4)*sqrt(2))+j;
d2=sqrt((sin (pi/4)*j)^2+((sin (pi/4)*j)+(size*4))^2);
%==========================================================================
d3=sqrt((sin (pi/4)*j)^2+((sin (pi/4)*j)+(size*4))^2);
%do=35*exp(-(0.015*100));
% in case R=125 or 145 mm/h
do=35*exp(-(0.015*96));
% in case R=96 mm/h
rC=1/(1+(d/do));
%%reduction factor of Carrier signal C
rI1=1/(1+(d1/do)); %%reduction factor of Interference signal I1
rI2=1/(1+(d2/do)); %%reduction factor of Interference signal I2
rI3=1/(1+(d3/do)); %%reduction factor of Interference signal I3
Ah=kh*R^alfa_h; % specific rain attenuation dB/km (Horizontal Polarization)
Av=kv*R^alfa_v; % specific rain attenuation dB/km (Vertical Polarization)
%==========================================================================
%==========================================================================
%rain attenuation in dB.
RAtt_h_C=Ah*d*rC ; % rain attenuation of Carrier(C)Horizontal pol.
RAtt_v_C=Av*d*rC ; % rain attenuation of Carrier (C)Vertical pol.
RAtt_h_I1=Ah*d1*rI1; % rain attenuation of Interference (I1) Horizontal
pol.
RAtt_v_I1=Av*d1*rI1; % rain attenuation of Interference (I1) Vertical pol.
RAtt_h_I2=Ah*d2*rI2; % rain attenuation of Interference (I2) Horizontal
pol.
RAtt_v_I2=Av*d2*rI2; % rain attenuation of Interference (I2) Vertical pol.
94 RAtt_h_I3=Ah*d3*rI3; % rain attenuation of Interference (I3) Horizontal
pol.
RAtt_v_I3=Av*d3*rI3; % rain attenuation of Interference (I3) Vertical pol.
%==========================================================================
% % %for drawing
grid;
hold on
plot(j, RAtt_h_C,'r')
plot(j, RAtt_v_C,'k')
hold off
end
95 APPEENDEX D
Average C/I of ALL LMDS with Rain and Without Rain Program
% this code is for calculating Average C/I when ALL LMDS with and without
% rain and without Site Diversity technique.
% f=26;
%frequency in GHz
% kh=0.1724;
% kv=0.1669;
% alfa_h=0.9884;
% alfa_v=0.9421;
%R=125;
%Johor Bahru rain rate in mm/h
%R=145;
%Taiping rain rate in mm/h
R=96;
%Jelebu rain rate in mm/h
f=24;
% frequency in GHz
kh=0.1425;
kv=0.1404;
alfa_h=1.0101;
alfa_v=0.9561;
size=3;
%size of the cell is (size*size)
w=(size*sqrt(2));
% the point at the corner of sector
for j=0.0001:0.005:w,
d=j; % distance of C from desired Base station (BS) to Terminal station
at(w)
d1=((size*4)*sqrt(2))+j;
%distance of I1 Base Station(BS1)
d2=sqrt((sin (pi/4)*j)^2+((sin (pi/4)*j)+(size*4))^2); %distance of I2
(BS2)
d3=sqrt((sin (pi/4)*j)^2+((sin (pi/4)*j)+(size*4))^2); %distance of I3
(BS3)
%==========================================================================
%do=35*exp(-(0.015*100));
% in case R=125 or 145 mm/h
do=35*exp(-(0.015*96));
% in case R=96 mm/h
rC=1/(1+(d/do));
%%reduction factor of Carrier signal C
rI1=1/(1+(d1/do)); %%reduction factor of Interference signal I1
rI2=1/(1+(d2/do)); %%reduction factor of Interference signal I2
rI3=1/(1+(d3/do)); %%reduction factor of Interference signal I3
Ah=kh*R^alfa_h; % specific rain attenuation dB/km (Horizontal
Polarization)
%==========================================================================
%==========================================================================
%rain attenuation in dB.
RAtt_h_C=Ah*d*rC ; % rain attenuation of Carrier(C)Horizontal pol.
RAtt_h_I1=Ah*d1*rI1; % rain attenuation of Interference (I1) Horizontal
pol.
RAtt_h_I2=Ah*d2*rI2; % rain attenuation of Interference (I2) Horizontal
pol.
96 RAtt_h_I3=Ah*d3*rI3; % rain attenuation of Interference (I3) Horizontal
pol.
%==========================================================================
%path loss in dB
pathlossC=92.45+20*log10(d*f);
pathlossI1=92.45+20*log10(d1*f);
pathlossI2=92.45+20*log10(d2*f);
pathlossI3=92.45+20*log10(d3*f);
%==========================================================================
Pt=2;
% power transmitted
Gt=18;
% gain of transmitter
Gr=38;
% gain of receiver
Lfm=1;
% fade margin loss
%==========================================================================
%==========================================================================
% atmosphere attenuation (ITU_R)
LatmC=d*0.1;
%of C
LatmI1=d1*0.1;
%of I1
LatmI2=d2*0.1;
%of I2
LatmI3=d3*0.1;
%of I3
%==========================================================================
%==========================================================================
%Total loss and power received of Desired Signal(C) at terminal station in
Rain
TL_h_C=pathlossC+Lfm+LatmC+RAtt_h_C;
Pr_h=Pt+Gt+Gr-TL_h_C;
%==========================================================================
%==========================================================================
%Total loss and interference power (I1, I2 and I3) at terminal station in
Rain
TL_h_I1=pathlossI1+Lfm+LatmI1+RAtt_h_I1;
I1_h=Pt+Gt+Gr-TL_h_I1;
TL_h_I2=pathlossI2+Lfm+LatmI2+RAtt_h_I2;
I2_h=Pt+Gt+Gr-TL_h_I2;
TL_h_I3=pathlossI3+Lfm+LatmI3+RAtt_h_I3;
I3_h=Pt+Gt+Gr-TL_h_I3;
%==========================================================================
%==========================================================================
% Average C/I at terminal station in case all signal with rain
RATIOh1=Pr_h-I1_h;
RATIOh2=Pr_h-I2_h;
RATIOh3=Pr_h-I3_h;
T_CI_AllRAIN_h=(RATIOh1+RATIOh2+RATIOh3)/3;
%==========================================================================
%Power received at terminal station of All Signals without rain
Pr=Pt+Gt+Gr-(pathlossC+Lfm+LatmC);
% Carrier (C) in dBW
I1=Pt+Gt+Gr-(pathlossI1+Lfm+LatmI1);
% Interference (I1) in dBW
I2=Pt+Gt+Gr-(pathlossI2+Lfm+LatmI2);
% Interference (I2) in dBW
I3=Pt+Gt+Gr-(pathlossI3+Lfm+LatmI3);
% Interference (I3) in dBW
%==========================================================================
%calculation of Carrier to Interferenc ratio C/I as a total all signal in
dB %without Rain
RATIO_I1=Pr-I1;
RATIO_I2=Pr-I2;
RATIO_I3=Pr-I3;
T_CI_AllnoRAIN=(RATIO_I1+RATIO_I2+RATIO_I3)/3;
%==========================================================================
%for drawing
grid;hold on plot(j, T_CI_AllRAIN_h,'r'); plot(j, T_CI_AllnoRAIN,'k');
hold off;end 97 APPEENDEX E
Average C/I of the Four Possibilities Cases Scenarios Program
% This code is for calculating Average C/I of the Four cases which have
%different situation related to With and without rain and without Site
%Diversity technique.
% f=26;
%frequency
% kh=0.1724;
% kv=0.1669;
% alfa_h=0.9884;
% alfa_v=0.9421;
%R=125;
%Johor Bahru rain rate in mm/h
%R=145;
%Taiping rain rate in mm/h
R=96;
%Jelebu rain rate in mm/h
f=24;
% frequency
kh=0.1425;
kv=0.1404;
alfa_h=1.0101;
alfa_v=0.9561;
size=3;
%size of the cell is (size*size)
w=(size*sqrt(2));
% the point at the corner of sector
for j=0.0001:0.005:w,
d=j; % distance of C from desired Base station (BS) to Terminal station
at(w)
d1=((size*4)*sqrt(2))+j; %distance of I1 Base Station(BS1)
d2=sqrt((sin (pi/4)*j)^2+((sin (pi/4)*j)+(size*4))^2); %distance of I2
(BS2)
d3=sqrt((sin (pi/4)*j)^2+((sin (pi/4)*j)+(size*4))^2); %distance of I3
(BS3)
%=========================================================================
%do=35*exp(-(0.015*100));
% in case R=125 or 145 mm/h
do=35*exp(-(0.015*96));
% in case R=96 mm/h
rC=1/(1+(d/do));
%reduction factor of Carrier signal C
rI1=1/(1+(d1/do));
%reduction factor of Interference signal I1
rI2=1/(1+(d2/do));
%reduction factor of Interference signal I2
rI3=1/(1+(d3/do));
%reduction factor of Interference signal I3
Ah=kh*R^alfa_h; % specific rain attenuation dB/km (Horizontal Polarization)
%==========================================================================
%==========================================================================
%rain attenuation in dB.
RAtt_h_C=Ah*d*rC ;
% rain attenuation of Carrier(C)Horizontal pol.
RAtt_h_I1=Ah*d1*rI1; % rain attenuation of Interference (I1) Horizontal
pol.
98 RAtt_h_I2=Ah*d2*rI2; % rain attenuation of Interference (I2) Horizontal
pol.
RAtt_h_I3=Ah*d3*rI3; % rain attenuation of Interference (I3) Horizontal
pol.
%==========================================================================
%==========================================================================
%path loss in dB
pathlossC=92.45+20*log10(d*f);
pathlossI1=92.45+20*log10(d1*f);
pathlossI2=92.45+20*log10(d2*f);
pathlossI3=92.45+20*log10(d3*f);
%==========================================================================
Pt=2;
% power transmitted
Gt=18;
% gain of transmitter
Gr=38;
% gain of receiver
Lfm=1;
% fade margin loss
%==========================================================================
%==========================================================================
% atmosphere attenuation (ITU_R)
LatmC=d*0.1;
%of C
LatmI1=d1*0.1;
%of I1
LatmI2=d2*0.1;
%of I2
LatmI3=d3*0.1;
%of I3
%==========================================================================
%==========================================================================
%Total loss and power received of Desired Signal(C) at terminal station in
Rain
TL_h_C=pathlossC+Lfm+LatmC+RAtt_h_C;
Pr_h=Pt+Gt+Gr-TL_h_C;
%==========================================================================
%==========================================================================
%Total loss and interference power (I1, I2 and I3) at terminal station in
%Rain
TL_h_I1=pathlossI1+Lfm+LatmI1+RAtt_h_I1;
I1_h=Pt+Gt+Gr-TL_h_I1;
TL_h_I2=pathlossI2+Lfm+LatmI2+RAtt_h_I2;
I2_h=Pt+Gt+Gr-TL_h_I2;
TL_h_I3=pathlossI3+Lfm+LatmI3+RAtt_h_I3;
I3_h=Pt+Gt+Gr-TL_h_I3;
%==========================================================================
%==========================================================================
%Power received at terminal station of All Signals without rain
Pr=Pt+Gt+Gr-(pathlossC+Lfm+LatmC);
% Carrier (C)in dBW
I1=Pt+Gt+Gr-(pathlossI1+Lfm+LatmI1);
%Interference (I1) dBW
I2=Pt+Gt+Gr-(pathlossI2+Lfm+LatmI2);
% Interference (I2) in dBW
I3=Pt+Gt+Gr-(pathlossI3+Lfm+LatmI3);
% Interference (I3) in dBW
%==========================================================================
%==========================================================================
%Average C/I Calculation at terminal station
%if Carrier in rain:
%I1 with rain while I2&I3 without rain (HORIZONTAL POLARIZATION)
Ratio11_h_dB=Pr_h-I1_h;
Ratio21_h_dB=Pr_h-I2;
Ratio31_h_dB=Pr_h-I3;
case1h=(Ratio11_h_dB+Ratio21_h_dB+Ratio31_h_dB)/3;
%==========================================================================
%==========================================================================
%Average C/I Calculation at terminal station
%if Carrier in rain:
%I1& (I2 or I3)with rain while(I3 or I2)without rain(HORIZONTAL
POLARIZATION)
99 Ratio12_h_dB=Pr_h-I1_h;
Ratio22_h_dB=Pr_h-I2_h;
Ratio32_h_dB=Pr_h-I3;
case2h= (Ratio12_h_dB+Ratio22_h_dB+Ratio32_h_dB)/3;
%==========================================================================
%==========================================================================
%Average C/I Calculation at terminal station
%if Carrier without rain:
%I1 without rain while I2&I3 with rain (HORIZONTAL POLARIZATION)
Ratio13_h_dB=Pr-I1;
Ratio23_h_dB=Pr-I2_h;
Ratio33_h_dB=Pr-I3_h;
case3h= (Ratio13_h_dB+Ratio23_h_dB+Ratio33_h_dB)/3;
%==========================================================================
%==========================================================================
%Average C/I Calculation at terminal station
%if Carrier without rain:
%I1&(I2 or I3)without rain while(I3 or I2)with rain(HORIZONTAL
POLARIZATION)
Ratio14_h_dB=Pr-I1;
Ratio24_h_dB=Pr-I2;
Ratio34_h_dB=Pr-I3_h;
case4h=(Ratio14_h_dB+Ratio24_h_dB+Ratio34_h_dB)/3;
%==========================================================================
%==========================================================================
% % %for drawing
grid;
hold on
plot(j,case1h,'r')
plot(j,case2h,'k')
plot(j,case3h,'g')
plot(j,case4h,'b')
hold off
end
100 APPEENDIX F
Average C/I of the Worst Case Scenario and Different LMDS Cell Sizes Program
without Site Diversity Technique
% this code is
for calculating Average C/I of the Worst Case scenario and
%different LMDS Cell Sizes without Site Diversity technique
% f=26;
%frequency
% kh=0.1724;
% kv=0.1669;
% alfa_h=0.9884;
% alfa_v=0.9421;
% R=125;
% Johor Bahru rain rate in mm/h
% R=145;
% Taiping rain rate in mm/h
R=96;
% Jelebu rain rate in mm/h
f=24;
% frequency
kh=0.1425;
kv=0.1404;
alfa_h=1.0101;
alfa_v=0.9561;
for size=0.5:.5:3
% Different Cell Size (size*size)
w=(size*sqrt(2));
% the point at the corner of sector
for j=0.0001:0.005:w,
% distance of All effective Base Stations (BSs) to Terminal station at (w):
d= j;
% from C (BS)
d1=((size*4)*sqrt(2))+j;
% from I1 (BS1)
d2=sqrt((sin (pi/4)*j)^2+((sin (pi/4)*j)+(size*4))^2);
% from I2 (BS2)
d3=sqrt((sin (pi/4)*j)^2+((sin (pi/4)*j)+(size*4))^2);
% from I3 (BS3)
%==========================================================================
% do=35*exp(-(0.015*100));
% in case R=125 or 145 mm/h
do=35*exp(-(0.015*96));
% in case R=96 mm/h
rC=1/(1+(d/do));
%reduction factor of Carrier signal C in km
rI1=1/(1+(d1/do));
%reduction factor of Interference signal I1 in km
rI2=1/(1+(d2/do));
%reduction factor of Interference signal I1 in km
rI3=1/(1+(d3/do));
%reduction factor of Interference signal I1 in km
Ah=kh*R^alfa_h;
% specific rain attenuation dB/km (Horizontal
Polarization)
%==========================================================================
%==========================================================================
% rain attenuation in dB.
RAtt_h_C=Ah*d*rC ;
% rain attenuation of Carrier(C)Horizontal pol.
RAtt_h_I1=Ah*d1*rI1; % rain attenuation of Interference (I1) Horizontal
pol.
RAtt_h_I2=Ah*d2*rI2; % rain attenuation of Interference (I2) Horizontal
pol.
RAtt_h_I3=Ah*d3*rI3; % rain attenuation of Interference (I3) Horizontal
pol.
%==========================================================================
101 %==========================================================================
% path loss in dB
pathlossC=92.45+20*log10(d*f);
pathlossI1=92.45+20*log10(d1*f);
pathlossI2=92.45+20*log10(d2*f);
pathlossI3=92.45+20*log10(d3*f);
%==========================================================================
Pt=2;
% power transmitted
Gt=18;
% gain of transmitter
Gr=38;
% gain of receiver
Lfm=1;
% fade margin loss
%==========================================================================
%==========================================================================
% atmosphere attenuation (ITU_R)
LatmC=d*0.1;
%of C
LatmI1=d1*0.1;
%of I1
LatmI2=d2*0.1;
%of I2
LatmI3=d3*0.1;
%of I3
%==========================================================================
%==========================================================================
% Total loss and power received of Desired Signal(C) at terminal station in
% Rain
TL_h_C=pathlossC+Lfm+LatmC+RAtt_h_C;
Pr_h=Pt+Gt+Gr-TL_h_C;
%==========================================================================
%==========================================================================
% Total loss and interference power (I1, I2 and I3) at terminal station in
% Rain
TL_h_I1=pathlossI1+Lfm+LatmI1+RAtt_h_I1;
I1_h=Pt+Gt+Gr-TL_h_I1;
TL_h_I2=pathlossI2+Lfm+LatmI2+RAtt_h_I2;
I2_h=Pt+Gt+Gr-TL_h_I2;
TL_h_I3=pathlossI3+Lfm+LatmI3+RAtt_h_I3;
I3_h=Pt+Gt+Gr-TL_h_I3;
%==========================================================================
%==========================================================================
% Power received at terminal station of All Signals without rain
Pr=Pt+Gt+Gr-(pathlossC+Lfm+LatmC);
% Carrier (C) in dBW
I1=Pt+Gt+Gr-(pathlossI1+Lfm+LatmI1);
% Interference (I1) in dBW
I2=Pt+Gt+Gr-(pathlossI2+Lfm+LatmI2);
% Interference (I2) in dBW
I3=Pt+Gt+Gr-(pathlossI3+Lfm+LatmI3);
% Interference (I3) in dBW
%==========================================================================
%==========================================================================
% Average C/I Calculation at terminal station
% if Carrier in rain:
% I1 with rain while I2&I3 without rain (HORIZONTAL POLARIZATION)
Ratio11_h_dB=Pr_h-I1_h;
Ratio21_h_dB=Pr_h-I2;
Ratio31_h_dB=Pr_h-I3;
case1h=(Ratio11_h_dB+Ratio21_h_dB+Ratio31_h_dB)/3;
%==========================================================================
%==========================================================================
%%%for drawing
grid;
hold on
plot(j,case1h,'r')
hold off
end
end
102 APPEENDEX G
Average C/I of the Worst Case Scenario by Using Site Diversity Program
% this code is for calculating Average C/I of the Worst Case scenario by
%using Site Diversity Technique.
% f=26;
%frequency
% kh=0.1724;
% kv=0.1669;
% alfa_h=0.9884;
% alfa_v=0.9421;
% R=125;
% Johor Bahru rain rate in mm/h
% R=145;
% Taiping rain rate in mm/h
R=96;
% Jelebu rain rate in mm/h
f=24;
% frequency
kh=0.1425;
kv=0.1404;
alfa_h=1.0101;
alfa_v=0.9561;
size=3
% Cell Size (size*size)
w=(size*sqrt(2));
% the point at the corner of sector
for j=0.0001:0.005:w,
%distance of All effective Base Stations (BSs)to Terminal station at(w):
d=sqrt((sin(pi/4)*j)^2+((2*size)+(sin(pi/4)*j))^2); %%*** SITE DIVERSITY***
d1=((size*4)*sqrt(2))+j;
% from I1 (BS1)
d2=sqrt((sin (pi/4)*j)^2+((sin (pi/4)*j)+(size*4))^2);
% from I2 (BS2)
d3=sqrt((sin (pi/4)*j)^2+((sin (pi/4)*j)+(size*4))^2);
% from I3 (BS3)
%==========================================================================
%do=35*exp(-(0.015*100));
% in case R=125 or 145 mm/h
do=35*exp(-(0.015*96));
% in case R=96 mm/h
rC=1/(1+(d/do));
%reduction factor of Carrier signal C in km
rI1=1/(1+(d1/do));
%reduction factor of Interference signal I1 in km
rI2=1/(1+(d2/do));
%reduction factor of Interference signal I1 in km
rI3=1/(1+(d3/do));
%reduction factor of Interference signal I1 in km
Ah=kh*R^alfa_h;
% specific rain attenuation dB/km (Horizontal
Polarization)
%==========================================================================
%==========================================================================
%rain attenuation in dB.
RAtt_h_C=Ah*d*rC ;
% rain attenuation of Carrier(C)Horizontal pol.
RAtt_h_I1=Ah*d1*rI1; % rain attenuation of Interference (I1) Horizontal
pol.
RAtt_h_I2=Ah*d2*rI2; % rain attenuation of Interference (I2) Horizontal
pol.
RAtt_h_I3=Ah*d3*rI3; % rain attenuation of Interference (I3) Horizontal
pol.
%==========================================================================
%==========================================================================
%path loss in dB
103 pathlossC=92.45+20*log10(d*f);
pathlossI1=92.45+20*log10(d1*f);
pathlossI2=92.45+20*log10(d2*f);
pathlossI3=92.45+20*log10(d3*f);
%==========================================================================
Pt=2;
%power transmitted
Gt=18;
%gain of transmitter
Gr=38;
%gain of receiver
Lfm=1;
% fade margin loss
%==========================================================================
%==========================================================================
% atmosphere attenuation (ITU_R)
LatmC=d*0.1;
%of C
LatmI1=d1*0.1;
%of I1
LatmI2=d2*0.1;
%of I2
LatmI3=d3*0.1;
%of I3
%==========================================================================
%==========================================================================
%Total loss and power received of Desired Signal(C) at terminal station in
%Rain
TL_h_C=pathlossC+Lfm+LatmC+RAtt_h_C;
Pr_h=Pt+Gt+Gr-TL_h_C;
%==========================================================================
%==========================================================================
%Total loss and interference power (I1, I2 and I3) at terminal station in
Rain
TL_h_I1=pathlossI1+Lfm+LatmI1+RAtt_h_I1;
I1_h=Pt+Gt+Gr-TL_h_I1;
TL_h_I2=pathlossI2+Lfm+LatmI2+RAtt_h_I2;
I2_h=Pt+Gt+Gr-TL_h_I2;
TL_h_I3=pathlossI3+Lfm+LatmI3+RAtt_h_I3;
I3_h=Pt+Gt+Gr-TL_h_I3;
%==========================================================================
%==========================================================================
%Power received at terminal station of All Signals without rain
Pr=Pt+Gt+Gr-(pathlossC+Lfm+LatmC); % Carrier (C)in dBW
I1=Pt+Gt+Gr-(pathlossI1+Lfm+LatmI1); %Interference (I1) dBW
I2=Pt+Gt+Gr-(pathlossI2+Lfm+LatmI2); % Interference (I2) in dBW
I3=Pt+Gt+Gr-(pathlossI3+Lfm+LatmI3); % Interference (I3) in dBW
%==========================================================================
%==========================================================================
%Average C/I Calculation at terminal station
%if Carrier in rain:
%I1 with rain while I2&I3 without rain (HORIZONTAL POLARIZATION)
Ratio11_h_dB=Pr_h-I1_h;
Ratio21_h_dB=Pr_h-I2;
Ratio31_h_dB=Pr_h-I3;
case1h=(Ratio11_h_dB+Ratio21_h_dB+Ratio31_h_dB)/3;
%==========================================================================
%==========================================================================
% % %for drawing
grid;
hold on
plot(j,case1h,'r')
hold off
end
104 APPEENDEX H
Average C/I of the Worst Case Scenario and Different LMDS Cell Sizes Program
with Site Diversity Technique
% this code is for calculating Average C/I of the Worst Case and
different %cell sizes and with Site Diversity Technique.
% f=26;
%frequency
% kh=0.1724;
% kv=0.1669;
% alfa_h=0.9884;
% alfa_v=0.9421;
% R=125;
% Johor Bahru rain rate in mm/h
% R=145;
% Taiping rain rate in mm/h
R=96;
% Jelebu rain rate in mm/h
f=24;
% frequency
kh=0.1425;
kv=0.1404;
alfa_h=1.0101;
alfa_v=0.9561;
for size=0.5:.5:3
% Different Cell Size (size*size)
w=(size*sqrt(2));
% the point at the corner of sector
for j=0.0001:0.005:w,
% distance of All effective Base Stations (BSs) to Terminal station at (w):
d=sqrt((sin(pi/4)*j)^2+((2*size)+(sin(pi/4)*j))^2); %%*** SITE DIVERSITY***
d1=((size*4)*sqrt(2))+j;
% from I1 (BS1)
d2=sqrt((sin (pi/4)*j)^2+((sin (pi/4)*j)+(size*4))^2);
% from I2 (BS2)
d3=sqrt((sin (pi/4)*j)^2+((sin (pi/4)*j)+(size*4))^2);
% from I3 (BS3)
%==========================================================================
% do=35*exp(-(0.015*100));
% in case R=125 or 145 mm/h
do=35*exp(-(0.015*96));
% in case R=96 mm/h
rC=1/(1+(d/do));
%reduction factor of Carrier signal C in km
rI1=1/(1+(d1/do));
%reduction factor of Interference signal I1 in km
rI2=1/(1+(d2/do));
%reduction factor of Interference signal I1 in km
rI3=1/(1+(d3/do));
%reduction factor of Interference signal I1 in km
Ah=kh*R^alfa_h;
% specific rain attenuation dB/km (Horizontal
Polarization)
%==========================================================================
%==========================================================================
% rain attenuation in dB.
RAtt_h_C=Ah*d*rC ;
% rain attenuation of Carrier(C)Horizontal pol.
RAtt_h_I1=Ah*d1*rI1; % rain attenuation of Interference (I1) Horizontal
pol.
RAtt_h_I2=Ah*d2*rI2; % rain attenuation of Interference (I2) Horizontal
pol.
RAtt_h_I3=Ah*d3*rI3; % rain attenuation of Interference (I3) Horizontal
pol.
%==========================================================================
105 %==========================================================================
% path loss in dB
pathlossC=92.45+20*log10(d*f);
pathlossI1=92.45+20*log10(d1*f);
pathlossI2=92.45+20*log10(d2*f);
pathlossI3=92.45+20*log10(d3*f);
%==========================================================================
Pt=2;
% power transmitted
Gt=18;
% gain of transmitter
Gr=38;
% gain of receiver
Lfm=1;
% fade margin loss
%==========================================================================
%==========================================================================
% atmosphere attenuation (ITU_R)
LatmC=d*0.1;
%of C
LatmI1=d1*0.1;
%of I1
LatmI2=d2*0.1;
%of I2
LatmI3=d3*0.1;
%of I3
%==========================================================================
%==========================================================================
% Total loss and power received of Desired Signal(C) at terminal station in
% Rain
TL_h_C=pathlossC+Lfm+LatmC+RAtt_h_C;
Pr_h=Pt+Gt+Gr-TL_h_C;
%==========================================================================
%==========================================================================
% Total loss and interference power (I1, I2 and I3) at terminal station in
% Rain
TL_h_I1=pathlossI1+Lfm+LatmI1+RAtt_h_I1;
I1_h=Pt+Gt+Gr-TL_h_I1;
TL_h_I2=pathlossI2+Lfm+LatmI2+RAtt_h_I2;
I2_h=Pt+Gt+Gr-TL_h_I2;
TL_h_I3=pathlossI3+Lfm+LatmI3+RAtt_h_I3;
I3_h=Pt+Gt+Gr-TL_h_I3;
%==========================================================================
%==========================================================================
% Power received at terminal station of All Signals without rain
Pr=Pt+Gt+Gr-(pathlossC+Lfm+LatmC);
% Carrier (C) in dBW
I1=Pt+Gt+Gr-(pathlossI1+Lfm+LatmI1);
% Interference (I1) in dBW
I2=Pt+Gt+Gr-(pathlossI2+Lfm+LatmI2);
% Interference (I2) in dBW
I3=Pt+Gt+Gr-(pathlossI3+Lfm+LatmI3);
% Interference (I3) in dBW
%==========================================================================
%==========================================================================
% Average C/I Calculation at terminal station
% if Carrier in rain:
% I1 with rain while I2&I3 without rain (HORIZONTAL POLARIZATION)
Ratio11_h_dB=Pr_h-I1_h;
Ratio21_h_dB=Pr_h-I2;
Ratio31_h_dB=Pr_h-I3;
case1h=(Ratio11_h_dB+Ratio21_h_dB+Ratio31_h_dB)/3;
%==========================================================================
%==========================================================================
%%%for drawing
grid;
hold on
plot(j,case1h,'r')
hold off
end
end