Laporan Projek Tahun Akhir berikut:
Tajuk: Microcellular System Design Parameters For UNIMAS New Campus Nama penulis: Dahlia Binti Hamdan
Matrik: 5298
telah dibaca dan disahkan oleh:
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Wan Azlan bin Wan Zainal Abidin Tarikh
Penyelia
P. KHIDMATMAKLUMATAKADEMIK U NIMAS
I miiniiiiwiiuinui
1000125598MICROCELLULAR SYSTEM DESIGN PARAMETERS FOR UNIMAS NEW
CAMPUS
DAHLIA BINTI HAMDAN
This project is submitted in partial fulfilment of
the requirements for the degree of Bachelor of Engineering with Honours (Electronics & Telecommunication Engineering)
Faculty of Engineering
UNIVERSITI MALAYSIA SARAWAK
2004
Dedicated with love to my supporting parents, sisters and my best friends.
Thanks for everything.
ACKNOWLEDGEMENT
I would like to express my gratitude to En. Wan Azlan bin Wan Zainal Abidin for his supervision and for all support and continuous encouragement he gave me in the whole of my campus life.
I also like to thank En. Mustapha bin Hj. Mustajir of Mendelsshon Engineering Sdn. Bhd and En. Zamhari bin Salleh of Maxis Sdn. Bhd for their helpful suggestions, information and support for my project.
Words of appreciation goes to the staff of Electronics & Communication/Computer
Engineering Department, lecturers and technicians who had helped me a lot during the years and especially in completing my project.
I also would like to thank my colleagues and friends especially my best friend Hasyimah for the good and bad times, for the friendship and for the support.
Finally, my love and gratitude dedicate to my family for the moral support and encouragement, especially to my beloved parents.
When I want to understand what is happening today, or to try and decide what will happen
tomorrow, I look back" - Oliver Wendell Holmes, Jr.
ABSTRAK
Pembukaan kampus baru UNIMAS yang dijangkakan pada pertengahan tahun 2004 pastinya akan meningkatkan lagi kadar bilangan populasinya dan ini termasuklah peningkatan pada kadar bilangan pengguna telefon mudahalih. Sehingga kini penggunaan telefon mudahalih yang semakin meningkat telah mempengaruhi permintaan terhadap sistem selular yang lebih baik dan efisien. Oleh hal yang demikian, projek ini akan mengkaji perlaksanaan sistem selular mikro terhadap kampus baru UNIMAS dengan menganggap tiada sistem seumpamanya telah wujud di kampus tersebut. Projek ini cuba mengenalpasti parameter bagi rekaan sistem berkenaan dan juga faktor-faktor yang terlibat di dalam rekaan sistem tersebut berdasarkan pemerhatian dan maklumat yang diperolehi daripada lawatan ke kampus baru UNIMAS.
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ABSTRACT
The opening of UNIMAS new campus in mid 2004 will tremendously increase the number of its population as well as the number of mobile phone subscribers. To date the vast use of mobile phone has affected the market demand for a better and efficient cellular system.
Therefore, this project will investigate the implementation of microcellular system design on UNIMAS new campus with assumption that there has not been any similar system applied to the campus. This project will try to determine the design parameters of the system and
factors that involve in the design of the system base on the observation and information gathered during a few time visits to the UNIMAS new campus.
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CONTENTS
APPROVAL LETTER APPROVAL SHEET
PROJECT TITLE DEDICATION
ACKNOWLEDGEMENT ABSTRAK
ABSTRACT CONTENTS
LIST OF TABLES LIST OF FIGURES
Chapter 1 INTRODUCTION
1.1 Thesis Background 1.2 Thesis Outline
1.3 Thesis Objectives 1.4 Methodology
Chapter 2 OVERVIEW OF CELLULAR ENVIRONMENT 2.1 Introduction to Cellular Concept
2.2 Concept of Frequency Reuse
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111
vii viii
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1 2 3
4 6
111
2.3 Handoff Mechanism 2.4 Cell Splitting
2.5 Radio Propagation Concepts 2.5.1 Interference
2.5.2 Propagation
2.5.3 Multipath and delay spread 2.6 Microcellular System
2.6.1 Outdoor system 2.6.1.1 Street microcell
2.6.1.2 Highway microcell 2.6.2 In-building system
Chapter 3 SYSTEM DESIGN
3.1 RF System Design
3.2 System Design Process
3.2.1 System design parameters 3.3 Technology Decision
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3.4 The Link Budget
3.4.1 Link budget items 3.5 Cell Sites
3.6 Coverage Requirement 3.6.1 Number of cells
3.7 Capacity Cell Sites Required
7 7 8 8
10
12
13 14 14 14 15
17 18 19 21 22 23 24 25 26 26
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3.7.1 RF traffic offloading 27
3.7.2 Radio growth 28
3.8 RF Design Guidelines 28
Chapter 4 DESIGN OF MICROCELLULAR SYSTEM:
RESULTS & DISCUSSIONS
4.1 Planning and Engineering a Cellular System 29 4.2 Microcellular System Design For UNIMAS New Campus 30
4.2.1 Site information
4.2.2 Determination of cell site
4.2.3 Estimated number of cell site 4.2.4 Channel group assignment
4.2.5 Cell site area
4.2.6 Traffic estimation 4.2.7 Link budget
4.3 Factors Affecting Design Quality of UNIMAS New Campus
4.3.1 Predicted coverage problems 4.3.2 Predicted capacity problems
4.4 Summarization of The Design Process
30 33 35 35 38 42 44
53 54 56 57
V
Chapter 5 CONCLUSION & RECOMMENDATION
5.1 Discussions and Conclusions 59
5.2 Recommendations
APPENDICES
61
63
REFERENCES 78
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LIST OF TABLES
Table Page
3.1 System design parameters 20
3.2 Link Budget 23
4.1 Forecast number of population in UNIMAS new campus 31
4.2 Information on UNIMAS new campus 33
4.3 Cell site information 40
4.4 Targeted traffic capacity, no. of call, no. of channel and
no. of blocked call for each cell 44
5.1 Proposed microcellular system design parameters for
UNIMAS new campus 61
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LIST OF FIGURES
Figure Page
2.1 A Seven-Cell Cluster 5
2.2 Cell splitting 8
2.3 Highway microcells clusters 15
3.1 Link budget components 22
3.2 Up and down link 23
4.1 UNIMAS site plan (built up area) 34
4.2 Estimated cell site locations and associated channel group 37 4.3 New condition of cells, transmitter antenna locations and the
coverage pattern 41
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CHAPTER I
INTRODUCTION
1.1 Thesis Background
This project describes the parameters involves in designing a microcellular
communication system on UNIMAS new campus. The concern of implementing the microcellular communication system is to provide a better coverage for the pedestrians and vehicles as well as for indoor communication. Upon implementing the design in such area with multi-buildings, there might be some shadow or black spot areas between the buildings due to the effect of obstructions that have to be considered. Henceforth, this project tries to customize any aspect of the environment and communication parameters and also the problems faced for indoor and outdoor microcellular system, in order to suit the system to the environment of UNIMAS new campus.
1.2 Thesis Outline
This chapter provides a brief overview to several issues relating to the design of cellular system and the implementation of it in UNIMAS new campus through every chapter in this report. Chapter 2 presents an overview of the elements in cellular system generally and the microcellular system intentionally as the foundation of the design. Chapter 3
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discusses the required design process and the important parameters involve in the design.
Chapter 4 discusses the implementation of the design parameters to the environment of UNIMAS new campus and also the results obtained by taking a few conditions in the campus design as the study cases. The selection of the areas concerned was made based on the assumption that the area might need a microcellular system design implementation due to a few criteria. This chapter also discusses the problems that might occur in the design process which must be comprehend in order to come out with a good design proposal.
Finally, Chapter 5 summarizes and concludes this thesis and the postmortem made herein.
Recommendations for future direction of the implementation of a better system design are outlined.
1.3 Thesis Objectives
To date the implementation of microcellular system in area around Kuching and Kota Samarahan are only in single commercial buildings such as in shopping complexes and government offices where the macrocellular coverage is unreachable. Thus, this project is concerned on the implementation of the microcellular system in a wide area so-called the suburban area with the range of buildings is mainly from 1 to 5 stories as found in UNIMAS new campus. In conjunction with this, the main objectives of this thesis are as follows:
To study the basic process of cellular system design To define the important design parameters
To obtain the basic design parameters of microcellular system design for UNIMAS new campus
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To determine the problems arise
To propose the microcellular system design parameters for UNIMAS new campus
1.4 Methodology
In order to complete this project, the information and data gathering are done through readings of journals, books and articles, site visiting and interviewing people related to the field. Besides the writer has had the opportunity to observe the installation of microcellular system antenna in Wisma Seberkas by DiGi and site troubleshooting for MAXIS mini mast base station on top of Alisan Hotel in Sri Aman. These had given some useful information and real approach on the elements that involve in cellular system as well as microcellular system generally.
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CHAPTER 2
OVERVIEW OF CELLULAR ENVIRONMENT
2.1 Introduction to Cellular Concept
Before planning a system, the engineer should first acquire an understanding of basic cellular system, including the regular hexagonal cell structure, reuse frequency, handoff, cell splitting, radio propagation concepts and some other principles.
The basic cellular concept handles the coverage problems by implementing the use of a large number of low-power transmitters designed to serve only a small area. The small coverage areas are called "cells". A cell is the basic geographic unit of a cellular system.
The term cellular comes from the honeycomb shape of the areas into which a coverage region is divided. Cells are base stations transmitting over small geographic areas that are represented as hexagons. Each cell size varies depending on the landscape. Because of constraints imposed by natural terrain and man-made structures, the true shape of cells is not a perfect hexagon. A cluster is a group of cells. No channels are reused within a cluster.
Figure 2.1 illustrates a seven-cell cluster. [14]
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Figure 2.1: A Seven-Cell Cluster
By reducing the total coverage area into small cells, it becomes possible to reuse the same frequencies in different cells. The problem with small cells was that not all mobile calls would be completed within a single cell. To deal with this problem, the idea of handoff was used. It is very expensive to build a system with quite a large number of cells. However, large-radius cells can evolve gracefully into small-radius cells over a period of time using cell splitting. When the traffic reaches a point in a particular cell such that existing allocation of channels in that cell can no longer support a good grade of service, that cell is subdivided into smaller cells with lower transmitter power to fit within the area of the former cell.
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2.2 Concept of Frequency Reuse
The amount of frequency spectrum available for mobile cellular use is limited;
therefore efficient use of the required frequencies is needed for mobile cellular coverage.
Base on this the idea of reusing the available frequencies had been implemented. Frequency reuse refers to the use of the same frequency carrier in different areas that are distant enough so that the interference caused by the use of the same carrier is not a problem.
The distribution of the frequency channels in a cellular network is dependent on several parameters, such as cellular geometry, signal propagation characteristics and signal interference. The assignment of frequency channels in the cellular concept is fixed, i. e. a set of frequency channels is statistically allocated to a cell. This same set is reused in another cell far enough to allow the use of the frequency channels with acceptable signal interference. [7] The exact coverage of the cell as well as frequency reuse depends on:
" The power of the transmitted signal
" The frequencies used
" The type of antenna
" The terrain over which the signal is sent
" Weather
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2.3 Handoff Mechanism
One of the goals of a cellular system is for a user to remain "in touch" even as they move through the system. When a user moves from the coverage area defining one cell into that of another, the system must provide the capability for that user to remain "in touch"
even while breaking the connection with one base station and establishing another connection with another base station. This operation is called ahandoff. Handoff is a process where the cellular system automatically switches channels to maintain voice transmission when a mobile telephone moves from one cell radio coverage area to another. Different
cellular technologies implement different way of handoff. [8]
2.4 Cell Splitting
Splitting usually occurs in groups and includes all cells in the reuse pattern as shown in Figure 2.2. As the traffic within a particular cell increases, the cell is split into smaller cells.
Decreasing the cell size with associated decrease in transmitted power of the base stations and the mobile stations and/or using reduced antenna height to cover a reduced area will increase the serving capacity of cellular system. The reduction in a cell size radius allows the available bands to be reused in noncontiguous cell groups. This approach allows the cellular carrier provider to decrease and increase the cell sizes to accommodate the growth or shrinking populations of its mobile subscriber base.
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Small cells, high density
Figure 2.2: Cell splitting
2.5 Radio Propagation Concepts
The major issues in radio propagation concepts include the following:
a) Interference b) Propagation
c) Multipath and delay spread
2.5.1 Interference
The carrier-to-interference or C/I ratio is one of the physical measures of RF channel quality. This ratio is logarithmically proportional to the signal quality enjoyed by the receiver of the signal. The larger the C/I ratio, the better the channel quality. C/I ratios of 17 dB are ideally used to determine the edge of coverage for a cell. If the measured C/I falls
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below this level, the mobile should be in the coverage region of another cell and a cell handoff should be performed. The interior of the cell should provide C/I ratios that exceed
17 dB, unless the mobile is located in an RF coverage "hole".
There are two kinds of RF interference possible: co-channel and adjacent channel.
Either of these forms of interference can occur if the cellular frequency reuse scheme is inadequate (i. e., the n in n-cell reuse is too small for the geography available and power level in use).
Co-channel interference results when two transmitters within range of a common receiver use the same channel (frequency) simultaneously. The receiver will receive a combination of the two signals and will be unable to make any sense of the combined signal.
In this case, the two channels can be said to have interfered with one another.
Adjacent channel interference occurs when two transmitters within range of a common receiver use adjacent channels (i. e., neighboring frequencies) simultaneously.
Because the physical characteristics of the RF channel causes some spill-over of the signal into neighboring frequencies, adjacent channel transmissions could interfere with one another.
Since the interference is caused by the simultaneous transmission on co-channels or adjacent channels within a cell, only one can transmit at a time. The earliest mobile phone systems used the same channel for the network and the mobile devices. This half-duplex mode of operation greatly hindered the efficiency of these early mobile RF systems. Current cellular systems are full-duplex. This is accomplished by using different physical channels in the forward channel direction (i. e., network to mobile) and the reverse channel direction
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(i. e., mobile to network). The channels used in each direction are sufficiently separated in the frequency domain so as to prevent interference.
Full-duplex operation means that the mobile and the base station must each have two RF transceivers (i. e., one transmitter, one receiver) simultaneously engaged. Even if no other transmitters are causing interference, a received RF signal can be garbled due to a phenomenon known as multipath or Rayleigh fading. This form of self-interference occurs when multiple out-of-phase copies of the same signal destructively interfere with one another due to reflections of the signal off of natural or man-made surfaces. In a fading situation, the reflected signal is delayed sufficiently that it is out-of-phase enough to interfere with the direct line-of-sight path. Multipath fading can occur when the mobile is stationary or in motion. [13]
2.5.2 Propagation
The radio channel places fundamental limitations on the performance of the mobile communication systems. The transmission path between the transmitter and the receiver can vary from simple direct line of sight to one that is severely obstructed by buildings and foliage. The speed of motion impacts how rapidly the signal level fades as a mobile terminal moves in space. Unlike wired channels that are stationary and predictable, radio channels are extremely random and do not offer easy analysis. The mechanism behind electromagnetic
wave propagation are diverse but can generally be attributed to reflection, diffraction, and scattering. Most cellular radio systems operate in urban areas where there is no direct line-of sight path between the transmitter and the receiver, and the presence of high-rise buildings
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causes severe diffraction loss. Because of the multiple reflection from various objects, the electromagnetic waves travel along different paths of varying lengths. The three basic propagation mechanisms are reflection, diffraction and scattering.
Reflection occurs when a propagating electromagnetic wave impinges upon an obstruction whose dimensions are very large when compared to the wavelength of the radio wave. Reflections from the surface of the earth and from buildings or walls produce reflected waves, which may interfere constructively or destructively at the receiver.
Diffraction occurs when the radio path between the transmitter and receiver is obstructed by a surface that has sharp irregularities (edges). The secondary waves resulting from the obstructing surface are present throughout the space and even behind the irregularity, giving rise to bending of waves about the irregularity, even when a line of sight does not exist. At high frequencies, diffraction like reflection depends on the geometry of the object, and the amplitude, phase, and polarization of the incident wave at the point of diffraction.
Scattering occurs when the medium through which the wave travels consists of objects with dimensions that are small compared to the wavelength and the number of obstacles per
unit volume is quite large. The measured path loss in a mobile radio environment is often less than what is predicted by reflection and diffraction models alone. This is because when a radio wave impinges on a rough surface, the reflected energy is spread out (diffused) in all directions due to scattering. Objects such as trees, lamp posts, and rough surfaces tend to scatter energy towards a receiver. [2]
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2.5.3 Multipath and delay spread
The communication quality between a mobile subscriber unit and the cell site depends on a variety of factors affecting the path over which the radio signal travels. Several types of signal impairments take place over the radio signal path. The four basic impairments experienced in a communication path involve path loss, shadowing, multipath and Doppler shift.
Path loss is a direct result of the distance between the transmitter and receiver in the communication path. Shadowing also called slow fading is caused by largely partial blockage or environmental absorption such as trees.
Multipath propagation is the predominant form of transmission path in an urban environment since more than one reflection in the transmission path is normal. The issues of multipath problems to a communication system show up a delay spread and Rayleigh fading.
In an analog communication system multipath, the same information taking multiple paths causes fading. The fading itself can sound like a flutter at low speeds. The multipath is a result of Rayleigh or fast fading when the receiving antenna moves through constructive and destructive wavefronts. The receiver's susceptibility to fading is a function of the frequency of operation and the receiver bandwidth. The higher the frequency the shorter the distance is between wave crests. The wider the bandwidth the less susceptible the receiver is to fading.
Delay spread, time dispersion, is to the digital radio system what multipath is to analog.
However, with a digital system the delay in the signal's arrival is more important than that of the signal's received level. Dispersion occurs when multiple signals arrive at different
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