MECOVERAGE PERFORMANCE OF 3G RADIO NETWORK.pdf

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COVERAGE PERFORMANCE OF 3G RADIO NETWORK

KING YEONG CHING

A project report submitted in partial fulfilment of the

requirements for the award of the degree of

Master of Electrical Engineering (Electronics and Telecommunications)

Faculty of Electrical Engineering

Universiti Teknologi Malaysia

MAY 2006


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ii


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To my beloved family


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ACKNOWLEDGEMENTS

Firstly, I would like to take this opportunity to express my sincere gratitude to

my supervisor, Professor Dr. Tharek Abdul Rahman, for his valuable guidance and

advice throughout the development of this project.

I also wish to thank to my friends and all the personal, whose have directly or

indirectly played a part in the completion of this project.

Last but not least, I would like to thank my beloved family who gave me the

moral support and encouragement.


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ABSTRACT

There has been an incredible growth in wireless communication technology

over the past decade. The significant increment is in subscribers, traffic and data

rate. The solution is the Wideband CDMA (WCDMA). All WCDMA systems have

a relation between coverage and capacity. WCDMA radio link budget is mainly

designed to estimate the allowable path loss in a 3G system. This result is then used

to estimate the cell range covered by a base station. In this project, a GUI is created

by using Visual C++ to enable the users to calculate the cell range or Eb/N0 ratio

easily. This project also mentioned about the relation between the coverage and

Eb/N0 ratio and how they could lead to a better cell range performance.


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ABSTRAK

Teknologi wayarles komunikasi telah mengalami perkembangan yang tidak

diduka sejak beberapa dekad yang lalu. Peningkatan yang paling ketara termasuk

jumlah langganan, trafik dan kadar data. Penyelesaiannya ialah jalur lebar CDMA

(WCDMA). Semua sistem WCDMA mempunyai hubungan di antara liputan and

muatan. WCDMA pautan radio bujet telah direka khas untuk mengira allowable

path loss dalam sistem 3G. Hasil kiraan ini kemudiannya akan digunakan untuk

mengira julat sel yang dirangkumi oleh satu base station. Dalam projek ini, satu

GUI akan direka dengan menggunakan Visual C++ untuk membolehkan pengguna

mengira sama ada julat sel atau nisbah Eb/N0 dengan mudah. Projek ini juga

menjelaskan hubungan di antara liputan dan nisbah Eb/N0 dan bagaimana

kedua-duanya boleh memberikan julat sel yang lebih bagus.


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TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENTS iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES x

LIST OF FIGURES xi

LIST OF SYMBOLS xiii

LIST OF ABBREVIATIONS xv

1 INTRODUCTION 1

1.1 Introduction 1

1.2 Project Objective 2

1.3 Project Scope 2

1.4 Project Background 3

2 WCDMA 4

2.1 Evolution from 2G System to 3G System 4

2.2 Requirements for 3G Technologies 8

2.3 Air Interfaces and Spectrum Allocations for 3G

System 9

2.4 WCDMA 12

2.4.1 WCDMA Characteristics 13


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2.4.2 Elements in a WCDMA Radio Network 16

2.4.2.1 User Equipment (UE) 17

2.4.2.2 Base Station (BS) 18

2.4.2.3 Radio Network Controller (RNC) 19

2.4.3 WCDMA Radio Network Planning 19

2.4.4 Objectives of Radio Network Planning 20

2.4.5 WCDMA Radio Network Planning Process 21

2.4.6 WCDMA Optimisation 25

2.4.6.1 Key Performance Indicator 27

2.4.6.2 Network Performance Monitoring 28

2.4.6.3 Coverage, Capacity and Quality

Enhancements 29

2.4.6.4 Parameter Tuning 30

2.5 Summary 33

3 PREDICTION ON WCDMA COVERAGE 34

3.1 Project Methodology 34

3.2 WCDMA Radio Network Dimensioning 35

3.3 WCDMA Radio Link Budget 36

3.4 Parameters in WCDMA Radio Link Budget 38

3.4.1 Common Parameters with 2G System 39

3.4.2 3G Specific Parameters 42

3.5 WCDMA Radio Link Budget Model 46

3.6 GUI of WCDMA Radio Link Budget 50

3.6.1 GUI of WCDMA Cell Range Calculation 51

3.6.1.1 GUI of Cell Range Calculation for

Voice Service 54


Circuit-Switched Service 55


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Packet-Switched Service 56

3.6.2 GUI of WCDMA Eb/N0 Calculation 58

3.6.2.1 GUI of Calculation of Eb/N0 for

Voice Service 60


Circuit-Switched Service 61


Packet-Switched Service 62

3.7 Summary 63

4 RESULT AND DISCUSSION 64

4.1 Coverage Area and Cell Range 64

4.2 Eb/N0 Requirement 65

4.3 Relationship between Cell Range and Eb/N0 Ratio 68

4.4 QoS Classes 71

4.5 Summary 73

5 CONCLUSION AND FUTURE WORK 75

5.1 Conclusion 75

5.2 Future Work 76

REFERENCES 77

Appendix A 78-105


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LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 Summary of Global Mobile Terrestrial 3G spectrum

requirements in 2010 10

2.2 The main parameters of 3G systems 14

2.3 Main differences between WCDMA and GSM air interfaces 16

3.1 Allowable path loss model 49

3.2 Assumptions for the mobile station 52

3.3 Assumptions for the base station 52

3.4 Calculation of cell range in the WCDMA radio link budget 53

3.5 Calculation of Eb/N0 in the WCDMA radio link budget 59

4.1 Different values ofK 64

4.2 Services in WCDMA system 66

4.3 Eb/N0 requirements for static mobile with BLER 0.01% 67

4.4 Eb/N0 requirements for 3 km/h pedestrian with BLER

0.01% 67

4.5 Eb/N0 requirements for 3 km/h in rural environment

with BLER 0.01% 67

4.6 Eb/N0 requirements for 3 km/h in macro cellular withBLER 0.01% 67

4.7 Eb/N0 and cell range for voice service 68

4.8 Eb/N0 and cell range for circuit-switched service 68

4.9 Eb/N0 and cell range for packet-switched service 69

4.10 3G QoS classes 73


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LIST OF FIGURES

FIGURE NO. TITLE PAGE

2.1 Upgrade GSM system to WCDMA services 6

2.2 GSM/WCDMA architecture 8

2.3 WARC-1992 IMT-2000 frequency allocation 12

2.4 Evolution to 3G 13

2.5 WCDMA radio access network 17

2.6 General radio network planning process 22

2.7 WCDMA radio network planning process 23

2.8 WCDMA optimization 26

3.1 GUI of WCDMA radio link budget 50

3.2 GUI of calculation of cell range 51

3.3 GUI of calculation of Eb/N0 51

3.4 GUI of calculation of cell range for voice service 54

3.5 GUI of result of cell range for voice service 55

3.6 GUI of calculation of cell range for circuit-switched service 56

3.7 GUI of result of cell range for circuit-switched service 56

3.8 GUI of calculation of cell range for packet-switched service 57

3.9 GUI of result of cell range for packet-switched service 58

3.10 GUI of calculation of Eb/N0 for voice service 60

3.11 GUI of result of Eb/N0 for voice service 60

3.12 GUI of calculation of Eb/N0 for circuit-switched service 61

3.13 GUI of result of Eb/N0 for circuit-switched service 61

3.14 GUI of calculation of Eb/N0 for packet-switched service 62

3.15 GUI of result of Eb/N0 for packet-switched service 62

4.1 Relationship between Eb/N0 and cell range for voice


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service 69

4.2 Relationship between Eb/N0 and cell range for circuit-

switched service 70

4.3 Relationship between Eb/N0 and cell range for packet-

switched service 70


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LIST OF SYMBOLS

A - Slope of the propagation model

BW - Bandwidth

B - Intercept of the propagation model

C/I - Carrier to Interference ratio

dc - Cell range (distance between base station and mobile station)

d - Propagation distance between the transmitter and receiver

E0/I0 - Received signal power spectral density ratio

Eb/N0 - Energy per bit to the thermal noise ratio

EC/I0 - Pilot channel chip energy to received signal power spectral density

ratio

EIRP - Equivalent Isotropic Radiated Power

f - Frequency of signal of interest

F - Noise figure

Gr - Gains for the receive antenna

Gt - Gains for the transmit antenna

hb - Height of the antenna of the base station

hm - Height of the antenna of the mobile station

Hz - Hertz

I - Total received interference in the base station

k - Boltzmanns constant

l - Attenuation due to propagation through the environment

L - Interference margin

Lsys - Total system loss

N0 - Thermal noise density

PG - Processing gain

Pj - Received signal power from user j


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PL - Allowable path loss

PN - Noise power

Pr - Received power at the receiver

Pt - Transmitted power

r - Maximum cell range

Rb - Bit rate

Rc - Chip rate

Rj - Bit rate of user j

S - Coverage area

T - Temperature in Kelvin

vj - Activity factor of user j

W - Chip rate

j - Orthogonality factor

DL - Downlink loading factor

UL - Uplink loading factor


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LIST OF ABBREVIATIONS

2G - Second Generation

3G - Third Generation

AC - Admission Control

AMR - Adaptive Mean Rate

BLER - Bit Error Rate

BS - Base Station

BSC - Base Station Controller

BSS - Base Station Subsystem

BTS - Base Transmit Station

CCPCH - Common Control Packet Channel

CN - Core Network

CPICH - Common Pilot Channel

CSR - Call Success Rate

DCR - Dropped Call Rate

DECT - Digital Enhanced Cordless Telecommunications

DRNC - Drifting Radio Network Controller

EIRP - Equivalent Isotropic Radiation Power

ETSI - European Telecommunication Standard Institute

EURO-COST - European Co-operative for Scientific and Technical Research

FACH - Fast Associated Channel

FCC - Federal Communications Commission

FDD - Frequency Division Duplex

FTP - File Transfer Protocol

GSM - Global System for Mobile Communications

GUI - Graphical User Interface

IMT-2000 - International Mobile Telecommunications 2000


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ITU - International Telecommunications Union

KPI - Key Performance Indicator

LOS - Line of Sight

ME - Mobile Equipment

MHA - Mast Head Amplifier

MMS - Multimedia Messaging Services

MSC - Mobile Switching Center

MUD - Multiuser Detection

NMS - Network Management System

PCH - Paging Channel

PCS - Personal Communications Services

PICH - Paging Indication Channel

QoS - Quality of Service

RACH - Random Access Channel

RAN - Radio Access Network

RBS - Radio Base Station

RF - Radio Frequency

RLB - Radio Link Budget

RNC - Radio Network Controller

Rx - Receiver

SIR - Signal-to-Interference ratio

SMS - Short Messaging Services

SNR - Signal-to-Noise ratio

SPA - Self Provided Applications

SRNC - Serving Radio Network Controller

TDD - Time Division Duplex

TDMA - Time Division Multiple Access

TE - Terminal Equipment

Tx - Transmitter

UE - User Equipment


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UMTS - Universal Terrestrial Mobile System

USIM - User Subscriber Identity Module

WARC - World Administrative Radio Conference

WCDMA - Wideband Code Division Multiple Access

WLL - Wireless Local Loop


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LIST OF APPENDICES

APPENDIX TITLE PAGE

A Visual C++ source codes 76


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CHAPTER 1

INTRODUCTION

1.1 Introduction

This report is mainly about the work done on the coverage performance of the

3G radio network. This report can be divided into five main chapters. Chapter 1

is the introduction about the project report structure, objective, scope and

background.

Chapter 2 is the literature review on the WCDMA systems such as the history,

the WCDMA characteristic, elements in the system, 3G system general planning and

optimization.

The work that had been done in this project is described in Chapter 3.

Chapter 3 described the parameters involved in the prediction on the cell range of

WCDMA system and the way how to calculate the maximum cell range by

generating the GUI using the Visual C++ programming language.

The result and discussion is presented in Chapter 4. The discussion is about

the relation between Eb/N0 and the cell range. Chapter 5 is the conclusion and the

recommended future work.


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1.2 Project Objective

The first objective of this project is to understand the concept of the 3G radio

network planning and optimization, especially the architecture of the 3G radio

network, and also the flow of the planning and optimization process. It is important

to understand the considerations that must be taken into account during the planning

and optimization process.

The second objective of this project is to generate a proper link budget for the

3G radio network. The link budget can be used to either calculate the cell range

covered by a base station when the Eb/N0 ratio is known or vice versa. The

calculations of the cell range or Eb/N0 ratio are focused on a specific environment for

three different types of service, the voice service, the circuit-switched data and the

packet-switched data. Each service has different data rate.

The third objective is to study how to optimise the coverage of the 3G radio

network based on the cell range. Therefore, it is a need to study the parameters that

affect the cell range because cell range is directly related to the network coverage.

Since the Eb/N0 ratio is the parameter that will affect most the cell range, the focus

will be given to study the relationship between this parameter and cell range.

1.3 Project Scope

The scopes of this project including the literature review, creating a GUI and

thesis preparation. The literature review helped to have a better understanding

about the 3G radio network planning and optimization. The WCDMA radio link

budget is created using the Visual C++ in order to simulate the input parameters and


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output the desired result/s. The result/s could be the cell range or the Eb/N0 ratio

based on the user selection. After that, the result/s is analyzed to determine the

relationship between the cell range and the Eb/N0 ration. Thesis preparation is

divided into two parts. The first part is the report writing for Project 1 while the

second part, is the total thesis write-up for the whole project.

1.4 Project Background

As the world moved towards an internet booming age in the twenty first

century, the requirement for data communication in mobile equipment become more

important. With broadband system becoming main stream products in the world

today, there is a need for more capacity to accommodate the increasing number of

subscriber for the mobile system.

The concept of 3G is based on the global International Mobile

Telecommunications (IMT-2000) initiative sponsored by the International

Telecommunications Union (ITU) to create a unified global set of standards that will

lead to commercial deployment of advanced wireless services. WCDMA was

developed in order to create a global standard for real-time multimedia services,

where it can support higher data rates, at anytime, anywhere.

Wideband-CDMA (WCDMA) is the air-interface technology widely used in

the 3G radio network. WCDMA interface different users can simultaneously

transmit at different data rates and data rates can even vary in time. Therefore, it is

a need to study the techniques used in WCDMA in the radio network planning

process and how to optimise the WCDMA performance especially for a better

coverage.


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CHAPTER 2

WCDMA

2.1 Evolution from 2G System to 3G System

Although the GSM mobile development process has evolved over the past

decade, it is important to compare the processes at the inception of each technology

to have an appreciation of the challenges facing WCDMA deployment today.

When the initial wave of GSM handsets appeared in the early 1990s, the product

realization and performance analysis requirements were much different than today's

WCDMA UE (User Equipment) product development cycle.

Initially, underlying GSM handset hardware and software was developed for

specific handset models rather than for generic platforms and, thus, the end-to-end

product development process was much simpler and more centralized. A far

smaller range of models was expected in the market.

Today's network operators demand a wide range of models to address

markets spanning from the adolescent to high-end corporate user. There is a strong

focus on accelerating time to market as devices have a much shorter shelf life since

handset styles and features change as quickly as fashion trends.


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The GSM air interface standard was created with voice as the primary

application. WCDMA, on the other hand, includes support for voice, high-speed

packet data, and multimedia applications. These applications are employed on a

wideband-CDMA-based air interface and a completely different radio network.

The UMTS specifications are orders of magnitude more complex than the GSM

standard with the support of new applications and a new WCDMA radio network

engineered for 3G.

The underlying WCDMA air interface is much more performance sensitive

and its operation shares many more similarities with its rival CDMA2000 than its

predecessor GSM. To achieve link-level performance gains over GSM's

equalization and frequency hopping techniques, WCDMA uses rake receiver

technology for diversity gain. The ability of the rake receiver to mitigate multi-path

interference and to perform soft-handovers must be evaluated over a variety of

real-world conditions.

Overall WCDMA system capacity, a critical metric for network operators,

has a soft limit dependent on interference levels and interference mitigation.

WCDMA employs a fast power control scheme 1500 Hz on both up and downlink

to deal with CDMA's inherent near-far interference issues. GSM, which features

a hard capacity due to its fixed frequency reuse scheme, employs a very slow (2 Hz)

power control scheme. Thus, finding the key performance breakpoints of the

WCDMA air interface implementation has a direct correlation to WCDMA system

capacity and network operator revenue.

With fewer features and a smaller number of infrastructure vendors, initial

GSM interoperability tests required a smaller scale of test scenarios prior to launch.

WCDMA's complex future-proof air interface standard allows many different


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ways to perform similar mobile functions, greatly increasing the change for

signalling interoperability mismatches between handset and infrastructure.

Early GSM handsets were built on a closed platform that did not allow the

range of complex, high-bandwidth services and applications expected to be deployed

on today's multimedia mobile devices. But over the years, a wide variety of mature

user services have been deployed on GSM networks. WCDMA must initially, at

least, equal and eventually exceed the services and performance available on GSM

networks to accelerate subscriber adoption.

While the respective initials launches of GSM and WCDMA share common

trials and tribulations, the WCDMA design verification and performance analysis

process must evolve to meet today's market requirements.

Figure 2.1 Upgrade GSM system to WCDMA services


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A GSM system can be upgraded to offer WCDMA services. Figure 2.1 shows

that two or more GSM channels are typically removed, replaced, or upgraded to have

WCDMA modulation and transmission capability.

Figure 2.2 shows the architecture of GSM/WCDMA. The GSM Base Station

Subsystem (BSS) and the WCDMA Radio Access Network (RAN) are both

connected to the GSM core network for providing a radio connection to the handset.

Hence, the technologies can share the same core network.

Furthermore, both GSM BSS and WCDMA RAN systems are based on the

principles of a cellular radio system. The GSM Base Station Controller (BSC)

corresponds to the WCDMA Radio Network Controller (RNC). The GSM Radio

Base Station (RBS) corresponds to the WCDMA RBS, and the A-interface of GSM

was the basis of the development of the Iu-interface of WCDMA, which mainly

differs in the inclusion of the new services offered by WCDMA.

The significant differences, apart from the lack of interface between the GSM

BSCs and an insufficiently specified GSM Abis-interface to provide multi-vendor

operability, are more of a systemic matter. The GSM system uses TDMA (Time

Division Multiple Access) technology with a lot of radio functionality based on

managing the timeslots. The WCDMA system on the other hand uses CDMA, as

described below, which means that both the hardware and the control functions are

different. Examples of WCDMA-specific functions are fast power control and soft

handover.


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Figure 2.2 GSM/WCDMA architecture

2.2 Requirements for 3G Technologies

In order to address the limitation of 2G system, development of a wireless

network that supports advanced services previously available only through

high-speed wired networks need to be done. The concept of 3G is based on the

global International Mobile Telecommunications (IMT-2000) initiative sponsored by

the International Telecommunications Union (ITU) to create a unified global set of

standards that will lead to commercial deployment of advanced wireless

services. The IMT-2000 goals and objectives for 3G are as follows:

Reduce telecommunications performance gap between wireless and existing

fixed networks:

Convergence across technologies and geographic boundaries


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Operate in both satellite and terrestrial environments

Coexistence with 2G systems

Bit rates up to 2 Mbps

Variable bit rate to offer bandwidth on demand

Multiplexing of services with different quality requirement on a single

connection, e.g. speech, video and packet data

Delay requirement from delay-sensitive real-time traffic to flexible

best-effort packet data

Quality requirements from 10% frame error to 10-6 bit error rate

Coexistence of second and third generation systems and inter-system

handovers for coverage enhancement and load balancing

Support of asymmetric uplink and downlink traffic, e.g. web browsing

causes more loading to downlink than to uplink

High spectrum efficiency

Coexistence of FDD and TDD modes

2.3 Air Interfaces and Spectrum Allocations for 3G Systems

Work to develop third generation mobile systems started when World

Administrative Radio Conference (WARC) of the ITU (International

Telecommunication Union), at its 1992 meeting, identified the frequencies around 2

GHz that were available for use by future third generation mobile systems, both

terrestrial and satellite. Within the ITU these third generation systems are called

International Mobile Telephony 2000 (IMT-2000). Table 2.1 summarizes existing

and forecasted spectrum requirements.


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Table 2.1 Summary of Global Mobile Terrestrial 3G spectrum requirements in

2010

RegionTotal 3G

spectrum

Existing mobile

terrestrial

allocation

Forecasted

additional

spectrum

(MHz) (MHz) (MHz)

Americas 390 230 160

Europe 555 395 160

Asia 480 320 160

The Federal Communications Commission (FCC), under Congress 1997

Budget Act, is required to auction 40 MHz of spectrum in the 2110 MHz to 2150

MHz band plus an additional 15 MHz from the 1990 MHz to 2110 MHz. The FCC

is contemplating reserving the spectrum for 3G. Third generation services there

must be implemented within the existing bands by replacing part of the spectrum

with third generation systems. This approached is referred to as reframing.

Europe and Japan basically followed these recommendations for FDD

systems. In the lower band, parts of the spectrum are currently used for Digital

Enhanced Cordless Telecommunications (DECT) and PHS, respectively. The FCC in

the United States has allocated a significant part of the WARC spectrum in the lower

band to 2G personal communications services (PCS) systems. Most of the North

American countries are following the FCC frequency allocation. In China, big parts

of the WARC spectrum are currently allocated to WLL application.

The spectrum allocation in Europe, Japan, Korea and USA is shown in Figure

2.3. In Europe and in most of Asia the IMT-2000 bands of 2 x 60 MHz (1920

1980 MHz plus 2110 2170 MHz) will be available for WCDMA FDD. The

availability of the TDD spectrum varies: in Europe it is expected that 25 MHz will be

available for licensed TDD use in the 1900 1920 MHz and 2020 - 2025 MHz bands.

The rest of the unpaired spectrum is expected to be used for unlicensed TDD


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applications (SPA: Self Provided Applications) in the 2110 2120 MHz band.

FDD systems use different frequency bands for uplink and downlink, separated by

the duplex distance, while TDD systems utilize the same frequency for both uplink

and downlink.

In Japan and Korea, the IMT-2000 FDD band is the same as in the rest of

Asia and in Europe. Japan has deployed PDC as a second generation system, while

in Korea IS-95 is used for both cellular and PCS operation. The PCS allocation in

Korea is different from the US PCS spectrum allocation, leaving the IMT-2000

spectrum fully available in Korea. In Japan, part of the IMT-2000 TDD spectrum is

used by PHS, the cordless telephone system.

In China, there is reservation for PCS or WLL (Wireless Local Loop) use on

one part of the IMT-2000 spectrum, though these have not been allocated to any

operators. Depending on the regulation decisions, up to 2 x 60 MHz of the

IMT-2000 spectrum will be available for WCDMA FDD use in China.

In the USA no new spectrum has yet been made available for third generation

systems. Third generation services can be implemented by reforming third

generation systems within the existing PCS spectrum. This will require replacing

part of the existing second generation frequencies with third generation systems.


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Figure 2.3 WARC-1992 IMT-2000 frequency allocation

2.4 WCDMA

The 3G systems aim to support a wide range of bearer services from voice

and low-rate to high-rate data services with up to at least 144 kbps in vehicular, 384

kbps in outdoor-to-indoor, and 2 Mbps in indoor and picocell environments.

Circuit-switched and packet-switched services for symmetric and asymmetric traffic

will be supported. The evolution of the mobile system to 3G system is shown in

Figure 2.4.

3G systems will be operated in all radio environments, including large

metropolitan urban and suburban areas, hilly and mountainous areas, and microcell,

picocell, and indoor environments. These requirements are quite well aligned in

North America, Asia, Europe, and the ITU. This enables a much wider application

range with 3G systems than with 2G systems. In addition, the ability for global

roaming will be supported in the system design. The 3G systems will be optimized

for vehicular, indoor, and fixed wireless environments.


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Wideband Code Division Multiple Access (WCDMA) technology is on the

brink of widespread rollout. This technology will initially complement and then

eventually replace current Global System for Mobile Communications (GSM)

systems as the mostly widely deployed air interface technology in the world.

WCDMA is based on radio access technique proposed by ETSI Alpha group and the

specifications were finalized in year 1999.

Figure 2.4 Evolution to 3G

2.4.1 WCDMA Characteristics

The objectives of WCDMA are:

Support of high-speed data (>384 kbps with wide area coverage and

up to 2 Mbps for indoor/local outdoor coverage)

High service flexibility with support of multiple parallel variable-rate

services on each connection


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Efficient packet access

High initial capacity and coverage with built-in support for future

capacity/coverage enhancing technologies, such as smart antennas

and advanced receiver structures (multiuser detection [MUD])

Support for inter-frequency handover for operation with hierarchical

cell structures

Easy implementation of dual-mode UMTS/GSM terminals as well as

handover between UMTS and GSM

The main parameters of 3G systems are shown in below Table 2.2.

Table 2.2 The main parameters of 3G systems

Parameters 3G Systems

Frequency band 1920~1980, 2110~2170 MHz

Multiple access WCDMA

Duplexing FDD

Bandwidth4.4~5 MHz with 200 kHz multiple

(4.7 MHz/carrier)

Bit rate

Variable (up to 2 Mbps/user,

384 kbps outdoor)

Chip pulse shaping Raised cosine (roll-off = 22%)

Modulation QPSK downlink, HPSK uplink

Power control 1500 commands/sec

Mobile station (MS) power 250 mW~2 W (max.)

Chip rate 3.84 Mcps

Spreading factor Variable: 4~512 chips/symbol

Spreading codes Orthogonal variable spreading factor

Scrambling codes Gold codes

Frame time 10 ms (divided into 15 timeslots)Channel coding CRC + Turbo + Conv. + ARQ

Voice coding AMR (Adaptive Multi Rate)

Interleaving depth 10 ms (voice); 20, 40, 80 ms (data)

Typical maximum voice capacity ~32 users/sector/MHz

Typical maximum cell range ~15 km (voice)

The differences in the air interface reflect the new requirement of the third

generation systems. The larger bandwidth of 5 MHz is needed to support higher bit


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rates. Transmit diversity is included in WCDMA to improve the downlink capacity

to support the asymmetric capacity requirements between downlink and uplink.

Transmit diversity is not supported by the second generation standards. The mixture

of different bit rates, services and quality requirements in third generation systems

requires advanced radio resource management algorithms to guarantee quality of

service and to maximize system throughput. Also, efficient support of

non-ideal-time packet data is important for the new services.

The higher chip rate of 3.84 Mcps in WCDMA gives more multipath diversity,

especially in small urban cells. Increased multipath diversity improves the

coverage. The higher chip rate also gives a higher trunking gain, especially for high

bit rates, than do narrowband second generation systems.

WCDMA has fast closed-loop power control in both uplink and downlink.

The downlink fast power control improves link performance and enhances downlink

capacity. It requires new functionalities in the mobile, such as SIR estimation and

outer loop power control.

Inter-frequency handovers are considered important in WCDMA, to

maximize the use of several carriers per base station. WCDMA is designed to

operate with asynchronous base stations, where this makes the handover in WCDMA

more efficient than in GSM.

The main differences between the second (GSM) and third generation

(WCDMA) air interface are shown in Table 2.3.


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Table 2.3 Main differences between WCDMA and GSM air interfaces

WCDMA GSM

Carrier

spacing/bandwidth5 Mhz 200 KHz

Frequency reuse factor 1 1 18Power control frequency 1500 Hz 2 Hz or lower

Quality control

Radio resource

management (RRM)

algorithms

Network planning

(frequency planning)

Frequency diversity

5 MHz bandwidth gives

diversity with Rake

receiver

Frequency hopping

Packet data schedulingLoad-based packet

scheduling

Time slot based

scheduling with GPRS

Downlink transmit

diversity

Supported for

improving downlink

capacity

Not supported by the

standard, but can be

applied

Users/cells/channels are

separated by:Codes Time or frequency

2.4.2 Elements in a WCDMA Radio Network

A WCDMA system includes various types of mobile communication devices

(called user equipment - UE) that communicate through base stations (node B) and a

mobile switching center (MSC) or data routing networks to connect to other mobile

telephones, public telephones, or to the Internet via a core network (CN). The

WCDMA system is compatible with both the 5 MHz wide WCDMA radio channel

and the narrow 200 kHz GSM channels. Figure 2.5 shows a WCDMA radio access

network which consists of user equipment (UE), node B/base station (BS) and the

radio network controller (RNC).


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Figure 2.5 WCDMA radio access network

2.4.2.1User Equipment (UE)

The mobile terminal is called user equipment. User equipment can be divided

into three parts, USIM, ME, and TE.

The USIM card (also known as SIM) contains authentication information and

associated algorithms, encryptions and subscriber-related information. In contrast,

the mobile equipment (ME) is user-independent. The Terminal equipment (TE) is

responsible for termination of the entire control and user-plane bearer with the help

of the ME.


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2.4.2.2Base Station (BS)

The base station is also known as node B in a WCDMA radio network. It is

more complex than the base station in GSM network. It consists of amplifier and

filters, transceiver, modulation/demodulation and spreading unit, and network

interface unit. Its functions include handover channel management, base-band

conversion (TX and RX), channel encoding and decoding, interfacing to other

network elements, etc.

The amplifiers are used to amplify the signal coming from the transceiver and

going towards the RF antenna (the downlink signal), while the filters select the

required frequencies coming in from the RF antenna (the uplink signal) and amplify

the signals for further processing before sending them to the receiver part of the

transceiver.

The transceiver is capable of transmitting and receiving signals, by handling

uplink and downlink traffic. It consists of one transmitter and one or more receivers.

The modulation/demodulation and spreading unit is responsible for

modulating the signal in the downlink direction and demodulating in the uplink

direction. It is responsible for summing and multiplexing the signals and also

processing the signals. This unit contains the digital signal processors that are

responsible for coding and decoding signals.

This unit acts as an interface between the base station and the transmission

network or any other network elements, such as co-sited cross-connect equipment.


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2.4.2.3Radio Network Controller (RNC)

The radio network controller (RNC) is similar to the BSC in GSM networks,

but is rather more complicated and has more interfaces to handle. The RNC

performs radio resource and mobility management functions such as handovers,

admission control, power control, load control, etc.

In fact the RNC plays a dual role in a WCDMA radio network, which should

be understood from a network planning perspective. A radio network controller can

be SRNC (serving RNC) or DRNC (drifting RNC). From one mobile, if the RNC

terminates both the data and related signalling then it is called the serving RNC. If

the cell that is used by this UE is controlled by an RNC other than the SRNC, then it

is called the DRNC.

2.4.3 WCDMA Radio Network Planning

As the launch of third generation technology approaches, operators are

forming strategies for the deployment of their networks. These strategies must be

supported by realistic business plans both in terms of future service demand

estimates and the requirement for investment in network infrastructure. The

requirement for network infrastructure can be achieved using system dimensioning

tools capable of assessing both the radio access and the core network components.

Having found an attractive business case, system deployment must be preceded by

careful network planning. The network planning tool must be capable of accurately

modelling the system behaviour when loaded with the expected traffic profile. In

the operation phase effective measurement based feedback loops are the core of the

effective operation of the network.


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The 3G traffic classes and user priorities, as well as the radio access

technology itself form the two most significant challenges when deploying a

WCDMA based third generation system. In the case of 3G networks the operators

task is to find cost wise feasible capacity and coverage trade-off, and still provide

competitive services. Furthermore, network management system should not only

identify a lack of capacity in the current network but also identify where there is

potential to introduce data services where they currently do not exist. Some of the

issues relevant for 3G planning are listed:

Introduction of multiple services

QoS requirements

Modelling of traffic distributions (for example traffic hot spots)

Mobility impact on planning

Hierarchical cell structures, and other special cell types

Site synthesis

Increasingly important role of network management system.

2.4.4 Objectives of Radio Network Planning

There are four main objectives of the radio network planning. The four

objectives are coverage, capacity, quality and costs.

Coverage

To obtain the ability of the network to ensure the availability of the

service in the entire service area

Capacity

To support the subscriber traffic with sufficient low blocking and

delay

Quality

By linking the coverage and capacity and still provide the QoS


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Costs

To enable and economical network implementation when the service

is established and a controlled network expansion during the life cycle

of the network

2.4.5 WCDMA Radio Network Planning Process

The general radio network planning process can be seen as in Figure 2.6.

The WCDMA radio network planning process starts with the pre-planning or strategy

phase. In this phase, the dimensioning of the network based on inputs and

assumptions for getting a desired coverage, capacity, quality and network

configuration is the most important.

Definition of coverage would include defining the coverage areas, service

probability and related signal strength. There are coverage-driven areas and

capacity-driven areas in a given network region. The average cell capacity

requirement per service area is estimated for each phase of network design, to

identify the cut-over phase where network design will change from a

coverage-driven to a capacity-driven process. The objective of coverage planning

in the coverage-driven areas is to find the minimum number of sites for producing

the required coverage.

The next phase includes site surveys, site acquisition, planning/measurements

and code planning. Candidate sites are searched for, and one of these is selected

based on the inputs from the transmission planning.


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After that, parameter plans are drawn up for each of the cell sites. There is a

parameter set for each cell that is used for network launch and expansion. This set

of parameters are measured and adjusted in order to achieve the required QoS.

Parameters settings are done after achieve the target.

The final radio plan consists of the coverage plans, capacity estimations,

interference plans, power budget calculation, parameter set plans, frequency plans,

etc.

Pre-planning/Strategy:

z Coverage

z Capacity

z Quality

z Site surveys

z

Site acquisitionz Planning/

Measurements

z Coverage

z Adjustments in the

radio network

(Measurements)

Final Radio Plan

Figure 2.6 General radio network planning process


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The WCDMA radio network planning process is shown in Figure 2.7. The

WCDMA radio network planning process can be divided into three phases:

Initial planning (dimensioning)

Detailed radio network planning

Network operation and optimisation

Each of these phases requires additional support functions like propagation

measurements, Key Performance Indicator (KPI) definitions etc.

Figure 2.7 WCDMA radio network planning process

Initial planning (dimensioning) provides the first and most rapid evaluation of

the network size as well as the associated capacity of elements involved. This

includes both the radio access network as well as the core network. In the

dimensioning phase, an approximate number of base station sites, base stations and

their configurations and other network elements are estimated, based on the

operators requirements and the radio propagation in the area. The dimensioning


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must fulfil the operators requirements for coverage, capacity and quality of service.

Capacity and coverage are closely related in WCDMA networks, and therefore both

must be considered simultaneously in the dimensioning of such networks.

In detailed planning, real propagation maps and operators traffic estimates in

each area are needed. The base station locations and network parameters are

selected by the planning tool and/or the planner. Capacity and coverage can be

analyzed for each cell after the detailed planning.

In the detailed planning phase the dimensioned site density is transferred on a

digital map taking the physical limitations coming, for example, from site acquisition,

into account. The WCDMA analysis itself is an iterative process, the capacity

requirements are taken into account as discrete MSs in the WCDMA simulation. In

the detailed planning phase multiple analyses is performed to verify if the set

requirements are actually met. In the planning phase the optimisation means can be

performed by interference control in terms of proper antenna and site configuration

and location selection or antenna tilting. Furthermore, network performance can be

brought closer to the required targets with utilization of, for example, mast head

amplifier (MHA) or diversity schemes.

In case the operators business strategy changes, dimensioning and detailed

planning can provide valuable information, related to the network expansion. The

measured traffic information can be imported to the planning tool and this

information can be further used when verifying the capacity and coverage

capabilities of the planned network.

When the network is in operation, its performance can be observed by

measurements, and the results of those measurements can be used to visualize and


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optimise network performance. The planning and the optimisation process can also

be automated with intelligent tools and network elements.

2.4.6 WCDMA Optimisation

The process of optimisation begins in the early phase of network planning,

right after the pre-planning process. The optimisation process starts with existing

network data and the master plan made during the initial phase of network planning.

Network optimisation is a process to improve overall network quality as

experienced by the mobile subscribers and to ensure that network resources are used

efficiently. Optimisation includes the analysis of the network and improvements in

the network configuration and performance. Figure 2.8 shows the general

WCDMA radio network optimisation. Statistics of the key performance indicators

(KPI) for the operational network are fed to the network status analysis tool, and the

radio resource management parameters can be tuned for better performance. An

example of the optimisation parameter is soft handover area optimisation. The

network status analysis tool could be an integrated part of the radio network planning

tool. The traffic growth in the network requires continuous interaction of the

planning tool and the operational network. The capability of the current network to

support the forecast traffic growth is analysed, and the radio network plan can be

further processed based on actual measured data.


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KPI

Definition

Network

Performance

Parameter

Tuning

Optimised

NetworkNetwork

Planning

Figure 2.8 WCDMA optimisation

The first phase of the optimisation process is to define the key performance

indicators (KPI). These consist of measurements in the network management

system and of field measurement data, or any other information which can be used to

determine the quality of service of the network. With the help of the network

management system it is possible to analyse the past, present and predicted future

performance of the network.

The performance of the radio resource management algorithms and their

parameters can be analysed using the key performance indicator results. The radio

resource management algorithms include handovers, power control, packet

scheduling, admission and load control.

The network quality analysis is designed to give an operator a view of

network quality and performance. The quality analysis and reporting consists of

planning the case, field measurements and network management system


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measurements. After the quality of service criteria have been specified and the data

has been analyzed, a survey report can be generated. For second generation

systems, quality of service has consisted, for example, of dropped call statistics,

dropped call cause analysis, handover statistics and measurement of successful call

attempts. For third generation systems with a greater variety of services, new

definitions of quality of service for quality analysis must be generated.

Automatic optimisation will be important in third generation networks, since

there are more services and bit rates than in second generation networks and manual

optimization would be too time consuming. Automatic adjustment should provide a

fast response to the changing traffic conditions in the network. It should be noted that

at the start of third generation deployment, only some of the parameters can be

automatically tuned, and therefore a second generation type optimisation process

must still be maintained.

2.4.6.1Key Performance Indicator

Deciding on key performance indicators is the most important part of the

process because it is here that the methodology of optimisation is decided. Owing

to the complexity of a WCDMA network, there is an immense number of parameters.

However, only a few of these parameters are chosen for optimisation, those that have

the most significant impact on the radio network.

The initial values of parameters are usually derived from standard formulas.

These key chosen parameters are the ones that are responsible directly for the

coverage, capacity and quality of the network. The main KPIs may include call

success/failure rate, dropped call rate, (soft) handover success rate, average


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throughput on uplink/downlink, and average throughput on various channels such as

RACH, FACH and PCH, etc. when defining the KPIs, it is important to know

whether or not tools are available to measure the performance of the chosen

parameters.

2.4.6.2Network Performance Monitoring

The networks performance can be monitored through drive tests and the

network management system (NMS). In a WCDMA radio network, real-time data

transfer delay is perhaps the most critical aspect to be monitored. Even within

real-time data, each application has to be monitored/measured against the backdrop

of its own QoS requirements.

With regard to the NMS measurements, as in GSM radio networks, most of

the measurements are performed on the RNC, based on the key performance

indicators on whose bases these measurements are run. The statistics collected

from drive testing and the NMS are then used in conjunction with some

post-processing tools that provide various types of output and reports.

The quality of the network is usually viewed from the perspective of mobile

subscribers. This is why drive tests are important. The quality can be assessed

right from the time when the first site goes live. The network management system

usually comes into place when the network is near launch or has been launched, so

can provide statistics when there are certain numbers of subscribers. The NMS

should have the capability to handle the various aspects of the WCDMA radio

network, which is in a multi-technology and multi-vendor environment.


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2.4.6.3Coverage, Capacity and Quality Enhancements

Coverage is directly related to link performance. An increase in coverage

will demand an increase in the average X power of a base station in the downlink

direction. If the system capacity is downlink-limited, then an increase in coverage

will lead to a decrease in capacity. If the system is uplink-limited, then the capacity

is not affected. Thus, link performance increase is directly related to the increase in

coverage.

There are many ways to improve the coverage. Parameters such as block

error rate, Eb/N0, power control headroom, etc., directly affect the power budget and

hence the coverage. Uplink coverage can be improved by decreasing the

interference margin or by reducing the base station noise figure, or even by

increasing the antenna gain. However, the processing gain and Eb/N0 are the two

major values affecting coverage. Concepts like antenna tilts are also used in

WCDMA radio networks to improve the coverage area.

Capacity and coverage are heavily inter-dependent in WCDMA networks.

The higher the uplink coverage, the lower is the uplink capacity, and vice versa. This

is because lower capacity means fewer mobile subscribers, which means less

interference. Moreover, the uplink power budget is used to calculate the cell range,

which is further used to calculate the downlink power budget.

The load factor along with the link budget calculations can be used to study

the capacity in the network. The load factor is used for capacity analysis for both

the uplink and downlink directions. The load factor is dependent upon Eb/N0,

processing gain, interference, activity factor, etc. Orthogonality and soft handovers

are further factors associated with the load factor in the downlink direction.


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The best way to improve capacity is always to increase the number of

cells/carriers. The increased number of sectors proportionately increases the

capacity of the network. Additionally, orthogonal codes should ideally be truly

orthogonal, but owing to multipath some orthogonality is lost, thereby increasing

interference. Multipath diversity improves the coverage but also reduces the

orthogonality. Multipath diversity is more important at the cell edges as it improves

the performance. Another way of improving capacity is by transmit diversity. If

multipath diversity is less, then the downlink transmit diversity increases the capacity

to quite an extent. Lower bit rates would also increase the capacity. This is

possible by using the adaptive mean rate (AMR) codes, AMR being the speech codec

scheme that is used in UMTS.

End-to-end QoS has to be considered in third generation networks, but here

we focus on the delay at the air-interface, which will have a direct impact on quality.

QoS is application-dependent, but the immediate concern is to reduce the

delay at the air interface for PS services. Unlike in GSM where voice quality is the

only big concern, in WCDMA attention turns to PS service requirements and

performance. Delay may or may not take place at the air interface (it may be due to

transmission or the core network), yet the first step for end-to-end quality is the

performance of the application at the air interface.

2.4.6.4Parameter Tuning

WCDMA networks have a huge number of parameters, and some of the key

ones are chosen, measured/analysed and optimized. These parameters can be

divided into various groups based on the functions they affect the most. These


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groups may include parameters affecting handover control, packet scheduling, power

control, call admission control, etc.

Soft handover gain is one of the parameters in the link budget calculations.

Soft handover gives some protection against both slow and fast fading. With regard

to slow fading, because of the lack of correlation between base stations, a mobile is

able to select a better base station (based on the measurements analysed in the RNC).

With regard to fast fading, through the effect of macro diversity combining, the

required Eb/N0 is reduced. Soft handovers also induce overhead in capacity

calculations, as at a given time a mobile is connected to more than one cell, thereby

increasing the capacity requirements. Thus, both the overheads and the gain should

be optimised.

The idea behind optimising the overheads is to save on downlink capacity.

A typical value of the soft handover overhead is 30-40%. Soft handover gain, on

the other hand, can be estimated by using parameters such as DCR, CSR (call

success rate), transmit and receive powers.

For capacity and coverage optimisation, it is very important to optimise the

handover control feature in these networks. One important parameter to mention is

the transmitting power of the CPICH. This parameter affects the coverage and it

should be set as low as possible. The optimum value of this parameter will

determine the coverage and capacity. This parameter also affects packet scheduling.

If the value of CPICH is not optimum, then either the network will be under-utilised

or there will be huge interference if the number of users is more than planned, thus

degrading the quality of the network. These parameters also affect the call success

rate and dropped call rates.


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Packet scheduling is one of the most important aspects when controlling

congestion in the network. Packet scheduling handles the non-real-time packet data,

deciding on the timings of packet initiation and the rate at which packets should be

delivered.

The NRT packet data is bursty in nature, containing one or more data calls.

Packet scheduling is done for both uplink and downlink for non-real-time bearers.

Packets can be scheduled by using time-division or code-division techniques, or

both. Packet scheduling and load control (inclusive of admission control) work in

tandem. A higher load will lead to higher interference, which means fewer calls

being admitted to the network. This affects the bits rate assigned to the NRT

packet data. Thus, for packet scheduling (i.e. less delay and higher bit rates for

NRT data), load control is an important parameter to analyse and optimise.

Transmitted power in the downlink and interference power in the uplink are

further important parameters for optimisation. When the thresholds of these two

parameters are crossed, preventive measures to control the load are initiated. From

the perspective of packet scheduling this is important, because assigning higher or

lower bit rates is dependent on the load control and AC).

Efficient and fast power control is the key to success of WCDMA technology.

Power control is based on the SIR. Power control has a direct effect on the

coverage area. Another aspect related to power control is interference that may lead

to capacity limitation. Both uplink and downlink power control is necessary, with

downlink control being the more critical. Power control of the common channels is

necessary, the most important ones being the CPICH, AICH, PICH and CCPCH.

However, this process is more one of control than of optimisation.


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The AC (admission control) function is directly related to the load control

process. The process is critical for both the RT and NRT traffic generators/users.

As the AC function is power-based and throughput-based, parameters related to both

those features are important for capacity and coverage optimisation. The two most

important parameters are then the transmitted power and received power, and

orthogonality and throughput in both uplink and downlink directions.

2.5 Summary

WCDMA system is the evolution from the second generation, GSM. The

3G system is designed to meet the requirements of the current demands in the

telecommunications world. Since there are differences in the air interfaces and the

parameters, therefore the elements in a WCDMA radio network system is different

from the 2G system. Due to this reason too, the planning process and optimization

process of the WCDMA radio network also have slightly different from the current

systems.


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CHAPTER 3

PREDICTION OF WCDMA COVERAGE

3.1 Project Methodology

The methodology in this project including generate a proper WCDMA radio

link budget for the 3G radio network, simulation of the input parameters, comparison

between the simulation results with the expected result, report and thesis writing.

The WCDMA radio link budget is planned to be designed using the Visual

C++ software. The users can select the cell range calculation for different types of

data rates. There are three different data rates, i.e. the 12.2 kbps voice service, 144

kbps circuit-switched data service, and 384 kbps packet-switched data service.

Users can also check the default values used for these three data types.

A GUI (Graphical User Interface) will be design so that the users can key in

the values of the input parameters according to their requirements. Calculation is

done automatically after all the input parameters had being entered. The output of

the radio link budget calculation is the maximum allowed propagation path loss

which in return determines the cell range.


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Radio link budget analysis is then carried on to study the optimisation of the

coverage. One of the parameters that affect the most the cell range will be chosen.

In this case, the Eb/N0 ratio is chosen. The factors that will affect the Eb/N0 ratio

will be studied in more detail. Analysis will be carried on to find out the

appropriate range of the Eb/N0 ratio that will provide the required QoS as in

mentioned in the specifications.

3.2 WCDMA Radio Network Dimensioning

WCDMA radio network dimensioning is a process through which possible

configurations and amount of network equipment are estimated, based on the

operators requirements related to the following:

Coverage

z Coverage regions

z Area type information

z Propagation conditions

Capacity

z Spectrum available

z Subscriber growth forecast

z Traffic density information

Quality of service

z Area location probability (coverage probability)

z Blocking probability

z End user throughput

The target of the dimensioning phase is to estimate the required site density

and site configurations for the area of interest. Initial RAN planning activities

include radio link budget (RLB) and coverage analysis, capacity estimation, and


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finally, estimation for the amount of base station hardware and sites, radio network

controllers (RNC), equipment at different interfaces, and core network elements.

System dimensioning provides the first, rapid evaluation of the possible

network configuration. This includes both the radio access network as well as the

core network. The dimensioning is based on a set of input parameters and the

provided result is relevant for that set of input parameters only. These parameters

include area, traffic and QoS related information. The quality is taken into account

in terms of blocking and coverage probability.

Dimensioning activities include radio link budget (RLB) and coverage

analysis, capacity estimation, and finally, estimations on the amount of sites and base

station hardware, radio network controller (RNC), equipment at different interfaces,

and core network elements.

RLB calculation is done for each service, and the tightest requirement

determines the maximum allowed isotropic path loss.

3.3 WCDMA Radio Link Budget

The WCDMA radio link budget is part of the network planning process. It

helps to dimension the required coverage, capacity and quality of service

requirement in the radio network.

The objective of the radio link budget design is to calculate the maximum cell

size under the given criteria:

Type of service (data type and speed)


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Type of environment (terrain, building penetration)

Behaviour and type of mobile (speed, maximum power level)

System configuration (BTS antennas, BTS power, cable losses,

handover margin)

Required coverage probability

Financial and economical factors

The WCDMA link budget calculations start from the uplink (reverse link)

direction. Uplink interference (noise from other mobiles) is usually the limiting

factor in WCDMA systems.

The starting point of a link budget calculation is to define the required data

rate(s) in each network areas and Eb/N0 (Energy per Bit to Noise power density ratio)

targets. Usually the operator predefines these, but simulation tools can be used to

tailor the Eb/N0. Simulation can be done by creating a uniform base station and a

mobile distribution plan with defined service profiles. Almost every UMTS vendor

has a simulation tool for operators to test their network plan models.

The next step is to gather vendor specific data like a BTS output power and a

receiver noise figure, defined and used cable systems (thicker the cable, more

expensive it is to install), used antenna types, usage of intelligent antenna systems in

specific areas, possible additional line amplifiers, used diversities (like antenna,

polarisation, receiver) etc.

For each geographical areas network operator has to define Eb/N0, data

services, a system loading factor, estimated mobile speeds, different penetration

losses, coverage reliability and a used fade margin. Soft handover area sizes will be

addressed later.


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Mobile power levels, the chip rate and the process gains are defined by the

UMTS standards. Soft handover gain and the thermal noise density are the same in

every UMTS system. Both parties also have to agree on propagation models after

drive tests.

The link budget gives a cell range and from that cell coverage area can be

calculated. Cell coverage overlap parameter is usually missing from the calculation

as it increases the cell count dramatically. Most network planners agree that

overlap should be 20-30 percent, but that relates directly to build cost. After all that,

the base station requirements for the each type of areas can to be calculated.

3.4 Parameters in WCDMA Radio Link Budget

Basically, there are several parameters that are needed to be input to the radio

link budget so that we can get the desired output. The input parameters of the

WCDMA radio link budget are as followed:

Power class

Antenna gain

Eb/N0 ratio

Path loss/cable loss/penetration loss

Receiver sensitivity

Data rate

Interference margin

Fast fading margin

Soft handover margin

Among these parameters, a few of them are 3G specific parameters and some

of them are common parameters with 2G system.


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3.4.1 Common Parameters with 2G System

EIRP (Effective Isotropic Radiation Power) is the maximum power radiated

in the direction of maximum antenna gain. It can be defined as the total effective

isotropic power including gains of antenna and losses of cables that is transmitted

towards the receiver with the assumption that the RF signal is radiated equally in all

directions in terms of an isotropic (omni directional) radiator. The power can be

calculated with the following equation:

tsyst GLPdBiEIRP +=)(

Where:

= Transmitted powertP

sysL = Total system loss

tG = Antenna gain.

Mobile station has lower gain (0dBi), base transmit station (BTS) antenna

gain varies from 8 dBi to 21 dBi depending upon the type of antenna used. This

gain can be increased by various techniques such as antenna diversity.

Eb/N0 is the ratio of the received bit energy to the thermal noise. Eb is

received energy per bit multiplied by the bit rate. N0 is the noise power density

divided by bandwidth. Link budget calculations are basically done to calculate the

Eb/N0 ratio and the interference signal density.

Cable attenuation figures are usually quoted in loss (dB) per 100m.

Theoretical loss may exceed the desired value, so preamplifiers may be used to

counter the cable loss. Connector losses are usually much less (0.1 dB).When the

budget needs to include a margin for the penetration loss in case service is planned


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for indoor users. Building attenuation varies greatly between buildings and is

affected by:

Building material

Wall thickness

The amount of windows

Presence of sun reflective shielding on windows

How deep into the building the user is

Whether the building itself has Line Of Sight (LOS) with the serving

base station

Angle of incidence of the incoming signal

On which storey of a building the receiver is located

When the signal travels along its path, it will cause some losses. The path

loss is depending on the distance, frequency and it is affected by various effects

dependent on atmospheric conditions.

The thermal noise density is generated by the environment. It is given by

the following equation:

/173.93-

001.0

1004.4

log10

/4.04x10

x2931038.1

21

21-

23

0

HzdBm

W

Wx

HzW

x

kTN

=

=

=

=

=

Where:

KelvinineTemperatur

constantsBoltzmann'

densitynoiseThermal0

=

=

=

T

k

N


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Noise power is obtained from:

FBWkTPN )(=

WhereFis the noise figure.

Receiver sensitivity in the link budget is defined as the minimum required

signal strength at the receiver input to produce a specified output signal having a

specified signal-to-noise (SNR) ratio. The receiver sensitivity has to be determined

first in WCDMA systems when performing the link budget calculations. In the

WCDMA systems, factors such as processing gain, receiver noise figure, required

minimum bit energy to noise ratio power spectral density ratio, Eb/N0 ratio and pilot

channel chip energy to received signal power spectral density ratio E0/I0 are

considered when determining the receiver sensitivity. It is often expressed in dBm.

In WCDMA system, the signal is transmitted at a larger bandwidth than the

original bandwidth. This phenomenon is known as spreading. The spread signal is

then transmitted to the receiver and is de-spread. In the de-spreading process, the

received signal is concentrated into the narrow band while the noise level remained

unchanged. This is because the cross-correlations between the code of the desired

user and the codes of other users are small. This leads to a higher SNR ratio of the

de-spread signal than the CDMA signal before the de-spreading. The increase of

signal power to attain the required bit energy to noise power spectral density ratio is

called the processing gain. Processing gain is also known as the spreading factor

and is defined as the ratio between the bandwidth or chip rate and the bit rate.

The Ec/Io (Pilot Channel Chip Energy to Received Signal Power Spectral

Density) ratio, is a special term that is used to describe the SNR of the pilot channel.

The Ec/Io is transmitted continuously by the base station to give an indication of the

power level so that the received power levels are balanced from mobiles from the


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same cell. The energy per chip Ec is different from energy per bit in that "chips"

refer to pseudorandom noise sequences that are spread.

3.4.2 3G Specific Parameters

WCDMA radio link budget calculations need to be done individually for

different applications with different data rate. For example, the ARM speech codec

voice service is 12.2 kbps, the circuit-switched data service is 144 kbps while the

packet-switched data service is 384 kbps.

Base station output power is shared between all connections on the base

stations, so the amount of power available for a certain connection will vary with

load and positions of the connected mobiles.

Since the same frequency is used on all cells, the link budget needs to include

margins for the interference created by other connections, both from the own cell and

other cell. This interference is often treated as an additional noise that is added to

the thermal noise.

The uplink loading factor, UL can be calculated as a sum of load factors of

allNuplink connections, in a cell.jL

=

=N

j

jUL L1

The Eb/N0 ratio is defined as energy per user bit divided by the noise spectral density:

=

j

b

N

E

0

Processing gain of user j

usersotherfromceInterferen

juserofSignal


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This can be written as:

j

j

jjj

b

PI

P

Rv

W

N

E

=

0

Where:

W = Chip rate

jP = Received signal power from userj

jv = Activity factor of userj

jR = Bit rate of userj

I = Total received interference in the base station.

Solving for givesjP

( )( )

W

PIRvN

E

P

jjj

j

b

j

=0

I

vRN

EW

P

jj

j

b

j

+

=

0

1

1

Since,

ILP jj =

The load factor of one connection is obtained:

jj

j

b

j

i

vRN

E

W

I

P

L

+

=

=

0

1

1

The interference from the other cells must be taken into account by the ratio of other

cell to own cell interference, i:

erferencecellownerferencecellotheri

intint=


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Now, the uplink load factor can be written as:

=

+=N

j

jUL Li1

)1(

=

+

+=N

j

jj

j

b

UL

vRN

E

Wi

1

0

1

1)1(

The load equation predicts the amount of noise rise over thermal noise due to

interference. The interference margin in the link budget must be equal to the

maximum planned noise rise.

)1log(10 ULL =

The downlink load factor, DL , can be defined based on a similar principle as

for the uplink, with a slightly different in the parameters.

[ ]=

++

=N

j

jj

j

j

b

jDL i

R

W

N

E

v1

0

)1(

Compared to the uplink load equation, the most important new parameter is

j , which represents the orthogonality factor in the downlink. WCDMA employs

orthogonal codes in the downlink to separate users, and without any multipath

propagation, the orthogonality remains when the base station signal is received by

the mobile. However, if there is sufficient delay spread in the radio channel, the

mobile will see part of the base station signal as multiple access interference.


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In the downlink, i, depends on the user location and is therefore different for

each userj. When the number of users increases, the loading increases, more

interference margin is needed in the power budget, and cell range decreases.

In WCDMA network, when the number of subscribers in the cell is low, good

quality can be achieved even at a long distance from the base station. On the other

hand, when the number of users in the cell is high, the large number of subscribers

generates a high interference level and subscribers have to get closer to the base

station to achieve good quality. The phenomenon where the cell shrinks due to high

capacity and shrunk due to low capacity is called cell breathing. Cell breathing

occurs as a function of load. Generally, interference is a function of the total cell

loading.

)1log(10 DLL =

All objects in the vicinity of a receiver cause reflections of the radio signal.

In the receiver, these reflections will add to one another, with different phase as a

result of different propagation distances. This gives rise to fast fading or

Rayleigh fading.

The fast fading margin is needed in the mobile station transmission power for

maintaining adequate closed loop fast power control. This applies especially to

slow moving pedestrian mobiles where they run a higher probability of being still in

a fading dip, and this fast power control is able to effectively compensate the fast

fading, that is the changes in the propagation conditions.

In the case of a slowly moving mobile station, the power control is able to

follow the fading channel and the average transmitted power increases. Increased

transmitted power is compensated by the fading channel.


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Shadow fading occurs due to obstacles like building. Handover, soft or hard,

give a gain against shadow fading by reducing the required fading margin.

Soft handover means a mobile on the boarder between two cells will be

connected to both, at each point in the time using the best connection. This gives

two benefits, where a mobile can always choose the strongest cell and it provides

diversity effects since an additional antenna is receiving the signal.

The additional antenna gain from increasing the number of antennas is

marginal except in the case when path loss to both base stations is exactly the same.

For these reasons, no soft handover gain is assumed in the link budget.

Soft handover gain is a function of mobile speed, the diversity combining

algorithm used in the receiver, and the other types of diversity that already exist in

the received signal.

3.5 WCDMA Radio Link Budget Model

In this project, three WCDMA radio link budget model are created for three

different services, the 12.2 kbps voice service, 144 kbps circuit-switched data and

384 kbps packet-switched data. The calculation in the radio link budget is based on

the condition where the service is in an urban macro cellular environment at a

planned uplink noise rise of 3 dB. A macrocell is referring to a cell range greater

than 1 km with high transmission power, normally more than 10 W. There are

many different propagation path loss in the macrocell.


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Basically, the calculation in the radio link budget of this project can be

divided into five parts:

Calculation of EIRP at the transmission side

Calculation of receiver sensitivity at the base station receiver

Calculation of the maximum path loss

Calculation of the allowable path loss

Calculation of the cell range

Wireless transmission is subject to two major sources of propagation

degradation, fading and interference. Fading is caused by propagation path loss and

multipath phenomena. Multipath propagation may be frequency selective leading

to intersymbol interference for high rate data transmission.

The mobile radio signal is usually treated by statistical basis. In wireless

transmission, the signal received is from the direct path, paths of scattering,

reflections and diffraction. Due to the propagation loss, the effect of the terrain

configuration generates small-scale long-term fading (shadow fading) which changes

with the atmosphere and electrical constants associated with obstructions, and so

forth. The buildings, traffic, motion and trees in the nearby environment would

cause the multipath fading on the received signal called short-term fading.

Any propagation model in the macrocell environment can be represented by:

),,,,( tenvironmenhhfdlGGPP mbrttr =

Where:

t.environmenthen throughpropagatiotoduenAttenuatio

antennareceivefor theGainsG

antennatransmitfor theGains

levelpowerdTransmitte

receiverat thepowerReceived

r

=

=

=

=

=

l

G

P

P

t

t

r


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48

The loss parameter is a function of:

stationbasetheofantennatheofHeight

stationmobiletheofantennatheofHeight

interestofsignalofFrequency

receiverandertransmittebetween thdistancenPropagatio

=

=

=

=

b

m

h

h

f

d

In the mobile radio environment, propagation is no longer in free space and

most often not having Line Of Sight (LOS). Other factors affecting the main path

loss include base and mobile antennas heights, operating frequency, and the presence

of various effects dependent on atmospheric condition.

Over the period of many years, a number of attempts at predicting the mean

path loss in the land mobile radio environment have been made. Among these

methods, the Okumura method has often been used for land mobile radio channels.

The Okumura method is based on extensive field measurements in various terrains

for frequencies from 100 MHz to 3 GHz. In attempt to simplify the results of

Okumura method, Hata developed an empirical formula which gave predictions

almost indistinguishable from those given by Okumura method over the limited

range.

However, the Hata model holds for path loss of lower frequency range. The

European Co-operative for Scientific and Technical research (EURO-COST)

extended the Hata model for the higher frequency range which is more applicable to

the 3G deployment.

Basically, all path loss models in the macrocell application can be expressed

as:

BdAP cL += )log(


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Where:

kminstation),mobileandstationbasebetween(distancerangeCell

modelnpropagatiotheofIntercept

modelnpropagatiotheofSlope

inloss,pathAllowable

=

=

=

=

c

L

d

B

A

dBP

Table 3.1 Allowable path loss model

Path Loss Model Slope (A) Intercept (B)

Free space 20 20log(f) + 32.44

Hata (Rural) 44.9 655log(hb)33.6 + 7.8log(f) 13.8log(hb)

4.8(logf)2 3.2[log(11.8hm)]2

Hata (Suburban) 44.9 655log(hb) 59.2 + 26.2log(f) 13.8log(hb) 3.2[log(11.8hm)

2 2[log(f/28)]2

Hata (Urban) 44.9 655log(hb)68.8 + 26.2log(f) 13.8log(hb)

[1.1log(f) 0.7]hm + 1.6log(f)

Hata (Dense urban) 44.9 655log(hb)74.5 + 26log(f) 13.8log(hb)

3.2[log(11.8 hm)]2

COST-231 (Rural) 44.9 655log(hb)10.3 + 15.6log(f) 13.8log(hb)

3.2[log(11.8 hm)]2 - 4.8(logf)2

COST-231

(Suburban)44.9 655log(hb)

45.9 + 33.9log(f) 13.8log(hb)

3.2[log(11.8hm)2 2[log(f/28)]2

COST-231 (Urban) 44.9 655log(hb)45.5 + 33.9log(f) 13.8log(hb)

[1.1log(f) 0.7]hm + 1.6log(f)

COST-231

(Dense urban)44.9 655log(hb)

54.3 + 33.9log(f) 13.8log(hb)

3.2[log(11.8 hm)]2

Table 3.1 exhibits the slope (A) and the intercept (B) of the Hatas and

COST-231 propagation model for different environments. The symbols are defined

as followed:

MHz2000MHz1500:model231-COST

MHz1500MHz300:modelHata

MHzinfrequency,Carrier

m10tom1meter,instation,mobiletheofHeight

m200tom30meter,instation,basetheofHeight

LoadIcon(IDR_MAINFRAME);

}

void CRLBDlg::DoDataExchange(CDataExchange* pDX)


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{

CDialog::DoDataExchange(pDX);

//{{AFX_DATA_MAP(CRLBDlg)

// NOTE: the ClassWizard will add DD

Documents

MECOVERAGE PERFORMANCE OF 3G RADIO NETWORK.pdf