1

UNIVERSITY OF NAIROBI

FACULTY OF ENGINEERING

DEPARTMENT OF ELECTRICAL AND INFORMATION ENGINEERING

PROJECT TITLE: CELL PLANNING IN WIRELESS COMMUNICATION

NETWORKS

PROJECT INDEX: 029

BY

OBADE JOHN KELVIN

F17/1388/2010

SUPERVISOR: PROF. VITALICE K. ODUOL

EXAMINER: PROF. ELIJAH MWANGI

Project report submitted in partial fulfillment of the

requirement for the award of the degree

of

BACHELOR OF SCIENCE IN ELECTRICAL AND ELECTRONIC

ENGINEERING OF

THE UNIVERSITY OF NAIROBI 2015

SUBMITTED ON: 24TH APRIL, 2014

I

DECLARATION OF ORIGINALITY

NAME OF STUDENT:

OBADE JOHN KELVIN

REGISTRATION NUMBER: F17/1388/2010

COLLEGE: Architecture and Engineering

FACULTY/ SCHOOL/ INSTITUTE: Engineering

DEPARTMENT: Electrical and Information Engineering

COURSE NAME: Bachelor of Science in Electrical and Electronic

Engineering

TITLE OF WORK: CELL PLANNING IN WIRELESS

COMMUNICATION NETWORKS

1) I understand what plagiarism is and I am aware of the university policy in this regard.

2) I declare that this final year project report is my original work and has not been submitted

elsewhere for examination, award of a degree or publication. Where other people’s work or

my own work has been used, this has properly been acknowledged and referenced in

accordance with the University of Nairobi’s requirements.

3) I have not sought or used the services of any professional agencies to produce this work.

4) I have not allowed, and shall not allow anyone to copy my work with the intention of passing

it off as his/her own work.

5) I understand that any false claim in respect of this work shall result in disciplinary action, in

accordance with University anti-plagiarism policy.

Signature:

…………………………………………………………………………………

Date:

…………………………………………………………………………………

II

DEDICATION

I dedicate this project to my family for their continued support and belief in me.

III

CERTIFICATION

This report has been submitted to the Department of Electrical and Information Engineering,

University of Nairobi with my approval as supervisor:

…………..………………………………

Prof. Vitalice K. Oduol

Date: …………………………….

IV

ACKNOWLEDGEMENTS

I would like to thank God for guiding me throughout my academic journey.

I would also like to acknowledge my supervisor, Prof. Vitalice K. Oduol, for his priceless

motivation, support and guidance throughout the project duration.

I extend my gratitude to all the lecturers and non-teaching staff of the Department of Electrical

and Information Engineering for their contribution towards my degree.

I am also grateful to my classmates for their moral support as I did the project

V

ABSTRACT

Wireless connectivity is being deployed in communication networks throughout the world. The

available spectrum is limited and thus it has to be used judiciously, to meet the objectives of the

network operator. This project addresses the cell planning problem in wireless communication

networks. The basic cell planning concepts are described and the cell planning process is

outlined in detail. Cell planning considerations in GSM, UMTS and LTE networks are also

outlined. A design and demonstration of cell planning in a GSM (TDMA) network is done for an

example scenario producing a nominal cell plan for a given focus zone using Atoll Radio

Planning Software - Version 2.7.1 (Build 2922).

VI

TABLE OF CONTENTS

DECLARATION OF ORIGINALITY ............................................................................................ I

DEDICATION ................................................................................................................................ II

CERTIFICATION ........................................................................................................................ III

ACKNOWLEDGEMENTS .......................................................................................................... IV

ABSTRACT ................................................................................................................................... V

TABLE OF CONTENTS .............................................................................................................. VI

LIST OF FIGURES ................................................................................................................... VIII

LIST OF TABLES ........................................................................................................................ IX

ABBREVIATIONS ....................................................................................................................... X

CHAPTER ONE: INTRODUCTION ............................................................................................. 1

1.1 Background of Study ........................................................................................................ 1

1.2 Problem Statement ........................................................................................................... 1

1.3 Objectives ......................................................................................................................... 1

1.4 Scope of Work .................................................................................................................. 2

1.5 Organization of the Report ............................................................................................... 2

CHAPTER TWO: LITERATURE REVIEW ................................................................................. 3

2.1 Multiple Access Techniques ............................................................................................ 3

2.2 The Cellular Concept ....................................................................................................... 5

2.3 What is Cell Planning? ..................................................................................................... 7

2.3.1 Objectives of Cell Planning ...................................................................................... 7

2.3.2 Cell Planning Process ............................................................................................... 8

2.3.3 Propagation Prediction and Modelling ................................................................... 11

2.3.3.1 Deterministic Path Loss Models ............................................................................. 11

2.3.3.2 Empirical Path Loss Models ................................................................................... 17

2.3.4 Monte Carlo Simulations ........................................................................................ 21

2.3.5 Channel Re-use ....................................................................................................... 21

2.3.6 System (Cell) Balance............................................................................................. 23

2.3.7 RF Emission Limits and Safety .............................................................................. 24

2.4 Planning Considerations for GSM (TDMA) Networks ................................................. 26

2.4.1 Link Budget ............................................................................................................ 26

2.4.2 GSM Frequency Spectrum ...................................................................................... 26

2.4.3 GSM Channels ........................................................................................................ 27

VII

2.4.4 Frequency Planning ................................................................................................ 29

2.4.5 Base Station Identity Code (BSIC) Planning .......................................................... 31

2.5 Planning Considerations in UMTS Networks ................................................................ 32

2.5.1 Link Budget ............................................................................................................ 32

2.5.2 UMTS Frequency Spectrum ................................................................................... 33

2.5.3 UMTS Channels...................................................................................................... 35

2.5.4 Code Planning ......................................................................................................... 37

2.5.5 Cell Breathing ......................................................................................................... 38

2.6 Planning Considerations for LTE (4G) Networks ......................................................... 39

2.6.1 Link Budget ............................................................................................................ 39

2.6.2 LTE Frequency Spectrum ....................................................................................... 39

2.6.3 Channel Bandwidths and Subcarriers ..................................................................... 41

2.6.4 Radio Channel Organization ................................................................................... 41

2.6.6 LTE Frequency Planning ........................................................................................ 43

CHAPTER THREE: DESIGN ...................................................................................................... 44

3.1 Frequency Planning in the GSM 900 Frequency Band .................................................. 44

3.1.1 Frequency Re-use Pattern ....................................................................................... 44

3.1.2 Control Channels .................................................................................................... 44

3.1.3 Traffic Channels (TCH) .......................................................................................... 44

3.1.4 Synthesized Frequency Hopping ........................................................................... 45

3.2 Allocation of Intra-technology Neighbours ................................................................... 49

3.3 Coverage Prediction ....................................................................................................... 49

3.3.1 Choice of Antenna .................................................................................................. 51

3.3.2 Propagation Path Loss Model ................................................................................. 54

3.3.3 Link Budget ................................................................................................................ 54

CHAPTER FOUR: RESULTS, DISCUSSION AND ANALYSIS ............................................. 55

CHAPTER FIVE: CONCLUSIONS AND RECOMMENDATIONS ......................................... 61

5.1 CONCLUSION .............................................................................................................. 61

5.2 RECOMMENDATIONS ............................................................................................... 61

BIBLIOGRAPHY ......................................................................................................................... 62

APPENDIX: .................................................................................................................................. 63

VIII

LIST OF FIGURES

Figure 2.1 FDMA............................................................................................................................ 3

Figure 2.2 A combination of FDMA and TDMA ........................................................................... 3

Figure 2.3 CDMA ........................................................................................................................... 4

Figure 2.4 Sectored cells ................................................................................................................. 6

Figure 2.5 Cell Planning Process .................................................................................................... 8

Figure 2.6 Two Ray Model ........................................................................................................... 12

Figure 2.7 Overhead View of the Ten-Ray Model ....................................................................... 14

Figure 2.8 Knife-Edge Diffraction ................................................................................................ 15

Figure 2.9 Scattering ..................................................................................................................... 16

Figure 2.10 Minimum Re-use Distance ........................................................................................ 22

Figure 2.11 Cell Breathing ............................................................................................................ 23

Figure 2.12 ICNIRP Reference Levels for 400MHz to 300GHz .................................................. 24

Figure 2.13 Occupational and Public Exposure ............................................................................ 25

Figure 2.14 3/9 Cell Repeat Pattern .............................................................................................. 29

Figure 2.15 4/12 Cell Repeat Pattern ............................................................................................ 30

Figure 2.16 Strict FFR (left) and SFR (right) Geometry with N=3 Cell-edge Reuse Factors ...... 43

Figure 3.1 3/9 Cell Repeat Pattern ................................................................................................ 44

Figure 3.2 Histogram of the Channel Distribution ....................................................................... 45

Figure 3.3 Digital Terrain Map (DTM) view................................................................................ 50

Figure 3.4 Images of the Focus Zone ............................................................................................ 50

Figure 3. 5 Clutter Classes View .................................................................................................. 51

Figure 3.6 K80010305_900_02V Horizontal Pattern ................................................................... 52

Figure 3.7 K80010305_900_02V Vertical Pattern ....................................................................... 52

Figure 3.8 K80010305_900_06V Vertical Pattern ....................................................................... 52

Figure 3.9 K80010305_900_06V Horizontal Pattern ................................................................... 52

Figure 4.1 Coverage by Signal Level ........................................................................................... 55

Figure 4.2 Coverage by Signal Level Properties .......................................................................... 55

Figure 4.3 Histogram based on Best Signal Level of Covered Areas .......................................... 56

Figure 4.4 Overlapping Zones ...................................................................................................... 57

Figure 4.5 Overlapping Zones Properties ..................................................................................... 57

Figure 4.6 Coverage by C/I Level ................................................................................................. 58

Figure 4.7 Coverage by C/I Level properties ................................................................................ 58

Figure 4.8 Histogram based on C/I Level of Covered Areas ........................................................ 59

Figure 4.10 Coverage by Transmitter ........................................................................................... 60

IX

LIST OF TABLES

Table 2.1 GSM Frequency Spectrum............................................................................................ 26

Table 2.2 FDD Frequency Bands [5] ............................................................................................ 33

Table 2.3 UMTS Absolute Radio Frequency Channel Number [5] ............................................. 34

Table 2.4 Duplex Distance [6] ...................................................................................................... 34

Table 2.5 UTRA/TDD Frequency Bands [6] ................................................................................ 34

Table 2.6 UTRA/TDD ARFCNs [6] ............................................................................................. 34

Table 2.7 UMTS-TDD [6] ............................................................................................................ 34

Table 2.8 LTE (FDD) Frequency Spectrum [3]............................................................................ 40

Table 2.9 LTE (TDD) Frequency Spectrum [3] ........................................................................... 40

Table 3.1 Frequency Groups for Control Channels ...................................................................... 44

Table 3.2 Frequency Groups for Traffic Channels ....................................................................... 45

Table 3.3 Hopping and Non-hopping Channels ........................................................................... 49

Table 3.4 Non-symmetric links..................................................................................................... 49

Table 3.5 Antennas ....................................................................................................................... 51

Table 3.6 Antennas used in the various Sites ............................................................................... 54

Table 4.1 Signal Levels in Different Areas of the Focus Zone .................................................... 56

Appendix Table 1 Key ICT Indicators for Developed and Developing Countries and the World

(totals) ........................................................................................................................................... 63

X

ABBREVIATIONS

ARFCN – Absolute Radio Frequency Channel Number

BSC – Base Station Controller

BTS – Base transceiver station

CS - Circuit Switched

DL- Downlink

EIRP - Effective Isotropically Radiated Power

ERP - Effective Radiated Power

FEC - Forward Error Correction

GSM – Global System for Mobile Communication

LoS – Line of Sight

MS – Mobile Station

MSC – Mobile Switching Centre

UE – Universal Equipment

UL – Uplink

UMTS – Universal Mobile Telecommunication System

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CHAPTER ONE: INTRODUCTION

1.1 Background of Study

All over the world, the demand for wireless communication services continues to increase

rapidly. According to statistics provided by the International Telecommunication Union (ITU),

the number of mobile-cellular subscriptions in the world increased from 2.205 billion in the year

2005 to 6.915 billion subscriptions in the year 2014. The number of active mobile-broadband

subscriptions has increased from 0.268 billion in the year 2007 to 2.315 billion subscriptions in

2014. The number of mobile-cellular subscriptions worldwide is approaching the number of

people on earth with mobile-cellular penetration reaching 90%. Wireless transmission sites are

being deployed by wireless service providers in various countries to meet this high demand.

Existing wireless service providers have to expand their capacity to meet the high demand and

more wireless service providers are joining the telecommunications industry. With a limited

spectrum available for wireless communication, wireless service providers have to share the

available spectrum.

1.2 Problem Statement

The need of tools for system design optimization and radio network planning has been triggered

by the tremendous growth in the demand for wireless communication services, with many

network operators joining the market. Wireless communication network design involves several

inter-dependent factors such as system capacity, traffic demand, cell coverage, topography and

propagation characteristics. The selection of the number of cells, cell locations, power at base

station and other design parameters have to be determined in the context of one another. The cell

locations can be determined based on the number of cells, the coverage performance, traffic

distribution, and propagation environments. Design parameters at base transceiver stations (BTS)

and mobile stations (MS) cannot be specified until the cell allocation is completed. For instance,

the channel assignment, which can improve system performances in terms of system capacity

and interference avoidance can only be determined after the architecture of the wireless

communication network has been specified. Finally, cell planning is not a one-time task as the

design has to be continually updated based on the mobile network scenario and hence such

provision should be included in the design tool.

1.3 Objectives

The objectives of this project were:

To study and describe (the need for) cell planning in wireless communication networks.

To design and demonstrate cell planning for an example scenario.

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1.4 Scope of Work

This project covers cell planning in wireless communication networks and a nominal cell plan

design for a selected focus zone in a GSM (TDMA) network.

1.5 Organization of the Report

The project is organized into five chapters as follows: the introduction, literature review, design,

results, analysis and discussion then the conclusions and recommendations. After the chapters

there is the bibliography and finally the appendix.

The introduction chapter discusses the background of study, problem statement, objectives and

the scope of work.

The literature review section outlines the cell planning process in detail. Planning considerations

for GSM, UMTS and LTE networks are described.

The design chapter focuses on the nominal cell plan design.

The results are given in the fourth chapter together with their analysis.

The fifth chapter concludes the findings of the entire project and recommends what should be

done for further works in line with that project.

References of the project are given under bibliography. The appendix has world

telecommunication statistics given by the International Telecommunications Union (ITU).

3

CHAPTER TWO: LITERATURE REVIEW

2.1 Multiple Access Techniques

2.1.1 Frequency Division Multiple Access (FDMA)

The frequency-division multiple access (FDMA) channel-access scheme is based on the frequency-

division multiplexing (FDM) scheme, which provides different frequency bands to different data-streams.

In the FDMA case, the data streams are allocated to different nodes or devices. An example of FDMA

systems were the first-generation (1G) cell-phone systems, where each phone call was assigned to a

specific uplink frequency channel, and another downlink frequency channel. Each message signal (each

phone call) is modulated on a specific carrier frequency.

Figure 2.1 FDMA [2]

2.1.2 Time Division Multiple Access (TDMA)

TDMA) channel access scheme is based on the time-division multiplexing (TDM) scheme, which

provides different time-slots to different data-streams (in the TDMA case to different transmitters) in a

cyclically repetitive frame structure. It allows several users to share the same frequency channel by

dividing the channel into different time slots. The users transmit in rapid succession, one after the other,

each using its own time slot. This allows multiple stations to share the same transmission medium (e.g.

radio frequency channel) while using only a part of its channel capacity. TDMA is used in the digital 2G

cellular systems such as Global System for Mobile Communications (GSM) and IS-136

Figure 2.2 A combination of FDMA and TDMA [2]

4

2.1.3 Code Division Multiple Access CDMA

CDMA is the dominant multiple access technique for 3G cellular systems. It is based on spread

spectrum and a special coding scheme (where each transmitter is assigned a code). In CDMA a

wider radio spectrum is used than the data rate of each of the transferred bit streams, and several

message signals are transferred simultaneously over the same carrier frequency, utilizing

different spreading codes. It is used in many mobile phone standards such as cdmaOne,

CDMA2000, and WCDMA (the 3G standard used by GSM carriers).

CDMA users share time and frequency slots but employ codes that allow the users to be separated by the

receiver.

2.1.4 Orthogonal Frequency Division Multiple Access (OFDMA)

OFDMA is based on the orthogonal frequency-division multiplexing (OFDM) digital modulation

scheme. Multiple access is achieved in OFDMA by assigning subsets of subcarriers to individual

users. This allows simultaneous low data rate transmission from several users.

2.1.5 Space Division Multiple Access (SDMA)

In Space Division Multiple Access (SDMA) different information is transmitted in different

physical areas. The sharing of channels is achieved by using physical separation methods.

Directional antennas are used to separate users sharing the same frequency. Examples include

simple cellular radio systems and more advanced cellular systems which use directional antennas

and power modulation to refine spacial transmission patterns.

Figure 2.3 CDMA [2]

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2.2 The Cellular Concept

Cellular network systems are used in providing both broadcast only (down-link) and 2-way (up-

link and downlink) communication. These systems must accommodate a large number of users

over a large geographic area with limited frequency spectrum, i.e., with a limited number of

channels. If a single transmitter/ receiver is used with only a single base transceiver station

(BTS), then sufficient amount of power may not be present at a huge distance from the BTS. A

high powered transmitter has to be used for a large geographic coverage area. High power radio

transmitters are harmful to the environment and therefore mobile communication calls for

replacing the high power transmitters with low power transmitters by dividing the coverage area

into small segments, called cells.

A cell is the area covered by a base transceiver station. It is the smallest building block of a

cellular system. Each cell has a low power transmitter with a coverage area equal to the area of

the cell. As signal propagation attenuates with distance (subject to clutter, fading and multi-path

effects) a distance can be defined beyond which repeater stations are used. Typically, to

minimize multi-coverage while providing 100% area coverage, a regular hexagonal grid is

frequently used as the best possible model for transmitter location. This technique of substituting

a single high powered transmitter with several low powered transmitters to support many users is

the backbone of the cellular concept.

2.2.1 Types of Cells

Based on size:

Macro-cells: Have a typical cell radius range from 1 to 35 km. Normally, the site location is

on a hilltop or a rooftop.

Micro-cells: Have a typical coverage range from 0.2 to 1 km. They can maintain indoor

coverage in the lower levels of buildings.

Pico-cells: Have a typical coverage range from 0.01 to 0.2km. They provide coverage in

indoor environment. Pico cells are used when the capacity need is extremely high in certain

hot spots.

Femto-cells: Have a typical coverage range of less than 10 meters. They provide coverage in

indoor environment. A femto-cell allows service providers to extend service coverage

indoors or at the cell edge, especially where access would otherwise be limited or

unavailable.

6

Cells can also be classified into omnidirectional cells and sectored cells.

Omnidirectional cells

An omni-directional cell (or omni-cell) is served by a BTS with an antenna which transmits

equally in all directions (360 degrees). Typically, omni-directional cells are used to gain

coverage, whereas sectored cells are used to gain capacity.

Sectored cells

Sectoring involves dividing an omnidirectional (360 degree) view of a cell site into non-

overlapping slices. It involves replacing an omni-directional antenna at the base transceiver

station by several directional antennas. Cell sectoring is done to overcome some limitations like

co-channel interference. Replacing a single omnidirectional antenna at a base transceiver station

with several directional antennas achieves capacity improvement by essentially rescaling the

system.

Figure 2.4 Sectored cells [1]

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2.3 What is Cell Planning?

The term cell planning refers to a collective series of processes designed to produce a

network plan that will meet a predefined set of cost and performance targets. Cell

planning can be described as all the activities involved in:

• Selecting the sites for the radio equipment

• Selecting the radio equipment

• Configuring the radio equipment

Every cellular network requires cell planning in order to provide adequate coverage,

capacity and call quality.

2.3.1 Objectives of Cell Planning

The objectives of cell planning are:

1. Provision of sufficient coverage (radio aspect):

An important requirement in cellular networks is the contiguous coverage of the service areas

without noticeable holes. Furthermore an adequate depth of outdoor and indoor coverage is

necessary to meet the operator’s marketing plans.

2. Provision of sufficient network capacity (traffic aspect):

The operator has to meet traffic demand at peak hours with a very low probability of call

blocking (congestion) and call dropping in order to avoid complaints from the subscribers.

3. Provision of good network quality (frequency aspect):

Since the number of frequencies a network operator can use is limited the frequencies must be

reused, for instance, in TDMA network systems. In order to receive a good quality radio network

planning is trying to separate the cells with equal frequencies as much as necessary.

4. Extendibility i.e. accommodation of network growth (forecast development):

This involves adapting to the future network development and expansion. It includes extension

of coverage to new areas for the case that an operator does not start with country-wide coverage

and expansion of the network capacity so that the quality of service is maintained at all times. A

provident planning is an important issue since network operators start with only a few

subscribers.

5. A cost effective network design:

Cost effectiveness means lowest possible cost over the life of the network while meeting the

quality targets.

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2.3.2 Cell Planning Process

Figure 2.5 Cell Planning Process [1]

2.3.2.1 Traffic and Coverage Analysis

Cell planning begins with traffic and coverage analysis. The analysis should produce information

about the geographical area and the expected capacity (traffic demand). The types of data

collected are:

Cost - Radio planning and economic planning are two separate functions that frequently

clash. However, they must be considered as two inputs with a common goal if a quality

network is to be built and to survive

Capacity

Coverage

Grade of Service (GoS) - which is the percentage of allowed congested calls and defines the

quality of service (QoS). The QoS will vary from service to service and need not be constant

across the entire network.

Start: Traffic and Coverage Analysis

Nominal Cell Plan

Surveys

System Design

System Implementat

ion

System Tuning

Initial Planning System Growth

9

Available frequencies

Speech quality

System growth capability

The basis for all cell planning is the traffic demand, i.e. how many subscribers use the

network and how much traffic they generate. The Erlang (E) is a unit of measurement of

traffic intensity. It can be calculated with the following formula:

𝐴 = 𝑛×𝑇

3600 ………….. (2.1)

where,

A = offered traffic from one or more users in the system

n = number of calls per hour

T = average call time in seconds

The geographical distribution of traffic demand can be calculated by the use of

demographic data such as:

• Population distribution

• Car usage distribution

• Income level distribution

• Land usage data

• Telephone usage statistics

• Other factors, like subscription/call charge and price of MSs

2.3.2.2 Nominal Cell Plan

A nominal cell plan can be produced from the data compiled from traffic and coverage analysis.

The nominal cell plan is a graphical representation of the network and looks like a cell pattern on

a map. Nominal cell plans are the first cell plans and form the basis for further planning.

Successive planning must take into account the radio propagation properties of the actual

environment. Such planning needs measurement techniques and computer-aided analysis tools

for radio propagation studies.

Radio planning software tools such as Atoll (by Forsk) and TEst Mobile System (TEMS) Cell

Planner (by Ericsson) can be used and they include prediction packages which provide:

Coverage predictions, composite coverage synthesis, co-channel interference (CCI) predictions

and adjacent channel interference (ACI) predictions. The radio planning software tools are

designed to simplify the process of planning and optimizing a cellular network.

10

2.3.2.3 Surveys

Once a nominal cell plan has been completed and basic coverage and interference predictions are

available, site surveys and radio measurements can be performed.

Site Surveys

Site surveys are performed for all proposed site locations. The following must be checked for

each site:

• Exact location

• Space for equipment, including antennas

• Cable runs and power facilities

• Contract with site owner

In addition, the radio environment must be checked to ensure that there is no other radio

equipment on site that causes problems.

Radio Measurements

Radio measurements are performed to adjust the parameters used in the planning tool to

reality i.e. adjustments are made to meet the specific site climate and terrain

requirements. For instance, parameters used in a cold climate will differ from those used

in a tropical climate.

Drive tests are done using a test transmitter mounted on a vehicle, and signal strength is

measured while driving around the site area. The results from these measurements can then be

compared to the values the planning tool produces when simulating the same type of transmitter.

The planning parameters can then be adjusted to match the actual measurements.

2.3.2.4 System Design

The final cell plan is produced after adjustment of the planning parameters to match the

actual measurements. Dimensioning of the BSC, and MSC/VLR can also be adjusted.

This final cell plan can then be used for system installation.

New coverage and interference predictions are run at this stage, resulting in Cell Design

Data (CDD) documents containing cell parameters for each cell.

2.3.2.5 System Implementation and Tuning

System tuning is the continuous monitoring of the installed system to determine how well it

meets demand. It involves:

• Checking that the final cell plan was implemented successfully

• Evaluating customer complaints

• Checking that the network performance is acceptable

• Changing parameters and taking other radio measurements, if necessary

11

2.3.2.6 System Growth/Change

Cell planning is not a one-time activity, it is an ongoing process. If the network needs to

be expanded because of an increase in traffic or because of a change in the environment

(e.g. a new building), then the operator must perform the cell planning process again,

starting with a new traffic and coverage analysis.

2.3.3 Propagation Prediction and Modelling

Two general methods are used for providing area coverage planning:

Deterministic Modelling

This type of modelling attempts to determine propagation conditions by mathematical modelling

of the relevant physical mechanisms. One approach might be to use a free space modelling

approach and then account for all obstructions/clutter in terms of the reflection, scattering,

diffraction, etc., caused. This would require extensive data defining the radio paths and the

computational load of this approach is considerable. Deterministic modelling is more applicable

in coverage predictions for small areas such as microcells and pico-cells (indoor areas). Several

tools exist for this purpose. The radio signals are usually modelled as rays and are often referred

to as ray-tracing tools.

Empirical Modelling

This approach is based on statistical analysis of a large of number of measurements from which

averages for a variety of power levels, frequencies, antenna heights etc. are obtained. These

average results can then be modelled mathematically to produce empirical formulae allowing

path loss to be calculated. Empirical modelling is the preferred method of carrying out coverage

prediction in large areas.

2.3.3.1 Deterministic Path Loss Models

Free-Space Path Loss

Consider a signal transmitted through free space to a receiver located at distance d from the

transmitter. Assume there are no obstructions between the transmitter and receiver and the signal

propagates along a straight line between the two. The channel model associated with this

transmission is called a line-of-sight (LOS) channel, and the corresponding received signal is

called the LOS signal or ray. Free-space path loss introduces a complex scale factor, resulting in

the received signal [2]

𝑟(𝑡) = 𝑅𝑒 {𝜆√𝐺𝑙𝑒

−𝑗2𝜋𝑑𝜆

4𝜋𝑑𝑢(𝑡)𝑒𝑗2𝜋𝑓𝑐𝑡} ……………………………… (2.2)

where,

√𝐺𝑙 is the product of the transmitting and receiving antenna field radiation patterns in

the LOS direction.

The phase shift 𝑒−𝑗2𝜋𝑑

𝜆 is due to the distance, d, the wave travels.

12

The power in the transmitted signal s(t) is Pt, so the ratio of received to transmitted power is:

𝑃𝑟

𝑃𝑡= (

√𝐺𝑙𝜆

4𝜋𝑑)2

……………… (2.3)

Thus, the received signal power falls off inversely proportional to the square of the distance d

between the transmitting and receiving antennas. The received power can be expressed in dBm

as:

Pr dBm = Pt dBm + 10log10 (Gl) + 20 log 10 (λ) − 20 log 10 (4π) − 20 log 10 (d) …… (2.4)

Free-space path loss is defined as the path loss of the free-space model and is given by:

𝑃𝐿 𝑑𝐵 = 10𝑙𝑜𝑔10𝑃𝑡

𝑃𝑟= −10𝑙𝑜𝑔10 (

√𝐺𝑙𝜆

4𝜋𝑑)2

………… (2.5)

The free-space path gain is thus

𝑃𝐺 = −𝑃𝐿 = 10𝑙𝑜𝑔10 (√𝐺𝑙𝜆

4𝜋𝑑)2

………….. (2.6)

Ray Tracing

Ray tracing techniques approximate the propagation of electromagnetic waves by representing

the wavefronts as simple particles. Thus, the reflection, diffraction, and scattering effects on the

wavefront are approximated using simple geometric equations instead of Maxwell’s more

complex wave equations. The error of the ray tracing approximation is smallest when the

receiver is many wavelengths from the nearest ‘scatterer’, and all the ‘scatterers’ are large

relative to a wavelength and fairly smooth. [2]

Two-Ray Model

The two-ray model is used when a single ground reflection dominates the multipath effect, as

illustrated in Figure 2.5. The received signal consists of two components: the LOS component or

ray, which is just the transmitted signal propagating through free space, and a reflected

component or ray, which is the transmitted signal reflected off the ground.

Figure 2.6 Two Ray Model [2]

13

The received LOS ray is given by the free-space propagation loss formula,

𝑟(𝑡) = 𝑅𝑒 {𝜆√𝐺𝑙𝑒

−𝑗2𝜋𝑑𝜆

4𝜋𝑑𝑢(𝑡)𝑒𝑗2𝜋𝑓𝑐𝑡} ………… (2.7)

The reflected ray is shown in Figure 2.6 by the segments x and x’. If we ignore the effect of

surface wave attenuation then, by superposition, the received signal for the two-ray model is:

𝑟2𝑟𝑎𝑦(𝑡) = 𝑅𝑒 {𝜆

4𝜋[√𝐺𝑙 𝑢(𝑡)𝑒

−𝑗2𝜋𝑙𝜆

𝑙+𝑅√𝐺𝑟 𝑢(𝑡−𝜏)𝑒

−𝑗2𝜋(𝑥+𝑥′)

𝜆

𝑥+𝑥′] 𝑒𝑗2𝜋𝑓𝑐𝑡} …………… (2.8)

Where,

𝜏 =𝑥+𝑥′− 𝑙

𝑐 is the time delay of the ground reflection relative to the LOS ray,

√𝐺𝑙 = √𝐺𝑎𝐺𝑏 is the product of the transmit and receive antenna field radiation patterns in

the LOS direction, R is the ground reflection coefficient, and

√𝐺𝑙 = √𝐺𝑐𝐺𝑑 is the product of the transmitting and receiving antenna field radiation

patterns corresponding to the rays of length x and x’, respectively.

The delay spread of the two-ray model equals the delay between the LOS ray and the reflected

ray = 𝑥+𝑥′− 𝑙

𝑐. If the transmitted signal is narrowband relative to the delay spread (τ << Bu

−1)

then u(t) ≈ u(t − τ) . With this approximation, the received power of the two-ray model for

narrowband transmission is:

𝑃𝑟 = 𝑃𝑡 {[𝜆

4𝜋]2

|√𝐺𝑙

𝑙+𝑅√𝐺𝑟 𝑒

−𝐽Δ𝜑

𝑥+𝑥′|2

} …………. (2.9)

where, 𝛥𝜑 =2𝜋(𝑥 + 𝑥’ – 𝑙)

𝜆 is the phase difference between the two received signal components.

If d denotes the horizontal separation of the antennas, ℎ𝑡 denotes the transmitter height and hr

denotes the receiver height, then using geometry we can show that:

𝑥 + 𝑥’ – 𝑙 = √(ℎ𝑡 + ℎ𝑟)2 + 𝑑2 − √(ℎ𝑡 − ℎ𝑟)2 + 𝑑2 ......... (2.10)

When d is very large compared to ht + hr we can use a Taylor series approximation to get:

𝛥𝜑 =2𝜋(𝑥 + 𝑥’ – 𝑙)

𝜆≈

4𝜋ℎ𝑡ℎ𝑟

𝜆𝑑 ……………….. (2.11)

The ground reflection coefficient is given by:

𝑅 = sin 𝜃− 𝑍

sin 𝜃 +𝑍 ……………….. (2.12)

Where;

𝑍 = {

√𝜖𝑟 − 𝑐𝑜𝑠2 𝜃

𝜖𝑟 for vertical polarization

√𝜖𝑟 − 𝑐𝑜𝑠2 𝜃 for horizontal polarization

14

and 𝜖𝑟 is the dielectric constant of the ground. For earth or road surfaces this

dielectric constant is approximately that of a pure dielectric (for which 𝜖𝑟 is real with a value of

about 15).

For asymptotically large d, x + x’ ≈ l ≈ d, θ ≈ 0, Gl ≈ Gr, and R ≈ −1. Substituting these

approximations into the above equation for the received power of the two-ray model for

narrowband transmission yields that, in this asymptotic limit, the received signal power is

approximately:

𝑃𝑟 = 𝑃𝑡 {[𝜆√𝐺𝑙

4𝜋𝑑]2

[4𝜋ℎ𝑡ℎ𝑟

𝜆𝑑]2} = 𝑃𝑡 [

√𝐺𝑙 ℎ𝑡ℎ𝑟

d2]2

……………. (2.13)

or, in dB, we have

𝑃𝑟 dBm = 𝑃𝑡 dBm + 10log10(𝐺𝑙) + 20log10(ℎ𝑡ℎ𝑟) − 40 log10(d) …… (2.14)

Ten-Ray Model (Dielectric Canyon)

This model assumes rectilinear streets with buildings along both sides of the street and

transmitter and receiver antenna heights that are close to street level. The building-lined streets

act as a dielectric canyon to the propagating signal. Theoretically, an infinite number of rays can

be reflected off the building fronts to arrive at the receiver; in addition, rays may also be back-

reflected from buildings behind the transmitter or receiver. However, since some of the signal

energy is dissipated with each reflection, signal paths corresponding to more than three

reflections can generally be ignored. When the street layout is relatively straight, back reflections

are usually negligible also. Experimental data show that a model of ten reflection rays closely

approximates signal propagation through the dielectric canyon. The ten rays incorporate all paths

with one, two, or three reflections: specifically, there is the LOS, the ground-reflected (GR), the

single-wall (SW) reflected, the double-wall (DW) reflected, the triple-wall (TW) reflected, the

wall-ground (WG) reflected and the ground-wall (GW) reflected paths. There are two of each

type of wall-reflected path, one for each side of the street. An overhead view of the ten-ray

model is shown in Figure 2.7:

Figure 2.7 Overhead View of the Ten-Ray Model [2]

For the ten-ray model, the received signal is given by:

𝑟10𝑟𝑎𝑦(𝑡) = 𝑅𝑒 {𝜆

4𝜋[√𝐺𝑙 𝑢(𝑡)𝑒

−𝑗2𝜋𝑙𝜆

𝑙+∑

𝑅𝑖√𝐺𝑥𝑖 𝑢(𝑡−𝜏𝑖)𝑒−𝑗2𝜋𝑥𝑖)

𝜆

𝑥𝑖

9𝑖=1 ] 𝑒𝑗2𝜋𝑓𝑐𝑡}…………… (2.15)

15

where xi denotes the path length of the ith reflected ray, 𝜏𝑖= (xi − l)/c and 𝐺𝑥𝑖 is the product of the

transmitting and receiving antenna gains corresponding to the ith ray.

General Ray Tracing

General Ray Tracing (GRT) can be used to predict field strength and delay spread for any

building configuration and antenna placement. For this model, the building database (height,

location, and dielectric properties) and the transmitter and receiver locations relative to the

buildings must be specified exactly. Since this information is site-specific, the GRT model is not

used to obtain general theories about system performance and layout; rather, it explains the basic

mechanism of urban propagation, and can be used to obtain delay and signal strength

information for a particular transmitter and receiver configuration in a given environment. It uses

geometrical optics to trace the propagation of the LoS and reflected signal components, as well

as signal components from building diffraction and diffuse scattering.

Diffraction occurs when the transmitted signal “bends around” an object in its path to the

receiver. Diffraction is most commonly modeled by the Fresnel knife edge diffraction model

due to its simplicity.

Figure 2.8 Knife-Edge Diffraction [3]

The geometry of this model is shown in the Figure 2.8, where the diffracting object is assumed to

be asymptotically thin, which is not generally the case for hills, rough terrain, or wedge

diffractors. The geometry of the above figure indicates that the diffracted signal travels distance

d + d’ resulting in a phase shift of 𝜑 =2𝜋(𝑑 + 𝑑’)

𝜆. Thus for h small relative to d and d’, the signal

must travel an additional distance relative to the LOS path of approximately

Δ𝑑 =ℎ2

2+𝑑 + 𝑑’

𝑑𝑑’ ……….. (2.16)

and the corresponding phase shift relative to the LOS path is approximately

𝛥𝜑 =2𝜋Δ𝑑

𝜆=

𝜋

2𝑣2 ………….. (2.17)

where

𝑣 = ℎ√2(𝑑 + 𝑑’)

𝜆𝑑𝑑’ is the Fresnel-Kirchoff diffraction parameter.

Approximations for knife-edge diffraction path loss (in dB) relative to LOS path loss are given

by Lee as

16

𝐿(𝑣)dB =

{

20 log10[0.5 − 0.62𝑣] − 0.8 ≤ 𝑣 < 0

20 log10[0.5𝑒 − .95𝑣] 0 ≤ 𝑣 < 1

20 log10 [0.4 − √0.1184 − (0.38 − 0.1𝑣)2] 1 ≤ 𝑣 < 2.4

20 log10 [0.225

𝑣] 𝑣 > 2.4

….. (2.18)

The knife-edge diffraction model yields the following formula for the received diffracted signal:

𝑟(𝑡) = 𝑅𝑒 {𝐿(𝑣)√𝐺𝑑𝑢(𝑡 − 𝜏)𝑒−𝑗2𝜋(𝑑+𝑑′)

𝜆 𝑒𝑗2𝜋𝑓𝑐𝑡} ……. (2.19)

where,

√𝐺𝑑 is the antenna gain and

𝜏 =𝛥𝑑

𝑐 is the delay associated with the diffracted ray relative to the LOS path.

Figure 2.9 Scattering [3]

A scattered ray, shown in Figure 2.9 by the segments s’ and s, has a path loss proportional to the

product of s and s’. The received signal due to a scattered ray is given by the bistatic radar

equation:

𝑟(𝑡) = 𝑅𝑒 {𝑢(𝑡 − 𝜏)𝜆√𝐺𝑠𝜎𝑒

−𝑗2𝜋(𝑠+𝑠′)

𝜆

(4𝜋)32𝑠𝑠′

𝑒𝑗2𝜋𝑓𝑐𝑡} ………. (2.20)

where,

𝜏 =𝑠 + 𝑠’ − 𝑙

𝑐 is the delay associated with the scattered ray, σ (in m2) is the radar cross

section of the scattering object, which depends on the roughness, size, and shape of the scatterer,

and √𝐺𝑠 is the antenna gain.

The path loss associated with scattering is

Pr dBm = Pt dBm+10 log10 (Gs) + 20 log10 (λ) + 10 log10 (σ) − 30 log10 (4π) − 20 log10 s−20

log10(s’) …………………(2.21)

17

The received signal is determined from the superposition of all the components due to the

multiple rays. Thus, if we have a LOS ray, Nr reflected rays, Nd diffracted rays, and Ns diffusely

scattered rays, the total received signal is

𝑟𝑡𝑜𝑡𝑎𝑙(𝑡) = 𝑅𝑒 {[𝜆

4𝜋] [√𝐺𝑙 𝑢(𝑡)𝑒

𝑗2𝜋𝑙𝜆

𝑙+ ∑

𝑅𝑖√𝐺𝑥𝑖 𝑢(𝑡−𝜏𝑖)𝑒−𝑗2𝜋𝑥𝑖)

𝜆

𝑥𝑖

𝑁𝑟𝑖=1 +

∑ 𝐿𝑗(𝑣)√𝐺𝑑𝑗𝑢(𝑡 − 𝜏𝑗)𝑒−𝑗2𝜋(𝑑𝑗+𝑑𝑗′)

𝜆𝑁𝑑𝑗=1 + ∑

√𝐺𝑠𝑘𝜎𝑘 𝑢(𝑡−𝜏𝑘) 𝑒

𝑗2𝜋(𝑠𝑘+𝑠𝑘′)

𝜆

𝑠𝑘𝑠𝑘′

𝑁𝑠𝑘=1 ] 𝑒𝑗2𝜋𝑓𝑐𝑡}

…….…………. (2.22)

where,

𝜏𝑖, 𝜏𝑗 𝑎𝑛𝑑 𝜏𝑘 are, respectively, the time delays of the given reflected, diffracted, or scattered ray

normalized to the delay of the LoS ray, as defined above.

2.3.3.2 Empirical Path Loss Models

Most mobile communication systems operate in complex propagation environments that cannot

be accurately modeled by free-space path loss or ray tracing. A number of path loss models have

been developed over the years to predict path loss in typical wireless environments such as large

urban macro-cells, urban micro-cells, and, more recently, inside buildings. These models are

mainly based on empirical measurements over a given distance in a given frequency range and a

particular geographical area or building.

The Okumura Model

This is one of the most common models for signal prediction in large urban macro-cells. This

model is applicable over distances of 1-100 Km and frequency ranges of 150-1500 MHz.

Okumura used extensive measurements of base station-to-mobile signal attenuation throughout

Tokyo to develop a set of curves giving median attenuation relative to free space of signal

propagation in irregular terrain. The base station heights for these measurements were 30-100 m,

the upper end of which is higher than typical base stations today. The empirical path loss formula

of Okumura at distance d parameterized by the carrier frequency fc is given by

PL (d) dB = L (fc, d) + Amu (fc, d) – G (ℎ𝑡) – G (ℎ𝑟) – GAREA ……………….. (2.23)

where,

L (fc,d) is free space path loss at distance d and carrier frequency fc

Amu (fc,d) is the median attenuation in addition to free space path loss across all

environments.

G (𝒉𝒕) is the base transceiver station antenna height gain factor

G (𝒉𝒓) is the mobile antenna height gain factor, and

GAREA is the gain due to the type of environment.

18

The values of Amu (fc, d) and GAREA are obtained from Okumura’s empirical plots. Okumura

derived empirical formulas for G (ht) and G (hr) as:

𝑮 (ℎ𝑡) = 20𝑙𝑜𝑔10 (ℎ𝑡

200) , 30𝑚 < ℎ𝑡 < 1000𝑚

𝑮(ℎ𝑟) = {10 log10 (

ℎ𝑟

3) , ℎ𝑟 ≤ 3𝑚

20 log10 (ℎ𝑟

3) , 3𝑚 < ℎ𝑟 < 10m

………. (2.24)

Correction factors related to terrain are also developed to improve the model accuracy.

Okumura’s mode has a 10 -14 dB empirical standard deviation between the path loss predicted

by the model and the path loss associated with one of the measurements used to develop the

model. [2]

Hata Model

The Hata model is an empirical formulation of the graphical path loss data provided by Okumura

and is valid over roughly the same range of frequencies, 150-1500 MHz. This empirical model

simplifies calculation of path loss since it is a closed-form formula and is not based on empirical

curves for the different parameters. The standard formula for empirical path loss in urban areas

under the Hata model is:

𝑃𝐿,𝑢𝑟𝑏𝑎𝑛(𝑑) dB = 69.55 + 26.16 log10(𝑓𝐶) − 13.82 log10(ℎ𝑡) − 𝑎(ℎ𝑟) + (44.9 −

6.55 log10(ℎ𝑡))log10(𝑑) …………………… (2.25)

The parameters in this model are the same as under the Okumura model, and a (ℎ𝑟) is a

correction factor for the mobile antenna height based on the size of the coverage area. For small

to medium sized cities, this factor is given by:

𝑎(ℎ𝑟) = (1.1 log10(𝑓𝐶) − 0.7)ℎ𝑟 − (1.56 log10(𝑓𝑐) − 0.8)dB …………….. (2.26)

and for larger cities at frequencies fc > 300 MHz by

𝑎(ℎ𝑟) = 3.2(log10(11.75ℎ𝑟))2 − 4.97 dB ……………….. (2.27)

Corrections to the urban model are made for suburban and rural propagation, so that these

models are, respectively:

𝑃𝐿 ,𝑠𝑢𝑏𝑢𝑟𝑏𝑎𝑛 (𝑑) = 𝑃𝐿 , 𝑢𝑟𝑏𝑎𝑛(𝑑) − 2 [log10 (𝑓𝐶

28)]2

− 5.4 ……….... (2.29)

and

𝑃𝐿, 𝑟𝑢𝑟𝑎𝑙(𝑑) = 𝑃𝐿 , 𝑢𝑟𝑏𝑎𝑛(𝑑) − 4.78[𝑙𝑜𝑔10(𝑓𝑐)]2 + 18.33log10(𝑓𝑐) − 𝐾 …….. (2.30)

where K ranges from 35.94 (countryside) to 40.94 (desert).

The Hata model does not provide for any path specific correction factors, as is available in the

Okumura model. The Hata model well-approximates the Okumura model for distances d > 1

Km. Thus, it is a good model for first generation cellular systems, but does not model

propagation well in current cellular systems with smaller cell sizes and higher frequencies.

Indoor environments are also not captured with the Hata model. [2]

19

COST 231 Extension to Hata Model (COST 231 Hata Model)

The Hata model was extended by the European cooperative for scientific and technical research

(EURO-COST) to between 1500MHz and 2000MHz as follows:

𝑃𝐿𝑢𝑟𝑏𝑎𝑛(𝑑)dB = 46.3 + 33.9 log10(𝑓𝑐) − 13.82 log10(ℎ𝑡) − 𝑎(ℎ𝑟)(44.9 − 6.55 log10(ℎ𝑡))log10(𝑑)

+ 𝐶𝑀………………………………… . (2.31)

where;

a (ℎ𝑟) is the correction factor for the mobile antenna height based on the size of the coverage

area, and

CM is 0 dB for medium sized cities and suburbs, and 3 dB for metropolitan areas.

This model is restricted to the following range of parameters: 1.5GHz < fc < 2 GHz, 30m < ht <

200 m, 1m < hr < 10 m and 1Km < d < 20 Km.

COST 231 Walfish-Ikegami Model

This model is designed for modelling cells up to about 5km in urban areas and at frequencies of

900MHz, 1800MHz and 1900MHz. COST-231 Walfisch-Ikegami model is an extension of

COST Hata model. It requires more extensive clutter data than the Hata models and it can be

used for frequencies above 2000 MHz. When there is Line of Site (LOS) between the transmitter

and receiver the path loss is given by the following formula:

𝑃𝐿 dB = 42.4 + 26 log10(𝑑) + 20 log10(𝑓) …….…….. (2.32)

While in Non-Line of Sight (NLOS) conditions, path loss is given as:

𝑃𝐿 dB = L0 + L𝑅𝑇𝑆 + L𝑀𝑆𝐷 ………………………..….. (2.33)

where L0 is the attenuation in free-space and is described as:

𝐿0 dB = 32.45 + 20 log10(𝑑) + 20 log10(𝑓) ………….. (2.34)

LRTS represents diffraction from rooftop to street, and is defined as:

𝐿𝑅𝑇𝑆 dB = −16.9 − 10 log10(𝑤) + 10 log10(𝑓) + 20 log10(ℎ𝑏 − ℎ𝑟) + 𝐿𝑂𝑅𝐼 ……….. (2.35)

Here LORI is a function of the orientation of the antenna relative to the street a (in degrees) and is

defined as:

𝐿𝑅𝑇𝑆 dB = {

−10 + 0.354𝑎 𝑓𝑜𝑟 0 < 𝑎 < 352.5 + 0.075(𝑎 − 35) 𝑓𝑜𝑟 35 < 𝑎 < 554 − 0.114 (𝑎 − 55) 𝑓𝑜𝑟 55 < 𝑎 < 90

………… (2.36)

LMSD represents diffraction loss due to multiple obstacles and is specified as:

𝐿𝑀𝑆𝐷 dB = 𝐿𝐵𝑆𝐻 + 𝑘𝐴 + 𝑘𝐷 log10(𝑑) + 𝑘𝐹 log10(𝑓) − 9 log10(𝑠𝑏) ………………….. (2.37)

where,

20

𝐿𝐵𝑆𝐻 dB = {−18 log10(1 + ℎ𝑡 − ℎ𝑏) 𝑓𝑜𝑟 ℎ𝑡 < ℎ𝑏

54 + 0.8(ℎ𝑡 − ℎ𝑏) 2𝑑 𝑓𝑜𝑟 ℎ𝑡 ≤ ℎ𝑏 𝑎𝑛𝑑 𝑑 > 0.5 𝑘𝑚………. (2.38)

𝑘𝐴 = {54 𝑓𝑜𝑟 ℎ𝑡 < ℎ𝑏

54 + 0.8(ℎ𝑡 − ℎ𝑏) 𝑓𝑜𝑟 ℎ𝑡 ≤ ℎ𝑏 𝑎𝑛𝑑 𝑑 > 0.5 𝑘𝑚……… (2.39)

𝑘𝐷 = {18 + 15 (

ℎ𝑡− ℎ𝑏

ℎ𝑏) 𝑓𝑜𝑟 ℎ𝑡 < ℎ𝑏

18 𝑓𝑜𝑟 ℎ𝑡 ≤ ℎ𝑏 𝑎𝑛𝑑 𝑑 > 0.5 𝑘𝑚…………………. (2.40)

𝑘𝐹 = {− 4 + k (𝑓

924)

Ericsson 9999 Model

This model is implemented by Ericsson as an extension of the Hata model. Hata model is used

for frequencies up to 1900 MHz. In this model, we can adjust the parameters according to

the given scenario. The path loss as evaluated by this model is described as:

𝑃𝐿 dB = a0 + a1 log10(𝑑) + a2 log10(ℎ𝑏) log10(𝑑) − 3.2 (log10(11.75))2 + g𝑓 …… (2.41)

where,

g𝑓 = 44.49 log10(𝑓) − 4.78 (log10(𝑓))2 …………… (2.42)

The values of a0, a1, a2 and a3 are constant but they can be changed according to the scenario

(environment). The defaults values given by the Ericsson model are a0 = 36.2, a1 = 30.2, a2 =

12.0 band a3 = 0.1. The parameter f represents the frequency.

2.3.3.3 Choice of Propagation Model

Planning macro cells

At 900MHz, the basic Okumura-Hata models is recommended

At 1800MHz and 1900MHz, the COST 231 Hata Model must be used

Planning micro cells

COST 231 Walfisch-Ikegami model is recommended.

Planning pico cells

Simple Power Law model can be used.

𝑃𝐿 𝑑𝐵 = 42.6 + 26 log10 𝑑 + 20 log10 𝑓 ……………………… (2.43)

20dB is added for each corner obstructing the LoS.

Tuning the Propagation Model

Almost all propagation modelling done for network planning is based on empirical models.

However, statistical models cannot produce results which fit every environment. In most cases

modelling will be based on a standard model such as the COST231 Hata Model, often with

additional features to incorporate as much information as possible. Empirical models are set up

only to copy a set of measurements taken in a limited variety of environmental conditions. In a

different environment, particularly a built environment, where building styles and materials

differ significantly, the parameters in the model will be inappropriate. Tuning is performed by

21

making direct comparisons between predicted signal levels and real measurements, typically

continuous wave (CW) measurements in a test site. The real measurements are then imported

into the planning tool and adjustments made to the parameter values of the chosen propagation

model in order to minimize errors in predictions.

2.3.3.4 Continuous Wave (CW) Testing Process

A temporary antenna in the area of interest is energized using a continuous wave (CW) signal

generated from a test transmitter. CW testing can be used to generate data for model calibration

purposes or to validate planning levels in difficult areas. For identification purposes, the test

transmitter can be arranged to provide a dummy Broadcast Control Channel (BCCH)

transmission instead of CW, if required, depending on the equipment capability.

2.3.4 Monte Carlo Simulations

Monte Carlo Simulations are used for prediction in UMTS and LTE networks. The Monte Carlo

Simulation is a general term for a mathematical approach to solving problems having a large

number of random characteristics. It can be used to model cellular network behavior. To simulate

network operation it is necessary to account for the effects of interference between users in both

the uplink and downlink directions. It is also necessary to model the effects of power control,

channel adaptation and mixed traffic. To achieve this, Monte Carlo simulation creates a series of

snapshots. For each of these snapshots users are randomly scattered over the ground area with

weightings for expected traffic density. The tool then uses defined radio parameters to estimate

transmitted power, cell load, interference, channel adaptation and, ultimately, connection success

rate. A number of snapshots are then combined to produce a statistical analysis of the probability

of coverage for various service types

2.3.5 Channel Re-use

Channel re-use is a key element of cellular system design. It determines how much interference

is experienced by different users, and therefore the system capacity and performance. Reuse

distance is the distance between the centers of cells that use the same channels.

Consider a cellular system with S duplex channels available for use and let N be the number of

cells in a cluster. If each cell is allotted K duplex channels with all being allocated unique and

disjoint channel groups we have:

S = KN, under normal circumstances.

Now, if the cluster is repeated M times within the whole area, the total number of duplex

channels, or, the total number of users in the system would be

𝑇 = 𝑀𝑆 = 𝐾𝑀𝑁

Clearly, if K and N remain constant, then

𝑇 ∝ 𝑀

If T and K remain constant, then

𝑁 ∝1

𝑀

22

Hence the capacity achieved is directly proportional to the number of times a cluster is repeated.

For a fixed cell size, small N decreases the size of the cluster which in turn results in an increase

in the number of clusters and hence the capacity. However for small N, co-channel cells are

located much closer and hence more interference. The value of N is determined by calculating

the amount of interference that can be tolerated for sufficient quality communication. Hence the

smallest N having interference below the tolerated limit is used. However, the cluster size N

cannot take on any value and is given only by the following equation:

𝑁 = 𝑖2 + 𝑖𝑗 + 𝑗2 i ≥ 0 , j ≥ 0

where, i and j are integer numbers.

Consider the cell diagram in Figure 2.9 where R is the hexagonal cell radius. Denote the location

of each cell by the pair (i,j). If channel Cn is used in the center cell and again in the shaded cell

then there would be exactly two cells between co-channel cells and reuse distance would be easy

to find. However, when Cn is reused in the cell adjacent to the shaded cell, there is not an integer

number of cells separating the co-channel cells. For hexagonal cells, it can be shown that the

distance between two adjacent cell centers = √3𝑅 where R is the radius of any cell. The

normalized co-channel cell distance Dn can be calculated by traveling 'i' cells along the u axis

and then traveling 'j' cells along the v axis.

Using law of vector addition,

𝐷𝑛2 = 𝑗2 𝑐𝑜𝑠2(300) + (𝑖 + 𝑗 𝑠𝑖𝑛(300))2 …………………….. (2.44)

which turns out to be

𝐷𝑛 = √𝑖2 + 𝑖𝑗 + 𝑗2 = √𝑁

Multiplying the actual distance √3𝑅 between two adjacent cells with it, we get

𝐷 = 𝐷𝑛√3𝑅 = √3𝑁𝑅 = √3𝑅√𝑖2 + 𝑖𝑗 + 𝑗2 …………………….. (2.45)

Figure 2.10 Minimum Re-use Distance [8]

23

2.3.6 System (Cell) Balance

An unbalanced system can result from either the DL range exceeding the UL range (UL limited)

or vice versa (DL limited). The ideal aim is to have a balanced system where the DL and UL

range are substantially equal in order to avoid the possibility of dropped calls or failed call setups

at the edge of an unbalanced cell.

The use of Low Noise Amplifiers (LNA) at the masthead is commonplace in GSM 1800/1900

installations and helps to ensure a balanced cell where uplink range is matched to downlink. In

most cellular systems, the UL tends to be weaker than the DL. This can be established by

calculating the uplink and downlink power budgets and then choosing an LNA whose

performance is just adequate to correct the difference.

Figure 2.11 Cell Breathing [1]

The best site for the LNA is as close to the antenna feed point as possible. The LNA will require

power for its operation and will also have internal switching to shunt downlink power around the

amplifier to the common antenna. The additional downlink loss may need adding to the

downlink losses overall and could reduce the range slightly. The LNA will also, in the case of

CDMA, bring capacity benefits because it will lower the noise level at the input to the Node B,

which is equivalent to lowering the overall interference level.

24

2.3.7 RF Emission Limits and Safety

The level of RF emission from a site is governed by two factors: license conditions and safety

considerations. The operator’s license will limit the EIRP per RF channel, e.g. 53 dBm. In some

countries, the operator may also be legally obliged to demonstrate that emissions from the site

comply with guidelines for limiting human exposure to the time-varying Electromagnetic Fields

(EMF) emitted from the antennas.

Effective Isotropically Radiated Power (EIRP)

It is the power launched from the antenna, corrected to the value that would have to be fed to the

theoretical isotropic reference antenna to give the same power. It is found by taking the

transmitter’s output power and processing this value through all gains and losses of the system

up to the point when it is launched from the antenna.

Effective Radiated Power (ERP) is found by using antenna gain referenced to a dipole (dBd) and

is 2.2 dB less than EIRP.

EIRP = PT – LC + GA

where PT – transmitter power in dBm

LC - cable losses in dB

GA – antenna gain in dBi

ICNIRP Guidelines

At the frequencies used by cellular systems, the guidelines define basic restrictions on exposure,

based on Specific Absorption Rate (SAR) in Watts per kilogram (Wkg-1) of body tissue. These

can be equated to reference levels, for the purpose of compliance testing, in terms of E-field

strength in volts per metre (Vm-1), H-field strength in Amperes per metre (Am-1), magnetic flux

density (μT) and plane wave power density (s) in Watts per square metre (Wm-2). If

measurement indicates that levels are below the reference level, then the basic restrictions are

being met. If measured levels exceed the reference level, it does not automatically follow that the

basic restrictions are being exceeded, and further investigation is necessary.

Occupational Exposure General Public Exposure

400 – 2000 MHz 𝐸 = 3𝑓

12 Vm−1

𝑆 =𝑓

40Wm−2

𝐸 = 1.375𝑓1

2 Vm−1

𝑆 =𝑓

200Wm−2

2000 – 300 MHz 𝐸 = 137 Vm−1

𝑆 = 50 Wm−2

𝐸 = 61 Vm−1

𝑆 = 10 Wm−2

Figure 2.12 ICNIRP Reference Levels for 400MHz to 300GHz [4]

f measured in MHz

averaged over any six minute period

unperturbed rms values

25

P–GSM + E–GSM 900

GSM (DCS) 1800 UMTS FDD

Uplink Downlink Uplink Downlink Uplink Downlink

f MHz 880 915 925 960 1710 1785 1805 1880 1920 1980 2110 2170

Occupational

Exposure 𝐸 Vm−1 89 90.8 91.2 93 124.1 126.7 127.5 130.1 131.5 133.5 137 137

𝑆 Wm−2 22 22.9 23.1 24 42.8 44.6 45.1 47 48 49.5 50 50

Public

Exposure 𝐸 Vm−1 40.8 41.6 41.8 42.6 56.9 58.1 58.4 59.6 60.3 61.2 61 61

𝑆 Wm−2 4.4 4.6 4.6 4.8 8.6 8.9 9 9.4 9.6 9.9 10 10

Figure 2.13 Occupational and Public Exposure

Compliance with Reference Levels

Compliance can be verified by calculation at the planning stage. Established sites can be verified

through direct measurement of the E field or power density using calibrated equipment. For a

single TRX, and assuming the worst case of continuous radiation, then from the EIRP it is

possible to calculate E field strengths and power densities along the bearing of strongest

radiation at a distance d from:

𝑆 =𝐸𝐼𝑅𝑃

4𝜋𝑑2 Wm−2 …………………….. (2.46)

𝐸 = √120𝜋S Vm−1 …………………….. (2.47)

26

2.4 Planning Considerations for GSM (TDMA) Networks

2.4.1 Link Budget

A power budget, which takes account of each element on the radio link, is required to determine

the transmission power required to produce a minimum required receive level at some distant

point. The elements include: path loss, shadow fade margin, minimum required SNR, body loss,

allowances for building and/or vehicle penetration loss, the Noise Figure (NF) of the receiver

and the basic noise floor in the communication channel. The noise floor in a 200 kHz channel is -

121dBm and the assumed NF for a GSM 900 Class 4 MS is 10dB. The minimum SNR is quoted

as 8 dB for a basic GSM link. This suggests that signals should have a minimum level of (-121 +

10 + 8) = - 103dBm comparing closely with the referenced sensitivity of -102dBm for a GSM

900 Class 4 MS.

2.4.2 GSM Frequency Spectrum

System Band Uplink (MHz) Downlink

(MHz)

Channel Number Equivalent

UMTS/LTE

Band

T-GSM-380 380 380.2–389.8 390.2–399.8 dynamic

T-GSM-410 410 410.2–419.8 420.2–429.8 dynamic

GSM-450 450 450.6–457.6 460.6–467.6 259–293 31

GSM-480 480 479.0–486.0 489.0–496.0 306–340

GSM-710 710 698.2–716.2 728.2–746.2 dynamic 12

GSM-750 750 777.2–792.2 747.2–762.2 438–511

T-GSM-810 810 806.2–821.2 851.2–866.2 dynamic 27

GSM-850 850 824.2–849.2 869.2–893.8 128–251 5

P-GSM-900 900 890.0–915.0 935.0–960.0 1–124

E-GSM-900 900 880.0–915.0 925.0–960.0 975–1023, 0-124 8

R-GSM-900 900 876.0–915.0 921.0–960.0 955–1023, 0-124

T-GSM-900 900 870.4–876.0 915.4–921.0 dynamic

DCS-1800 1800 1,710.2–1,784.8 1,805.2–1,879.8 512–885 3

PCS-1900 1900 1,850.2–1,909.8 1,930.2–1,989.8 512–810 2

Table 2.1 GSM Frequency Spectrum

27

2.4.3 GSM Channels

2.4.3.1 GSM Physical Channels

The time domain over the air interface is divided into 217 frames (of duration 4.615ms) per

second. Each frame is divide into eight timeslots (of duration 0.577ms) numbered 0 to 7. A non-

hopping physical channel comprises a single Absolute Radio Frequency Channel Number

(ARFCN) and timeslot. The Mobile Station (MS) maintains the same timeslot on both uplink and

downlink. A frequency-hopping physical channel comprises a set of ARFCN. The MS maintains

the same timeslot number on both UL and DL, but changes ARFCN on a frame-by-frame basis

i.e. frequency hops 217 times.

The physical channel must support both user traffic and network signalling. This is achieved

using a system of 26, 51 and 52-frame multi-frames. The 52-frame multi-frame maybe used for

networks supporting GPRS.

2.4.3.2 GSM Logical Channels

Logical channels are defined functions which can be supported within a physical channel. One

physical channel can support a number of logical channels. A logical channel is implemented on

the air interface using a multiframe structure depending on the type of channel being

implemented. They include traffic channels and control channels.

Traffic Channels

Full Rate Traffic Channel (TCH/F)

Supports encoded/protected speech at a gross rate of 22.8 kbit/s or Forward Error Correction

(FEC) coded, Circuit Switched (CS) data at 14.4, 9.6, 4.8 or 2.4 kbit/s (TCH/F14.4/F9.6/F4.8 or

F2.4).

Half Rate Traffic Channel (TCH/H)

Supports second generation speech vocoders at a gross rate of 11.4kbit/s, or FEC coded data at

4.8 or 2.4kbit/s.

A full rate channel requires one physical channel whereas two half-rate channels can be

supported by a single physical channel.

Control Channels

i) Broadcast Control Channels (BCH)

There are three types:

a) Frequency Correction Channel (FCCH) – used for frequency control of the MS in respect

of the BTS

b) Synchronization Channel(SCH)) – used for frame synchronization of the MS

c) Broadcast Control Channel (BCCH) – used for general broadcast functions.

BCCH channel types are downlink (DL) only

28

ii) Common Control Channels (CCCH)

Includes:

a) Paging Channel (PCH) used in the downlink direction only to inform mobiles of

incoming calls

b) Random Access Channel (RACH) used in the uplink direction only by mobiles initiating

a call. In this case the mobile is requesting the allocation of a Stand-Alone Dedicated

Control Channel (SDCCH) for signaling purposes

c) Access Grant Channel (AGH) used for signal allocation of a SDCCH to the MS

d) Cell Broadcast Channel (CBCH) used for downlink only cell broadcast

e) Notification Channel (NCH)

iii) Dedicated Control Channels (DCCH)

a) Stand-Alone Dedicated Control Channel (SDCCH) – is a bidirectional channel used to

convey the signalling messages between the mobile and the network at Call Setup, and

for activities such as Location Updating, Supplementary Service Control and SMS

Traffic

There are two types:

SDCCH/4 – has four sub-channels

SDCCH/8 – has eight sub-channels

b) Associated Control Channels (ACCH)

These channels are always located with either a traffic channel or a SDCCH. They are

bidirectional and support the transfer of information such as signal measurements, power

adjustment commands and handover instructions

Slow Associated Control Channel (SACCH)

Is associated with either traffic channels or SDCCHs. It has a low data rate that is sufficient to

support, for instance, power control commands in the DL or signal level measurement of

adjacent cells in the UL

Fast Associated Control Channel (FACCH)

Is associated with either a full-rate or half-rate traffic channel. It facilitates the rapid transfer of

data, such as handover commands, by means of bit stealing technique. It is actually supported by

stealing bits from the traffic channel leading to a reduction in traffic quality.

29

2.4.4 Frequency Planning

Frequency planning is concerned with reusing radio frequencies as tightly as possible without

causing unacceptable interference.

2.4.4.1 Frequency Reuse Patterns

Common frequency reuse or cell repeat patterns used for GSM are 3/9, 4/12 and 7/21

3/9 Cell Repeat Pattern

Three sites each serving three cells are used to form a cluster of nine cells.

C/I in 3/9 Cell Repeat Pattern

In theory this pattern leads to a C/I of > 9 dB. Extra measure need to be taken to reduce the

impact of interference. Appropriate measures include frequency hopping and dynamic power

control.

C/A in 3/9 Cell Repeat Pattern

The geographically adjacent cells A1 and C3 use adjacent radio carriers. This implies a C/A of

0dB for MSs operating on the boundary of A1 and C3. Although this is better than the -9dB

figure quoted for GSM, it is a high level of interference and frequency hopping and dynamic

power control are used to minimize the interference.

Figure 2.14 3/9 Cell Repeat Pattern

30

4/12 Cell Repeat Pattern

Four sites each serving three cells are used to form a cluster of twelve cells.

C/I in 4/12 Cell Repeat Pattern

In theory this pattern leads to a C/I of > 12 dB. The use of frequency hopping and dynamic

power control, although beneficial, are not actually required.

7/21 Cell Repeat Pattern

Seven sites each serving three cells are used to form a cluster of twenty one cells.

2.4.4.2 Slow Frequency Hopping (SFH)

In SFH, channels retain their timeslot but hop in the frequency domain between designated

carriers on a burst-by-burst basis, i.e. at the rate of 217 hops per second. This technique is

employed to minimize the effects of (Rayleigh) fast fading and interference.

A number of parameters have to be set for a MS and BTS to communicate using a frequency

hopping channel. These include:

Timeslot Number (TN)

Mobile Allocation (MA), which lists the carrier frequencies over which hopping will

occur

Mobile Allocation Index Offset (MAIO), which defines the carrier frequency upon which

hopping must commence

TDMA Frequency Number (FN), which is the future FN on which hopping should

commence

Hopping Sequence Number (HSN), from which the hopping sequence will be derived.

HSN 0 defines cyclic hopping. HSN 1-63 define pseudo-random sequences

Figure 2.15 4/12 Cell Repeat Pattern [8]

31

Baseband Hopping

The baseband data for a subscriber using a hopping channel is directed through electronic

switching to a different transmitter with each burst. Thus the TRX tuning does not alter, but the

bursts being transmitted to that particular MS frequency hop.

Synthesizer Hopping

The baseband data for a subscriber using a hopping channel is directed to the same transmitter at

all times but the tuning of the TRX is changed on a burst-by-burst basis under the control of the

hopping algorithm. This requires very fast tuning and fast settling synthesizers. The advantage of

Synthesizer Hopping is that a TRX can hop over many frequencies being constrained only by the

frequency plan.

2.4.5 Base Station Identity Code (BSIC) Planning

Every GSM cell transmits a BSIC in the Synchronization Channel (SCH). The structure of the

BSIC results in 64 different identities, eight for each of the eight possible National Colour Codes

(NCC).

NCC – National Colour Code BCC – Base-station Colour Code

e.g. if NCC = 001 and BCC = 011 then BSIC = 00001011

32

2.5 Planning Considerations in UMTS Networks

2.5.1 Link Budget

The link budget in a CDMA system must account for interference levels. The interference level

for a cell can be calculated if its capacity is known. If traffic distribution and traffic types are

known, then cell capacity can be calculated for a given coverage. In order to calculate cell

coverage it is necessary to calculate a link budget.

Load Factor (Lj)

This is an indicator of how close a link is operating with respect to its theoretical maximum

capacity. Loading reduces coverage hence it is undesirable to plan a system for a very high load

factor. Ideally, the system should be dimensioned such that cells operate with a load factor

allowing a margin of safety

The load factor for an individual UE Lj is the ratio of wanted signal power, 𝑃𝑜 , against total

interference power, Itotal, for that UE.

L𝑗 = 𝑃𝑜

Itotal=

1

1+ 𝑊

(𝐸𝑏𝑁𝑜

)𝑅𝑗𝑣𝑗

……………….. (2.48)

𝜂𝑈𝐿 = (1 + 𝑖)∑Lj

𝑁

𝑗=1

= (1 + 𝑖)∑

{

1

1 + 𝑊

(𝐸𝑏𝑁𝑜)𝑅𝑗𝑣𝑗}

𝑁

𝑗=1

………… . (2.49)

Where;

𝜂𝑈𝐿 = UL load factor

i = neighbor cell interference factor

j = an individual UE

N = number of UEs in the cell

W = chip rate

𝐸𝑏 = energy per bit

𝑁𝑜 = noise spectral density

𝑅𝑗 = bit rate for UE

𝑣𝑗 = activity factor for UE

𝜂𝐷𝐿 = ∑1

1+ 𝑊

(𝐸𝑏𝑁𝑜

)𝑅𝑗𝑣𝑗

𝑁𝑗=1 ((1 − 𝛼𝑗) + 𝑖𝑗) ……………….. (2.50)

Where

𝜂𝐷𝐿 = DL load factor

𝑖𝑗 = neighbor cell interference factor

j = an individual UE

N = number of UEs in the cell

W = chip rate

33

𝐸𝑏 = energy per bit

𝑁𝑜 = noise spectral density

𝑅𝑗 = bit rate for 𝑈𝐸𝑗

𝑣𝑗 = activity factor for 𝑈𝐸𝑗

𝛼𝑗 = orthogonality factor

Noise Rise

This is a measure of the increase in noise caused by the interference level in the cell. This

interference includes both intra-cell and inter-cell sources. The noise rise can be calculated from

serving and neighbour cell operating load factors. Thus a higher load factor results in a higher

noise rise.

Noise Rise = 1

1 − 𝜂

Noise Rise in dB = −10 log10(1 − 𝜂) ……………. (2.51)

Interference Margin

This is used to account for predicted noise rise. As part of the planning process an assessment of

operating load factor will indicate a noise rise. The interference margin should be set such that

the link budget is valid for the required noise rise. However, in setting interference margin, hence

link budget, the cell size is determined. This in turn will affect the predicted load factor, leading

to a reassessment. Thus an iterative process is required to arrive at suitable parameters for system

planning and simulations.

2.5.2 UMTS Frequency Spectrum

The bands for 3rd Generation operation are:

• 806–960 MHz

• 1710–1885 MHz

• 2500–2690 MHz

UMTS Terrestrial Radio Access (UTRA)/FDD

UTRA/FDD is designed to operate in either of three paired bands as shown in the table below.

Each channel is identified by a UMTS Absolute Radio Frequency Channel Number (UARFCN).

The nominal channel band spacing is taken to be 5 MHz.

UTRA/FDD Frequency Bands

Operating Band UL Frequencies DL Frequencies

I 1920–1980 MHz 2110–2170 MHz

II 1850–1910 MHz 1930–1990 MHz

III 1710–1785 MHz 1805–1880 MHz

Table 2.2 FDD Frequency Bands [5]

34

UARFCNs

Operating Band Transmit-Receive Frequency Separation

I 190 MHz

II 80 MHz

III 95 MHz

Table 2.3 UMTS Absolute Radio Frequency Channel Number [5]

Duplex Distance

Operating Band UL Frequencies DL Frequencies

I 1920–1980 MHz 2110–2170 MHz

II 1850–1910 MHz 1930–1990 MHz

III 1710–1785 MHz 1805–1880 MHz

Table 2.4 Duplex Distance [6]

UMTS Terrestrial Radio Access (UTRA)/TDD

UTRA/TDD Frequency Bands

Region Frequency Bands

1 1900–1920 MHz, 2010–2020 MHz

2 1850–1910 MHz, 1930–1990 MHz, 1910–1930 MHz

Table 2.5 UTRA/TDD Frequency Bands [6]

UTRA/TDD ARFCNs

Region Frequency Range UARFCN

1 1900–1920 MHz, 2010–2025 MHz 9512 to 9588, 10062 to 10113

2 1850–1910 MHz, 1930–1990 MHz,

1910–1930 MHz

9262 to 9538, 9662 to 9938,

9562 to 9638

Table 2.6 UTRA/TDD ARFCNs [6]

UMTS-TDD Frequency Bands

Operating Band Frequency Band Frequency (MHz) UARFCN Channel Number

A (lower) IMT 1900 – 1920 9504 – 9596

A (upper) IMT 2010 – 2025 10054 – 10121

B (lower) PCS 1850 – 1910 9254 – 9546

B (upper) PCS 1930 – 1990 9654 – 9946

C PCS (Duplex-Gap) 1910 – 1930 9554 – 9646

D IMT-E 2570 – 2620 12854 – 13096

E 2300 – 2400 11504 – 11996

F 1880 - 1920 9404 – 9596

Table 2.7 UMTS-TDD [6]

35

2.5.3 UMTS Channels

2.5.3.1 Logical Channels

The logical channels used for the transfer of signalling information in FDD mode are:

Broadcast Control Channel (BCCH) is a downlink broadcast channel carrying system

information.

Paging Control Channel (PCCH) is a downlink channel carrying paging messages. It is used

when the network does not know the location cell of the UE, or the UE is using sleep mode

procedures.

Common Control Channel (CCCH) is a bidirectional channel carrying control information

between the network and the UE. It is used when the UE has no RRC connection with the

network.

Dedicated Control Channel (DCCH) is a point-to-point bidirectional channel carrying

dedicated control information between the network and the UE.

The logical channels used for the transfer of user information in FDD mode are:

Dedicated Traffic Channel (DTCH) is a dedicated point-to-point channel carrying user

information between the network and the UE. It may be used in both the uplink and downlink

directions.

Common Traffic Channel (CTCH)

2.5.3.2 Transport Channels

Information is transferred from the Medium Access Control (MAC) layer and mapped into the

physical channels via a set of transport channels. Transport channels are classified into common

channels and dedicated channels. Information in common channels will require in-band

identification of the UE. For dedicated channels the UE’s identity is associated with the channel

allocation.

The common transport channels for FDD mode are:

Random Access Channel (RACH) is a contention-based channel in the uplink direction and is

used for initial access or non-real-time dedicated control or traffic data.

Common Packet Channel (CPCH) is a contention-based channel used for the transmission of

bursty traffic data in a shared mode. Fast power control is used.

Forward Access Channel (FACH) is a common downlink channel without power control. It is

used for relatively small amounts of data.

Downlink Shared Channel (DSCH) is used in shared mode by several UEs to carry control or

traffic data.

Broadcast Channel (BCH) is a downlink broadcast channel used to carry system information

across a whole cell.

Paging Channel (PCH) is a downlink broadcast channel used to carry paging and notification

messages across a whole cell.

Dedicated Channel (DCH) is used in the uplink or downlink direction to carry user

information to or from the UE.

36

2.5.3.3 Physical Channels

Downlink (DL) Physical Channels

The DL physical channels carrying higher-layer information are:

Physical Downlink Shared Channel (PDSCH) is used to carry the DSCH. It is shared by

multiple users by way of code multiplexing. The PDSCH is always associated with one or more

DL Dedicated Physical Channels (DPCHs).

Secondary Common Control Physical Channel (SCCPCH) is used to carry the transport

channels PCH and FACH in the DL direction.

Primary Common Control Physical Channel (PCCPCH) is used in the DL direction to

broadcast the BCH across a cell. There will be only one of these on each cell.

Dedicated Physical Data Channel (DPDCH) and Dedicated Physical Control Channel

(DPCCH). The DPDCH is a bidirectional channel used to carry higher-layer information from

the transport channel DCH. It is multiplexed with the DPCCH that provides the layer 1 control

and synchronization information. Once multiplexed, the two are referred to as a DPCH. One

DPCCH may be associated with one or more DPDCHs.

The DL channels carrying control and synchronization are:

Paging Indicator Channel (PICH) is used to carry Paging Indicators (PI used to enable

discontinuous reception of the PCH being carried on an associated SCCPCH.

Synchronization Channel (SCH) is a DL channel used during cell search. It consists of primary

and secondary sub-channels, and conveys information to the UE concerning the time alignment

of a cell’s codes and frame structures.

Common Pilot Channel (CPICH) is used to provide the phase reference for the SCH,

PCCPCH, AICH and the PICH. There will be only one Primary CPICH in a cell.

Acquisition Indicator Channel (AICH) carries Acquisition Indicators (AI) used to

acknowledge UE random access attempts, and grant permission for a UE to continue with its

random access transmission.

CPCH – Access Preamble Acquisition Indicator Channel (AP-AICH) carries access

preamble acquisition indicators which correspond with the access preamble signature transmitted

by the UE.

CPCH – Collision Detection/Channel Assignment Indicator Channel (CD/CA-ICH) is used

to acknowledge the collision detection access preamble.

CPCH – Status Indicator Channel (CSICH) uses the unused part of the AICH channel to

indicate CPCH physical channel availability so that access is only attempted on a free channel.

Uplink (UL) Physical Channels

Physical Random Access Channel (PRACH) is a contention-based channel used to carry

higher-layer information in the form of the RACH.

Dedicated Physical Channel (DPCH) is ultimately used to carry the transport channel DCH.

37

Physical Common Packet Channel (PCPCH) carries the common packet transport channel,

which comprises access preambles, collision detection preamble, power control preamble and a

message part.

2.5.4 Code Planning

2.5.4.1 DL Code Requirements

The DL code requirements include: synchronization, cell resolution, and physical channel

resolution. There are three code types utilized in the UMTS DL direction.

- Synchronization requires short, highly orthogonal codes. Therefore, hierarchical Golay

codes are used in conjunction with Hadamard codes.

- Cell resolution requires noise-like spectral characteristics and good cross-correlation

characteristics; consequently, Gold code segments are used. The codes used for cell

resolution are referred to as cell scrambling codes.

- Channel resolution requires maximal orthogonality which is provided through the use of an

orthogonal code set in a code tree. The codes used for channel resolution are referred to as

spreading codes.

Synchronization Codes

The set of synchronization codes available consists of one primary and 16 secondary codes. All

the codes are potentially available on all cells. The single primary code will always be present in

all cells. In addition, each cell will be broadcasting one of 64 sequences consisting of 15

secondary codes.

Cell Scrambling Codes

The cell scrambling codes are complex-valued 10 ms segments of Gold codes. There are 512

primary cell scrambling codes; each cell will be allocated one of these (unique to a cell within its

immediate geographic area). The set of 512 primary codes is organized into 64 groups of 8.

These 64 groups map to the secondary synchronization code sequences. Each of the 512 primary

cell scrambling codes is also associated with 15 additional secondary cell scrambling codes.

Thus there are a total of 8192 cell scrambling codes defined. These secondary scrambling codes

could be used to subdivide a cell into sub-cells, thus providing a means of increasing capacity in

a cell, or dealing with traffic hotspots.

DL Spreading Codes

A set of Orthogonal Variable Spreading Factor (OVSF) codes in the form of a code tree is

defined for spreading and channel resolution in the DL direction. The use of the code tree

enables orthogonal codes to be applied across the length of one complete baseband symbol for a

range of different possible baseband rates. Thus at low rates with long-duration baseband

symbols, long codes from the top of the tree can be selected. At high rates with short-duration

baseband symbols, codes from the root of the tree can be selected. The result is the maintenance

38

of good orthogonality between DL channels running at either the same or different rates. Codes

from different levels of the tree may be used simultaneously. There are some limitations,

however. Firstly, a code may only be used if no other code on the path to the root of the tree is

already in use. Secondly, once a code is in use no other code derived from it may be used.

2.5.4.2 Uplink Code Requirements

UL Scrambling Codes

The two options for UL scrambling codes are complex-valued 10 ms segments of Gold codes

and complex-valued S(2) codes. While similar in structure and characteristic, the UL Gold code

segments are from a different and much larger set of codes than that used in the DL direction. In

total there are 16,777,216 codes available. The Gold code segments are sometimes referred to as

‘long’ codes. From the set of Gold code segments, the first 8192 codes are reserved for PRACH

operation and the next 32,768 codes are reserved for PCPCH operation. In both these cases

groups of codes taken from these sets will be allocated to particular cells within the planning

process. The remainder of the Gold code segments are available for DPCH operation and are not

part of the planning process. The Gold code segments may optionally be replaced with S(2)

codes for use in the PCPCH and DPCH only. The S(2) codes are sometimes referred to as short

codes. The set of S(2) codes is the same size as that of Gold codes and there is a direct mapping

from one to the other. The S(2) codes will be used if the Node B equipment supports Multi-User

Detection (MUD).

UL Spreading Codes

UL spreading is performed using the same set of OVSF codes as is used in the DL direction for

channel resolution. However, in the UL direction a pair of OVSF codes will be allocated to a

physical channel in order to differentiate between I and Q information flows.

2.5.5 Cell Breathing

UL Cell Breathing

The load on the cell increases with increase in the number of active mobiles in the cell. The

interference will grow to the extent that distant mobiles will be dropped due to the poor signal-

to-noise ratio, effectively causing the cell to shrink. As mobile connections are terminated the

interference reduces and the cell size increases. This is known as cell breathing.

DL Cell Breathing

Downlink cell breathing also occurs as the cell becomes loaded. However, this is caused by the

fact that the base station employs a linear power amplifier. As more connections are established

in the cell each mobile will be given proportionally less power, causing the range of the cell to

reduce. With fewer connections each mobile may be apportioned more power, effectively

increasing the cell range.

39

2.6 Planning Considerations for LTE (4G) Networks

2.6.1 Link Budget

A link budget must be performed in both the UL and DL directions. The chief inputs to a link

budget are radio factors such as transmit power, receiver sensitivity, feeder losses and antenna

gains. The overall aim is to find a maximum path loss that is acceptable in both UL and DL

directions. However, for LTE, the link budget is not static because it is affected by vary

operation conditions and service requirements implying that other margins need to be included to

reflect these varying possibilities. Multiple link budgets are usually required to give a full picture

of likely system performance.

High capacity cellular systems are assumed to operate under high interference conditions and an

additional interference margin is necessary to account for this. The interference margin reflects

the interference that will occur between users with the same frequency resource. The magnitude

of the interference margin depends on the implementation options selected by the operator such

as spectrum division and frequency planning strategy, or the use of MIMO options.

2.6.2 LTE Frequency Spectrum

There are currently 15 bands for FDD operation ranging from frequencies of approximately

700MHz to 2.7GHz. There are also 8 bands identified for TDD operation ranging from

approximately 1900MHz to 2.6GHz.

E-

UTRA

Band

UL Range

(MHz)

DL Range

(MHz)

Duplex

mode

Channel

bandwidths

(MHz)

Common Name Frequenc

y Band

(MHz)

Duplex

Spacin

g

(MHz)

1 1920 – 1980 2110 – 2170 FDD 5, 10, 15, 20 IMT 2100 190

2 1850 – 1910 1930 – 1990 FDD 1.4, 3, 5, 10, 15, 20 PCS blocks A-F 1900 80

3 1710 – 1785 1805 – 1880 FDD 1.4, 3, 5, 10, 15, 20 DCS 1800 95

4 1710 – 1755 2110 – 2155 FDD 1.4, 3, 5, 10, 15, 20 AWS-1 1700 400

5 824 – 849 869 – 894 FDD 1.4, 3, 5, 10 CLR 850 45

7 2500 – 2570 2620 – 2690 FDD 5, 10, 15, 20 IMT-E 2600 120

8 880 – 915 925 – 960 FDD 1.4, 3, 5, 10 E-GSM 900 45

9 1749.9 – 1784.9 1844.9 – 1879.9 FDD 5, 10, 15, 20 UMTS 1700 /

Japan DCS

1800 95

10 1710 – 1770 2110 – 2170 FDD 5, 10, 15, 20 Extended AWS 1700 400

11 1427.9 – 1447.9 1475.9 – 1495.9 FDD 5, 10 Lower PDC 1500 48

12 699 – 716 729 – 746 FDD 1.4, 3, 5, 10 Lower SMH blocks

A/B/C

700 30

13 777 – 787 746 – 756 FDD 5, 10 Upper SMH block

C

700 −31

14 788 – 798 758 – 768 FDD 5, 10 Upper SMH block

D

700 −30

40

17 704 – 716 734 – 746 FDD 5, 10 Lower SMH blocks

B/C

(subset of band 12)

700 30

18 815 – 830 860 – 875 FDD 5, 10, 15 Japan lower 800 850 45

19 830 – 845 875 – 890 FDD 5, 10, 15 Japan upper 800 850 45

20 832 – 862 791 – 821 FDD 5, 10, 15, 20 EU Digital

Dividend

800 −41

21 1447.9 – 1462.9 1495.9 – 1510.9 FDD 5, 10, 15 Upper PDC 1500 48

22 3410 – 3490 3510 – 3590 FDD 5, 10, 15, 20 3500 100

23 2000 – 2020 2180 – 2200 FDD 1.4, 3, 5, 10, 15, 20 S-Band (AWS-4) 2000 180

24 1626.5 – 1660.5 1525 – 1559 FDD 5, 10 L-Band (US) 1600 −101.5

25 1850 – 1915 1930 – 1995 FDD 1.4, 3, 5, 10, 15, 20 Extended PCS

blocks A-G

1900 80

26 814 – 849 859 – 894 FDD 1.4, 3, 5, 10, 15 Extended CLR 850 45

27 807 – 824 852 – 869 FDD 1.4, 3, 5, 10 SMR 850 45

28 703 – 748 758 – 803 FDD 3, 5, 10, 15, 20 APT 700 55

30 2305 – 2315 2350 – 2360 FDD 5, 10 WCS blocks A/B 2300 45

31 452.5 – 457.5 462.5 – 467.5 FDD 1.4, 3, 5 450 10

Table 2.8 LTE (FDD) Frequency Spectrum [3]

E-

UTRA

Band

DL Range

(MHz)

Duplex

mode

Channel bandwidths

(MHz)

Common Name Frequency

Band (MHz)

33 1900 – 1920 TDD 5, 10, 15, 20 Pre-IMT

(subset of band 39)

2100

34 2010 – 2025 TDD 5, 10, 15 IMT 2100

35 1850 – 1910 TDD 1.4, 3, 5, 10, 15, 20 PCS (Uplink) 1900

36 1930 – 1990 TDD 1.4, 3, 5, 10, 15, 20 PCS (Downlink) 1900

37 1910 – 1930 TDD 5, 10, 15, 20 PCS (Duplex spacing) 1900

38 2570 – 2620 TDD 5, 10, 15, 20 IMT-E (Duplex

Spacing)

(subset of band 41)

2600

39 1880 – 1920 TDD 5, 10, 15, 20 DCS-IMT gap 1900

40 2300 – 2400 TDD 5, 10, 15, 20 2300

41 2496 – 2690 TDD 5, 10, 15, 20 BRS / EBS 2500

42 3400 – 3600 TDD 5, 10, 15, 20 3500

43 3600 – 3800 TDD 5, 10, 15, 20 3700

44 703 – 803 TDD 3, 5, 10, 15, 20 APT 700

Table 2.9 LTE (TDD) Frequency Spectrum [3]

41

2.6.3 Channel Bandwidths and Subcarriers

Evolved Universal Terrestrial Radio Access Network (E-UTRAN)/LTE is designed to work in a

variety of bandwidths ranging initially from 1.4MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz to

20MHz. The E-UTRAN scheme allows for two fixed subcarrier spacing options; 15 kHz in most

cases, with an optional 7.5 kHz spacing scheme, only applicable for TDD operation and intended

for very large cells in an SFN (Single Frequency Network).

2.6.4 Radio Channel Organization

For both UL and DL operation subcarriers are bundled together in groups of 12. This grouping is

referred to as Resource Block (RB). The number of resource blocks available in the system is

dependent on bandwidth, varying between 100 for 20MHz bandwidth to just 6 for 1.4MHz

channel bandwidth. The nominal spectral bandwidth of an RB is 180 kHz for the standard 15

kHz subcarrier spacing implying that there is a difference between the stated channel bandwidth

and the transmission bandwidth. The difference acts as a guard band. OFDMA channels are

allocated within an operator’s licensed spectrum allocation. The centre frequency is identified by

an EARFCN (E-UTRA Absolute radio Frequency Channel Number). The precise location of the

EARFCN is an operator decision, but they must be placed on a 100 kHz raster and the

transmission bandwidth must not exceed the operator’s licensed spectrum.

2.6.5 LTE Channels

2.6.5.1 LTE Physical Channels

Downlink

Physical Broadcast Channel (PBCH) carries system information for UEs requiring access to the

network. It only carries what is termed Master Information Block, MIB, messages.

Physical Control Format Indicator Channel (PCFICH) informs the UE about the format of the

signal being received. It indicates the number of OFDM symbols used for the PDCCHs, whether

1, 2, or 3.

Physical Downlink Control Channel (PDCCH) carries mainly scheduling information of

different types: downlink resource scheduling, uplink power control instructions, uplink resource

grant and indication for paging or system information

Physical Hybrid ARQ Indicator Channel (PHICH) is used to report the Hybrid ARQ status. It

carries the HARQ ACK/NACK signal indicating whether a transport block has been correctly

received. The HARQ indicator is 1 bit long - "0" indicates ACK, and "1" indicates NACK.

Uplink

Physical Uplink Control Channel (PUCCH) provides the various control signalling

requirements. It includes the ability to carry Scheduling Requests (SRs).

Physical Uplink Shared Channel (PUSCH) is the uplink counterpart of PDSCH

Physical Random Access Channel (PRACH) is used for random access functions. This is the

only non-synchronized transmission that the UE can make within LTE.

42

2.6.5.2 LTE Transport Channels

Downlink

Broadcast Channel (BCH). The LTE transport channel maps to Broadcast Control Channel

(BCCH)

Downlink Shared Channel (DL-SCH) is the main channel for downlink data transfer. It is used

by many logical channels.

Paging Channel (PCH): To convey the PCCH.

Multicast Channel (MCH): This transport channel is used to transmit MCCH information to

set up multicast transmissions.

Uplink

Uplink Shared Channel (UL-SCH) is the main channel for uplink data transfer. It is used by

many logical channels.

Random Access Channel (RACH) is used for random access requirements.

2.6.5.3 LTE Logical Channels

Control channels:

Broadcast Control Channel (BCCH) provides system information to all mobile terminals

connected to the eNodeB.

Paging Control Channel (PCCH) is used for paging information when searching a unit on a

network.

Common Control Channel (CCCH) is used for random access information, e.g. for actions

including setting up a connection.

Multicast Control Channel (MCCH) is used for Information needed for multicast reception.

Dedicated Control Channel (DCCH) is used for carrying user-specific control information, e.g.

for controlling actions including power control, handover, etc.

Traffic channels:

Dedicated Traffic Channel (DTCH) is used for the transmission of user data.

Multicast Traffic Channel (MTCH) is used for the transmission of multicast data.

43

2.6.6 LTE Frequency Planning

2.6.6.1 Fractional Frequency Re-use (FFR)

Frequency planning techniques have been proposed for LTE systems to mitigate inter-cell

interference instead of standard universal frequency reuse. Fractional Frequency Reuse (FFR) is

one such strategy that partitions a cell into several regions and applies different reuse factors in

each region. FFR increases spatial distance between neighboring interferers significantly

reducing inter-cell interference. The two main types of FFR are Strict FFR and Soft Frequency Reuse.

a. Strict FFR

In a Strict FFR system, users in the interior of the cells universally share a common sub-band of

frequencies, while the cell edge users’ bandwidth is partitioned based on a reuse factor of N,

requiring a total of N+1 sub-bands. It is termed ‘strict’ because interior users do not share any

spectrum with edge users, which reduces interference for both interior users and edge cell users

b. Soft Frequency Reuse (SFR)

SFR employs a similar partitioning strategy as Strict FFR, with the exception that interior users

can share the same bandwidth as edge users in adjacent cells. As a result, cell interior users

typically transmit at lower power levels than the cell-edge users in order to reduce interference to

neighboring cells. While SFR is more bandwidth efficient than Strict FFR, it allows more

interference to both cell interior and edge users.

Since the cell partitions are based on the geometry of the network, the locations of the users are

important in order to determine the frequency partitions. However, the average received SINR of

users in a cell, which is usually a good indicator of the distance of the user from the BTS, can be

used to determine user classifications. The BTS then classifies users with average SINR less than

a predetermined threshold as edge users and the rest as interior users.

Figure 2.16 Strict FFR (left) and SFR (right) Geometry with N=3 Cell-edge Reuse Factors [7]

2.6.6.2 1.1.3 Single Frequency Network (SFN)

The available spectrum is used as a single channel. This results to considerable interference and

therefore loss of capacity at the edges of the cell, but potential for very high capacity within the

cell area

2.6.6.3 1.3.3 Frequency Reuse Pattern

The available spectrum is split into three (3) channels. This provides a degree of frequency

planning such that adjacent cells will not be using the same frequency.

44

CHAPTER THREE: DESIGN

3.1 Frequency Planning in the GSM 900 Frequency Band

3.1.1 Frequency Re-use Pattern

A 3/9 cell repeat pattern was used i.e. a cluster of 9 cells with 3 sectored cells being served by a

single site.

Figure 3.1 3/9 Cell Repeat Pattern [8]

Theoretical minimum reuse distance, 𝐷 = √3𝑁𝑅 = √3𝑅√𝑖2 + 𝑖𝑗 + 𝑗2

Using a radius of 1.0km, D = √3 ∗ 3 ∗ 1000𝑚 = 3000𝑚 = 3.0𝑘𝑚

The total number of carriers = 50 carriers

3.1.2 Broadcast Control Channels

Frequency Groups ( for 20 carriers)

A1 B1 C1 A2 B2 C2 A3 B3 C3

1 2 3 4 5 6 7 8 9

10 11 12 13 14 15 16 17 18

19 20

Table 3.1 Frequency Groups for Control Channels

3.1.3 Traffic Channels (TCH)

Frequency Groups ( for 30 carriers)

A1 B1 C1 A2 B2 C2 A3 B3 C3

21 22 23 24 25 26 27 28 29

30 31 32 33 34 35 36 37 38

39 40 41 42 43 44 45 46 47

48 49 50

45

Table 3.2 Frequency Groups for Traffic Channels

Histogram of the Channel Distribution

3.1.4 Synthesized Frequency Hopping

Synthesized Frequency Hopping was used for traffic channels (TCH) in order to minimize

adjacent cell interference between cell A1 and cell C3 in the 3/9 cell repeat pattern used.

Hopping Sequence Numbers (HSN) vary from 0 – 63 with each HSN representing a different

hopping sequence. HSN 0 initiates a cyclic hopping sequence. The traffic load used for

simulation purposes was 1.

Transmitter TRX

type

Frequency

domain

Traffic

load

Timeslot

configuration Hopping Mode HSN

Site1_1 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site1_1 TCH GSM 900 TCH 1 TCH Synthesized Hopping 22

Site1_2 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site1_2 TCH GSM 900 TCH 1 TCH Synthesized Hopping 36

Site1_3 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site1_3 TCH GSM 900 TCH 1 TCH Synthesized Hopping 25

0

2

4

6

1 2 3 4 5 6 7 8 9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

Load

ChannelsFigure 3.2 Histogram of the Channel Distribution

46

Site2_1 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site2_1 TCH GSM 900 TCH 1 TCH Synthesized Hopping 4

Site2_2 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site2_2 TCH GSM 900 TCH 1 TCH Synthesized Hopping 16

Site2_3 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site2_3 TCH GSM 900 TCH 1 TCH Synthesized Hopping 11

Site3_1 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site3_1 TCH GSM 900 TCH 1 TCH Synthesized Hopping 25

Site3_2 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site3_2 TCH GSM 900 TCH 1 TCH Synthesized Hopping 19

Site3_3 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site3_3 TCH GSM 900 TCH 1 TCH Synthesized Hopping 1

Site4_1 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site4_1 TCH GSM 900 TCH 1 TCH Synthesized Hopping 29

Site4_2 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site4_2 TCH GSM 900 TCH 1 TCH Synthesized Hopping 33

Site4_3 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site4_3 TCH GSM 900 TCH 1 TCH Synthesized Hopping 8

Site5_1 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site5_1 TCH GSM 900 TCH 1 TCH Synthesized Hopping 23

Site5_2 BCCH GSM 900 BCCH 1 BCCH Non Hopping

47

Site5_2 TCH GSM 900 TCH 1 TCH Synthesized Hopping 35

Site5_3 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site5_3 TCH GSM 900 TCH 1 TCH Synthesized Hopping 14

Site6_1 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site6_1 TCH GSM 900 TCH 1 TCH Synthesized Hopping 3

Site6_2 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site6_2 TCH GSM 900 TCH 1 TCH Synthesized Hopping 5

Site6_3 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site6_3 TCH GSM 900 TCH 1 TCH Synthesized Hopping 17

Site7_1 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site7_1 TCH GSM 900 TCH 1 TCH Synthesized Hopping 34

Site7_2 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site7_2 TCH GSM 900 TCH 1 TCH Synthesized Hopping 20

Site7_3 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site7_3 TCH GSM 900 TCH 1 TCH Synthesized Hopping 6

Site8_1 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site8_1 TCH GSM 900 TCH 1 TCH Synthesized Hopping 27

Site8_2 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site8_2 TCH GSM 900 TCH 1 TCH Synthesized Hopping 30

Site8_3 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site8_3 TCH GSM 900 TCH 1 TCH Synthesized Hopping 26

48

Site9_1 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site9_1 TCH GSM 900 TCH 1 TCH Synthesized Hopping 12

Site9_2 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site9_2 TCH GSM 900 TCH 1 TCH Synthesized Hopping 63

Site9_3 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site9_3 TCH GSM 900 TCH 1 TCH Synthesized Hopping 31

Site10_1 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site10_1 TCH GSM 900 TCH 1 TCH Synthesized Hopping 13

Site10_2 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site10_2 TCH GSM 900 TCH 1 TCH Synthesized Hopping 10

Site10_3 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site10_3 TCH GSM 900 TCH 1 TCH Synthesized Hopping 32

Site11_1 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site11_1 TCH GSM 900 TCH 1 TCH Synthesized Hopping 28

Site11_2 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site11_2 TCH GSM 900 TCH 1 TCH Synthesized Hopping 18

Site11_3 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site11_3 TCH GSM 900 TCH 1 TCH Synthesized Hopping 21

Site12_1 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site12_1 TCH GSM 900 TCH 1 TCH Synthesized Hopping 7

Site12_2 BCCH GSM 900 BCCH 1 BCCH Non Hopping

49

Site12_2 TCH GSM 900 TCH 1 TCH Synthesized Hopping 15

Site12_3 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site12_3 TCH GSM 900 TCH 1 TCH Synthesized Hopping 19

Site13_1 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site13_1 TCH GSM 900 TCH 1 TCH Synthesized Hopping 24

Site13_2 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site13_2 TCH GSM 900 TCH 1 TCH Synthesized Hopping 2

Site13_3 BCCH GSM 900 BCCH 1 BCCH Non Hopping

Site13_3 TCH GSM 900 TCH 1 TCH Synthesized Hopping 9

Table 3.3 Hopping and Non-hopping Channels

3.2 Allocation of Intra-technology Neighbours

Average number of neighbours = 5

Non-symmetric links: 11

TRANSMITTER NEIGHBOURS CAUSE TRANSMITTER NEIGHBOURS CAUSE

Site10_1 Site6_1 Adjacent Site4_2 Site7_2 Adjacent

Site11_2 Site13_2 Adjacent Site4_3 Site3_3 Adjacent

Site11_3 Site7_3 Adjacent Site5_3 Site1_3 Adjacent

Site12_2 Site10_2 Adjacent Site8_1 Site9_1 Adjacent

Site3_1 Site1_1 Adjacent Site9_3 Site2_1 Adjacent

Site4_1 Site1_1 Adjacent

Table 3.4 Non-symmetric links

3.3 Coverage Prediction

Prediction Tool: Atoll Radio Planning Software - Version 2.7.1 (Build 2922)

Focus Zone Area = 40.839 km2

Focus Zone Coordinates

36°54'41.72"E - 1°9'54.92"S, 36°54'33.54"E - 1°11'21.88"S, 36°54'50.58"E - 1°12'45.87"S,

36°56'45.21"E - 1°12'48.95"S, 36°58'40.31"E - 1°12'43.9"S, 36°58'44"E - 1°11'15.43"S,

36°58'35.72"E - 1°9'47.77"S, 36°56'37.23"E - 1°9'45.95"S, 36°54'41.72"E - 1°9'54.92"S

50

Digital Terrain Model (DTM) View

Images of the Focus Zone

Figure 3.3 Digital Terrain Map (DTM) view

Figure 3.4 Images of the Focus Zone

51

Clutter Classes View

3.3.1 Choice of Antenna

The antennas in the table below were used.

Name Manufacturer Gain

(dBd)

Beam-

width

Fmin

(MHz)

Fmax

(MHz)

Horizontal

Width

Vertical

Width

Electrical

Tilt (0)

Maximum

Input Power

K80010305_

900_02V

Kathrein

K80010305V02

17.2 64.8 790 960 64.8 8.1 2 500W per input

(at 500C)

K80010305_

900_06V

Kathrein

K80010305V02

17.1 65.3 790 960 65.3 7.8 6 500W per input

(at 500C)

Table 3.5 Antennas

Figure 3. 5 Clutter Classes View

52

K80010305_900_02V Antenna

K80010305_900_06V Antenna

The antenna heights ranged from 30m – 35m

Figure 3.7 K80010305_900_02V Vertical Pattern Figure 3.6 K80010305_900_02V Horizontal Pattern

Figure 3.8 K80010305_900_06V Vertical Pattern Figure 3.9 K80010305_900_06V Horizontal Pattern

53

Transmi

tter Antenna

Height

(m)

Azimu

th (°)

Mechanic

al

Downtilt

(°)

Additional

Electrical

Downtilt

(°)

EIRP

(W)

Powe

r (W)

Losse

s

(dB)

Traffic

Channels

(TCH)

BCCH

Site1_1 K80010305_900_02V 35 0 0 0 56.75 35 7.27 3 23 32 41 50 3

Site1_2 K80010305_900_02V 30 120 0 0 56.75 30 7.27 14 26 35 44 14

Site1_3 K80010305_900_06V 30 240 0 0 56.75 30 7.27 9 29 38 47 9

Site2_1 K80010305_900_02V 30 280 0 0 56.75 30 7.27 17 28 37 46 17

Site2_2 K80010305_900_02V 30 40 2 1

53 7.27 2 22 31 40 49 2

Site2_3 K80010305_900_02V 30 160 0 0 56.75 30 7.27 5 25 34 43 5

Site3_1 K80010305_900_02V 30 0 0 0 56.75 30 7.27 19 21 30 39 48 19

Site3_2 K80010305_900_02V 30 120 0 0 56.75 30 7.27 13 24 33 42 13

Site3_3 K80010305_900_02V 30 240 0 0 56.75

30 7.27 7 27 36 45 7

Site4_1 K80010305_900_02V 30 0 0 0 56.75 30 7.27 11 22 31 40 49 11

Site4_2 K80010305_900_02V 30 120 0 0 56.75 30 7.27 14 25 34 43 14

Site4_3 K80010305_900_02V 35 240 2 1 56.75 30 7.27 8 28 37 46 8

Site5_1 K80010305_900_02V 30 0 0 0 56.75

30 7.27 10 21 30 39 48 10

Site5_2 K80010305_900_02V 30 120 0 0 56.75 30 7.27 4 24 33 42 4

Site5_3 K80010305_900_02V 30 240 0 0 56.75 30 7.27 16 27 36 45 16

Site6_1 K80010305_900_02V 30 0 0 0 56.75 30 7.27 2 22 31 40 49 2

Site6_2 K80010305_900_02V 30 120 0 0 56.75

30 7.27 5 25 34 43 5

Site6_3 K80010305_900_06V 30 240 0 0 56.75 30 7.27 17 28 37 46 17

Site7_1 K80010305_900_02V 30 0 0 0 56.75 30 7.27 1 21 30 39 48 1

Site7_2 K80010305_900_02V 30 120 0 0 56.75 30 7.27 4 24 33 42 4

Site7_3 K80010305_900_02V 30 240 0 0 56.75

30 7.27 16 27 36 45 16

Site8_1 K80010305_900_02V 35 0 0 0 56.75 30 7.27 12 23 32 41 50 12

Site8_2 K80010305_900_02V 30 120 0 0 56.75 30 7.27 5 26 35 44 5

Site8_3 K80010305_900_02V 30 240 0 0 56.75 30 7.27 18 29 38 47 18

Site9_1 K80010305_900_02V 30 0 0 0 56.75 30 7.27 11 22 31 40 49 11

Site9_2 K80010305_900_06V 30 120 0 0 56.75 30 7.27 14 25 34 43 14

Site9_3 K80010305_900_02V 30 240 0 0 56.75 30 7.27 8 28 37 46 8

Site10_1 K80010305_900_02V 30 0 0 0 56.75 30 7.27 3 23 32 41 50 3

Site10_2 K80010305_900_02V 30 120 0 0 56.75 30 7.27 14 26 35 44 14

54

Site10_3 K80010305_900_02V 30 240 0 0 56.75 30 7.27 9 29 38 47 9

Site11_1 K80010305_900_02V 30 0 2 1 58.61 45 7.27 2 22 31 40 49 2

Site11_2 K80010305_900_02V 30 120 0 0 56.75 30 7.27 5 25 34 43 5

Site11_3 K80010305_900_02V 30 240 0 0 56.75 30 7.27 17 28 37 46 17

Site12_1 K80010305_900_02V 30 0 0 0 59.07 50 7.27 19 21 30 39 48 19

Site12_2 K80010305_900_02V 30 120 0 0 56.75 30 7.27 13 24 33 42 13

Site12_3 K80010305_900_02V 30 240 0 0 56.75

30 7.27 7 27 36 45 7

Site13_1 K80010305_900_02V 30 0 0 0 56.75 30 7.27 10 21 30 39 48 10

Site13_2 K80010305_900_02V 30 120 0 0 56.75 30 7.27 13 24 33 42 13

Site13_3 K80010305_900_02V 30 240 0 0 56.75 30 7.27 7 27 36 45 7

Table 3.6 Antennas used in the various Sites

3.3.2 Propagation Path Loss Model

The Okumura-Hata model was used because it is recommended for coverage prediction in macro

cells in the GSM 900 frequency band.

3.3.3 Link Budget

The transmission power required to produce a minimum required signal level at some distant

point was determined using a link (power) budget. The noise floor in a 200 kHz channel is -

121dBm and the assumed NF (Noise Figure) for a GSM 900 Class 4 MS is 10dB. The minimum

SNR is quoted as 8 dB for a basic GSM link. Thus,

minimum signal level = (-121 + 10 + 8) = - 103dBm

This compares closely with the referenced sensitivity of -102dBm for a GSM 900 Class 4 MS. A

threshold of -99dBm was used for the signal level.

55

CHAPTER FOUR: RESULTS, DISCUSSION AND ANALYSIS

Coverage by Signal Level

Figure 4.1 Coverage by Signal Level

Figure 4.2 Coverage by Signal Level Properties

56

Histogram based on Covered Areas

Figure 4.3 Histogram based on Best Signal Level of Covered Areas

From the above histogram, signal levels in different areas of the focus zone were tabulated as

shown in the table below:

Signal level Area (km2) Percentage of the Focus Zone (%)

-40dBm 6.22 15.2

-50dBm – -40dBm 18.38 45

-55dBm – -50dBm 11.8 28.9

-60dBm – -55dBm 4.15 10.2

-70dBm – -60dBm 0.3 0.7

Table 4.1 Signal Levels in Different Areas of the Focus Zone

The threshold value for the receive signal obtained from the link budget is -103dBm while the

referenced sensitivity for a GSM 900 Class 4 MS is -102dBm. The threshold value used for

simulation purposes was -99dBm. From the coverage by signal level results, the signal levels in

the focus zone were above the threshold with the least signal level within the focus zone being -

70dBm.

57

Overlapping Zones

Figure 4.4 Overlapping Zones

Figure 4.5 Overlapping Zones Properties

58

Coverage by C/I Level

Figure 4.6 Coverage by C/I Level

Figure 4.7 Coverage by C/I Level properties

59

Figure 4.8 Histogram based on C/I Level of Covered Areas

From the above results, 86% of the focus zone area had C/I level above 18dB. The theoretical

value of C/I level expected for a network based on the GSM 900 band and a 3/9 cell repeat

pattern is >9dB. From the coverage prediction by C/I level results, 99% of the focus zone area

had a C/I level greater than 9dB.

60

Coverage by Transmitter

The coverage by transmitter prediction results show that the whole focus zone was fully covered

with no noticeable holes. There are overlaps at the cell edges

Figure 4.9 Coverage by Transmitter

61

CHAPTER FIVE: CONCLUSIONS AND RECOMMENDATIONS

5.1 CONCLUSION

Cell planning in wireless communication networks has been studied and planning considerations

for GSM, UMTS and LTE networks have been described in detail. With limited spectrum, cell

planning in wireless communication networks is very important in provision of sufficient

coverage, sufficient network capacity and good network quality. A nominal cell plan for a

selected focus zone was successfully produced using Atoll Radio Planning Software - Version

2.7.1 (Build 2922). Prediction results based on coverage by signal level and coverage by C/I

level were obtained using the radio planning software (Atoll).

5.2 RECOMMENDATIONS

I recommend nominal cell planning for LTE or CDMA networks in future works in order to

make use of Monte Carlo simulations in coverage predictions.

62

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63

APPENDIX:

ITU World Telecommunication Statistics

(millions)

2005 2006 2007 2008 2009 2010 2011 2012 2013 2014*

Fixed-telephone subscriptions

Developed 570 565 546 544 562 553 540 526 515 511

Developing 673 696 708 705 692 676 661 652 643 636

World 1,243 1,261 1,254 1,249 1,254 1,229 1,201 1,178 1,158 1,147

Mobile cellular Subscriptions

Developed 992 1,127 1,243 1,325 1,383 1,404 1,411 1,447 1,490 1,515

Developing 1,213 1,618 2,125 2,705 3,257 3,887 4,453 4,785 5,171 5,400

World 2,205 2,745 3,368 4,030 4,640 5,290 5,863 6,232 6,662 6,915

Active mobile-broadband subscriptions

Developed N/A N/A 225 336 450 554 707 828 939 1,050

Developing N/A N/A 43 86 165 253 475 726 991 1,265

World N/A N/A 268 422 615 807 1,182 1,554 1,930 2,315

Fixed (wired)-broadband subscriptions

Developed 148 188 219 250 271 291 306 321 332 345

Developing 71 96 127 161 197 236 282 315 341 366

World 220 284 346 411 468 526 588 635 673 711

Note:

Rounded values. N/A: Not available.

Regions in this table are based on the ITU BDT Regions

Appendix Table 1 Key ICT Indicators for Developed and Developing Countries and the World

(totals) [9]