LAPPEENRANTA UNIVERSITY OF TECHNOLOGY

DEPARTMENT OF INFORMATION TECHNOLOGY

Shyam Babu Mahato

Performance Evaluation of Six-Sectored Configuration in Hexagonal

WCDMA (UMTS) Cellular Network Layout

Master of Science Thesis

Subject approved by the department council on 11.10.2006

Examiner: D.Sc. Jouni Ikonen

Supervisor: Prof. Jukka Lempiäinen

ii

ABSTRACT

Lappeenranta University of Technology

Department of Information Technology

Shyam Babu Mahato

Performance Evaluation of Six-Sectored Configuration in Hexagonal WCDMA

(UMTS) Cellular Network Layout

Master of Science Thesis, 2007, 78 pages

Examiner: D.Sc. Jouni Ikonen

Supervisor: Prof. Jukka Lempiäinen

Keywords: Performance, Coverage, Capacity, Radio Network Planning, WCDMA,

UMTS, Hexagon

The objective of this master’s thesis is to evaluate the optimum performance of six-

sectored hexagonal layout of WCDMA (UMTS) network and analyze the performance at

the optimum point. The maximum coverage and the maximum capacity are the main

concern of service providers and it is always a challenging task for them to achieve

economically. Because the optimum configuration of a network corresponds to a

configuration which minimizes the number of sites required to provide a target service

probability in the planning area which in turn reduces the deployment cost. The optimum

performance means the maximum cell area and the maximum cell capacity the network

can provide at the maximum antenna height satisfying the target service probability.

Hexagon layout has been proven as the best layout for the cell deployment. In this thesis

work, two different configurations using six-sectored sites have been considered for the

performance comparison. In first configuration, each antenna is directed towards each

corner of hexagon, whereas in second configuration each antenna is directed towards each

side of hexagon. The net difference in the configurations is the 30 degree rotation of

antenna direction. The only indoor users in a flat and smooth semi-urban environment area

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have been considered for the simulation purpose where the traffic distribution is 100

Erl/km2 with 12.2 kbps speech service having maximum mobile speed of 3 km/hr.

The simulation results indicate that a similar performance can be achieved in both the

configurations, that is, a maximum of 947 m cell range at antenna height of 49.5 m can be

achieved when the antennas are directed towards the corner of hexagon, whereas 943.3 m

cell range at antenna height of 54 m can be achieved when the antennas are directed

towards the side of hexagon. However, from the interference point of view the first

configuration provides better results. The simulation results also show that the network is

coverage limited in both the uplink and downlink direction at the optimum point.

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FOREWORD

The research work for this Master of Science thesis was carried for the Laboratory of

Communication Engineering, Department of Information Technology, Lappeenranta

University of Technology, with kind support of Institute of Communication Engineering,

Tampere University of Technology.

First of all, I would like to thank the IMPIT program of Lappeenranta University of

Technology for selecting me as a M.Sc. student and providing funding for the study

period. I would like to express my deepest and sincere gratitude to my supervisor Prof.

Jukka Lempiäinen, Institute of Communication Engineering, for his invaluable support

and providing deep knowledge during the course Radio Network Planning. I would also

like to thank Institute of Communication Engineering, Tampere University of Technology,

for accepting me as a JOOPAS student for the course Radio Network Planning and

providing the best environment for my research work.

I am grateful to my thesis examiner D.Sc. Jouni Ikonen, Department of Information

Technology, for his excellent comments and encouragements during the research work. I

would like to thank M.Sc. Oleg Chistokhvalov, Department of Information Technology,

for his kind and valuable discussions about the pre-task of the research work.

I am most grateful to M.Sc. Jarkko Itkonen and M.Sc. Balázs P. Tuzson of European

Communications Engineering (ECE) for their constant discussions about the research

work on net meeting, providing simulation parameters, technical support and

encouragements during the research work. I wish to thank M.Sc. Panu Lädekorpi, M.Sc.

Tero Isotalo, D. Sc. Jarno Niemelä and my colleague Jussi Turkka, all of Institute of

Communication Engineering, for their kind discussions and providing the license of

installing Nokia NetAct Planner Tool.

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Finally, I would like to express my deepest love to my parents for their parenting,

guidance, and love throughout the early days of my life.

Tampere 20.8.2007

Shyam Babu Mahato

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TABLE OF CONTENTS

ABSTRACT ii

FOREWORD iv

TABLE OF CONTENTS vi

LIST OF ABBREVIATIONS viii

LIST OF SYMBOLS x

1 INTRODUCTION 1

2 UMTS NETWORK ARCHITECTURE 4

2.1 Core Network(CN) 4

2.2 UMTS Terrestrial Radio Access Network (UTRAN) 7

2.2.1 Radio Network Controller (RNC) 7

2.2.2 Node-B 8

2.3 User Equipment (UE) 8

3 RADIO PROPAGATION 9

3.1 Multipath Propagation 9

3.2 Angular Spread 11

3.3 Delay spread and Coherence Bandwidth 11

3.4 Fast Fading and Slow Fading 12

3.5 Propagation Slope 14

4 RADIO NETWORK PLANNING 16

4.1 Pre-Planning (Dimensioning) 17

4.1.1 Radio Link Budget (RLB) 18

4.1.2 COST-231-Hata Model 29

4.1.3 Cell Capacity and Cell Range (Coverage Area) Estimation 30

4.1.3.1 Cell Capacity Estimation 30

4.1.3.2 Cell Range (Coverage Area) Estimation 33

4.2 Detailed Planning 35

4.2.1 Planning Tool 35

4.2.2 Coverage Planning 35

vii

4.2.3 Capacity Planning 38

4.3 Optimization 46

5 SIMULATION AND ANALYSIS 47

5.1 Simulation Methodology 48

5.2 Network Configuration 50

5.3 Simulation Environment and Parameters 51

5.4 Analysis Method 53

5.5 Analysis Results 55

6 CONCLUSIONS 65

REFERENCES 67

viii

LIST OF ABBREVIATIONS

2G Second Generation 3G Third Generation AUC Authentication Center BCH Broadcast Channel BS Base Station BSC Base Station Controller BTS Base Transceiver CDMA Code Division Multiple Access CIR Carrier to Interference Ratio CN Core Network CPICH Common Pilot Channel DL Downlink EIR Equipment Identity Register EIRP Effective Isotropic Radiated Power GGSN Gateway GPRS Support Node GMSC Gateway MSC GPRS General Packet Radio Service GSM Global System of Mobile Communication HLR Home Location Register IM Interference Margin IMEI International Mobile Station Equipment Identity ISDN Integrated Services Digital Network ISI Inter-Symbol Interference KPI Key Performance Indicator LNA Low Noise Amplifier ME Mobile Equipment MGW Media Gateway MS Mobile Station MSC Mobile Switching Center NF Noise Figure P1 Publication 1 P-CCPCH Primary-Common Control Physical Channel PCH Physical Channel PCH Gain Power Control Headroom Gain PR Power Rise P-SCH Primary-Sysnchronisation Channel P-SCH Primary-Synchronization Channel

ix

PSTN Public Switched Telephone Network QoS Quality of Service RAN Radio Access Network RLB Radio Link Budget RNC Radio Network Controller RX Receiver S-CCPCH Secondary-Common Control Physical Channel SCH Synchronization Channel SfHO Softer Handover SGSN Serving GPRS Support Node SHO Soft Handover SIM Subscriber Identity Module SIR Signal-to-Interference Ratio SNR Signal-to-Noise Ratio S-SCH Secondary- Synchronization Channel STD Standard Deviation TX Transmitter TXP Transmitted Power UE User Equipment UL Uplink UMTS Universal Mobile Telecommunication System UTRA UMTS Terrestrial Radio Access UTRAN UMTS Terrestrial Radio Access Network Uu UMTS air interface WCDMA Wideband CDMA VLR Visitor Location Register

x

LIST OF SYMBOLS BC Coherence bandwidth BD Doppler bandwidth BS Signal bandwidth C Area correction factor c Light speed DS Delay spread Eb/No Energy received per chip to the total power spectral density Ec/Io Energy received per chip to the total interference power f Frequency GLNA LNA gain Gr Receiver gain Gt Transmitter gain hb Base station antenna height hm Mobile station antenna height i Other-to-own cell interference LCABLE Cable loss Lp Path loss N Number of terminals n Propagation exponent N0 Thermal noise density NFBS Noise figure of BS NFLNA Noise figure of LNA Ns Number of sectors Pr Received power Pt Transmitted power R User bit rate TC Coherence time TS Symbol period W Chip rate α Orthogonality factor α (hm) Mobile station antenna gain function β Bearer control overhead factor η Loading factor ηUL Uplink load λ Wavelength ν Activity factor ξ Sectorization gain

1

1 INTRODUCTION

The coverage and the capacity are the significant issues in the planning process of cellular

mobile networks. In WCDMA (UMTS) systems, coverage and capacity planning are taken

in account simultaneously because capacity requirements and traffic distributions

influence the coverage. Since UMTS radio interface is based on WCDMA technology,

each user in the network directly affects the others. This means, each user’s signal is

treated as interference to others. Hence, an important part of radio network planning in

WCDMA system is to simultaneously optimize the coverage and control the interference

to maximize the capacity. The target of the thesis is to evaluate the maximum performance

of hexagon layout having six-sectored sites.

Figure 1.1 Three-Sectored Site Layouts

The hexagon shape has been traditionally used as a basis of the network layout design for

cellular networks [1-3]. Two basic network layouts (Fig. 1.1(a) & (b)) with three-sectored

2

sites have become widely used during the cellular evolution [6]. The demand of cellular

service is increasing day by day which in turn has forced the network operator to update

their existing services so that they can provide the needs of market. Increasing sectors in

the existing site is one way of increasing the capacity of the network. A third network

layout (Fig. 1.1(c)) with three-sectored site has been designed in [4-6] as an alternative

network layout with the concept of dividing a hexagon in 6-cell. The network

performances of three-sectored site designs (Fig.1.1) with hexagon divided in 1-cell, 3-cell

and 6-cell have been evaluated in [4-6] and it is seen that the 6-cell alternative design has

comparatively better performance. Though the 6-cell design with three-sectored site can

provide double coverage and capacity than the 3-cell design with three-sectored site, it can

be easily noticed that to implement a 6-cell hexagon (Fig 1.1(c)), we must need six sites

which in turn increases the implementation cost.

Figure 1.2 Six-Sectored Site Layouts

In this thesis, a network layout was designed by six-sectored site (Fig. 1.2) with hexagon

divided in 6-cell and its performance was evaluated. Two topology layout designs have

3

been considered for the comparison. The first topology layout was considered by pointing

each antenna towards each corner of the hexagon (Fig.1.2 (a)), whereas the second

topology layout was considered by pointing each antenna towards each face of the

hexagon (Fig.1.2 (b)). In each topology, the site is located at the center of the hexagon.

The only difference between the topologies is the 30 degree rotation of the antenna

directions. However, the shape of cell’s dominance area is different which leads to a

different behavior when considering coverage and interference properties. The main

parameters in a network topology are cell size, site location, cell layout, antenna type,

antenna azimuth and antenna height [5-6]. For the simulation purpose, a total of 19 sites

with 6-sectored have been considered to find the optimum point regarding the cell size and

the base station antenna height.

The optimum performance of a network configuration is achieved when a given planning

area can be covered with minimum number of cells offering the required service of quality

and the capacity. This optimization minimizes the cost of the network which is driven by

the number of cells and the sites.

4

2 UMTS NETWORK ARCHITECTURE

The Universal Mobile Telecommunication System (UMTS) is one of the third-generation

(3G) mobile phone technologies. It uses WCDMA as the underlying standard for air

interface and is standardized by the 3rd Generation Partnership Project (3GPP). The UMTS

network is based on GSM and GPRS network [7-11]. The UMTS network elements and

their interfaces are shown in Figure 2.1. It consists of three main sections:

1. Core Network (CN)

2. UMTS Terrestrial Radio Access Network (UTRAN)

3. User Equipment (UE)

2.1 Core Network (CN)

The Core Network is a backbone network of telecommunication system that provides

connections among different devices. The basic 3G CN architecture is based on GSM

5

network with GPRS. The main functions of the CN are to provide switching, routing and

transit for user traffic. The 3G Core Network is divided into two domains: circuit switched

and packet switched domains [9, 13].

The circuit switched domain elements are:

• Mobile Switching Center (MSC)

A Mobile Switching Center is a telecommunication switch or exchange within a cellular

network architecture which is capable of interworking with location databases. The main

task of MSC is to route, switch and transmit the circuit switched data received from Radio

Network Controller (RNC) to the PSTN / ISDN networks via GMSC and vice versa. MSC

is the core element of GSM network.

• Visitor Location Register (VLR)

The Visitor Location Register is a network database which keeps the information about all

the roaming mobile customers required for call handling and mobility management.

Whenever an MSC detects a new mobile subscriber, in addition to creating a new record

in the VLR, it also updates the HLR (Home Location Register) of the mobile subscriber

[3].

• Gateway MSC (GMSC)

The Gateway MSC is the main routing element for the circuit switched data from the

UMTS network to the PSTN/ ISDN network or vice-versa. A GMSC is the MSC that

determines which visited MSC the subscriber who is being called currently located. All

mobile-to-mobile calls and PSTN to Mobile calls are routed through GMSC. It terminates

the PSTN signaling and traffic formats and converts this to protocols employed in mobile

networks. For mobile terminated calls, it interacts with HLR to obtain routing information.

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The packet switched domain elements are:

• Serving GPRS Support Node (SGSN)

A Serving GPRS Support Node (SGSN) is responsible for the delivery of packet switched

data received from Radio Network Controller (RNC) to the Gateway GPRS Support Node

or vice-versa. Its main tasks include packet routing and transfer, mobility management,

logical link management.

• Gateway GPRS Support Node (GGSN)

Like GMSC is the main routing element for circuit switched data to the PSTN or ISDN

network, GGSN is the main routing element for the packet switched data of UMTS

network to the Ethernet network.

Besides the circuit switched and the packet switched elements, the shared elements of both

the domains are:

• Equipment Identity Register (EIR)

The Equipment Identity Register is a database that keeps a list of mobile phones

(identified by their IMEI), which are to be banned from the network or monitored. When a

mobile requests services from the network, its IMEI (International Mobile Equipment

Identity) is checked against the EIR and then decides whether to allow the service or

banned.

• Home Location Register (HLR)

The Home Location Register is a central database that contains information of each

mobile phone subscriber that is authorized to use the network. More precisely, the HLR

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stores the information of every SIM card issued by the mobile phone operator. It is

responsible for the maintenance or user subscription information.

• Authentication Center (AUC)

The function of AUC is to authenticate each SIM card that attempts to connect the GSM

network. Once the authentication is successful, the HLR is allowed to manage the SIM

and services.

2.2 UMTS Terrestrial Radio Access Network (UTRAN)

The Radio Access Network (RAN) is also called UMTS Terrestrial RAN (UTRAN) and

the radio access (radio interface) is also called UMTS Terrestrial Radio Access (UTRA)

[7]. UTRAN is the main section of the mobile network evolution. The main changes are

occurring in this section for the evolution of new technology. UTRAN consists of two

elements:

1. Radio Network Controller (RNC)

2. Node B

2.2.1 Radio Network Controller (RNC)

The RNC is the governing element in the UMTS radio access network (UTRAN) which is

responsible for controlling the Node-Bs. The RNC in UMTS networks functions

equivalent to the Base Station Controller (BSC) functions in GSM/GPRS networks. The

RNC connects to the Circuit Switched Core Network through MSC (which is also known

as Media Gateway, MGW) and Packet Switched Core Network through SGSN.

The main function of the RNC is management of radio channels (Uu-, or Air-, interface)

and terrestrial channels (towards the MGW and SGSN) and mobility management. The

8

resource and the mobility management functionality includes: radio resource control,

admission control, channel allocation, power control settings, handover control, load

control, macro diversity, broadcast signaling, packet scheduling, security functions, open

loop power control [13].

2.2.2 Node B

The Node B is that element in the UMTS network which provides the physical radio link

between the User Equipment (UE) and the network. The Node B in UMTS networks

provides functions equivalent to the Base Transceiver Station (BTS) in GSM/GPRS

networks. Node B is typically physically co-located with existing GSM BTS to reduce the

cost of UMTS implementation.

The Node B is responsible for air interface processing and some Radio Resource

Management functions such as: air interface transmission / reception, modulation

/demodulation, CDMA physical channel coding, micro diversity, error handling, closed

loop power control [13].

2.3 User Equipment (UE)

The terminal is known as the user equipment. The UMTS UE is based on the same

principles as the GSM MS, i.e., the separation between mobile equipment (ME) and the

UMTS subscriber identity module (SIM) card (USIM) [7]. The USIM card contains the

subscriber-related information such as authentication, encryptions.

9

3 RADIO PROPAGATION

The mobile communication uses air interface for transmission and reception of signal. The

interface between the base station (Node B) and the mobile station (UE) in UMTS is

known as Uu-interface (UMTS radio interface) which is the propagation path of radio

signal between the mobile station and the network. This interface in UMTS is based on

WCDMA technology. The UMTS radio interface has different behaviors for different

propagation environments. The propagation environment can be classified into outdoor

and indoor environment. The outdoor environment can be further classified into

macrocellular environment and microcellular environment. Depending on the buildings or

other obstacles density, a macrocellular environment contains an urban, suburban and

rural type of area. Detailed knowledge of radio propagation and characterization of the

propagation medium is an essential step required for successful performance analysis.

Propagation model plays an important role in modeling the behavior of radio signal in

different propagation environment. There are many propagation models such as Okumura-

Hata model, Ray Tracing model, COST-231-Hata model which help in modeling the radio

propagation. The COST-231-Hata model is used in this simulation which is described in

later chapter. Each propagation environment has its own propagation characteristics,

which can be defined by the following parameters: [12]

• Multipath Propagation

• Angular Spread

• Delay spread and Coherence Bandwidth

• Fast Fading and Slow Fading

• Propagation Slope

3.1 Multipath Propagation

Multipath propagation occurs due to reflections, diffractions, and scatterings from

different obstacles such as buildings, street lamps, trees in the radio path [14-16]. The

10

multipath waves coming from different directions combine at the receiver antenna to give

a resultant signal which can vary widely in amplitude and phase depending on the

distribution of the intensity and the relative propagation time of the component waves.

Figure 3.1 Cellular Environment

The path exhibit differing attenuations and have different lengths, so that the receiver

observes several relatively delayed and attenuated versions of the signal. The effect of

different time delays is to introduce relatively phase shifts between the component waves.

As a result, the superposition of the different components induces either destructive or

constructive addition, depending on the relative phases. As the mobile moves around in

space, or in case of stationary mobile unit, due to moving obstacles such as cars, people,

etc., the structure of the multipath medium changes and spatial variations appear as time-

variation in the received signal. The Figure 3.1 illustrates the described propagation

scheme in a macrocellular radio environment, where the base station antennas are

typically located above the average roof-top level.

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3.2 Angular Spread

Angular spread describes the deviation of the signal incident angle. It can be calculated in

two planes, horizontal or vertical. The received power from the horizontal plane is still the

most important because of obstructing constructions: most of the reflecting surfaces are

related to the horizontal propagation and thus multiple BTS to MS propagation paths exist

more in horizontal plane.

The horizontal angular spread is around 5-10 [12] degree in macrocellular and very wide

in microcellular and indoor environments because the reflecting surfaces surround the

base station antenna. The angular spread has a significant effect on antenna installation

direction and on the selection and implementation of traditional space diversity reception.

The vertical angular spread influences, additionally, the base station antenna array tilting

angle. The angular spread is also a key parameter when the performance of the adaptive

antennas is discussed because the optimization of the Carrier-to-Interference Ratio (CIR)

depends strongly on the incident angles of the carrier and on the interference signals.

Thus, the performance of the adaptive antennas is lower or more difficult to achieve in the

microcellular environments than in the macrocellular environments.

3.3 Delay Spread and Coherence Bandwidth

Due to multipath propagation of the radio signal, the same signal arrives at the receiver

end at different times with different angles of arrival which causes the signal to spread in

time. The arrival time difference between the first multipath signal and the last one is

called the delay spread (DS), as shown in Figure 3.2. The delay would be unimportant if

the entire signal components arrived at the receiver with the same delay. However, the

signal actually becomes spread in time, and the symbol arrives at the receiver with

duration equal to the transmitted duration plus the delay range of the channel. The symbol

12

is therefore still arriving at the receiver when the initial energy of the next symbol arrives,

and this energy creates ambiguity in the demodulator of the new symbol which is known

as inter-symbol interference (ISI). [15]

Figure 3.2 Delay Spread

The bandwidth over which the channel’s transfer function remains virtually constant is

called the coherence bandwidth. In other words, the maximum bandwidth over which two

frequencies of a signal are likely to experience comparable or correlated amplitude fading

is called coherence bandwidth. Coherence bandwidth ( ) is related to delay spread

as:

1 2 .⁄ (3.1)

The channel is wideband when the signal bandwidth is large compared with the coherence

bandwidth.

3.4 Fast Fading and slow Fading

A channel can be classified either as a fast fading or slow fading channel depending upon

how rapidly the transmitted radio signal changes as compared to the rate of change of the

channel [3]. Figure 3.3 depicts an example of fading channel. We can note that the signal

strength varies rapidly as time elapsed. It is because either mobile station or the

surrounding object is moving due to which multipath effects occurred and the receiver

receives different components of same signals at different times.

Ds

P

t

13

Figure 3.3 An Example of Fading Channel [3]

In fast fading channel, the impulse response of the channel changes rapidly within the

symbol duration. That is, the coherence time of the channel is smaller than the symbol

period of the transmitted signal. This causes frequency dispersion (also called time

selective fading) due to Doppler spreading, which leads to signal distortion. The signal

distortion due to fast fading increases with the increase of Doppler spread relative to the

bandwidth of the transmitted signal. Therefore, a signal undergoes fast fading if [3]

, 3.2

where, is the symbol period, is the coherence time, is the bandwidth of the

transmitted signal and is the Doppler spread bandwidth.

In slow fading channel, the impulse response of the channel changes at a rate much slower

than the transmitted radio signal. In this case, the channel may be assumed to be a static

over one or several reciprocal bandwidth intervals. In the frequency domain, this implies

that the Doppler spread of the channel is much less than the bandwidth of the transmitted

signal. Therefore, a signal goes slow fading if [3]

, · 3.3

0 50 100 150 200 250-30

-25

-20

-15

-10

-5

0

5

10

Elapsed Time (ms)

Sig

nal S

treng

th (d

B)

14

It should be emphasized that the fast fading and the slow fading deal with the relationship

between the time rate of change in the channel and the transmitted signal, and not with the

path loss models. Fast fading is quite similar in all environments but depends on the speed

of the receiver.

3.5 Propagation Slope

The propagation slope characterizes the behavior of propagation environment. It indicates

that by how much a radio signal is attenuated over a distance in an environment.

Attenuation due to propagation limits the usability of the radio signal for the

communication purposes. The received power at a distance r from the isotropic radiator in

an environment is given by [17]:

, 3.4

where, is signal wavelength in meters, n is the path loss exponent, is the transmitted

power, is the receiving antenna gain and , is the transmitting antenna gain

where, are the angles measured in the vertical and horizontal directions

respectively. The path loss in dB can be written as:

10 log1

,4

16.22 10 log . 10 log , 3.5

where, f is the system frequency given by

· 3 · 10 ⁄ · 3.6

The path loss exponent (n) in case of free space is 2, i.e. the propagation slope is

20 ⁄ . But the path loss exponent changes with the environment according to the

values given in Table 1.

15

Table 1: An Example of Path Loss Exponents According to Environment Type [3]

Environment Path Loss Exponent

Free Space 2

Ideal Specular Reflection 4

Urban Cells 2.7-3.5

Urban Cells with shadowing 3-5

In building, LOS 1.6-1.8

In building, obstructed path 4-6

In factory, obstructed path 2-3

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4 RADIO NETWORK PLANNING

The radio network planning process for WCDMA is nearly the same as for GSM with

consideration of some parameters during the planning. The radio network planning

process can be divided into three phases [7, 9, 10, and 12]:

• Pre-planning phase (also called system dimension)

• Detailed planning phase and

• Post-planning or optimization phase

Each of the phases requires additional considerations such as propagation conditions,

traffic distributions. The process of 3G radio network planning is illustrated as shown in

Figure 4.1.

Figure 4.1 Radio Network Planning Process [9]

The planning of the radio network starts from the pre-planning phase. In the pre-planning

phase, a rough number of network elements with its configuration are estimated for the

target planning area based on the user traffic demand and the coverage requirements. The

radio link budget and a suitable propagation model are used for the estimation of cell

range for a certain base station antenna height. The number of the base stations required to

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achieve the desired coverage and quality is also dependent on the capacity of the base

stations. After the estimation of cell range and antenna height, the planning process goes

to the detailed planning phase. The network is configured in detail such as site location,

antenna direction, antenna type, antenna beam width, antenna downtilt, cable loss, antenna

gains and so on. All the parameters from the link budget are assigned to the elements in a

radio planning tool. A virtual network is built on the digital map by the help of a suitable

radio network planning tool. The network is simulated and the results of the coverage

predictions are analyzed on each pixel of the planning area on digital map. The detailed

planning is first done in the simulator and the real site survey is investigated for the

deployment of service. In the optimization phase, the result from the network performance

is verified and compared with the required target. If the result is not satisfied, then some

parameters such as site location, antenna height etc are changed until the result is within

the reasonable limit. Actually, optimization phase starts from the beginning of the pre-

planning phase and last to the life of the network.

4.1 Pre-Planning (Dimensioning)

In the dimensioning phase, an approximate number of base stations and their

configurations are estimated to cover a certain area and to serve a certain capacity based

on operator’s requirement and the radio propagation in the area as well as network layout.

Moreover, one critical parameter for a detailed planning phase is the base station antenna

height, which must be defined in order to be able to define the characteristics of the radio

propagation channel [12]. Pre-planning phase includes radio link budget (RLB) and

coverage analysis, capacity estimation and lastly estimation of the amount of base station

hardware and sites.

The Figure 4.2 illustrates the coverage and capacity dimensioning process used in the

following sections. The link budget and the propagation model form an important part of

prediction of cell range. The cell coverage is estimated based on the type of the cell

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layout. On the other hand, the cell capacity is calculated based on the load and the

interference in the system. The cell area occupied by the cell capacity is then estimated

based on the traffic distribution. Finally, the cell coverage obtained from the coverage and

capacity planning is synchronized by tuning the base station antenna height in the

propagation model. In this way, we can get the initial dimensioning of cell coverage and

cell capacity with a base station antenna height.

Figure 4.2 Dimensioning Process

4.1.1 Radio Link Budget (RLB)

The radio link budget gives the path loss between the base station and the mobile station.

It is needed for the estimation of maximum path loss between the base station and the

mobile station. The RLB calculations help in defining the cell range along with the

coverage thresholds. The coverage threshold is a downlink power budget that gives the

signal at the cell edge (border of the cell) for a given location probability. Link budget

calculations are done for both the uplink and the downlink. As the power transmitted by

the mobile station antenna is less than the power transmitted by the base station antenna,

the uplink power budget is more critical than the downlink power budget. Due to this

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reason, the path loss in the limited direction is used for the calculation of cell range. A

general approach to calculate the path loss is described as below [9]:

Uplink (UL) Path Loss (PL) Calculations:

4.1

where,

=

=

Downlink (DL) Path Loss (PL) Calculations:

4.2

where,

=

=

MSBS

Downlink

Uplink

Figure 4.3 Path Loss direction

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A practical example of radio link budget calculation used in the simulation is shown in

table 2. The descriptions of parameters apply to both the uplink and downlink directions

unless specifically stated otherwise. For the downlink direction, the base station is the

transmitting end and the mobile station is the receiving end. For the uplink direction, the

mobile station is the transmitting end and the base station is the receiving end. The

frequency is set to 2140 MHz which is the middle frequency of European UMTS

downlink frequency band. The chip rate of WCDMA is 3.84 Mcps. The data rate of

spreading code is called the chip rate. The network load is assumed to be 60 % in uplink

and 50 % in downlink direction. The speech users with 12.2 kbps bit rate are observed.

The calculation of link budget is described as below.

(g) Thermal Noise Density (dBm/Hz):

Thermal noise density, No, is defined as the noise power per Hertz at the receiver input

which is given by the logarithmic of the product of Boltzmann’s constant and the

temperature. The thermal noise density at 20 is calculated as:

10 · log /0.001 173.93 4.3

where, 1.38

273 20 293 .

(h) Receiver Noise Figure (dB):

Receiver noise figure is the noise of the receiving system to the receiver input. The noise

figure of Node B was set to 4 dB and of UE to 8 dB.

21

Table 2: An Example of Radio Link Budget Used in Simulation

GENERAL INFO Units Value

Downlink Frequency MHz 2140 a

Chip Rate Mcps 3.84 b

Temperature K 293 c

Boltzmann's Constant J/K 1.38E-23 d

SERVICE INFO UPLINK DOWNLINK

Units Value Value

Load % 60 50 e

Bit Rate kbps 12.2 12.2 f

RECEIVING END BS MS

Thermal Noise Density dBm/Hz -173.9325 -173.9325 g = 10*log(d*c)

Receiver Noise Figure dB 4.0 8.0 h

Receiver Noise Density dBm/Hz -169.9325 -165.9325 i = g+h

Receiver Noise Power dBm -104.0892 -100.0892 j = 10*log(b)+i

Interference Margin (Noise Rise) dB 3.9794 3.0103 k = -10*log(1-e)

Total Interference Level dBm -100.1098 -97.0789 l = j+k

Required Eb/No dB 5.0 8.0 m

Processing Gain dB 24.9797 24.9797 n = 10*log(b/f)

Receiver Sensitivity dBm -120.0895 -114.0586 o = l+m-n

Rx Antenna Gain dBi 18.0 0.0 p

LNA Noise Figure dB 2.0 0.0 q

LNA Maximum Gain dB 12.0 0.0 r

LNA Insertion Loss dB 0.0 0.1 s

NF Improvement using LNA linear scale 1.9210 t = h*x/(q+1/r*(h*x-1)) ( in UL)

dB 2.8353 -0.1000 t = -s ( in DL)

Feeder/Cable Loss dB/m 0.0610 0.0000 u

Feeder/Cable Length m 20.0 0.0 v

Connector Loss dB 0.0 0.0 w

Total Feeder/Cable Loss dB 1.2200 0.0000 x = u*v+w

Antenna Diversity Gain dB 0.0000 0.0000 y (included in Eb/No)

Soft Handover Diversity Gain dB 2.0 3.0 z

Power Control Headroom dB 3.0 0.0 A

Required Signal Power dBm -138.7048 -116.9586 B = o-p-t+x-y-z+A

22

TRANSMITTING END MS BS

TX Power per Connection dBm 21.0 33.0 C

Cable/Feeder Loss dB 0.0000 1.2200 D

TX Antenna Gain dBi 0.0 18.0 E

Peak EIRP dBm 21.0000 49.7800 F = C-D+E

ISOTROPIC PATH LOSS dB 159.7048 166.7386 G = F- B

PLANNING THRESHOLD

SHO Gain dB 3.0 3.0 H

Body Loss dB 3.0 3.0 I

Propagation Slope dB/dec 35.0 35.0 J

Outdoor Coverage Probability % 0.95 0.95 K

Outdoor Slow Fading STD dB 7.0 7.0 L

Outdoor Slow Fading Margin dB 4.30 4.30 M

Outdoor Planning Threshold dBm -131.4048 -109.6586 N = B+I+M

Indoor Coverage Probability % 0.90 0.90 O

Indoor Slow Fading STD dB 9.0 9.0 P

Indoor Slow Fading Margin dB 7.4200 7.4200 Q

Building Penetration Loss dB 15.0 15.0 R

Indoor Planning Threshold dBm -113.2848 -91.5386 S = B+I+Q+R

MAXIMUM PATHLOSS

Outdoor dB 152.4048 159.4386 T = F-N

Indoor dB 134.2848 141.3186 U = F-S

(i) Receiver Noise Density (dBm/Hz):

Receiver noise density is the noise power per Hertz including the thermal noise and the

receiver noise figure of the system at the receiver input.

173.93 48 169.93165.93 / . 4.4

(j) Receiver Noise Power (dBm):

Receiver noise power is the total noise power seen at the receiver input within the noise

bandwidth. That is,

23

( 10 · log

10 · log 3.84 10 169.93165.93 104.089

100.089 4.5

where, W is the chip rate.

(k) Interference margin or Nose Rise (dB):

Interference margin is also called noise rise. It is the margin due to loading in the system.

The interference margin is needed in the link budget because the loading of the cell, the

load factor, affects the coverage. The more loading is allowed in the system, the larger is

the interference margin needed in the uplink, and the smaller is the coverage area. For

coverage-limited cases a smaller interference margin is suggested, while in capacity-

limited cases a larger interference margin should be used in the link budget. Typical

values for the interference margin in the coverage-limited cases are 1.0-3.0 dB,

corresponding to 20-50% loading [7].

Figure 4.4 Loading Effect

The interference margin is calculated as

10 · log 1 4.6

10 · log 1 0.60.5 3.979

3.010

where, η is the loading factor.

0

2

4

6

8

10

12

14

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

Interferen

ce M

argin (dB)

Loading (%)

24

Using equation (4.6), a graph of interference margin vs. loading is plotted in Figure 4.4.

We can notice that the interference margin is increases rapidly when the load in the system

increases. If the load in the system is too high, say 90%., we need 10 dB margins to

balance the interference. This means we are using more power to control the interference

only. If the load increases ideally 100%, then the system cannot work at all. Hence,

loading plays a vast role in the system performance.

(l) Total Interference Level (dBm):

Total interference level is the total noise power seen at the receiver input including the

noise rise. Hence,

104.089100.089 3.979

3.010 100.10997.078 . 4.7

(m) ⁄ :

⁄ is the KPI of the QoS. It is the ratio of the received bit energy to the

thermal noise. is the received energy per bit multiplied by the bit rate. is the noise

power density divided by bandwidth. Typically, E N⁄ values of 5 dB in UL and 8 dB in

DL are used for speech connection.

(n) Processing Gain (dB):

The ratio between the transmitted modulation bandwidth and the information signal

bandwidth is called spreading factor and the logarithmic value of the spreading factor is

known as processing gain. If the data rate is smaller than the chip rate, then it provides a

gain to the signal to interference ratio after dispreading in both directions. Processing gain

is WCDMA-specific parameter.

10 · log ⁄ 4.8

10 · log ..

24.979

where, W is the chip rate and R is the user bit rate.

25

(o) Receiver Sensitivity (dBm):

Receiver sensitivity is the minimum signal level needed at the receiver input which just

satisfies the ⁄ requirements over the total interference level.

4.9

100.10997.078 58 24.979

24.979 120.089114.058 .

That is, -120.089 dBm is the receiver sensitivity of base station and -114.058 dBm is the

receiver sensitivity of mobile station.

(p) Rx Antenna Gain (dBi):

Rx antenna gain is the receiving antenna gain compared to isotropic radiator (an antenna

which radiates equally in all directions). Typically, antenna gains in base station are high

because of directional antenna. A value of 18 dBi is used for the base station receiving

antenna gain in the simulation. Antenna used in the mobile stations is presumed Omni-

directional and therefore their gain is assumed to be 0 dBi.

(q) LNA Noise Figure (dB), (r) LNA Maximum Gain (dB), (s) LNA Insertion Loss (dB), (t)

Total LNA Gain or Improvement (dB):

Low Noise Amplifier (LNA), also called Mast Head Amplifier (MHA), is used as an

effective method to improve the cell coverage in uplink direction. This is achieved by

amplifying the received signal by LNA before the receiver losses. It is used just after the

receiving antenna. Figure 4.5 depicts the situation how LNA is used. The noise figure of a

system having cascade amplifiers is calculated by Friis formula:

12 1

13 1

1 · 2 4.10

The improvement of noise figure in the system after using LNA is calculated as the ratio

between the NF without LNA and with LNA. That is,

4.11

·1 · · 1

26

where, is the noise figure of base station, is the cable loss, is the noise

figure of LNA, is the gain of LNA.

Using given parameters, the improvement of noise figure in the system after LNA is 2.835

dB. Hence, using LNA in this simulation, a 2.835 dB gain is achieved in uplink direction.

Besides the gain improvement in uplink direction, LNA has negative effect in downlink

direction. It produces some insertion loss in downlink direction. Hence, in power budget,

we have used the insertion loss of 0.1 dB in downlink direction.

(x),(D) Cable, Connector, and the Combiner Loss (dB):

These are the combined losses of all the transmission system components between the

transmitter output and the antenna input. Combiner loss is taken in account only in

downlink direction. Typically, cable loss depends on the frequency and its diameter. Thin

cable has more loss than thick cable. Cable loss is higher at higher frequency. The cable

loss in the base station side is assumed to be 0.061 . A 100 m cable length is used in

the simulation. The net cable loss in base station side is 1.22 dB. The cable loss in mobile

side is assumed to be 0 dB. In this simulation, there are no connector and combiner losses.

(y) Antenna Diversity Gain (dB):

It is the gain provided by the receiver diversity or transmitter diversity antenna. Antenna

diversity gain has to be taken in account separately only if the diversity is used and it is

not included in the ⁄ requirements.

27

(z) Soft Handover Diversity Gain (dB):

It is defined as the macro-diversity gain against fast fading caused by the multi path

propagation. The soft handover diversity gain is the different in the uplink and the

downlink directions due to a different macro-diversity combining method.

(A) Power Control Headroom (dB):

This is commonly known as the fast fading margin. Some margin is needed in the mobile

station transmission power for maintaining adequate closed-loop fast power control in

unfavorable propagation conditions such as near the cell edge. This applies specially to

pedestrian users, where ⁄ to be maintained is more sensitive to the closed-loop

power control [10]. Power control headroom is taken into account in the uplink power

budget. It is taken into account because at the cell edge, the mobile station transmitter is

transmitting continuously at full power and thus cannot follow the fading according to the

uplink power control commands.

(B) Required Signal Power (dBm):

This is the required signal power needed at the receiving end for the connection.

. 4.12

The required signal power in UL is -138.704 dBm and in DL is -116.958 dBm.

(C) Tx Power per Connection (dBm):

It is the maximum transmitter power per traffic channel at the transmitter output for a

single traffic channel. A traffic channel is defined as the communication path between a

mobile station and a base station used for user and signaling traffic.

(F) Peak EIRP (dBm):

Peak Effective Isotropic Radiated Power is the resultant output power of the transmitter

ready to transmit after system losses and the transmitter antenna gain.

. 4.13

28

(G) Isotropic Path Loss (dB):

Isotropic path loss is the path loss between the transmitting and receiving end.

4.14

.

(H) SHO Gain (dB):

The soft handover phenomenon gives an additional gain against the fast fading that takes

place in the network. Due to the soft handover phenomenon, mobile connectivity to a base

station gives a better signal quality. Thus due to macro diversity combinations, the soft

handover gain has a positive impact on the base station. The total soft handover gain is

assumed to be between 2.0 and 3.0 [7], including the gain against slow and fast fading.

(I) Body Loss (dB):

Body loss is the loss of signal by the user’s body. The loss occurs when the user’s body

lies in the path of signal between the base station and the mobile station. That is, the body

loss depends on how the mobile station antenna is oriented towards the base station

antenna. Typical value of 3 dB is assumed as body loss.

(J) Propagation Slope (dB/decade):

Propagation slope characterizes the type of environment. It indicates that how much signal

is attenuated by distance in an environment. The propagation slope of 35 dB/decade is

used.

(K) Outdoor Coverage Probability (%), (L) Outdoor Slow Fading STD (dB), (M) Outdoor

Slow Fading Margin (dB), (O) Indoor Coverage Probability (%), (P) Indoor Slow Fading

STD (dB), (Q) Indoor Slow Fading Margin (dB), (R) Building Penetration Loss (dB):

These are the planning thresholds for the outdoor and indoor users. In this simulation, only

indoor planning thresholds are used. Building penetration loss of 15 dB with 9 dB indoor

slow fading margin is used in both the UL and DL direction.

. 4.15

29

Maximum Path Loss:

The difference between the required signal power and the peak EIRP is the maximum

allowed path loss. The maximum allowed path loss of 134.284 dB is calculated for UL

and 141.318 dB for DL. It is clear that UL direction is limited and due to this reason the

cell was dimensioned based on UL path loss.

4.1.2 COST-231-Hata Model

The COST-231-Hata model [18] is the extension of Hata’s propagation model. It is used

for the coverage calculation in macro-cell environment where the base station antenna

height is above the average rooftop level of the buildings adjacent to the base station. The

propagation model describes the average signal propagation in that environment, and

converts the maximum allowed propagation loss in dB to the maximum cell range in

kilometers [7].

The COST-231-Hata Model in the form of propagation loss is given as:

46.3 33.9 13.82

44.9 6.55 4.16

where is the path loss (dB), is the frequency (MHz), is the base station antenna

height (m), is the mobile station antenna height (m), is the mobile station

antenna gain function (dB), d is the distance between the base station and the mobile

station (km), and C is the area correction factor (dB). The mobile station antenna gain

function is given as:

For a medium or small city

1.1 0.7 1.56 0.8 . 4.17

And for a large city

8.29 1.54 1.1 200 3.2 11.75 4.97 200

4.18

30

The area correction factor is given as:

0

3

4.19

4.1.3 Cell Capacity and Cell Range (Coverage Area) Estimation

The coverage and the capacity in UMTS have their direct impact on each other [19-25].

The more the users served by a network means the more capacity the system has but at the

same time the load of the system increases beyond the limit in proportion of increasing

users due to which the interference in the system increases which in turns degrades the

service. In such a limiting case, the users at the far distance must have to move towards

the base station to serve properly which means the cell range decrease which is also

known as cell breathing.

On the other hand, if the users want to get proper service without moving towards the base

station, then they must have to use their full transmit powers to overcome the interference

which consumes the power of the traffic channels that means there is the decrease of

capacity. Hence, in UMTS we must have to take in account both the coverage and

capacity planning simultaneously. To synchronize the cell range in both the coverage and

capacity planning, let us first calculate the cell area from the capacity planning and then

use this cell area in the coverage planning to find the base station antenna height and cell

range.

4.1.3.1 Cell Capacity Estimation

The capacity of a system means the total number of subscribers the system can serve at a

time satisfying the required quality of service. Since WCDMA (UMTS) is interference

limited, the capacity of such a system varies time to time which depends on the present

31

situation of the system. The main parameters affecting the capacity of WCDMA system

are the present load of the system, the other-to-own cell interference which is also known

as little i, the signal energy per bit divided by the noise spectral density, the activity factor

of the users, the user’s bit rate and the orthogonality of the users. The orthogonality1 of the

users affect only in the downlink direction.

According to [10, Eq. (3.6), p78], the uplink load equation is given as

1

1·

· · 1 · 4.20

where,

= the uplink load factor

N = the total number of users

= the signal energy per bit divided by the noise spectral density of user k

W = the wideband chip rate

= the bit rate of user k

= the activity factor of user k

= the other-to-own cell interference

= the number of sectors and

= the sectorisation gain.

If the service in the system is only voice and all N users have the same rate of R, then the

eq. (4.20) is reduced to

·1

1 · ⁄· · 1 · . 4.21

1 The orthogonality represents how well the noise rejection  is  improved between traffic channel and cell. 

That is, how well the mobile station is able to decode its code. 

 

32

Including the bearer control-overhead factor2 ( in the speech service, the eq. (4.21) can

be written as

·1

1 · ⁄· · 1 · . 4.22

Based on the uplink load equation (4.22), the example of capacity calculation used in the

simulation is shown in table 3.

Table 3: An Example of Capacity Calculation based on Load Equation GENERAL INFO Units Value

Frequency MHz 2140 a

Chip Rate Mcps 3.84 b

Tempereature K 293 c

Boltzmann's Constant J/K 1.38E-23 d

SERVICE INFO UPLINK DOWNLINK

Units Value Value

Load % 60 50 e

Bit Rate kbps 12.2 12.2 f

Required Eb/No dB 5 8 g

3.162 6.310 g = 10^(g/10)

Activity Factor % 50 50 h

Other-to-Own Cell Interference % 89 89 i

Bearer Control-Overhead Factor % 25 25 j

Number of Sectors 6 6 k

Sectorisation Gain 5.02 5.17 l [10, Table 3.21, p132]

Total Number of Users in Uplink 38.971475 Using eq.(4.22)

The all terminals in the planning area are distributed uniformly having traffic density

of 100 / . One erlang (Erl) is the equivalent of one call for an hour. Here, one

2 The bearer control overhead factor accounts for the fact that control channel power is transmitted even 

during the inactive periods of a call [21]. 

33

erlang represents one terminal or user. Then, the area occupied by the total number of

terminals in a cell is calculated as

⁄ 38.971475

100 . . 4.23

Hence, from the capacity planning the cell area is 0.38971475 km2.

4.1.3.2 Cell Range (Coverage Area) Estimation

The Figure 4.6 illustrates the cell dimensioning. The cell area (shaded area) is given by

2 ∆ 212 2 2 · 4.24

Figure 4.6 Cell Dimensioning

From the right angled triangle ABC,

2⁄ · 4.25

34

If the hexagon is regular, i.e., the side length l and the radius r are equal, then √ ,

and hence the area of the cell is

√34 · 4.26

The area of the cell in both the Figure 4.6 (c) and 4.6 (d) is the same though the shape of

the area or the dominance area is different. With the reference of service, the cell range

can be defined as the maximum distance an antenna can serve a user. Using this definition

the cell range in Figure 4.6 (a) and 4.6 (b) is the same i.e., the radius (r) of the hexagon.

Using the Eq. (4.26), the cell range corresponding to the area 0.38971475 km2 (from the

capacity planning) is

4 0.38971475

√30.948687 km . · 4.27

The COST-231-Hata model is a well known model for the estimation of cell range and

antenna height in the macro-cell environment. For the mobile station antenna height of 1.5

m, frequency 2140 MHz and the cell range of 0.948687km, the COST-231-Hata model

(Eq. (4.16)), for medium city reduces to

158.1241 13.6702 · · 4.28

Using the above equation (4.28) and the path loss from the link budget calculation, the

base station antenna height ( ) can be calculated. From the link budget calculation, it is

seen that the path loss in the uplink direction is limited. Hence we must use the uplink

path loss. The maximum path loss in the uplink direction for the indoor user is 134.2848

dB. Then the corresponding base station antenna height is calculated as

10. .

. 55.45 m · 4.29

Hence, from the capacity and coverage planning the cell range of 948.68 m can be

achieved by the base station antenna height of 54.45 m. The cell area is 0.38971475 km2.

Therefore, 948.68 m cell range and 54.45 m base station antenna height are the results

from the pre-planning.

35

4.2 Detailed Planning

After dimensioning phase is over, the detailed planning starts by defining the site

properties such as site locations, base station configurations, network layout, antenna

selections and antenna directions. Along with this, the all-important process of defining

parameters settings takes place. The detailed planning process is sometimes referred to as

pre-launch optimization, and radio network planning tools have an important role in this

phase. The output of the detailed coverage and the capacity planning are the base station

locations, configurations and parameters (See Appendix B for detailed configuration).

4.2.1 Planning Tool

Radio network planning tool plays a significant role in the daily work of network

operators [10]. In the second generation (2G) systems, detailed planning concentrated

strongly on coverage planning but in the third generation (3G) systems, a more detailed

interference planning and capacity analysis than simple coverage optimization is needed

[7]. The planning tool used for the simulation of 3G system is a static simulator that is

based on average conditions, and snapshots of the network can be taken. A detailed

description of the planning tool (Nokia NetAct Planner 4.2) used in this thesis can be

found in [22] or in the documentation of [21].

4.2.2 Coverage Planning

For the coverage planning, the first task is to set up all the attributes obtained as a result of

pre-planning into the planning tool. These attributes include: propagation models and

corresponding correction parameters; equipments definitions like feeder length and

attenuation; and antenna equipment parameters in terms of electrical properties like gain

and radiation patterns. Furthermore, amplifier equipment properties are defined in terms of

36

gain and noise figures. Finally, Node B (base station) and its sector equipment properties

are defined. Typically, these involve transmitting power parameters (from the power

budget), antenna line configuration (i.e., feeder and antenna type, antenna diversity,

amplifiers), noise rise limitations and noise figures (See Appendix B for more detailed)

[12]. In the coverage planning process, the goal is to meet the set up coverage criteria for

the service. The parameters required as input to perform the initial coverage planning are

summarized in Table 4. A brief description of table 4 is described in next page.

Table 4: Parameters Needed for Coverage Planning [12]

Entity Parameters Remark

Propagation

model

Prediction frequency

Correction parameters Model

Clutter

Diffraction

Topography

Morphography

Antenna Gain

Radiation pattern

Beam width Vertical, horizontal

Feeder Attenuation Frequency, Feeder loss,

connector loss,

Amplifier Gain

Noise figure

Loss Insertion loss

Node B Location Geographical location

Number of hardware channels

Maximum number of soft handover

connections

37

Sector configuration

Transmit powers Node B transmit power

Pilot channel power

Maximum power of

traffic connection

Common channel powers

Antenna diversity Transmit / Receive

Amplifier

Feeder

Antenna Type

Tilt

Direction

Height

Service Coverage calculation area

Coverage thresholds

The propagation model is a mathematical attempt to model the real radio environment as

closely as possible. The parameters needed for the propagation model are: the prediction

frequency and correction parameters to model the environment. The prediction frequency

of 2140 MHz is used in the propagation model for the prediction of path loss in each pixel

of the planning area. The COST-231-Hata model is used in the simulator for the

calculation of propagation loss. The clutter defines the type of the planning area such as

open land, water, forest, roads, suburban, urban, industry and so on. The diffraction is a

multiplying factor for the diffraction calculation. The topography corrections are based on

the terrain height profile generated for each path during the calculations. Usually, the

propagation loss is predicted for an urban area; therefore, a correction is needed for other

areas like suburban, rural etc. Morphography corrections are based on the terrain type.

The parameters needed for antennas are: gain, radiation pattern, vertical and horizontal

beam width. The feeder (cable) related parameters are: frequency, cable loss, connector

38

loss. The amplifier used in the simulation is Low Noise Amplifier (LNA) which increases

the uplink power budget. The parameters needed for LNA are: gain, noise figure, insertion

loss. The Node B (Base Station) is the pillar of the UTRAN. A number of parameters are

assigned to each Node B such as: its geographical location, number of hardware channels,

maximum number of soft handover connections, sector configuration, transmits powers,

antenna diversity, amplifier, feeder, and antenna. The Node B transmission power is

divided into three parts: Pilot Channel Power, Common Channel Power and

Synchronization Channel Power. The Pilot Power is the power dedicated by the base

station for the transmission of the Common Pilot Channel (CPICH). The CPICH is used to

facilitate channel estimation at the terminal and provide a reference for the user equipment

(UE) measurements [21]. Only receiving antenna diversity was used in the simulation.

The antenna is characterized by its type, tilting (electrical or mechanical), direction,

height. The service defines the type of service (speech or circuit switched data or packet

switched data) and the level of service probability in the planning area.

4.2.3 Capacity Planning

In capacity planning phase, interference estimations are of vital importance which is

accomplished with simulations of the network design. Typically, Monte Carlo simulations

are used to aid in providing a foundation for capacity simulations of the network design.

Monte Carlo simulations simulate the outcome of a service establishment for a number of

users randomly distributed in the network. The resulting outcome is collected in what is

commonly called a “snapshot”. The simulation process is repeated until a satisfactory

number of snapshots are generated to give a statistically significant output [12].

The parameters required for a Monte Carlo simulation are:

• bit rate

• service

• terminal type

39

• Bit rate definition

For bit rate, the necessary definitions are mainly related to corrections of ⁄

requirement values accounting for user equipment speed and gain from soft or softer

handover connections. The corrections possible to define are: [12]

- Mobile transmitting power corrections

- Average power rise gain corrections

- Power control headroom gain corrections

- Downlink ⁄ target reductions

Examples of such definitions are depicted in Figures 4.7 to 4.10.

Figure 4.7 Mobile Transmitting Power Corrections

A mobile station in soft and softer handover situation effectively sees an uplink gain and

this allows the mobile station to transmit at lower power. The mobile transmit power

(TXP) gain depends on two factors: the mobile speed and the difference between the best

two uplink ⁄ values achieved by cells in the mobile’s active set. As shown in Figure

4.7, for example, if the mobile is in soft handover situation with 3 km/hr speed and the

difference between the two uplink ⁄ values is 0 dB, then the mobile TXP gain

increases by 2dB.

40

The average power rise (PR) gain correction parameters are shown in Figure 4.8. Due to

fast power control, a mobile transmit power varies in a way which causes a rise in the

average interference experienced in the surrounding cells. This average power rise for the

interference caused by the mobile is lower for the mobiles in soft handover situation. The

PR gain also depends on two factors: the mobile speed and the difference between the best

two uplink ⁄ values achieved by cells in the mobile’s active set.

Figure 4.8 Average Power Rise Gain Correction Parameters

The power control headroom (PCH) gain correction parameters are shown in Figure 4.9.

When the low-speed mobile station is approaching the cell edge, the mobile station

transmission power continuously reaches its maximum limit and a situation occurs where

the closed-loop power control is unable to compensate the fast fading which in turn leads

to higher UL ⁄ requirement. To model this situation, a power control headroom

margin is required in the link budget for the uplink direction. This headroom is smaller for

mobile station in soft handover situation. The PCH gain also depends on two factors: the

41

mobile speed and the difference between the best two uplink ⁄ values achieved by

cells in the mobile’s active set.

Figure 4.9 Power Control Headroom Gain Correction Parameters

The downlink gain reduction correction parameters are shown in Figure 4.10. This

describes the reduction in downlink target ⁄ that occur in soft handover situation.

This gain depends on two factors: the mobile speed and the difference between the two

highest pilot ⁄ values. The Max TX Power is set to 31 dBm. If the Max TX Power is

less than the combined Pilot Channel, Common Channel and Synchronization Channel

Power, then the cell will be turned off (that is, will have no transmit power).

42

Figure 4.10 Downlink Target Reduction Correction Parameters

• Service definition

The service definition requirement defines the service type. In this thesis, only the circuit

switched service is considered. An example of service definition is shown in Figure 4.11.

The activity factor describes the proportion of time the service is active. The service

activity factor of 50% was chosen for both the uplink and downlink direction.

43

Figure 4.11 General Parameters of Service Definition

• Terminal Type definition

In modern cellular network, subscribers can have different types of mobile terminals with

different properties. The terminal type definition requirement is to have service-dependent

terminal definitions available, e.g., UE dynamic range, UE transmitting power, body loss,

antenna gain, and noise figure of UE. Apart from the necessary terminals or UE

parameters, the terminal definitions need parameters to define the terminal properties in

terms of amount and terminal distribution density [12]. The service that the terminal is

using also defined. The model of terminal velocity is also defined.

Examples of terminal definitions are shown in Figure 4.12 to 4.15.

44

Figure 4.12 Terminal Location

The Figure 4.12 shows that all the terminals are located in only one type of clutter named

inland water. The clutter named “inland water” is a kind of clutter created for the

simulation environment which accounts a smooth surface area with zero meter ground

height. The Figure 4.13 shows how the terminals (traffic) are distributed. The terminals

were distributed inside the planning area surrounded by a polygon as 100 terminals per

square kilometers. The Figure 4.14 describes the assignment of UE-specific parameters.

The Max Mobile Power is the limit of mobile transmission power. If the calculated

required transmit power is higher than this figure, then the terminal connection will be

rejected. The TX Dynamic Range sets the minimum TX power of the terminal. The

minimum power (dBm) is given by the subtraction of TX Dynamic Range (dB) from the

Max Mobile Power (dBm). The required pilot SIR is the minimum pilot signal-to-

interference power needed for a connection. The power step size is the power quantization

step for the terminal. The body loss is the loss of signal through absorption by user.

45

Figure 4.13 Terminal Distribution

Figure 4.14 UE-Specific Parameters

46

Figure 4.15 UE Mobility Parameters

The Figure 4.15 shows the mobility of mobile station. The maximum mobile speed of 3

km/hr was assigned.

4.3 Optimization

The process of optimization begins in the early phase of network planning, right after pre-

planning. Optimization contains different kinds of planning-related actions to solve the

problem. It involves continuous trouble shooting; it could also be called re-planning

because all planning phases and their results must be checked before any modifications

can be made to the actual plan. Optimization is slightly different from the network

planning, focusing more on performance optimization by configuration changes (e.g.,

improving coverage by antenna height adjustments) than on launching. In our work, the

optimization results are the maximum cell range and the maximum antenna height the

network design can provide meeting the target service probability.

47

5 SIMULATION AND ANALYSIS

After dimensioning and verifying all the parameters in the detailed planning, the

simulation starts from coverage prediction in each pixel of the planning area. Static

simulation offers the most promising way for radio network planning [11]. As a result of

simulations, a static planning tool provides an estimate of average network behavior by

using a given network configuration, parameters, and traffic layer (including service

requirements and distribution). For this purpose a static planning tool seems to be

sufficient, as the whole radio network planning is typically based on average values (e.g.

slow fading margins, etc.) [11]. The Diagram below describes the simulation process [21].

Figure 5.1 Simulation Process

48

As shown in Figure 5.1, the simulation process can be divided in three phases:

- simulation set up phase

- simulation running phase and

- result view phase

In simulation set up phase, a simulation network is created by creating terminals, defining

services, crating cells and so on. The terminals with its parameters are created and then

spread inside the planning area. The service is defined in the planning area and parameters

required for uplink and downlink are assigned to the service. The terminals are assigned

with the defined services. The cell with its required parameters is created and is assigned

with the carriers. After creation of simulation network, the desired are and cells are chosen

for the simulation.

In the simulation run phase, a fixed number of snapshots and convergence limit are

chosen. The simulation then starts with a fixed number of iterations and snapshots. If the

convergence is not with the limit then the simulation run again. In result view, we can

view the result in two ways: displaying output on the digital map and viewing output as

report. By displaying the output array (for example, coverage probability, handover area

and so on) on the map, we can easily identify the problem area by observing. By view the

report, we can analyze the result in numerically. If the result is not satisfactory and we

have found the proper reason for problem, we go back to the simulation set up phase and

changes the particular parameter relevant the problem and then run the simulation again

and again. In this way, lastly we get the satisfied result.

5.1 Simulation Methodology

In the static planning tool (Nokia NetAct Planner 4.2) [21], the actual performance

estimation is normally divided into two parts: coverage predictions and performance

analysis (Monte-Carlo analysis).

49

Coverage Analysis

In coverage analysis, an array of path loss is calculated on each pixel of the planning area.

The path loss is calculated for each antenna on each site using the selected propagation

model. The predictions of path loss of each site are based on the propagation model as

well as the network configurations such as antenna radiation pattern, antenna down tilt.

The time taken to create the prediction arrays depends on the model used, the number of

sites, and the size of the radius [21]. The COST-231-Hata propagation model was used for

the prediction of path loss. The planning area used in the simulation has same type of

clutter (smooth) with area correction factor of -5 dB for the whole simulation area.

Performance Analysis (Monte-Carlo Analysis)

“In the performance analysis part, the predicted paths losses are utilized for solving the

required transmit power needs iteratively in the uplink and downlink direction. In the

capacity analysis during Monte Carlo process, the behavior of the network is analyzed

over various instances of time or “snapshots”, where mobile terminals are placed in

randomly determined locations according to the traffic distribution. At the beginning of

each snapshot, base station’s and mobile station’s powers are typically initialized to the

level of thermal noise power. Thereafter, the path losses matrices are adjusted with

mobile-dependent standard deviations of slow fading. After this initialization, the transmit

powers for each link between base station and mobile station are calculated iteratively in

such a manner that the SNR requirements for all connections are satisfied for uplink and

downlink” [25].

50

5.2 Network Configurations

A macro-cellular network was configured in a shape of regular hexagonal grid of 19 sites

(base station) with 6-sectored, i.e., the total number of cells or sectors are 114 19 6 .

The site location was selected at the center of the hexagon. In the first case of

configuration, each antenna is pointing towards each corner of the hexagon (Fig 5.2 (a)),

whereas in the second configuration, towards each face of the hexagon (Fig. 5.2 (b)).

Figure 5.2 Network Configuration

Antennas used were with 5 degree electrical downtilt, 18 dBi gain, 33 degree horizontal

beam width and 6.5 degree vertical beam width. For network configurations having more

sectors, the electrical downtilt value of 5 to 7 degree can provide better results [5]. The

antenna electrical downtilt is a technique where the radiation pattern of an antenna array is

down-tilted uniformly in all horizontal directions by adjusting the relative phases of the

antenna elements [P1, 25]. In first configuration (Fig. 5.2 (a)), the antenna directions were

0°, 60°, 120°, 180°, 240° 300° whereas, 30°, 90°, 150°, 210°, 270° 330° in the

second configuration (Fig. 5.2 (b)).

51

5.3 Simulation Environment and Parameters

The simulation environment was considered as a smooth flat surface with area correction

factor of -5 dB representing a suburban environment. All the users were considered to be

inside a building with slow fading standard deviation of 9 dB and a 15 dB Building

Penetration Loss. Only speech service (12.2 kbps) was considered. The maximum mobile

speed of 3 km/hr was considered. The network was loaded with a homogeneous traffic

distribution of 100 ⁄ .

Table 5: Cell Related Parameters

Pilot Power 33 dBm

P-CCPCH Power 28 dBm

S-CCPCH Power 33 dBm

P-SCH Power 30 dBm

S-SCH Power 30 dBm

Node B’s Noise Figure 4 dB

Orthogonality Factor 0.65

Table 5 gathers the cell related parameters used in the performance analysis. The Pilot

power is the power dedicated by the base station for the transmission of the Common Pilot

Channel (CPICH). The CPICH is used to facilitate channel estimation at the terminal and

provide a reference for the UE measurements. The P-CCPCH (Primary-Common Control

Physical Channel) power corresponds to the power dedicated to the P-CCPCH which

carries the Broadcast Channel (BCH) that conveys the basic network information required

by the terminal for connection. The S-CCPCH (Secondary-Common Control Physical

Channel) power is the power dedicated for the transmission of the S-CCPCH which

conveys paging and control information. The P-SCH (Primary-Synchronization Channel)

power and S-SCH (Secondary- Synchronization Channel) power are the peak power

dedicated to the SCH (Synchronization Channel) for cell search. The Node B’s Noise

Figure is used to calculate the background (thermal) noise for a cell. The Orthogonality

52

Factor represents how well the noise is rejected between the traffic channels on the same

cell. The orthogonality depends on the multipath conditions. In case of no multipath the

orthogonality is 1 which means the interference from the serving cell is cancelled and so

UE is able to decode its code easily.

Table 6: Radio Resource Management (RRM) Related Parameters

Uplink Noise Rise 4 dB

Maximum Node B TX Power 41.5 dBm

Soft Handover Window 3 dB

Active Set Size 3

Maximum UL Power per Connection 21 dBm

Maximum DL Power per Connection 40 dBm

Table 6 represents the RRM parameters used in the analysis. The Uplink Noise Rise is a

limit which indicates that the uplink noise due to the increment of load in the system

should not increase this limit. The Maximum Node B TX Power is the maximum power

the Node B can transmit. If the Maximum Node B TX Power is less than the combined

Pilot Channel, Common Channel and Synchronization Channel Power, then the cell will

be turned off, that is there will have no transmit power. The Soft Handover Window is a

factor which determines whether a cell should lie in the mobile’s active set size or not.

This is specified on a per cell basis. The Active Set Size is a number which tells the

maximum number of cells to which a mobile is connected simultaneously. If the active set

size is 3, then one of these cells will always be the serving cell and the other two cells will

be the handover cells. The Maximum UL/DL Power per Connection is the maximum

power required for a radio link connection in uplink and downlink direction.

Table 7 represents the corrections of ⁄ requirement values accounting for user

equipment speed and gain from soft or softer handover connections. Due to Soft/Softer

Handover (SHO/SfHO) various performance improvements can be achieved [5, 10]. The

parameters in table 7 are described earlier in the section 4.2.3 from Figure 4.7 to 4.10.

53

Table 7: SHO/SfHO Improvements at 3 km/hr

Improvement vs. SHO/SfHO link difference 0 dB 3 dB 6 dB

UL ⁄ Reduction – SHO 2 dB 1 dB 0 dB

UL ⁄ Reduction – SfHO 3 dB 2 dB 1 dB

DL ⁄ Reduction – SHO/SfHO 3 dB 2 dB 1 dB

PR Gain – SHO 0 dB 0 dB 0 dB

PR Gain – SfHO 1.5 dB 1 dB 0.5 dB

PCH Gain – SHO 1 dB 0.5 dB 0 dB

PCH Gain – SfHO 2 dB 1.5 dB 1 dB

5.4 Analysis Method

The target of the analysis was to find the maximum cell range still achieving the target

service probability. The service probability is the ratio between the successful connections

and the attempted connections. The maximum cell area was found for a 95 % service

probability, i.e., the probability that the user is served by the system in any location within

the area. For the analysis purpose, an area in the center of both the topologies (Fig. 5.3,)

was selected based on the symmetry and interference point of view because this analysis

area represents the continuous networks. We can notice that inside the analysis area (the

shaded thicker hexagon), there are 18 cells in the first topology (Fig. 5.3 (a)), whereas

only 12 cells in the second topology (Fig. 5.3 (b)). Actually, in the second topology (Fig.

5.3 (b)), the analysis area (shaded area) covered also half portion of two cells in small

hexagon but due to complexity we did not account these halve cells for the analysis. In

other ways, we can say that the analysis area (the shaded thicker hexagon) in the second

topology consists of 12 antennas (6 at the center of the analysis area and 1 at each corner

of the analysis area).

54

Figure 5.3 Analysis Areas (The shaded area inside the thicker hexagon)

The target service probability may not be achieved either by the lack of coverage or

capacity. The coverage limited problem will occur whenever the transmitter does not have

sufficient power to satisfy the received signal quality at the receiver, whereas the capacity

limited problem with occur whenever the maximum downlink capacity (DL transmit

power or the maximum uplink capacity, noise rise) of the cell is exceeded [5].

Antenna height and the cell range are the main design parameters for the

network configuration considered in this analysis. The achieved service probability is a

function of both of these parameters as in [5]

, .

The target of the analysis is to find the maximum cell range still delivering the required

service probability of 95 %. That is,

& , 95%

55

5.5 Analysis Results

A. Optimum Performance Analysis

A number of simulations were done with multiple combinations of cell range and antenna

height to find the optimum performance for both network configurations. The simulation

results are shown below. Each result in the service probability arrays corresponds to a

combination of cell range and antenna height. Each row represents an antenna height and

each column represents a cell range.

Case a) Antenna Direction: 0/60/120/180/240/300

Service Probability (%) = [0.9627 0.9288 0.8808 0.8525 0.8133 0.7145

0.9749 0.9536 0.9151 0.8806 0.8329 0.7267

0.9782 0.9617 0.9172 0.8736 0.8210 0.7196

0.9780 0.9616 0.9087 0.8607 0.8090 0.7114

0.9776 0.9597 0.8939 0.8435 0.7917 0.6995

0.9775 0.9472 0.8563 0.8052 0.7565 0.6685]

Antenna Height (m) = [30 40 50 55 60 70] T

Cell Range (m) = [808 908 1008 1058 1108 1208]

Case b) Antenna Direction: 30/90/150/210/270/330

Service Probability (%) = [0.9555 0.9182 0.8694 0.8407 0.8068 0.7170

0.9732 0.9474 0.9082 0.8765 0.8324 0.7295

0.9801 0.9607 0.9139 0.8726 0.8195 0.7199

0.9821 0.9637 0.9074 0.8585 0.8076 0.7100

0.9833 0.9641 0.8931 0.8415 0.7893 0.6956

0.9850 0.9566 0.8604 0.8083 0.7558 0.6690]

Antenna Height (m) = [30 40 50 55 60 70] T

Cell Range (m) = [808 908 1008 1058 1108 1208]

56

The surface plot of service probability vs. cell range and antenna height is shown in Figure

5.4. From the plot we can notice that the performance is almost similar in both the

configurations. The plot also tells that whenever the antenna height is increasing the

service probability is decreasing.

Figure 5.4 Surface Plot of Service Probability Plot vs. Cell Range and Antenna Height

800 9001000

1100 12001300 30

40

50

60

70

0.65

0.7

0.75

0.8

0.85

0.9

0.95

1

Antenna H

eight (m

)

Case a (Antenna Direction: 0/60/120/180/240/300)

Cell Range (m)

Serv

ice

Prob

abili

ty

800 9001000

1100 12001300 30

40

50

60

70

0.65

0.7

0.75

0.8

0.85

0.9

0.95

1

Antenna H

eight (m

)

Case b (Antenna Direction: 30/90/150/210/270/330)

Cell Range (m)

Ser

vice

Pro

babi

lity

57

To find the optimum cell range and antenna height, a service probability plane of 0.95

(95%) was plotted through the interpolated surface (the plot of service probability vs. cell

range and antenna height) as shown in Figure 5.5a and 5.6a. Each point at the interception

of the plane and the interpolated surface represents 95% service probability corresponding

to an antenna height and a cell range. The task of the plot was to find the maximum cell

range and antenna height satisfying 95% service probability.

(a) Plot of Service Probability Plane through Interpolated Surface

(b) Plot of Cell Range vs. Antenna Height for 95% Service Probability

Figure 5.6 Optimum Performance Plot for Antenna Azimuth 0/60/120/180/240/300

58

The plot of cell range vs. antenna height for 90% service probability in Figure 5.6b and

5.7b indicate that when the antenna height is increasing the cell range is also increasing

and reaches a maximum point beyond which the cell range goes down if the antenna

height is further increased. The maximum cell range of 947 m at antenna height 49.5 m

was found for the configuration where the antennas are directed towards the corner of the

hexagon, whereas maximum cell range of 943.3 m at antenna height 54 m was found for

the configuration where the antennas are directed towards the base of the hexagon.

(a) Plot of Service Probability Plane through Interpolated Surface

(b) Plot of Cell Range vs. Antenna Height for 95% Service Probability

Figure 5.7 Optimum Performance Plot for Antenna Azimuth 30/90/150/210/270/330

59

B. Pilot Signal Strength at Optimum Point

The pilot signal strength plot of both configurations at the optimum point is shown in

Figure 5.8. The lowest signal can be found at the side of hexagon in first configuration

(Fig. 5.8 (a)), whereas at the corner of hexagon in second configuration (Fig. 5.8 (b)). It is

because the main beam is directed towards the corner in (a) and towards the side in (b).

The Antenna Azimuth 0 and Antenna Azimuth 30 mean the antenna direction starting

from 0 degree in first configuration and 30 degree in second configuration.

(a) Antenna Azimuth 0 (b) Antenna Azimuth 30

Figure 5.8 Pilot Signal Strength Plot

0

0,1

0,2

0,3

0,4

0,5

‐95 ‐90 ‐85 ‐80 ‐75 ‐70 ‐65 ‐60 ‐55

P(CP

ICH level <x)

Pilot Signal Strength x (dBm)

(c) Pilot Signal Strength PDF

Azimuth: 0Azimuth: 30

60

From the probability distribution plot of CPICH (Common Pilot Channel) power, it is seen

that the second configuration (Azimuth: 30) has larger coverage area covered with pilot

level below -82.5 dBm. It is because the second configuration has larger antenna height

and more interference. The average pilot strength is almost equal i.e., -75.5 dBm for

azimuth 0 and -74.5 dBm for azimuth 30.

C. EC/IO at Optimum Point

The EC/IO is the received chip energy relative to the total power spectral density which is

used as a link performance indicator in downlink. The distribution of EC/IO over the

analysis area is shown in Figure 5.9 (a) & (b).

(a) Antenna Azimuth 0 (b) Antenna Azimuth 30

Figure 5.9 EC/IO Plot

0

0,05

0,1

0,15

0,2

0,25

‐18 ‐16 ‐14 ‐12 ‐10 ‐8 ‐6

P(Ec/Io = x)

Ec/Io x (dB)

(c) Ec/Io PDF

Azimuth: 0Azimuth: 30

61

The lowest EC/IO level can be found at the middle of the side of hexagon in first

configuration (Fig. 5.9 (a)) and at the corner of hexagon in second configuration (Fig. 5.9

(b)). The probability distribution function plot of EC/IO (Fig. 5.9 (c)) shows that the

configuration (b) has higher portion of area with low EC/IO value which means the layout

(b) has high interference because the antennas are directing towards each other whereas

configuration (a) has higher portion of area with high EC/IO value.

D. Pilot Pollution at Optimum Point

The cells which are not in the active set size but provide an EC/IO level higher than the

pilot pollution threshold are termed as pilot polluters for the terminal.

(a) Antenna Azimuth 0 (b) Antenna Azimuth 30

Figure 5.10 Number of Pilot Polluters Plot

0

0,1

0,2

0,3

0,4

0,5

0 1 2 3 4

P(No. of P

ilot P

olluters = x)

Number of Pilot Polluters x

(c) Number of Pilot Polluters PDF

Azimuth: 0Azimuth: 30

62

The mean number of pilot polluters plot in the analysis area is shown in Figure 5.10.

From the probability distribution function plot of pilot polluters (Fig. 5.10 (c)), it indicates

that the configuration (b) has comparatively larger portion of coverage area having high

number of pilot polluters (>1.9) and low number of pilot polluters (<1.3).

E. Coverage and Capacity at Optimum Point

The results of coverage and capacity performance analysis are shown in table 8. The result

shows maximum cell range of 947 m with antenna height of 49.5 m and 943.3 m with

antenna height of 54 m for the first and second configurations respectively. The cell area

corresponding to 947 m cell range provides 0.3883 km2. Then, the total area covered by a

site is 2.3298 (= 6*0.3883) km2. From the three-sectored configuration performance [6],

the maximum cell range is 680 with antenna height of 31 m. The cell area corresponding

to 680 m cell range in three-sectored configuration provides 0.4004 km2 which means the

total area covered by a site in three-sectored layout is 1.2013 (=3*0.4004) km2. It means

the ratio of the area provided by six-sectored site to the three-sectored is 2.3298/1.2013

=1.939. Geometrically, it should be exactly double. But for the continuous coverage, we

must need some overlapping area between the adjacent cells for the successful handover.

Table 8: Analysis Results

Parameters Antenna Azimuth: 0 Antenna Azimuth: 30

Cell Range 947 m 943.3 m

Cell Area 0.3883 km2 0.3853 km2

Antenna Height 49.5 m 54 m

UL Little i 0.92 0.99

Noise Rise 3.271dB 3.380 dB

Number of Primary Links 37.415 37.175

Number of SHO Links 10.289 11.356

SHO Overhead 27.5% 30.5%

63

Percentage of Failure due to

DL Eb/No Range 16.48% 14.34%

DL Eb/No (Capacity) 1.13% 1.46%

UL Eb/No Range 94.94% 91.45%

Noise Rise (Capacity) 9.36% 15.48%

For the capacity analysis, from the three-sectored configuration performance [6], the total

number of primary links is 38.4. Then, the total number of primary links provided by a

three-sectored site is 3*38.4 = 115.2. Now, in case of six-sectored configuration, the

number of primary links for the first configuration is 37.415. Then, the total number of

primary links provided by a six-sectored site is 6*37.415 = 224.29. The ratio of the

capacity provided by a six-sectored site to the three-sectored site is 224.49/115.2 = 1.948

which is nearly double. Theoretically, it should be exactly double but due to increase of

sectors, the number of SHO links increases which consumes the recourses of traffic

channels. It is because in SHO area a mobile station has two or more links at a time due to

which a large portion of SHO region would increase the SHO overhead in the downlink

traffic. The high value of little i (other-to-own cell interference) and the SHO overhead

show that the cell overlapping in the second configuration is comparatively higher than in

the first configuration. The point is clear because in the second configuration the two

antennas are directing towards each other. The SHO overhead of 27.5% and 30.5% mean

1.27 and 1.3 radio links per user are utilized in the first and second configurations

respectively. The noise rise is also higher in second configuration.

The terminals can fail to connect due to many reasons. The main reasons for failure in

both the configurations are UL Eb/No Range and DL Eb/No Range. This means either the

base station or the mobile station does not have sufficient power to send their signals to

each other. This situation occurs when the terminal is located at the side of the hexagon in

the first configuration and at the corner of the hexagon in the second configuration. The

reason of failure due to noise rise indicates that the interference in the system is about to

64

reach the limit set in the planning parameter. The number of SHO links is also higher in

the second configuration which consumes the recourses of capacity.

65

6 CONCLUSIONS

The target of the thesis was to evaluate the optimum performance of six-sectored

configuration in hexagonal layout of WCDMA network. The two different configurations

were considered. The configurations were differed by 30 degree rotation of antenna

direction. The analysis of the configurations shows that a very similar maximum cell area

can be achieved. The results show that a maximum of 947 m cell range at antenna height

of 49.5 m can be achieved when the antennas are directed towards the corner of hexagon,

whereas 943.3 m cell range at antenna height of 54 m can be achieved when the antennas

are directed towards the side of hexagon for indoor coverage in semi-urban environment

where the traffic distribution is 100 Erl/km2.

The capacity analysis shows that the second configuration has high level of other to own

cell interference (little i) and SHO overhead which means higher overlapping. The main

reasons of failure at the optimum point are UL Eb/No Range, DL Eb/No Range. The UL/DL

Eb/No Range indicates that the network is coverage limited in both uplink and downlink

direction at the optimum point. This situation comes when the mobile station is at the side

of hexagon in first configuration and at the corner of hexagon in second configuration. In

this situation, either the base station or the mobile station does not have sufficient power

to reach their signal to each other. We can solve the coverage limited problem by

increasing the transmission power in both the uplink and downlink direction depending

upon the situation of problem. But this technique is not used frequently instead there are

many other techniques to solve the coverage limited problem such as using higher-order

transmit/receive diversity, booster for power amplifier in downlink, high gain low noise

amplifier in uplink, repeaters.

It is concluded that using six-sectored site we can get nearly double the coverage and the

capacity than the three-sectored site which is useful to meet the capacity demand in the

market. From the economic point of view, deployment cost can also be reduced because

higher cell range means higher coverage area which in turn reduces the number of sites

66

required in the planning area. It can be concluded that the network configuration where the

antennas are directed towards the corner of hexagon can provide better performance than

the configuration where the antennas are directed towards the side of the hexagon.

67

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