impact of antenna beamwidth, propagation slope and ... · propagation slope and coverage...

TAMPERE UNIVERSITY OF TECHNOLOGY Institute of Communications Engineering

FRANCESC BORRÀS TORÀ

Impact of Antenna Beamwidth,

Propagation Slope and Coverage

Overlapping on Capacity in WCDMA

Networks Diplomityö Master of Science Thesis Subject approved by the department council on 4.06.2003 Supervisor: Prof. Jukka Lempiäinen

Preface The work for this Master´s thesis was carried out in the radio communications group, in

the Institute of Communications Engineering, at Tampere University of Technology

(TUT), in the project �Planning and Topology of 3G Networks�.

I would like to thank Professor Jukka Lempiäinen for his help and my friend Jarno

Niemelä for his patience, personal abnegation and valuable support during my work. In

addition, I would like to thank all TUT personal: Sami (systems administrator), Tarja

(department secretary) and so many others for their efficiency and exquisite manner

during this wonderful year.

Furthermore, I would like to thank my roommate at TUT, Tuomo Kuusisto, for his

pleasant company, co-operation and fruitful working environment during all these

months.

I would also like to thank my home university in Barcelona, Universitat Politècnica de

Catalunya (UPC), for all these years of learning in an extraordinary environment.

Moreover, I would like to thank my sister Neus Borràs for her dedication and valuable

contribution for the fulfilment of this work and my girlfriend Mercè Gabaldà for her

patience during my stay in Finland.

Finally, I would specially like to thank my parents for their touching love, support and

understanding during my studies, since without this nothing would have been possible.

Tampere (Finland), 16.06.2003

Francesc Borràs Torà [email protected]

Colon 13

43748 Ginestar (Tarragona)

SPAIN

Telephone: + 34 977 409 041

ABSTRACT 3

Abstract

TAMPERE UNIVERSITY OF TECHNOLOGY Degree program in Information Technology Telecommunication Engineering Borràs Torà, Francesc: Impact of Antenna Beamwidth, Propagation Slope and Coverage Overlapping on Capacity in WCDMA Networks Master of Science thesis, 104 p. Examiner: Prof. Jukka Lempiäinen Institute of Communications Engineering August 2003 Keywords: UMTS, WCDMA, radio network planning, antenna beamwidth, antenna height, cell range, sectorisation Mobile communications sector has experienced a great growth during 1990�s. Nowadays, tendency is to provide global coverage and high capacity for high speed data services in a more flexible way. Universal Mobile Telecommunications System (UMTS) has been standardized to provide high capacity and global coverage. The air interface selected for UMTS is Wideband Code Division Multiple Access (WCDMA). This solution offers to operators a big number of significant advantages over alternative technologies, including increased network capacity, longer battery life for terminals and enhanced privacy for users. However, such benefits come at the cost of additional network complexity. This is why a background in GSM deployment is no guarantee of success in UMTS. Last estimates are that operator spending on the radio network planning of UMTS system will account for more than 60% of total capital expenditure. For this reason a robust network implementation (correct choices for key parameters like antenna beamwidth, antenna height, number of sectors/site, etc.) is critical if operators want to optimize capacity levels and enable multimedia services, which are a key element of the UMTS value proposition. In this work, impact on coverage and capacity of the system for different network configurations is investigated by using Nokia Networks static radio network planning tool NetAct WCDMA Planner 4.0, which uses Monte-Carlo simulations. After completed all these simulations, results are analysed and main conclusions are explained in order to make easier future works in the same area. To conclude, point out something significant: air interface technology (WCDMA), basic algorithms and radio network planning techniques are radically different respect to GSM, therefore, operators must demonstrate technical leadership and deployment experience in all these aspects. Only then can they expect to achieve the required levels of radio performance for tomorrow´s 3G services.

TIIVISTELMÄ 4

Tiivistelmä

TAMPEREEN TEKNILLINEN YLIOPISTO Tietotekniikan koulutusohjelma Tietoliikennetekniikan laitos Borràs Torà, Francesc: Antennin keilanleveyden, etenemiskertoimen ja peiton limittäisyyden vaikutus WCDMA verkon kapasiteettiin Diplomityö, 104 s. Tarkastaja: Prof. Jukka Lempiäinen Elokuu 2003 Avainsanat: UMTS, WCDMA, radioverkkosuunnittelu, antennin keilanleveys, antennin korkeus, solun säde, sektorointi Matkaviestinjärjestelmät ovat kokeneet suuren kasvun 1990-luvun aikana. Tänä päivänä suuntaus on tuoda käyttäjien ulottuville maailmanlaajuinen peitto ja korkeat datanopeudet joustavalla tavalla. Universal Mobile Telecommunication Systems (UMTS) on standartoitu täyttämään nämä odotukset korkeasta kapasiteetista ja maailmankattavasta peitosta. UMTS:n ilmarajapinnan pääsytekniikaksi valittiin laajakaistainen koodijakotekniikka (Wideband Code Division Multipe Access, WCDMA). Tämä tekniikka tarjoaa operaattoreille lukemattomia etuja vaihtoehtoisien tekniikkojen lisäksi. Näitä ovat mm. parantunut verkon kapasiteetti, matkapuhelimen akun pidentynyt käyttöaika ja käyttäjien yksityisyyden parantuminen. Parannukset ovat kuitenkin aiheuttaneet verkon kompleksisuuden kasvun. Tämän vuoksi GSM-verkon kaltaisella radioverkkosuunnittelulla ei taata menestystä UMTS-verkkosuunnittelun saralla. Viimeisimmän arvion mukaan yli 60% operaattorien kustannuksista aiheutuu UMTS-radioverkkon implementoinnista. Tämän vuoksi joustava radioverkon implmentointi (tärkeiden verkkoparametrien määrittäminen kuten antennin keilanleveyden, antennin korkeuden, sektoreiden lukumäärän jne.) on kriittistä, mikäli operaattorit haluavat optimoida verkon kapasiteetin ja tarjota multimedia palveluita, jotka ovat UMTS verkon uusia, keskeisiä ominaisuuksia. Tässä diplomityössä on tutkittu eri verkkokonfiguraatioiden vaikutusta radioverkon peitoon ja kapasitteettiin käyttämällä Nokia Networks:in Monte-Carlo �simulaatioita hyödyntäävää radioverkkosuunnitteluohjelmaa NetAct WCDMA Planner 4.0. Tulosten analysointi ja johtopäätöset on tehty helpottamaan tulevaisuuden verkkosuunnittelua. Tärkeäksi lopputulokseksi on saatu, että ilmarajapinnan pääsytekniikka (WCDMA), perus algoritmit ja radioverkkon suunnittelutekniikka ovat erilaisia verrattuna GSM:ään, ja sen vuoksi operaattoreiden on hyödynnettävä kaikkea teknista osaamista ja kokemusta näiltä saroilta. Vasta tämän jälkeen he voivat saavuttaa vaaditut suorituskykyvaatimukset huomisen 3G-palveluille.

EXTRACTE 5

Extracte

UNIVERSITAT TECNOLÒGICA DE TAMPERE Programa de graduació en Tecnologies de la Informació Enginyeria de Telecomunicació Borràs Torà, Francesc: Impacte de lÁmple de Feix de les Antenes, de les Pèrdues de Propagació i del Solapament de la Cobertura sobre la Capacitat de Xarxes WCDMA Projecte Final de Carrera, 104 p. Examinador: Prof. Jukka Lempiäinen Institut dÉnginyeria de les Comunicacions Agost 2003 Paraules clau: UMTS, WCDMA, planificació de xarxes ràdio, ample de feix, alçada dántena, tamany de cel.la, sectorització El sector de les comunicacions mòbils ha experimentat un gran creixement durant els anys 90. Actualment, la tendència és proporcionar cobertura global i gran capacitat dúna forma més flexible per serveis de dades dálta velocitat. El Sistema Universal de Telecomunicacions Mòbils (UMTS) ha estat estandaritzat per proporcionar alta capacitat i cobertura global. La interfície aèria sel.leccionada per UMTS és Accés Múltiple per Divisó de Codi en Banda Ampla (WCDMA). Aquesta solució ofereix als operadors un gran nombre de significatius avantatges sobre tecnologies alternatives, incloent major capacitat de la xarxa, vida més llarga per les bateries dels terminals i augment díntimitat pels usuaris. No obstant, aquests beneficis arriben gràcies al cost de complexitat addicional de la xarxa. Aquest és el motiu pel qual léxperiència en GSM no és garantia d´èxit en UMTS. Les últimes estimacions indiquen que la despesa dún operador en la planificació de xarxes ràdio UMTS superarà més del 60% del capital total invertit. Per aquesta raó una implementació robusta de la xarxa (el.leccions correctes per paràmetres clau com ample de feix de les antenes, alçada de les mateixes, nombre de sectors/cel.la, etc.) és crítica si els operadors volen optimitzar els nivells de capacitat i activar serveis multimèdia, els quals són un element clau del valor de la proposició UMTS. En aquest treball séstudia límpacte sobre la cobertura i la capacitat del sistema per diferents configuracions de la xarxa, utilitzant léina estàtica de planificació de xarxes ràdio de Nokia Networks, el NetAct WCDMA Planner 4.0, el qual utilitza simulacions Monte-Carlo. Després de completar aquestes simulacions, els resultats són analitzats, explicant les principals conclusions per tal de fer més fàcils futurs treballs en la mateixa àrea. Per acabar, assenyalar quelcom significatiu: la interfície aèria (WCDMA), els algoritmes bàsics i les tècniques de planificació de xarxes ràdio són radicalment diferents respecte a GSM, per tant, els operadors han de demostrar liderat tècnic i experiència en el desplegament en tots aquests aspectes. Només llavors poden esperar aconseguir els nivells de prestació exigits pels serveis de tercera generació del futur.

CONTENTS 6

CONTENTS

PREFACE........................................................................................................................ 2

ABSTRACT..................................................................................................................... 3

TIIVISTELMÄ ............................................................................................................... 4

EXTRACTE .................................................................................................................... 5

1.- INTRODUCTION ..................................................................................................... 8

2.- UMTS.......................................................................................................................... 10

2.1.- STANDARDIZATION ....................................................................................... 11

2.2.- QoS CLASSES .................................................................................................... 11

2.3.- NETWORK ARCHITECTURE.......................................................................... 13

2.3.1.- UMTS RADIO ACCESS NETWORK........................................................ 14

2.3.2.- CORE NETWORK...................................................................................... 14

2.4.- CHANNEL STRUCTURE.................................................................................. 15

3.- WCDMA RADIO ACCESS...................................................................................... 21

3.1.- MULTIPLE ACCESS ......................................................................................... 22

3.2.- CDMA ................................................................................................................. 23

3.3.- DS-CDMA........................................................................................................... 25

3.4.- WCDMA.............................................................................................................. 33

3.4.1.- RADIO PROPAGATION CHARACTERISTICS IN WCDMA ................ 37

4.- PLANNING OF WCDMA RADIO NETWORKS................................................. 43

4.1.- DIMENSIONING................................................................................................ 44

4.2.- DETAILED PLANNING .................................................................................... 46

4.2.1.- CONFIGURATION PLANNING................................................................ 46

4.2.2.- COVERAGE PREDICTIONS ..................................................................... 52

4.2.3.- TOPOLOGY PLANNING ........................................................................... 57

4.3.- OPTIMIZATION................................................................................................. 61

4.4.- CELL TYPES ...................................................................................................... 61

5.- SIMULATIONS......................................................................................................... 65

5.1.- SIMULATION SETUP ....................................................................................... 66

CONTENTS 7

5.2.- RESULTS............................................................................................................ 69

5.2.1.- SCENARIO 1: 3-SECTOR CASE .............................................................. 70

5.2.2.- SCENARIO 2: 6-SECTOR CASE .............................................................. 76

5.2.3.- OPTIMUM CONFIGURATIONS .............................................................. 82

6.- CONCLUSIONS........................................................................................................ 86

7.- REFERENCES .......................................................................................................... 89

APPENDIX...................................................................................................................... 94

List of Acronyms ......................................................................................................... 94

List of Tables ............................................................................................................... 98

List of Figures .............................................................................................................. 99

Simulation Parameters ............................................................................................... 102

1.- INTRODUCTION 8

1.- INTRODUCTION Third generation (3G) mobile telecommunication systems are being deployed and

expected to be globally running very soon. The next generation mobile systems are

designed to enhance the wireless communications in many ways. 3G technologies

provide wideband radio with high spectral efficiency and support for multimedia and

packet switched traffic. Due to the increasing demand during the last years, as shown in

Figure 1.1, 3G offers greater capacity, higher data rates, a wider mix of communication

services and better technology compared to the existing second generation (2G) systems.

At this regard, main differences between 2G and 3G systems are listed in Table 1.1.

Figure 1.1 Increase of mobile telephone and Internet users in the last 10 years.

2G 3G

Data rate [Kbps]

115.2 Vehicular: 144 Pedestrian: 384 (macro cells) Indoor office: 2048 (pico cells)

Spreading bandwidth [MHz] 1.25 1.25, 3.75, 5, 10 and 15 Interfrequency HO No Yes

Optional MUD No Yes Signalling framelength [ms] 20 5 and 20

Data framelength [ms] 20 20, 40 and 80 Multirate services No Yes

Power control Slow quality loop Open & fast closed loop Coherent detection Non-coherent reverse link Coherent reverse link

Table 1.1 2G vs 3G.

1.- INTRODUCTION 9

The new wideband characteristics and the flexibility to introduce new services

will be exploited in a variety of mobile devices and innovative seamless applications.

Examples of the proposed services include multimedia applications such as mobile video

conferencing and web browsing. Nevertheless, there will probably not be any single

application that is going to dominate the next generation market, and it is expected that

3G will breed success through its flexibility and a wide range of personal services.

Nonetheless, 3G systems will have a very high potential because they will be able to

support various simultaneous connections, for example speech, Internet connection and

videoconference, with high quality, especially in voice services.

Wideband code division multiple access (WCDMA) has emerged as a main

stream air interface solution for the next generation networks. It has been also selected as

a radio transmission technology (RTT) for UMTS (Universal Mobile

Telecommunications System), which is the european third generation mobile

communications system developed by ETSI (European Telecommunications Standards

Institute).

The most essential elements of the third generation mobile systems have been

already standardized, and basic operational requirements and system architecture are

already well understood. However, there is plenty of room for innovations and

enhancements in many areas within 3G.

This thesis is organized using the top-down approach. First, a general introduction

to UMTS is presented in chapter 2. Then, chapter 3 gives a presentation of the WCDMA

principles, including radio propagation characteristics in WCDMA networks. Radio

network planning for 3G systems is studied in chapter 4. Described planning is enough to

illustrate the basic used mechanisms for an operator in its network design. This chapter

introduces the main purpose of this thesis: study the impact of antenna beamwidth,

propagation slope and coverage overlapping on capacity in WCDMA cellular networks.

This analysis is covered in detail in the next chapter, number 5, by using a static radio

network planning tool provided by Nokia Networks: NetAct WCDMA Planner 4.0, which

uses Monte-Carlo simulations. Finally, conclusions are presented in chapter 6.

2.- UMTS 10

2.- UMTS

UMTS (Universal Mobile Telecommunications System) is one of the major new

third generation mobile communications systems being developed within the framework,

which has been defined by ITU (International Telecommunications Union) and known as

IMT-2000 (International Mobile Telephony). UMTS facilitates convergence between

telecommunications, IT, media and content industries. It has potential to provide end

users with data rates up to 2 Mbps, and it lends itself to give individuals the freedom to

choose among a wide range of services currently in existence or soon to exist. Some

examples of the new services are video telephony and quick access to information and

fast data downloads, for instance, on Internet directly for people on the move.

In this chapter, the standardization process for the 3rd generation mobile

telecommunications system and the different varieties of quality of service on it are

explained. After this, used network architecture and channel structure in this system are

shown in order to understand clearly how it works.

2.- UMTS 11

2.1.- STANDARDIZATION

International Telecommunications Union is coordinating 3G standardization.

Within ITU, the third generation systems are called International Mobile Telephony

2000. Regional standardization organizations, such as ETSI in Europe, have specified

their proposals to fulfil the IMT-2000 requirements. The third generation system is called

UMTS within ETSI.

In the standardization forums, wideband CDMA has emerged as the most widely

adopted third generation air interface [1]. In addition, ETSI selected WCDMA as the

basic access scheme in January 1998. WCDMA specification is produced in 3GPP (Third

Generation Partnership Project) [2], which is the joint standardization project of the

standardization bodies from Europe, Japan, Korea, the USA and China.

Nowadays (June´03), UMTS licenses have been awarded in more than fifteen

countries. Experimental systems are made with field trials and commercial services are

being launched in Japan and other places. Standards and industrial interest groups

mentioned above can be found in [3-6]. 2.2.- QoS CLASSES

UMTS has been designed to support a variety of quality of service (QoS)

requirements that are set by end users and end-user applications. The third generation

services will vary from simple voice telephony to more complex data applications

including voice over IP (VoIP), video conferencing over IP (VCoIP), web browsing, e-

mail and file transfer. 3GPP has identified four different main traffic classes for UMTS

according to the nature of traffic: conversational class, streaming class, interactive class

and background class [7].

The best-known use of conversational class is telephony speech. With Internet

and multimedia, a number of new applications, for example, VoIP and video

conferencing tools will require this scheme. Real time conversation is always performed

between peers of human end users. This is the only traffic type where the required

characteristics are strictly imposed by human perception. Real time conversation is

2.- UMTS 12

characterized by the fact that the transfer time and time variation between information

entities must be low and preserved.

Streaming class is applied when the transferred data is processed as a steady and

continuous stream. Accordingly, the streaming class is characterized by the preserved

time variation between information entities of the stream, but it does not have any

requirements on low transfer delay. Thus, the acceptable delay variation over

transmission media (jitter) is much higher than in the conversational class. An example of

this scheme is the user looking at real-time video or listening to real-time audio.

When the end user, either a machine or human, is on-line requesting data from

remote equipment (i.e., a server), interactive class scheme applies. Examples of

interactive human interaction with remote equipment are web browsing, database

retrieval and server access. Examples of machine interaction with remote equipment are

polling for measurement records and automatic database enquiries. Interactive class is

characterized by request response pattern (round trip delay and response time) and

preserved payload content (low Bit Error Rate). Applications such as e-mail and SMS,

download of databases and reception of measurement records generate distinctive

background class traffic. Background traffic scheme is characterized by the fact that the

destination is not expecting the data within a certain time, but that the data integrity must

be preserved during the delivery. The UMTS QoS classes are summarized in Table 2.1.

TRAFFIC CLASS Conversational Class

Streaming Class

Interactive Class

Background Class

FUNDAMENTAL CHARACTERISTICS

• Preserve time relation (variation) between information entities of the stream

• Conversational pattern (stringent & low delay)

• Preserve time relation (variation) between information entities of the stream

• Request response pattern

• Preserve payload content

• Destination is not expecting the data within a certain time

• Preserve

payload content

EXAMPLE OF APPLICATION

- Voice - Video

telephony - Video games

- Streaming multimedia

- Web browsing

- Network games

- Background download of e-mails

Table 2.1 QoS classes in UMTS.

2.- UMTS 13

The requirements of the QoS classes are met by negotiating appropriate QoS

attribute values for each established or modified UMTS bearer. Traffic parameter set

consists of eight different attributes: maximum bit rate (Kbps), guaranteed bit rate

(Kbps), delivery order (yes/no), SDU (Service data unit) size information (bits),

reliability, transfer delay (seconds), traffic handling priority and allocation/retention

policy [7].

2.3.- NETWORK ARCHITECTURE

UMTS network architecture will be an evolution of GSM and GPRS network,

thus resembling very much of their architecture. It consists of two parts: UMTS terrestrial

radio access network (UTRAN) and core network (CN).

UTRAN provides the air interface for UMTS terminals and core network is

responsible for switching and routing of calls and data connections to external networks.

The UMTS system architecture with the interfaces is depicted, by using a tree diagram, in

Figure 2.1 [8]. The interfaces are defined open to allow the equipment at the endpoints to

be from two different manufacturers. A complete description of the network architecture

and the interfaces between the logical network elements can be found in 3GPP technical

specifications (TS) [3].

Figure 2.1 UMTS network architecture.

2.- UMTS 14

2.3.1.- UMTS Radio Access Network

UTRAN consists of one or more radio network subsystems (RNS). Each radio

network subsystem consists of a radio network controller (RNC), several nodes B

(UMTS base stations) and user equipment (UE).

The radio network controller is responsible for the control of radio resources of

UTRAN. It plays a very important role in power control (PC), handover control (HC),

admission control (AC), load control (LC) and packet scheduling (PS) algorithms, which

are at least partially located at RNC. RNC interfaces the core network via Iu interface and

uses Iub to control one node B. The Iur interface between RNCs allows soft handover

between RNCs.

Node B is equivalent to the GSM base station (BS/BTS), and it is the physical

unit for radio transmission and reception with cells. Node B performs the air interface

processing, which includes channel coding, interleaving, rate adaptation and spreading.

The connection with the user equipment is made via Uu interface, which is actually the

WCDMA radio interface. Node B takes part in softer handover process and it is also

responsible for inner closed-loop power control. User equipment is based on the same

principles as the GSM mobile station (MS), and it consists of two parts: mobile

equipment (ME) and the UMTS subscriber identity module (USIM). Mobile equipment is

the device that provides for radio transmission, and the USIM is the smart card holding

the user identity and personal information.

2.3.2.- Core Network

UMTS is based on an evolved core GSM network integrating circuit and packet

switched traffic. The entities of CN, shown in Figure 2.2, are home location register

(HLR), mobile services switching center/visitor location register (MSC/VLR), gateway

MSC (GMSC), serving GPRS support node (SGSN) and gateway GPRS support node

(GGSN).

The home location register is a database in charge of the management of mobile

subscribers. It holds the subscriber and location information enabling the charging and

routing of calls towards the MSC or SGSN, where the mobile station is registered at that

time.

2.- UMTS 15

The mobile switching center constitutes the interface between the radio system

and the fixed networks. The MSC performs all necessary functions in order to handle the

circuit switched services to and from the mobile stations. A mobile station roaming in an

MSC area is controlled by the visitor location register in charge of this area.

Gateway MSC is the switch at the point where UMTS public land mobile network

(PLMN) is connected to external circuit switched networks. All incoming and outgoing

circuit switched connections go through GMSC.

Serving GPRS support node has similar functionality to that of MSC/VLR, but it

is used for packet switched services. Gateway GPRS support node has the same

functionality for the packet domain as the GMSC has for the circuit domain.

All these elements and their interconnections are shown in Figure 2.2.

Figure 2.2 Block diagram of the UTRAN and CN.

2.4.- CHANNEL STRUCTURE

There are two dedicated channels and one common channel on the uplink. User

data is transmitted on the dedicated physical data channel (DPDCH). Control information

is transmitted on the dedicated physical data channel (DPDCH) too. The random access

channel is a common access channel.

Each DPDCH frame on a single code carries 160 x 2k bits (16 x 2k Kbps), where k

changes between 0, 1, ... and 6, corresponding to a spreading factor of 256/2k with the

2.- UMTS 16

3.84 Mcps of chip rate. Multiple parallel variable rate services can be time multiplexed

within each DPDCH frame. The overall DPDCH bit rate is variable on a frame-by-frame

basis. In most cases, only one DPDCH is allocated per connection, and services are

jointly interleaved sharing the same DPDCH. However, multiple DPDCHs can also be

allocated (e.g. to avoid a too low spreading factor at high data rates).

The dedicated physical control channel (DPCCH) is needed to transmit pilot

symbols for coherent reception, power control signaling bits and rate information for rate

detection. Two basic solutions for multiplexing physical control and data channels are

time multiplexing and code multiplexing. A combined IQ and code multiplexing solution

(dual-channel QPSK) is used in WCDMA uplink to avoid electromagnetic compatibility

(EMC) problems with discontinuous transmission (DTX). The major drawbacks of the

time multiplexed control channel are the EMC problems that arise when DTX is used for

user data. One example of a DTX service is speech. During silent periods no information

bits need to be transmitted, which results in pulsed transmission as control data must be

transmitted in any case.

The rate of transmission of pilot and power control symbols causes severe EMC

problems to both external equipment and terminal interiors. This EMC problem is more

difficult in the uplink direction since mobile stations can be close to other electrical

equipments. The IQ code multiplexed control channel is shown in Figure 2.3.

Figure 2.3 Parallel transmission of DPDCH and DPDCCH channels when data is present/absent.

Since pilot and power control are on a separate channel, no pulse like

transmission takes place. Interference to other users and cellular capacity remains the

same as in the time multiplexed solution.

2.- UMTS 17

The random access burst consists of two parts, a preamble part of length 16 x 256

chips (1 ms) and a data part of variable length. The WCDMA random access scheme is

based on a slotted ALOHA technique with the random access burst structure as shown in

Figure 2.4.

Figure 2.4 Structure of WCDMA random access burst.

Before the transmission of a random access request, the mobile terminal should

carry out the following tasks:

• Achieve chip, slot and frame synchronization to the target base station from the

synchronization channel (SCH) and obtain information about the downlink scrambling

code also from the SCH.

• Retrieve information from BCCH about the random access code(s) used in the target

cell/sector.

• Estimate the downlink path loss, which is used together with a signal strength target to

calculate the required transmit power of the random access request.

It is possible to transmit a short packet together with a random access burst

without setting up a scheduled packet channel. No separate access channel is used for

packet traffic related random access, but all traffic shares the same random access

channel. More than one random access channel can be used if the random access capacity

requires such an arrangement [9].

2.- UMTS 18

In the downlink, there are three common physical channels. The primary and

secondary common control physical channels (CCPCH) carry the downlink common

control logical channels (BCCH, PCH and FACH), finally, the SCH provides timing

information and is used for handover measurements by the mobile station.

The dedicated channels (DPDCH and DPCCH) are time multiplexed. The EMC

problem caused by discontinuous transmission is not considered difficult in downlink

since there are signals to several users transmitted in parallel at the same time and base

stations are not so close to other electrical equipment.

In the downlink, time multiplexed pilot symbols are used for coherent detection.

Since the pilot symbols are connection dedicated, they can be used for channel estimation

and to support downlink fast power control. In addition, a common pilot time multiplexed

in the BCCH channel can be used for coherent detection.

The primary CCPCH carries the BCCH channel and a time multiplexed common

pilot channel. The primary CCPCH is allocated at the same channelization code in all

cells. A mobile terminal can thus always find the BCCH, once the base station's unique

scrambling code has been detected during the initial cell search.

The secondary physical channel for common control carries the PCH and FACH

in time multiplex within the super frame structure. The channelization code of the

secondary CCPCH is transmitted on the primary CCPCH. The SCH consists of two

subchannels, the primary and secondary SCHs. The SCH minimizes the acquisition time

of the long code. The unmodulated primary SCH is used to acquire the timing for the

secondary SCH. The modulated secondary SCH code carries information about the long

code group to which the long code of the BS belongs. In this way, the search of long

codes can be limited to a subset of all the codes.

The primary SCH consists of an unmodulated code of length 256 chips, which is

transmitted once in every slot. The primary synchronization code is the same for every

base station in the system and is transmitted time aligned with the slot boundary. The

secondary SCH consists of one modulated code of length 256 chips, which is transmitted

in parallel with the primary SCH.

Multiple services of the same connection are multiplexed on one DPDCH.

Multiplexing may take place either before or after the inner or outer coding. After service

2.- UMTS 19

multiplexing and channel coding, the multiservice data stream is mapped to one DPDCH.

If the total rate exceeds the upper limit for single code transmission, several DPDCHs can

be allocated [9].

Typical power allocations for the downlink common channels are shown in Table

2.2 .

Activity

[%]

Percentage of

the maximum

base station

power

[%]

Power allocation

with 20 W.

maximum power

[W]

Common pilot channel

(CPICH)

100

10

2.0

Primary synchronization

channel (SCH)

10

6

1.2

Secondary synchronization

channel (SCH)

10

4

0.8

Primary common control

physical channel (CCPCH)

90

5

1.0

Total common channels - ~ 15 ~ 3

Table 2.2 Typical powers for the downlink common channels.

WCDMA has two different types of packet data transmission possibilities. Short

data packets can be appended directly to a random access burst. This method, called

common channel packet transmission, is used for short infrequent packets, where the link

maintenance needed for a dedicated channel would lead to an unacceptable overhead.

When using the uplink common channel, a packet is appended directly to a

random access burst. Also, the delay associated with a transfer to a dedicated channel is

avoided. Note that for common channel packet transmission only open loop power

control is in operation. Common channel packet transmission should therefore be limited

to short packets that only use a limited capacity. The packet transmission on a common

channel is illustrated in Figure 2.5.

2.- UMTS 20

Figure 2.5 Packet transmission on a common channel.

Larger or more frequent packets are transmitted on a dedicated channel. A large

single packet is transmitted using a single-packet scheme where the dedicated channel is

released immediately after the packet has been transmitted. In a multipacket scheme the

dedicated channel is maintained by transmitting power control and synchronization

information between subsequent packets.

Base stations in WCDMA do not need to be synchronized, and therefore, no

external source of synchronization, such us GPS, is needed for the base stations.

Asynchronous base stations must be considered when designing soft handover algorithms

and when implementing position location services.

Before entering soft handover, the mobile station measures observed timing

differences of the downlink SCHs from two base stations. The mobile station reports the

timing differences back to the serving base station and the timing of a new downlink soft

handover connection is adjusted.

3.- WCDMA RADIO ACCESS 21

3.- WCDMA RADIO ACCESS

In this chapter, WCDMA radio access technique, as a type of CDMA, is

explained. CDMA type techniques are based on multiple access, for this reason and first

of all, there is an explanation about multiple access techniques and the way the common

transmission medium is shared between users.

The aim is showing the foundation, advantages and problems of these systems

because this will allow us to have a higher understanding of the work. Nevertheless,

neither this particular text nor the text in its entirety intends to study these systems. The

chapter ends with the air interface technology for 3rd generation network architecture

(WCDMA), including also main characteristics of the radiowave propagation in

WCDMA cellular networks.


3.1.- MULTIPLE ACCESS

The basis for any mobile system is its air interface design, and particularly the

way the common transmission medium is shared between users, that is, multiple access

scheme [10]. Multiple access scheme defines how the radio spectrum is divided into

channels, and how the channels separate the different users of the system. WCDMA is

the multiple access method selected by ETSI as basis for UMTS air interface technology.

Multiple access schemes can be classified into groups according to the nature of

the protocol [11]. The basic branches are contentionless (scheduling) and contention

(random access) protocols.

The contentionless protocols avoid the situation in which two or more users

access the channel at the same time by scheduling the transmissions of the users. This can

be done in a fixed fashion by allocating each user a static part of the transmission

capacity, or in a demand-assigned fashion, in which scheduling only takes place between

the users that have something to transmit.

The fixed-assignment technique is used in Frequency Division Multiple Access

(FDMA) and in Time Division Multiple Access (TDMA), which are combined in many

contemporary mobile radio systems such as GSM [12]. In a FDMA system, the total

system bandwidth is divided into several frequency channels that are allocated to users.

In a TDMA system, one frequency channel is divided into time slots that are allocated to

users, and the users only transmit during their assigned time slots. Examples of demand-

assignment contentionless protocols are token bus and token ring LAN´s described by the

IEEE in the 802.4 and 802.5 standards [13].

With the contention protocols, a user cannot be sure that the transmission will not

collide, since other users may be accessing the channel at the same time. If several users

transmit simultaneously, their transmissions will fail. Contention protocols, for example

ALOHA-type protocols [14], resolve conflicts by waiting a random amount of time until

retransmitting the collided message. CDMA, and thus WCDMA, is very different from

the techniques explained above. In principle, it is a contentionless protocol allowing a

number of users to transmit at the same time without conflict. However, contention will

occur if the number of simultaneously transmitting users rise above some threshold. In

CDMA, each user is assigned a distinct code sequence (spreading code) that is used to


encode the user's information-bearing signal. The receiver retrieves the desired signal by

using the same code sequence at the reception. The division of TDMA, FDMA and

CDMA channels into time-frequency plane is illustrated in Figure 3.1.

Figure 3.1 Multiple access schemes: (a) FDMA (b) TDMA (c) CDMA.

3.2.- CDMA

Spread spectrum techniques use transmission bandwidth that is many times

greater than the information bandwidth of any user. All radio resources are allocated to

all users simultaneously. In CDMA, all communicating units transmit at the same time

and over the same frequency. Multiple access is achieved by assigning each user or

channel a distinguished spreading code (chip code). This chip code is used to transform a

user�s narrowband signal to a much wider spectrum prior to transmission. The receiver

correlates the received composite signal with the same chip code to recover the original

information-bearing signal.

The ratio of the transmitted bandwidth BT to information bandwidth BI is an

important concept in CDMA systems. It is called processing gain or spreading factor, Gp,

of the spread spectrum system and it is given by Eq. 3.1. The capacity of the system and

its ability to reject interference are directly proportional to Gp. Wide CDMA bandwidth,

that is high chip code rate, gives higher processing gains and thus better system

performance.

(Eq. 3.1)

When multiple users transmit a spread spectrum signal at the same time, the

receiver is able to distinguish the information signal, since each user's distinct code has

[ ]

=

I

Tp B

BdBG log10


good auto and cross correlation properties. Thus, as the receiver decodes (despreads) the

received signal, the transmitted signal power is increased above the noise, while the

signals of the other users remain spread across the total bandwidth. The principle of the

spreading and despreading is illustrated in Figure 3.2. In Figure 3.2a, the data signal of

user 1 is spread into wideband signal. Figure 3.2c shows the spreading operation for

several other users. Figure 3.2b illustrates the received wideband signal, which consists

of the signals from all the users, inclusive user 1. Figure 3.2d shows the signal powers

after the despreading operation with the code of user 1. The signal of user 1 is retrieved

by the receiver, whereas the rest of the signals appear random and are experienced as

noise.

Figure 3.2 Principle of spread spectrum technique:

(a) User 1 signal spreading (b) The received signal

(c) Spreading for several users (d) Despread signal for user 1

The described multiple access fully distinguishes CDMA from other multiple

access systems. This makes the radio resource management of CDMA very challenging,

since there is no absolute upper limit on the number of users that can be supported in

each cell. This feature of CDMA is also called soft capacity. If the users are allowed to

enter the system without any restrictions, the interference may increase to intolerable

levels, thus damaging the quality of reverse links by causing power outage of some

terminals.


The propagation conditions include path loss, shadowing and fast-fading and the

components of the total interference are cross-correlation interference of users´ signals

and background noise. Overall, the CDMA systems are interference limited systems.

Main advantages of CDMA systems are as follows:

- Increased capacity

- Improved voice quality, eliminating the audible effects of multi path fading

- Enhanced privacy and security

- Improved coverage characteristics which reduce the number of cell sites

- Reduced average transmitted power, thus increasing talk time for portable devices

- Lower interference level to other electronic devices

- Reduction in the number of calls dropped due to handoff failures

- Coexistence with previous technologies, due to CDMA and analog operate in two

spectra with no interference

A general classification of CDMA is depicted in Figure 3.3.

Figure 3.3 Classification of CDMA types.

3.3.- DS-CDMA

Since the transmission bandwidth is very large and each user is transmitting

continuously, there are some special properties in addition to uniqueness that the used

spreading codes must fulfil because of time and frequency overlap:


• the crosscorrelations between different spreading codes with all possible relative

shifts should be very low to make the detection of the desired user's signal possible

from the sum of all possible simultaneous users.

• the autocorrelation of every spreading code should be as close to the one of white

noise as possible to allow the possibility of multi path diversity, this also simplifies

channel estimation and synchronization.

If these properties are fulfiled, then we can receive and detect the desired user's

signal as efficiently as possible. By applying the despreading specific function to the

desired user´s received signal despreads only this desired user's signal and all the other

signals remain wideband (low power-density signals) and can be filtered out very

efficiently. Also possible narrowband interference becomes a wideband (low power

density signal) and can be filtered out almost completely. The reception and despreading

in the presence of a narrowband interferer is illustrated in Figure 3.4 [15].

Figure 3.4 Despreading of a wideband signal in the presence of a narrowband interferer.

In DS-CDMA the original information-bearing signal, that is, data signal is

modulated on a carrier, which is spread by a high rate binary code sequence (chip code)


∑=

+=N

nknnba

NkR

1

1)(

)sin()(2)( 0ttxPtsd ω⋅=

to produce a bandwidth much larger than the original bandwidth. Logical binary symbols,

bits 0 and 1, are suggested to be considered as mapped to real values �1 and +1 during

the spreading operation. Various modulation techniques can be used for the code

modulation, but usually some form of phase shift keying (PSK) such as binary phase shift

keying (BPSK), quadrature phase shift keying (QPSK) or minimum phase shift keying

(MSK) is employed [11], [16-18].

The modulated wideband signal is transmitted through the radio channel. During

the transmission, the modulated signal suffers from interference caused by the signals of

other users. The desired signal together with interference reaches the receiver. At the

reception, the receiver correlates the composite signal with the chip code of the desired

signal. The multiplication by the distinct ± binary spreading waveform filters out large

part of interference and the original data is recovered. The cross-correlations of the code

sequences of different users should be small in order to get a large power ratio of the

desired signal to the interfering signals. The discrete cross-correlation between two

different codes is given by [16]:

(Eq. 3.2)

where an and bn are the elements of the two sequences with code period N, and k is the

time lag between the signals. In the following, the use of DS-CDMA will be illustrated

with examples by using the simplest form of spreading modulation, that is, BPSK. In

BPSK modulation, the phase of the carrier is shifted 180 degrees in accordance with the

transmitted digital bit stream. In the examples, a single bit transition, from 1 to 0 or from

0 to 1, causes a phase shift whereas two successive bits with equal values do not result in

a phase shift. Let x(t) be the data stream that is to be modulated by a carrier having power

P and radian frequency ω. Then, the modulated stream, sd(t), can be defined as [16]:

(Eq. 3.3)

As an example, let the data stream being modulated to be (1 0) as in Figure 3.5a.

The BPSK modulated data signal, sd(t), is shown in Figure 3.5d. The wideband BPSK

spreading is accomplished by multiplying sd(t) by a function c(t) that takes on values ±1.

The transmitted wideband signal, st(t), can thus be represented by [16]:


)sin()()(2)( 0ttxtcPtst ω⋅=

[ ])(sin)()()(2)( 0´´

ddddt TtTtxTtcTtcPts −−−−⋅= ω

G (Eq. 3.4) Let the chip code sequence c(t) to be (1 0 1 0), with processing gain four, as

shown in Figure 3.5b. When modulo-2 addition is used, the spread data will be as shown

in Figure 3.5c. The resulting transmission wave is depicted in Figure 3.5e. As previously

noted, the signal will be despread at the receiving end using the same code as in

transmission. After demodulation and despreading, the original data will be recovered.

The received signal has a propagation delay Td that is determined by the path length. The

signal, st'(t), coming out of the receiver´s correlator is [16]:

rtrtrtrtrtrt(Eq. 3.5)

where T'd is the receiver�s best estimate of the transmission delay. It can be seen that if

the chip code c(t) at the receiver is correctly synchronized with the chip code at the

transmitter (i.e., T'd = Td), the original data is recovered after despreading and

demodulation.

Figure 3.5 Example of generation of the CDMA transmitted signal:

(a) User data (b) Spreading sequence (c) Spread data

(d) Modulated data signal (e) Transmitted signal

As a second example, the spreading and despreading is illustrated with three

users. Let the data and the chip sequence of user 1, which are shown in Figure 3.6a, be

the same as those used in Figure 3.6a and Figure 3.6b. Let the data of user 2 be (1 0) and


the spreading code (1 0 0 1). They are shown in Figure 3.6c. In addition, let the data

stream of user 3 to be (0 0) and the spreading code (1 1 0 0), as shown in Figure 3.6e. The

selected processing gain is again 4. Figure 3.6b, Figure 3.6d and Figure 3.6f illustrate the

spread signals of users 1, 2 and 3, respectively. The resulting composite signal of all the

users is given by Figure 3.6g. Figure 3.6h shows the effect of the despreading operation

when the despreading is applied to user 1 [17]. The decoded chips are integrated to give

the decoded data. The retrieved signal is the original one, since the multiplication of the

composite signal by the user 1 chip code cancels the interfering codes from others users.

This is because the cross-correlation, R(k), between the chip codes is zero, as the codes

were selected orthogonal in the example.

Figure 3.6 2nd example of generation of the CDMA transmitted signal:

(a) User 1 data and the spreading sequence (b) Encoded user 1 data

(c) User 2 data and the spreading sequence (d) Encoder user 2 data

(e) User 3 data and the spreading sequence (f) Encoded user 3 data

(g) Composite data and spreading sequence for user 1

(h) Decoded chip and data for user 1

It should be noted that orthogonal codes are completely orthogonal only for zero

delay. For other delays, orthogonal codes have poor cross-correlation properties. Thus,

they are suitable only if all the users of the same channel are synchronized in time to the


accuracy of a small fraction of one chip. This is why PN (Pseudo-random Noise-like)

codes are necessary in the reverse link. WCDMA uses Gold sequences, which is a class

of PN-code, for cell and user separation, both in the downlink and in the uplink, and

orthogonal codes for channel separation [19]. The performance and interference

resistance properties of Gold and other scrambling codes are evaluated in [20]. The

choice of the spreading code is very important, as it is the basic building block of any

CDMA system. Many families of spreading codes, with satisfactory auto and cross-

correlation properties, exist [16-17], [21]. In the actual systems, the processing gain is

usually much larger than four, the value that was used in the previous examples. A large

processing gain is, of course, highly beneficial in suppressing interference. For instance,

the chip rate of WCDMA is 3.84 Mcps, which allows large spreading.

Key elements which are fundamental for the performance of DS-CDMA systems

are the following:

• Power control (PC): It solves the near-far problem. That is a situation, in which a

mobile device close to a base station is received at higher power than a mobile

located further away. The first mobile is an interferer for the second one and if the

signal-to-interference ratio (SIR) is not enough for the second mobile, its signal will

not be detected for the BS. Power control solves this by increasing the output power

as the mobile moves away from the base station, and by decreasing the transmit

power as the mobile moves closer to the base station. Power control measures the SIR

and sends commands to the transmitter on the other end to adjust the transmission

power accordingly. Power control is used in both directions in WCDMA, in the

downlink controls inter cell interference (other-cell interference) and in the uplink

controls intra cell interference (own-cell interference).

• Soft handover: Handover (handoff) is the action of switching a call in progress from

one cell to another without interruption when a mobile station moves from one cell to

another, improving the service quality (specially in voice services) and avoiding

inconvenient breaks in transmission. Neighboring cells in FDMA and TDMA cellular

systems do not use the same frequencies. In those systems, a mobile station performs

a hard handover when the signal strength of a neighboring cell exceeds the signal

strength of the current cell with some threshold. In CDMA systems, the universal


frequency reuse with factor of one is used (consequence of sharing the same part of

the spectrum). Thus, the previous approach would cause excessive interference in the

neighboring cells. For this reason it is not feasible to perform an instantaneous

handover, which would naturally solve this problem. The solution in CDMA systems

is soft handover (SHO) and softer handover. SHO is the procedure in which a mobile

user may receive and send the same call simultaneously from and to two or more base

stations. In this way, the transmission power of a mobile can be controlled by the

prevailing base station that receives the strongest signal. Softer HO is a handover

between sectors but, on the contrary than SHO, in the same base station.

Seen from the mobile station, there are very few differences between softer and

soft handover. However, in the uplink direction, soft handover differs significantly

from softer handover because the received data from different BS is routed to the

RNC for combining. This is typically done so that the same frame reliability indicator

as provided for outer loop power control is used to select the best frame between both

possible candidates within the RNC. This selection takes place after each interleaving

period, i.e. every 10 - 80 ms.

• Multi path signal reception: In a multi path channel, the original transmitted signal

reflects from obstacles such as buildings and mountains and several copies of the

signal, with slightly different delays, arrive at the receiver. From each multi-path

signal's point of view, other multi-path signals can be regarded as interference and

they are suppressed by the processing gain like other interfering signals in the same

channel. However, CDMA uses the RAKE technique, in which the receiver has

several parallel correlators that process the multi path components independently, and

align them for optimal combining, as we will see.

• RAKE receiver: It is shown in Figure 3.7. A RAKE receiver consists of a bank of

correlators, where each one of them is used to detect separately one of the strongest

multi path components. This receiver is basically a diversity receiver based on the

fact that the multi path components in a CDMA system are uncorrelated if the relative

delays are larger than the chip period. In practice RAKE receivers have several

fingers and are capable of adjusting the tap positions to track the time-variant

channels. This means that for the operation of the RAKE receiver, it is necessary to


identify and track major multi path components, i.e., to estimate their relative delays

τk(t) and complex weights hk(t). The estimation of these parameters is most easily

performed by transmitting periodic preambles or pilot symbols. As in any other

diversity receiver, the outputs from the correlators are weighted and added to

compute a reliable decision variable. If the maximal ratio combining technique,

which gives the highest reduction of fading, is used, and the weighting coefficient is

the complex conjugate of the corresponding channel tap value hk*(t). So in RAKE

receiver each multi path signal component is despread separately and the results are

combined into a new decision variable for actual decision.

Figure 3.7 Basic block diagram of a RAKE receiver in a L - tap channel (I&D ≡ integrate and dump).

• Multi user detection (MUD): The simple single user receiver based on the RAKE

concept is good but still far from optimum. An optimum receiver would detect jointly

all the users' signals (of course knowing all the codes). Optimum multi user detectors

are, however, extremely complex to implement and that is why many kinds of

suboptimum detectors have been proposed. Knowing the codes and their correlations,

the most common kinds of multi user detectors are: linear detectors (decorrelator)

and interference cancellers (parallel or successive).

The main benefits of DS-CDMA are:

• Multi path diversity: As it has been said before, true world radio channels are nearly

always of multi path nature, meaning that there exists more than just a single path


between the transmitter and the receiver (the received signal is a sum of multiple

replicas of the transmitted signal, each one of them delayed and attenuated

differently). In the normal case, this leads to intersymbol interference (ISI) which is

extremely destructive if not compensated by an equalizer. Using spread spectrum

modulation and spreading code with white noise, like autocorrelation function, the

delayed copies of the transmitted signal will look just like any other wideband

interfering signal (after despreading) and can be rejected by the receiver filtering

operation, or even a more advanced receiver can take advantage of these different

multi paths and combine the signal energy from all the multi paths together: multi

path diversity.

• Rejection of narrowband interference: As shown in Figure 3.4, the spread spectrum

receiver rejects quite powerfully possible narrowband interference because the

interference exhibits the despreading operation at the receiver but not the inverse

operation.

• Low Probability of Intercept (LPI) / Privacy: Because the direct sequence method

distributes the signal power over a very wide frequency band, the power-density is

very low. To despread the signal energy, the spreading code needs to be known, so

this makes very difficult any unauthorized access.

3.4.- WCDMA

Wideband CDMA is a network asynchronous scheme developed as a joint effort

between ETSI and ARIB. Since it has an asynchronous network, different long codes

rather than different phase shifts of the same code are used for the cell and user

separation [4], [22].

It is an extension of DS-CDMA architecture by using a large bandwidth of at least

5 MHz. That is the nominal bandwidth for all third-generation proposals. There are

several reasons for choosing this bandwidth:

1.- Data rates of 144 and 384 Kbps, the main targets of 3rd generation systems, are

achievable within 5 MHz bandwidth with a reasonable capacity. Even a 2 Mbps peak rate

can be provided under limited conditions.


2.- Lack of spectrum calls for reasonably small minimum spectrum allocation, especially

if the system has to be deployed within the existing frequency bands occupied already by

2nd generation systems.

3.- The 5 MHz bandwidth can resolve (separate) more multi paths than narrower

bandwidths, increasing diversity and thus improving performance.

Larger bandwidths of 10, 15 and 20 MHz have been proposed to support higher

data rates more effectively. Figure 3.8 shows an example for the operator bandwidth of

15 MHz with three cell layers [23].

Figure 3.8 Frequency use with WCDMA.

The carrier spacing has a raster of 200 KHz and can vary from 4.2 to 5.4 MHz.

The different carrier spacings can be used to obtain suitable adjacent channel protections

depending on the interference scenario. Larger carrier spacing can be also applied

between operators and within one operator´s band in order to avoid inter and intra

operator interference, respectively. Inter frequency measurements and HO´s are

supported by WCDMA to use several cell layers and carriers.

The main characteristic WCDMA items are the following:

• High chip rate (3.84 Mcps) and data rates (up to 2 Mbps)

• FDD and TDD modes


• Channel bandwidth about 5 MHz with center frequency raster of 200 KHz

• Provision of multi rate services

• 10 ms frame with 15 time slots

• Packet data

• Fast power control in the downlink

• Asynchronous base stations

• Complex spreading

• A coherent uplink using a user dedicated pilot

• Additional pilot channel in the downlink for beam-forming

• Seamless inter frequency handover

• Inter system handovers, e.g., between GSM and WCDMA

• Support for future advanced technologies like multi user detection (MUD) and smart

adaptive antennas

There are three major techniques for obtaining a spread-spectrum signal:

frequency hopping (FH), time hopping (TH) and direct sequence (DS) spreading [16].

They are briefly reviewed in the following:

• Direct sequence spread spectrum (DS-SS): The data is directly coded by a high chip

rate (spreading) code by multiplying the information-bearing signal with a

pseudorandom ± binary waveform. The receiver knows how to generate the same

code, and correlates the received signal with that code to extract the original data.

UMTS is based on DS-CDMA.

• Frequency hopping spread spectrum (FH-SS): The carrier frequency at which the data

is transmitted is changed rapidly according to the spreading code. By using the same

code, the receiver knows where to find the signal at any given time.

• Time hopping spread spectrum (TH-SS): The information-bearing signal is not

transmitted continuously. Instead, the signal is transmitted in short bursts where the

bursts´ times are decided by the spreading code.

Two or more of the above mentioned SS modulation techniques can be used

together in a hybrid modulation (HM), combining the respective advantages.


The main parameters of WCDMA for UMTS are listed in Table 3.1 [11].

Channel bandwidth 1.25, 5, 10 and 20 MHz

Downlink RF channel structure Direct spread with 3.84 Mcps

Roll-off factor for chip shaping 0.22

Frame length 10 or 20 ms (optional)

Spreading modulation

Balanced QPSK (downlink)

Dual channel QPSK (uplink)

Complex spreading circuit

Data modulation

QPSK (downlink)

BPSK (uplink)

Coherent detection

User dedicated time multiplexed pilot

(downlink and uplink) without common

pilot in downlink

Channel multiplexing in uplink

Control and pilot channel time

multiplexed, I&Q multiplexing for data

and control channel

Multirate Variable spreading and multicode

Spreading factors 4 – 512

Power control Open and fast closed loop (1.6 KHz)

Spreading (downlink)

Variable length orthogonal sequences

for channel separation, Gold sequences

218 for cell and user separation

(truncated cycle 10 ms)

Spreading (uplink)

Variable length orthogonal sequences

for channel separation, Gold sequences

241 for user separation (different time

shifts in I and Q channels, truncated

cycle 10 ms)

Handover Soft HO + Interfrequency HO

Table 3.1 Main parameters WCDMA for UMTS.


3.4.1.- Radio Propagation Characteristics in WCDMA The UMTS operates in the frequency band of 2000 MHz which is more than

double compared to the 900 MHz and clearly higher than 1800 MHz which are typically

used in the GSM (1900 MHz in the USA). These differences in the operating frequencies

mean that the radio propagation is not equivalent and the base station coverage areas of

the GSM system are not necessarily valid in the UMTS frequency band.

As in 2G, it is necessary to know the radiowave attenuation in the different cell

types of the network, which are classified according to the grouping of different classes

depicted in Figure 3.9. Each of these classes has a different propagation environment

with characteristic properties of the radio propagation channel.

Figure 3.9 Radio propagation environment classes.

The radio propagation channel typical to each radio propagation environment

class can be characterized by the following main properties:

1.- Propagation slope (attenuation due to propagation)

2.- Delay spread

3.- Fast (Rician and Rayleigh) and slow fading characteristics

4.- Angular spread

In order to understand these important concepts, they are briefly explained in the

following:

1.- Propagation slope: Attenuation due to propagation limits the usability of the

radiowave for the telecommunication purposes. When the carrier frequency is high (>3


( )φθπλ

,4

2

GGPr trtrP

=

[ ] ( ) [ ] [ ]( ) ( )( )φθλπ

φθ,log10log2045.324

,1log10

2

trtr

GGMHzfKmsrrGG

dBL ⋅−⋅+=

=

GHz) the coupling loss becomes high due to high free space attenuation, high scattering

losses and high attenuation even due to rain. For example light and infrared are good but

the cell area is restricted to line of sight (LOS).

When the carrier frequency is low (<100 MHz) the equipment size becomes large

(antennas, etc) and there are spectrum problems. Therefore, 100 MHz to 3 GHz is

optimal frequency area for the mobile telecommunications.

The received power at a distance r from the isotropic radiator in free space can be

written as [24]:

(Eq. 3.6)

where λ is signal wavelength in meters, Gr and Gt(θ,φ) are receiving and transmitting

antenna gain respectively and Pt is transmitted power. It gives the received power in watt.

The path loss exponent in Eq. 3.6 changes with the environment according to the values

given in Table 3.2.

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

Table 3.2 Path loss exponents according to the environment type.

Path loss in free space can then be written as [24]:

(Eq. 3.7)

where f is system frequency, which is given by Eq. 3.8:

(Eq. 3.8) sec/103 8 mcf ⋅==⋅λ


The total received field is a sum of the field components: direct field and ground

reflected fields due to multi path propagation. Figure 3.10 shows a two ray-model in

multi path propagation.

Figure 3.10 Two ray-model in multi path propagation.

2.- Delay spread: In order to understand the difference between GSM and UMTS radio

interface performance, the most important property of the channel is the delay spread. It

describes the amount of multi path propagation in the propagation environment of the

radio link. The delay spread can be calculated from the typical (estimated or measured)

power delay profile (PDP), which describes the signal power as a function of the delay.

Power delay profile can be presented also as impulse response of the channel. Figure 3.11

shows an example of power delay profile based on the channel model defined in [25].

Figure 3.11 Channel impulse response of a typical urban channel.


τπSfc 2

1=∆

Power delay profile and delay spread are time domain properties of the radio

channel. The effect of the multi path to the radio channel can also be described by the

frequency domain properties of the radio channel. In the frequency domain, multi path

causes frequency selective fading and signals at different frequencies have different

fading (amplitude and phase). The frequency response of the channel can be calculated as

Fast Fourier Transformation (FFT) of complex impulse response of the channel. One

frequency domain property of the channel is coherence bandwidth ∆fc. It can be

calculated from the time domain property delay spread and it is given by [26]:

(Eq. 3.9)

where Sτ is the delay spread in seconds. Thus, the coherence bandwidth is the minimum

frequency separation of two multi path carriers, which have significantly uncorrelated

fading.

Table 3.3 shows the calculated coherence bandwidths typical for different radio

propagation environments (NB ≡ narrowband, WB ≡ wideband. The system is

narrowband when the radio signal bandwidth is much smaller than the coherence

bandwidth of the radio channel and wideband when it is much higher).

Delay spread [µs] ∆fc [MHz] WCDMA GSM IS-95

Bandwidth [MHz] - - 3.84 0.27 1

Macrocellular

Urban 0.5 0.32 WB NB/WB WB

Rural 0.1 1.6 NB/WB NB NB

Hilly 3 0.053 WB WB WB

Microcellular < 0.1 > 1.6 NB/WB NB NB/WB

Indoor < 0.01 > 16 NB NB NB

Table 3.3 Characteristics for different radio propagation environments.

3.- Fading: In radio communications, the channel is not gaussian because the received

power is changing sharply with the movement of the mobile terminals. Mobile

communications channel is a Rayleigh channel (because these falls in the received power

follow a Rayleigh distribution) and these drops in the received power level are also called

fading. There are two different types of fading:


• slow fading: caused by shadowing due to buildings, hills, etc. It can be modeled with

lognormal (normal in dB) probability density function (pdf), with an standard

deviation between 6 and 8 dB. This pdf is shown in Figure 3.12.

Figure 3.12 Log-normal distribution.

• fast fading: caused when the mobile moves in a multi path environment. The signal

envelope is random variable and depends on random phases of multi path

components. With a small mobile station movement, the received power can change

radically. It can be modeled with Rayleigh pdf, shown in Figure 3.13.

Figure 3.13 Rayleigh distribution.

An example of a Rayleigh channel response is shown in Figure 3.14. These

sudden falls in the received power level (fading) are caused by shadowing and multi path

propagation [27].


Figure 3.14 Frequency response of Rayleigh channel.

4.- Angular spread: It 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 the horizontal plane.

The horizontal angular spread is around 5-10 degree in macro cells 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.

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 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.

4.- PLANNING OF WCDMA RADIO NETWORKS 43

4.- PLANNING OF WCDMA RADIO NETWORKS

The UMTS deployment must be preceded by careful network planning. The

network planning tool must be capable of accurately modeling the system behaviour

when loaded with the expected traffic profile.

The WCDMA planning process can be divided into three phases which are initial

planning (dimensioning), detailed radio network planning and network operation, and,

finally, optimization. Each of these phases is studied in detail in this chapter. To

conclude, planned cell structure in UMTS cellular networks is analysed.

UMTS radio network planning is described in this chapter following the steps

indicated in [26] and in [28]. It is largely researched in those references.


4.1.- DIMENSIONING

The network planning tool should model the system behaviour with the expected

characteristics of the traffic. They describe the mixture of services being used by the

population of users. In order to accurately predict the radio coverage the system features

associated with WCDMA must be taken into account in the network modeling process.

In WCDMA network multiple services coexist. Different services (voice, data)

have different processing gains, Eb/N0 performance and thus different receiver SNR

requirements. In current 2nd generation systems´ coverage planning process the base

station sensitivity is constant and the coverage threshold is the same for each base station.

In the case of WCDMA the coverage threshold is dependent on the number of users and

used bit rates in all cells, thus it is cell and service specific.

Each phase of the WCDMA planning process, depicted in Figure 4.1 [28],

requires additional support functions like propagation measurements, key performance

indicator definitions, etc. In a cellular system where all the air interface connections

operate on the same carrier the number of simultaneous users is directly influencing on

the receivers´ noise floors. Therefore, in the case of UMTS the planning phases cannot be

separated into coverage and capacity planning, as in 2G system.

Initial planning (i.e. system dimensioning) provides the first and most rapid

evaluation of the network element count as well as the associated capacity of those

elements. This includes both the radio access network (UTRAN) as well as the core

network (CN). The target of the initial planning phase is to estimate the required site

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

knowledge of the size of the covered area, specification of the frequency band (for the

radio propagation characteristics), calculation of the path loss in both directions (from the

power budget, also called radio link budget), coverage analysis, capacity estimation, and

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

controllers (RNCs), equipment at different interfaces and CN elements. The service

distribution, traffic density, traffic growth estimates and QoS requirements are essential

already in the initial planning phase, when the quality is taken into account in terms of

blocking and coverage probability. Power budget calculation is done for each service (in


this work only speech service has been considered), and the tightest requirement shall

determine the maximum allowed isotropic path loss.

Figure 4.1 WCDMA radio network planning process.

If the radio network is new there have to be several scenarios on how to exceed

the coverage thresholds in different traffic situations. If an existing network is extended,

the traffic history over the area has to be used to identify traffic increases during the next

1-3 years.

The required number of base stations can be tuned by changing the base station

antenna height to correspond to the number accordingly based on traffic requirements for

the coverage area. Because traffic is increasing year after year, this analysis has to be

done based on differing traffic demands, with the final network configuration and

deployment strategy dependent on this long term analysis. If this long term analysis is not

done, the base station antennas will not be located correctly and the radio network

configuration will not be cost-efficient due to overcapacity or load and will require

continuous reconfigurations, which can not be avoided but they can be minimized.

Steadily increasing demands upon coverage cause changes, as in coverage thresholds,


and these changes have to be taken into account at the dimensioning stage because they

strongly influence base station site locations.

4.2.- DETAILED PLANNING

In the detailed planning phase the traffic distribution is used to allocate the

predicted traffic to the planned cells. This may lead to situations in which the load

between the cells can vary remarkably (some cells may have a load that is very close to

the maximum acceptable load and some cells may have a fairly low load). In this phase,

coverage targets are also checked.

All the cells are identical in the dimensioning phase but in the detailed planning

coverage predictions can be quite different between the cells due to propagation

environment and traffic distribution.

Detailed UMTS planning is divided in three phases which are configuration

planning, coverage predictions and topology planning (site configurations).

4.2.1.- Configuration Planning

Target in this phase is to estimate the maximum range of a cell. For this reason, a

power budget calculation is needed. In the power budget the antenna gains, cable losses,

diversity gains, fading margins, etc are taken into account. There are a few WCDMA

specific items in the link budget respect to the current TDMA based radio access system

like GSM.

The power budget is divided into five parts, which are general information,

service information, receiving end, transmitting end and isotropic path loss. The output of

the power budget calculation is the maximum allowed propagation path loss which in

return determines the cell range and thus the amount of sites needed.

General information of the power budget calculation is given in Table 4.1.


Parameter Value

Frequency [MHz] 2000

Chip rate [Mcps] 3.84

Reference temperature [K] 293

Boltzman´s constant [J/K] 1.38E-23

Table 4.1 General information of the power budget calculation.

Power budget is calculated for speech service (outdoor users with soft and softer

HO). Air interface bit rate for speech service is 15 Kbps in both directions, UL and DL.

Used load in the power budget calculation is in both directions, uplink and downlink,

75%. Data services have not been considered in this work.

Receiving end parameters are thermal noise density, interference degradation

margin, total noise power at the receiver, processing gain, required Eb/N0, receiver

sensitivity estimation, Low Noise Amplifier (LNA) gain, power control headroom or fast

fading margin and soft HO diversity gain.

Thermal noise density defines the noise floor due to thermal noise. When the

receiver noise figure is added, it is called noise power level at receiver and it is given by

[26]:

(Eq. 4.1)

where k is Boltzman´s constant, T0 is reference temperature in Kelvin, W is the CDMA

modulation bandwidth (3.84 MHz) and F is the noise figure of the receiver. It gives the

noise power in the case of an empty cell in watt.

The interference degradation margin is a function of the cell loading. The more

loading is allowed in the system, the larger interference margin is needed in uplink and

the smaller is the coverage area. Load in uplink direction is given by [28]:

(Eq. 4.2)

( )( )∑

=

++

=N

k

kkkb

UL i

RNEW1

0

11

1

α

η

WFkTPN 0=


where N is the total number of active users in a cell, (Eb/N0)k is the requirement of bit

energy to noise ratio for user k, R is user bit rate, α is user activity factor (voice activity)

and i is interference from other cells. It gives the load in %.

The downlink dimensioning is following the same logic as the uplink. For a

selected cell range the total base station transmit power ought to be estimated. In this

estimation the soft handover connections must be included. In the downlink equation

there is a new parameter called orthogonality, which shows the degree in which the users

in the same cell interfere with each other. With a orthogonality factor of 100% the users

do not cause interference for other users in the same cell [29]. If the power is exceeded

either the cell range ought to be limited or number of users in a cell has to be reduced.

Load in downlink direction is given by [26]:

(Eq. 4.3)

where ν is the orthogonality factor. Like the Eq. 4.2, it gives the load in %.

In the power budget calculation, in uplink direction the limiting factor is the

mobile station transmission power because it is much lower than the total base station

transmitted power. In downlink direction the limit is the total base station transmitted

power because of noise rise (transmission point-to-multipoint). When balancing the

uplink and downlink service areas both links must be considered.

The interference degradation margin to be taken into account in the power budget

due to a certain loading η (either in UL or DL) is [26]:

(Eq. 4.4)

where η is the load. It gives the interference degradation margin in dB. The load is always

compared to the maximum capacity of the cell (called pole capacity) so it is always in

between 0 % and 100%. Figure 4.2 shows that the interference degradation margin grows

towards infinity if load increases to 100%. In practice, when the interference degradation

margin is fixed, the maximum allowed load of the network is known.

( )η−−= 1log10 10L

( ) ( )[ ] k

N

kk

kbDL i

RW

NEανη ⋅+−=∑

=1

0 1


Figure 4.2 Interference degradation margin as a function of load.

Total noise power at the receiver is the noise floor including thermal noise, noise

generated by the receiver (noise figure) and interference.

Processing gain is the achieved gain due to spreading process and it is given by

Eq. 3.1.

Required Eb/N0 that is needed to be able to demodulate the signal shows ratio

between the received energy per bit and noise energy. It has to be selected based on the

service (speech or data).

In the link budget the BS receiver noise density is estimating the noise level over

one WCDMA carrier. The required receiver SNR contains the processing gain and the

loss due to the loading. The required signal power at the receiver, S, also called receiver

sensitivity, depends on the SNR requirement, receiver noise figure and system

bandwidth, and it is given by [28]:

(Eq. 4.5)

where [28]

(Eq. 4.6)

the noise power level at receiver, PN, is given by Eq. 4.1 and η is the load.

NPSNRS ⋅=

( ) ( )η−⋅=

10 WRNESNR b


Cable losses may cause limitations in the power budget in the UL direction,

especially when long cables are used. The UL direction can be improved by introducing a

Low Noise Amplifier (LNA) next to the receiving antenna. The LNA has to have a low

noise figure in order to improve the received field strength level at the base station

receiving end. The LNA has two important parameters when analysing its performance,

which are noise figure and gain. The target is to have as low a noise figure for the

amplifier as possible. Typical values are around 1.5 dB, which is almost the minimum

value. Gain due to LNA is typically 3.5-4 dB. The LNA also has an effect on the

performance of diversity reception because it depends on the received signal levels of the

main and diversity branches.

Power control headroom or fast fading margin is, as interference degradation

margin and soft HO diversity gain, a CDMA specific item in the power budget. Some

margin is needed in the mobile station transmission power for maintaining closed loop

fast power control in unfortunate propagation conditions like the cell edge. This is

applicable especially for pedestrian users where the Eb/N0 to be maintained is more

sensitive to the closed loop power control. It has been studied more in [30-31].

Handovers provide gain against shadow fading by reducing the required fading

margin. By making handovers, the mobile can select a better communication link.

Furthermore, soft HO (macro diversity) gives and additional gain against fast fading by

reducing the required Eb/N0 relative to a single radio link. The amount of gain is a

function of mobile speed, diversity combining algorithm used in the receiver and power

delay profile of the radio channel and it consists of two parts: this above mentioned gain

against fast fading and gain against slow fading.

Transmitting end in the WCDMA power budget is similar to current GSM power

budget. But there are two main differences. First is that BTS power is given per user in

WCDMA (in GSM one user gets the full transmission power when using the time slot

while in WCDMA the output power of a BTS is shared between the control channel and

all the users in a sector/cell. For this reason, if a user could use the full power of a

WCDMA base station this would mean that there cannot be other users in that sector/cell

at that moment) and second is that in WCDMA base stations there is a different


combining respect to GSM thus there are no combiner loss in the WCDMA power

budget.

The next step is to estimate the maximum cell range and cell coverage area in

different environments/regions. The power budget is estimating the maximum allowed

isotropic path loss, which is calculated in the same way as it is for a GSM cell. In

WCDMA power budget there can be remarkable differences in isotropic path losses

between UL and DL, basically due to asymmetry in traffic (especially in packet data) and

possible different bit rates in the UL and DL. Then, the isotropic path loss is used for cell

range calculations in a similar way as it is used in GSM.

WCDMA power budget in simulations is calculated in Table 4.2.

Parameter UL DL

Thermal noise [dBm] -108.15 -108.15 A

RX noise figure [dB] 5 9 B

Noise power at receiver [dBm] -103.15 -99.15 C=A+B

Interference margin [dB] 6.02 6.02 D

Total noise power at receiver [dBm] -97.13 -93.13 E=C+D

Processing gain [dB] 24.08 24.08 F

Required Eb/N0 [dB] 5 8 G

RX sensitivity [dBm] -116.21 -109.21 H=E-F+G

RX antenna gain [dB] 18 0 I

Cable loss / Body loss [dB] 2.5 3 J

LNA gain [dB] 4 0 K

Soft HO diversity gain [dB] 1.5 3 L

Power control headroom [dB] 2 2 M

Required signal level [dBm] -135.21 -107.21 N=H-I+J-K-L+M

TX power [dBm] 21 33 O

Cable loss / Body loss [dB] 3 2.5 P

TX antenna gain [dBi] 0 18 Q

Peak EIRP [dBm] 18 48.5 R=O-P+Q

Allowed propagation loss [dB] 153.21 155.71 S=-N+R

Table 4.2 WCDMA power budget in simulations.


( ) [ ]( ) ( ) ( )( ) [ ]( ) KkmsdhChMHzfBAdBL bb −⋅−+−+= loglog55.6log82.13log

4.2.2.- Coverage Predictions

Next step is to estimate the coverage probability. This means that the standard

deviation for the log-normal fading and the propagation model exponent (according to the

values given in Table 3.2) must be set.

In the indoor case, the indoor loss is from 15 to 18 dB and the standard deviation

for log-normal fading margin calculation is set to 10-12 dB. In the outdoor case, typical

standard deviation value is 7 to 10 dB.

In real WCDMA cellular networks the coverage areas of cells overlap and the

mobile station is able to connect to more than just one serving cell. If more than one cell

can be detected the location probability increases and is higher than determined for a

single isolated cell.

In macro cells the base station is usually above rooftops and it is not possible to

calculate analytically the signal strength because of very complex propagation media.

Therefore, the empirical or semi empirical propagation models should be used. Once the

maximum allowed propagation loss in a cell is known, it is easy to apply any known

propagation model for the cell range estimation. The propagation model should be chosen

so that it optimum describes the propagation conditions in the area. The restrictions of the

model are related to the distance from the base station, the base station effective antenna

height, the mobile antenna height and the frequency. One typical example for macro

cellular environment is Okumura-Hata which is a empirical propagation model.

The Okumura-Hata model is widely used for coverage prediction in macro cells.

Based on measurement data made by Okumura in Tokyo in 1968, this data set was fitted

to mathematical model by Hata in 1980. Basic model was made for urban areas but

additionally correction factors for suburban areas and rural areas, irregular terrains and

for different base station and mobile station antenna heights have been applied. This

model is not applicable when the base station antenna is below rooftops.

The Okumura-Hata model can be written as shown in Eq. 4.7 [24].

llll(Eq. 4.7)

according to the values given in Table 4.3.


Value at frequency between 150 MHz and 1 GHz

Value at frequency between 1.5 and 2 GHz

A 69.55 46.30 B 26.16 33.90

Table 4.3 Okumura-Hata model parameters as a function of frequency. where hb is the base station antenna height in meters, d is the link distance in kilometers, f

is the center frequency in MHz, C is a tunable parameter which depends on propagation

environment (44.9 as a default value but it can vary between 44 and 47) and, finally, K is

an addition correction factor due to topology or morphology which has 0 as a default

value.

Figure 4.3 shows an example of path loss as a function of distance, by using

Okumura-Hata model [24].

Figure 4.3 Path loss as a function of distance by using Okumura-Hata model.

Eq. 4.8 presents an example of Okumura-Hata path loss model for an urban macro

cell with base station antenna height of 25 meters and carrier frequency of 2000 MHz.

More about this has been studied in [32].

(Eq. 4.8)

( ) [ ]( )kmsrdBL log7.359.138 ⋅+=


Table 4.4 shows typical maximum allowed path loss of existing GSM and

WCDMA systems.

GSM 900

GSM 1800

WCDMA

speech

WCDMA

64 Kbps

WCDMA

144 Kbps

Maximum path loss [dB] 160 154 156 157 154

Table 4.4 Typical maximum allowed path loss of existing GSM and WCDMA systems.

According to the power budget calculation (see Table 4.2) maximum allowed path

loss is 153.21 dB. Slow fading margin (which is typically 10 dB) has to be considered in

the cell range calculation and it should be subtracted from the maximum allowed path

loss before using Eq. 4.8. According to this, cell range cannot be more than 1.3 kms.

After choosing the cell range the coverage area can be calculated. The coverage

area for one cell in hexagonal configuration can be calculated with [28]:

(Eq. 4.9)

where S is the coverage area, r is the maximum cell range and K is a constant, depending

on the network topology. Its value changes according to the site configuration, as shown

in Table 4.5.

SITE CONFIGURATION onmi. 2-sectored 3-sectored 6-sectored

K 2.6 1.3 1.95 2.6

Table 4.5 K-values for the site area calculation.

According to the example given in Eq. 4.8, coverage area by using 6-sectored

sites is 4.4 km2/cell (26.4 km2/site). Total coverage area when 19 base stations are placed

is 500 km2, which is approximately the land area of Tampere. Large variations of this

calculated value due to, for example, coverage overlapping should be taken into account

in real implementation (if even small amount of coverage overlapping, theoretical total

coverage area, this 500 km2, will decrease heavily). For this reason, accurate choices for

those parameters concerning to the topology of the network, like antenna beamwidth, are

key technical elements in topology planning, which is explained in detail in section 4.2.3.

2rKS ⋅=


Once the site coverage area is known the site configurations in terms of channel

elements, sectors and carriers has to be selected so that the supported traffic density can

fulfil the requirements.

Special emphasis has to be given to the consideration of mutual influence of

coverage and capacity (as indicated in Figure 4.4) [29]. As it has been said before, the

coverage is limited by the uplink because of the maximum available transmission power

of the mobile while the downlink sets limitations on the capacity due to the increasing

interference level [33-34].

Figure 4.4 Mutual influence of coverage and capacity in WCDMA networks.

For this reason, in the very beginning the operator should have knowledge and

vision of the subscriber distribution and growth since it has a direct impact on the

coverage. Finding the correct configuration for the network so that the traffic

requirements are met and the network cost minimized is not a simple task: the number of

carriers, sectoring, loading, number of users and cell range all have a great impact on the

final result.

As coverage and capacity depend on the instantaneous traffic distribution and

influence each another, a simulation combining the uplink and downlink analysis in an

adequate way is required. Figure 4.5 shows how this influence affects the network design

and how this process can be done.


Figure 4.5 Impact of coverage and capacity on WCDMA network design.

The evaluation of the optimized base station locations can be done when the

planning threshold is defined. It means that the reasonable QoS level for the different

geographical locations have to be agreed: first major national areas, cities and roads

where coverage has to exist and then subareas of them such as urban and suburban areas.

The planning threshold also concerns whether the service has to be extended inside

vehicles and buildings in different areas.

The planning threshold itself is defined as in the GSM by starting from the mobile

station sensitivity (threshold is for the DL direction) and by adding the required planning

margins to the sensitivity level. The required margins in the WCDMA system are:

• slow fading margin (shadowing)

• macro diversity or soft HO gain

• power control headroom (fast fading margin)

• body loss

• antenna orientation loss

• in-vehicle or indoor penetration loss

• interference margin

The planning threshold is calculated by adding all these components to the mobile

station sensitivity.


4.2.3.- Topology Planning

As is has been said, coverage and capacity planning of UMTS WCDMA cellular

networks cannot be separated, since they are connected to each other. Topology planning

in 3rd generation networks combines coverage and capacity planning which contains

definition of site locations and configuration together with base station antenna

configuration, since these elements influence much on the service coverage and system

capacity of the UMTS network.

Service coverage and system capacity together with sufficient QoS and

economical implementation costs are the most essential factors that determine an

operator´s site density and site configuration for a given planning area. Site densities and

configuration of a UMTS network mainly determine coverage and capacity of a site. In

urban environments, the traffic requirements are much higher than in rural areas and thus

the site density and configuration is different for these cases. Moreover, used

implementation strategy for site configuration defines the over all coverage and capacity

of that particular site. Site locations, the number of sectors and their directions together

with antenna configuration have to be considered in such a manner that given service

coverage, system capacity and QoS requirements are satisfied with reasonable

implementation costs.

Coverage and capacity planning are linked together via power budget calculation

and load equations. This phenomenon makes it impossible to handle coverage and

capacity separately. Because of coverage depends on the loading of the network, system

level simulations are needed in order to determine the performance of UMTS network in

different planning scenarios.

The capacity of UMTS network is known to be interference limited, i.e. soft

capacity limited. For these systems, the Erlang capacity cannot be directly calculated

from Erlang-B formula, since it would give too pessimistic results. It over-estimates the

capacity need since each service is handled alone in the system calculations. If the system

is code limited, the capacity can be estimated from Erlang-B model. In code limited

situation the noise rise in the network is not causing outage or blocking, since the

communication between links is limited by the number of codes. Hence, in code limited


situation the behaviour of WCDMA network is like FDMA/TDMA based systems and

therefore Erlang-B formulas can be used. In noise limited situations the communication is

limited due to noise rise of the system, not due to the available number of codes.

In contrast to GSM networks, the capacity of UMTS network is said to be soft

blocked. In soft blocked networks the interference rise in a cell causes the blocked calls

instead of the blocking would be caused by the lack of available traffic channels or in

case of UMTS available number of codes.

Main elements in UMTS topology planning are sectoring, antenna beamwidth,

site separation, antenna height and tilting.

The term sectoring refers to increasing the number of sectors belonging to a site

[35]. In existing cellular networks, 3-sectored sites are commonly used. It has been

proposed and researched in many papers that even higher sectoring order, like 6-sectored

sites, would bring coverage and capacity enhancements for UMTS networks.

Omnidirectional base station antennas are typically used in small micro cells or

in indoor cells. Two-sectored base stations are used mainly in sectored micro cells or to

provide roadside coverage. Standard macrocellular solution for low or average loaded

networks would be use of 3-sectored sites and in macrocellular environment for high

capacity needs, 6-sectored sites would provide the best solution.

Sectoring is used in UMTS system to increase the system capacity as well as the

service coverage. It seems to be intuitive that adding more antennas to base station site

configuration increases the capacity of the site. Increasing number of sectors at the base

station site requires also place for addition hardware: when the number of sectors is

doubled, the amount of hardware is also doubled.

The effect of sectoring has two perspectives: if widebeam antennas are used,

coverage threshold is better but the interference level is also higher. Three and six-

sectored sites are depicted in Figure 4.6.


Figure 4.6 Cell structure for three and six sectors/site. Base station antenna beamwidth plays an important role in UMTS network

performance. With proper antenna beamwidth, especially the number of softer HO

connections can be controlled. Figure 4.7 shows the effect of the antenna beamwidth over

sector overlapping.

Figure 4.7 Coverage vs interference level.

Overlapped areas are possible softer HO areas, which are needed in UMTS

network in order to maintain the interference level as low as possible during sector HO

procedure. But too large softer HO areas consumes limited radio resources of the base

station. Wider base station antenna beamwidth also increases the interference level of the


neighbouring sector and thus reduces the capacity. The importance of base station

antenna beamwidth is emphasized in higher sectoring order [36].

Site separation is another key element of UMTS topology planning. Having sites

close to each other (big overlap between the cell sites) means that achieved coverage is

good in indoor as well as in outdoor locations. Conversely, this means also higher

interference levels in the network and decreased capacity values [37]. The capacity also

decreases due to higher number of soft HO connections. When the base stations are

placed far apart the cell ranges belong too long and this situation yields for high

transmission power for the mobiles located near the cell edges. Thus, the amount of

coverage overlapping is always on optimization tasks and a trade of between coverage

and capacity requirements.

Base station antenna height affects on the propagation signal near the base station

antenna. Until certain distance, the propagation near the base station antenna happens

with propagation slope of 20 dB/dec. This distance where the propagation slope changes

is called breakpoint distance. After this point, the propagation slope is determined by the

environment.

Use of higher antenna positions yields for larger coverage areas but also for

higher interference levels for surrounding cells [38]. Without tilting the base station

antenna, the interference level of the neighbouring cells increases and the capacity

decreases.

Antenna tilt is a key parameter in controlling interference and it is used, either in a

mechanical way or in an electrical manner, in order to minimize the ratio of interference

[39]. Tilt also affects the throughput at a site, making it a key differentiator when it

comes to QoS. Changing the elevation pattern offers a great opportunity for optimization.

Antenna tilt has not been used in this work.

When one of these elements is changed, the performance of the system is also

changing: sector overlapping grows with antenna height and antenna beamwidth and

when higher site separation is used the interference level between cells is lower but path

loss is higher. These are only some examples about how those parameters concerning to

the topology of the network are affecting to the system performance. More about that can

be found in [40].


Used values in simulations for those key elements of the topology planning are

shown in Table 4.6. These values have been chosen because of typical macro cellular

network layout and configuration are used. As it has been said, antenna tilt has not been

used in this work.

ANTENNA

BEAMWIDTH

[degree]

SITE

SEPARATION

[kilometers]

ANTENNA

HEIGHT

[meters]

3-SECTOR CASE 65 – 90 1.5 – 2.0 – 2.5 25 – 45

6-SECTOR CASE 33 – 65 1.5 – 2.0 – 2.5 25 – 45

Table 4.6 Simulation values of the network topology parameters.

Simulations will combine all these values in two different scenarios (three and six

sectors/site) and the objective will be to study their impact on capacity in the designed

WCDMA network. .

4.3.- OPTIMIZATION

WCDMA system needs, like GSM, continuous monitoring because the mobile

users´ location and traffic behaviour varies all the time. This monitoring requirement is

only emphasized in the WCDMA because the traffic demand can vary strongly and this

variation influences directly the radio network quality. The better and more accurately the

traffic amount and locations can be modelled the better and more efficiently the radio

network can be designed and implemented.

Main indicators that should be monitored are traffic, soft HO percentage, average

transmitted and received power, drop calls, handovers per call and per cell, throughput

and BER [26].

4.4.- CELL TYPES

For optimal UMTS performance, it is proposed that UMTS network is planned by

using a hierarchical cell structure (HCS): macro, micro and pico cells [41-43]. In general,

QoS and capacity requirements need to be guaranteed in the smallest cells, which are the

most critical cells. A possible use of the hierarchical cell structure is shown in Figure 4.8.


Figure 4.8 A hierarchical cell scenario in UMTS.

Large cells guarantee a continuous coverage for fast moving mobiles while small

cells are necessary to achieve good spectrum efficiency and high capacity for hot spot

areas. With flexible deployment, it could be possible for an operator to redeploy pico cell

channels for macro cells outside of urban cells in some locations.

The FDD macro cellular network provides a wide area of coverage and it is used

for high speed movement mobiles. Micro cells are used at street level for outdoor

coverage to provide extra capacity where macro cells could not scope. Those micro cells

would not be hexagonal in shape but rather canyonlike, reflecting the topography of a

street and be typically 200 - 400 m in distance. Pico cells would be deployed mainly in

indoor areas where there is a demand for high data rate services such as laptops

networking or multimedia conferencing. Such cells may be in the order of 50 m (typical

value) in distance. A limiting factor will be the range of these terminals when used for

high data rate services. Maximum bit rate for macro cells is hoped to be 384 Kbps and

until 2 Mbps for pico cells.

Main characteristics of these cell types, which are summarized in Table 4.7, are as

follows:


MACRO CELLS

• Cell range >1 km

• High transmission powers (>10 Watt)

• High gain, directive antennas (Ga = 10 - 20 dB)

• Data rates until 384 Kbps

• Basic coverage and capacity over large area in the first phase of network roll-out

• Low isolation between cells

• High delay spread, fast moving mobiles

• Propagation phenomena very difficult to compute analytically

• Many different propagation paths

• Lots of scattering

MICRO CELLS

• Cell range 100 m to 1 km

• Medium to high transmission powers (>1Watt)

• BS cabinet can be outdoors or indoors (long cabling in some cases)

• Medium gain antennas (Ga = 5 - 10 dB, θ3dB = 60 � 120 degree)

• Data rates even higher than 384 Kbps

• Hot-spot capacity and continuous micro coverage in some cases

• Both outdoor and indoor coverage

• Good isolation between adjacent cells

� buildings isolate cells

� good spectral efficiency

• Low minimum coupling loss close to antenna (50 - 60 dB)

• Low delay spread: only few strong propagation paths

• LOS propagation: line of sight


• Street corner effect:

� when the mobile moves from

LOS to NLOS the signal strength

might drop 20 - 30 dB

� fast moving mobiles are problematic

• Very high site density up to 20 - 30 sites per km2

PICO CELLS

• Cell range from 10 m to 100 m

• Two solutions: pico BS or distributed antenna systems (DAS)

• Small (pico BS) to high (DAS) transmission powers

• Low gain antennas (Ga = 2 dB)

• Data rates until 2 Mbps

• Hot-spot capacity / indoor coverage

• Problems:

� interaction with outdoor cells: power leaking

� low isolation

� different powers

• Low minimum coupling loss (35 - 50 dB)

• Very low delay spread: only few strong propagation paths → low multi path diversity

and good orthogonality

• Application areas: offices, shopping malls, railway stations, airports, hotels�

CELL TYPE RANGE APPLICATION

Umbrella cells Up to several hundred of

Kms.

Satellite mobile Filling supply gaps

Support traffic peaks Hyper cells > 20 kms. Rural areas Macro cells 1 km. – 20 kms. Highways and suburban areas Micro cells 100 m. – 1 km. Cities and urban areas Pico cells < 100 m. In-building (offices, hotels, etc)

Table 4.7 Ranges and applications of the different UMTS cell types.

5.- SIMULATIONS 65

5.- SIMULATIONS

In this chapter the simulator is presented, including its characteristics and how is

it working. After this, simulations results are depicted, classified by number of sectors

used in the sectoring process. Finally, the best configurations for both cases of sectoring

are compared in order to know the best shape for our design.

5.- SIMULATIONS 66

5.1.- SIMULATION SETUP

Nokia´s simulator NetAct WCDMA Planner 4.0 is used in its static simulation

type. Static simulation is a method where the performance of the network is analysed

over various instances in time or snapshots, where User Equipments (UEs) are in

statistically determined places. The ability of each terminal to make its connection to the

network is calculated through an iterative process.

Various failure mechanisms are typically considered, such us maximum mobile

transmission power, maximum Node B power reached, no available channels or low pilot

Ec/Io.

The performance of the network is then analysed from the results of the snapshots

carried out. Monte-Carlo analysis has been used in this thesis as used in WCDMA

Planner. It is a form of static simulation which requires hours of computing time.

NetAct WCDMA Planner 4.0 offers also the possibility of run dynamic

simulations. In those simulations, UEs moving through the network in successive time

steps are simulated. A mobile list is generated and solved for the first time step. The

simulation may consider time to be split into chip periods, bit periods and time steps

(SNR considered). Successive time steps are then simulated and are dependent upon the

results of the previous time slot. New mobiles are simulated coming into the network and

terminating their calls.

Main advantages and disadvantages of these WCDMA simulation methods are

shown in Table 5.1

Method Accuracy Complexity Taken time

Static calculation

Not very accurate,

particularly with

global margins

Relatively

straightforward to

use once

configured

Shortest

Static simulation

Reasonable but

does not deal with

dynamic network

performance

More difficult to

configure and gives

more complicated

results

Moderate

depending on the

number of UEs

and calls

Table 5.1 Advantages and disadvantages of WCDMA simulation methods.

5.- SIMULATIONS 67

Method Accuracy Complexity Taken time

Dynamic

simulation

Quite high

assuming no bad

assumptions are

made to speed it

up

Difficult to judge

results

Extremely long if

multiple runs are

performed for

statistical validity

Table 5.1 (cont.) Advantages and disadvantages of WCDMA simulation methods.

What is Monte-Carlo simulation? Traditionally, TDMA/FDMA network planning

used static analysis and calculated the margins for a tuned propagation model in order to

protect the system of interferences. Gains were applied to allow for the soft handover

technique. However, as the level of intra cell and inter cell interference varies between

cells, this approach gave misleading results in early networks. Thus, in CDMA networks,

coverage and cell capacity are too interrelated to be predicted accurately with static

analysis to derive margins and gains.

An alternative approach has developed based around simulating networks by

using Monte-Carlo algorithms. Existent WCDMA Planner in NetAct WCDMA Planner

4.0 uses this approach as it provides a good balance between accuracy and usability.

A large number of randomized snapshots are taken of the network performance

for different UEs or terminals over time. In these snapshots, the UEs are in statistically

determined positions and generated independently for each snapshot.

The number of terminals in an active session in a pixel is determined by using a

Poisson distribution with a mean given by the number of terminals in the traffic array.

This means that the total number of terminals in a snapshot is Poisson distributed and so

it will vary from snapshot to snapshot.

These snapshots are then used in calculations to obtain statistically valid

measurements giving an estimate of the mean network performance.

An advantage of using the static Monte-Carlo simulation approach is that it takes

less time than dynamic simulation (where you look at mobiles moving through the

network). Repeated static simulation proves its value for detailed optimization of site

configurations, problem areas and radio resource management algorithms.

5.- SIMULATIONS 68

Used simulation environment is given by a digital map of Tampere area, which is

a city similar to Tarragona in Spain (number of people, geography and other

characteristics are quite the same).

Nineteen base stations (the first two interfering tiers and the central base station)

in hexagonal grid are placed in Tampere area in order to provide UMTS speech service to

the city. Figure 5.1 shows the digital map of Tampere used in the simulations and these

nineteen base stations in the case where three sectors/site have been used. The hexagon

limits the simulation area, so there are terminals only inside it.

Figure 5.1 Digital map of the simulation area.

The simulator needs as inputs a digital map, the network layout, where are

defined the number of sectors/site and the cell range; the traffic raster, which contains the

mobile distribution in the network and many other parameters which are needed by the

Monte-Carlo simulation and, finally, the site configuration, where the antenna parameters

5.- SIMULATIONS 69

(beamwidth and antenna positions) are set. All these parameters are chosen according to

the values shown in Table 4.6, in section 4.2.3. After this, the initialization phase has

concluded.

Once this values have been read, coverage predictions should be calculated by

using the propagation model (Okumura-Hata, which is explained in section 4.2.2).

Calculus of coverage predictions requires hours of computing time and it needs all the

resources of the computer.

After this, next step is starting the Monte-Carlo simulation. All the Monte-Carlo

simulations have been run with 10.000 snapshots in order to get reliable results. The total

number of terminals (users) in the network, according to its load level, is shown in Table

5.2.

LOAD LEVEL No. OF TERMINALS

Not loaded 2000

3 - SECTOR CASE Semi-loaded 3000

Loaded 4000

Not loaded 2000

6 - SECTOR CASE Semi-loaded 4000

Loaded 6000

Table 5.2 Total number of terminals in the network according to its load level.

5.2.- RESULTS

Results are classified by the number of sectors/site used in the sectoring process.

For each scenario (three and six sectors/site), obtained results are classified by the site

separation used in the simulations.

First, results are compared in order to know the performance of the network when

antenna height and antenna beamwidth are changed. Finally, only the best configurations

are compared between them in order to analyse the behaviour of the network when

different cell spacings are used.

5.- SIMULATIONS 70

5.2.1.- Scenario 1: 3-Sector Case

3-SECTORED SITES OF 1.5 km.

2000 T 3000 T 4000 T

90 degree / 25 m

Service probability [%] 100 96.9 79.6Mean # of mobiles in soft HO [%] 19.6 19.3 20.5Mean # of mobiles in softer HO [%] 12 12 13Uplink load [%] 42 61.3 67.2Other-to-own cell interference 0.94 0.942 0.914DL TX. power [dBm] 35.2 38.6 40.4Throughput [kbps/sector] 289.6 420.9 469.1Noise rise [dB] 2.39 4.18 4.88

90 degree / 45 m

Service probability [%] 97.7 79.6 55.7Mean # of mobiles in soft HO [%] 38.1 40.6 43.3Mean # of mobiles in softer HO [%] 9.6 10.5 11.4Uplink load [%] 53.5 63.6 58.8Other-to-own cell interference 1.535 1.48 1.43DL TX. power [dBm] 37.5 40.2 41.3Throughput [kbps/sector] 336.6 415.7 394.9Noise rise [dB] 3.4 4.43 3.89

65 degree / 25 m

Service probability [%] 100 98.7 86.1Mean # of mobiles in soft HO [%] 18.9 18.5 19.1Mean # of mobiles in softer HO [%] 4.8 4.7 5Uplink load [%] 38.6 57.3 66.4Other-to-own cell interference 0.744 0.751 0.729DL TX. power [dBm] 34.6 37.8 39.7Throughput [kbps/sector] 271.9 401.4 470.5Noise rise [dB] 2.14 3.77 4.81

65 degree / 45 m

Service probability [%] 98.8 86.7 65.1Mean # of mobiles in soft HO [%] 33.5 34.9 37.6Mean # of mobiles in softer HO [%] 3.7 4 4.4Uplink load [%] 48.7 62.8 62.6Other-to-own cell interference 1.212 1.188 1.153DL TX. power [dBm] 36.5 39.6 40.9Throughput [kbps/sector] 312.7 412.6 421.8Noise rise [dB] 2.97 4.385 4.32

Figure 5.2 Results of 3-sectored sites, 1.5 km. site separation.

In this case, base stations are close to each other. For this reason the interference

level is increasing quickly if wide and/or high antennas are used (degrading too much the

service probability when the network is loaded). According to the results shown in Figure

5.2, the best antenna configuration is 65 degree antenna beamwidth and 25 meters of

antenna height. Because of the distance between base stations is small, coverage is good

and this antenna configuration supplies a good interference level.

5.- SIMULATIONS 71

Figure 5.3 shows sector throughput as a function of DL traffic power for different

antenna configurations.

250

300

350

400

450

500

34 35 36 37 38 39 40 41 42

DL. AVERAGE TRAFFIC POWER [dBm]

SEC

TOR

TH

RO

UG

HPU

T [K

bps/

sect

or]

90_25

90_45

65_25

65_45

Figure 5.3 Sector throughput vs downlink traffic power with 3-sectored sites, 1.5 km. site separation.

When the transmitted power exceeds 40 dBm, the network starts to be saturated in

all cases, except for the best configuration (65_25), where the saturation area begins later.

Following the same tendency, Figure 5.4 shows the service probability as a function of

sector throughput, also for the different antenna configurations.

75

80

85

90

95

100

250 300 350 400 450 500

SECTOR THROUGHPUT [Kbps/sector]

SER

VIC

E PR

OB

AB

ILIT

Y [%

]

90_2590_4565_2565_45

Figure 5.4 Service probability vs sector throughput with 3-sectored sites, 1.5 km. site separation.

5.- SIMULATIONS 72


2000 T 3000 T 4000 T

90 degree / 25 m

Service probability [%] 99.7 96.9 82.7Mean # of mobiles in soft HO [%] 16.1 15.8 16.2Mean # of mobiles in softer HO [%] 12.4 12.3 13.1Uplink load [%] 39.4 57.8 65.5Other-to-own cell interference 0.824 0.833 0.798DL TX. power [dBm] 34.9 38.1 39.8Throughput [kbps/sector] 281.3 409.5 471Noise rise [dB] 2.22 3.84 4.7

90 degree / 45 m

Service probability [%] 99.9 93.3 69.7Mean # of mobiles in soft HO [%] 26.6 26.8 29.1Mean # of mobiles in softer HO [%] 11.9 12.2 13.6Uplink load [%] 46 64.5 64.5Other-to-own cell interference 1.131 1.128 1.086DL TX. power [dBm] 36.1 39.6 41Throughput [kbps/sector] 309.8 435.6 445.3Noise rise [dB] 2.71 4.55 4.53

65 degree / 25 m

Service probability [%] 99.6 98.5 87.8Mean # of mobiles in soft HO [%] 16.5 16 16.2Mean # of mobiles in softer HO [%] 5.1 5 5.2Uplink load [%] 36.3 53.9 63.8Other-to-own cell interference 0.645 0.658 0.63DL TX. power [dBm] 34.3 37.4 39.2Throughput [kbps/sector] 266.7 394 469.6Noise rise [dB] 2 3.47 4.52

65 degree / 45 m



This configuration is, according to the results shown in Figure 5.5, a medium case

and use of wide and high antennas is now better supported, compared to sites of 1.5

kilometers, because the degradation of the service probability, which is caused by this

use, is not so important, except in the worst case (wide and high antennas). The best

antenna configuration is still 65 degree and 25 meters. This configuration gives better

results in both aspects: service probability and capacity, especially when the network is

loaded.

5.- SIMULATIONS 73

Figure 5.6 shows sector throughput as a function of DL traffic power for different

antenna configurations.

250

300

350

400

450

500

550

34 35 36 37 38 39 40 41 42

DL. AVERAGE TRAFFIC POWER [dBm ]

SEC

TOR

TH

RO

UG

HPU

T [K

bps/

sect

or]

90_25

90_45

65_25

65_45


The same effect appears again: when the transmitted power exceeds 40 dBm, the

network starts to be saturated but this time also for the best configuration. Figure 5.7

shows the service probability, much better compared to sites of 1.5 kilometers (especially

in the worst cases: 65_45 and 90_45) as a function of sector throughput.

75

80

85

90

95

100

250 300 350 400 450 500


SER

VIC

E PR

OB

AB

ILIT

Y [%

]

90_25

90_45

65_25

65_45


5.- SIMULATIONS 74


2000 T 3000 T 4000 T

90 degree / 25 m

Service probability [%] 99.1 95.1 80.5Mean # of mobiles in soft HO [%] 16.6 16.7 17.5Mean # of mobiles in softer HO [%] 12.6 12.6 13.6Uplink load [%] 39.2 57 64.3Other-to-own cell interference 0.86 0.866 0.832DL TX. power [dBm] 34.7 37.9 39.7Throughput [kbps/sector] 280.9 405 464.3Noise rise [dB] 2.21 3.78 4.59

90 degree / 45 m

Service probability [%] 99.9 94.3 75.9Mean # of mobiles in soft HO [%] 21.8 22 23.2Mean # of mobiles in softer HO [%] 12.6 12.6 13.7Uplink load [%] 43.5 61.7 66.4Other-to-own cell interference 1.035 1.03 0.998DL TX. power [dBm] 35.5 38.8 40.4Throughput [kbps/sector] 297.1 421.5 460.6Noise rise [dB] 2.52 4.24 4.79

65 degree / 25 m

Service probability [%] 99.1 97.1 86.1Mean # of mobiles in soft HO [%] 17.1 16.8 17.5Mean # of mobiles in softer HO [%] 5 5 5.3Uplink load [%] 35.9 53.2 62.8Other-to-own cell interference 0.672 0.684 0.656DL TX. power [dBm] 34.2 37.2 39.2Throughput [kbps/sector] 265.7 390 464.7Noise rise [dB] 1.98 3.41 4.43

65 degree / 45 m

Service probability [%] 99.9 96.6 82.3Mean # of mobiles in soft HO [%] 22.5 22.2 23Mean # of mobiles in softer HO [%] 4.5 4.5 4.8Uplink load [%] 40.2 58.4 66Other-to-own cell interference 0.839 0.842 0.816DL TX. power [dBm] 34.9 38.2 39.9Throughput [kbps/sector] 281.2 407.5 467.1Noise rise [dB] 2.27 3.89 4.77


This is the case where has been used the maximum spacing between base stations,

2.5 kilometers. For this reason, the impact of using wide and high antennas is now

minimum, as we can see in Figure 5.8. When the site separation is bigger, the

interference level is lower and, even if the network is loaded, there is not a big

degradation of the service probability, except in the worst case, which is another time 90

degree and 45 meters. However, the best configuration, especially from the capacity point

of view, has not changed: it is still 65 degree and 25 meters. But in the aspect of service

probability this is the best configuration only when there is a big number of terminals in

the network.

5.- SIMULATIONS 75

Figure 5.9 shows sector throughput as a function of DL traffic power for the

different antenna configurations.

250

300

350

400

450

500

34 35 36 37 38 39 40 41 42

DL. AVERAGE TRAFFIC POWER [dBm ]

SEC

TOR

TH

RO

UG

HPU

T [K

bps/

sect

or]

90_25

90_45

65_25

65_45


This time the network starts to be saturated before the transmitted power arrives

to 40 dBm, except for 65_25 (best case) and for 90_45 (worst case), in which the capacity

decreases very quickly after the transmitted power has exceeded the level of 40.4 dBm.

To conclude this analysis, Figure 5.10 shows the service probability, which is not very

affected for the antenna configuration, as a function of sector throughput.

75

80

85

90

95

100

250 300 350 400 450 500


SER

VIC

E PR

OB

AB

ILIT

Y [%

]

90_2590_4565_2565_45


5.- SIMULATIONS 76

5.2.2.- Scenario 2: 6-Sector Case

6-SECTORED SITES OF 1.5 kms.

2000 T 4000 T 6000 T

33 degree / 25 m

Service probability [%] 100 100 96.8Mean # of mobiles in soft HO [%] 24.2 23.2 23Mean # of mobiles in softer HO [%] 4.1 4 3.9Uplink load [%] 20.1 40.1 58.1Other-to-own cell interference 0.79 0.803 0.801DL TX. power [dBm] 30.7 34.9 38.2Throughput [kbps/sector] 141.9 281.9 409Noise rise [dB] 0.98 2.27 3.89

33 degree / 45 m

Service probability [%] 100 99.4 85.1Mean # of mobiles in soft HO [%] 41.8 39.9 41.9Mean # of mobiles in softer HO [%] 2.3 2.3 2.3Uplink load [%] 24.8 49.1 61.4Other-to-own cell interference 1.208 1.219 1.171DL TX. power [dBm] 31.9 36.7 39.7Throughput [kbps/sector] 167.4 329.2 427.5Noise rise [dB] 1.25 3.03 4.26

65 degree / 25 m

Service probability [%] 100 99.4 83.8Mean # of mobiles in soft HO [%] 20.5 20 21Mean # of mobiles in softer HO [%] 36.3 34.5 37.1Uplink load [%] 24.9 50 63Other-to-own cell interference 1.409 1.434 1.386DL TX. power [dBm] 32 36.8 40.1Throughput [kbps/sector] 172.2 338 437.2Noise rise [dB] 1.25 3.06 4.37

65 degree / 45 m

Service probability [%] 100 92.2 64.1Mean # of mobiles in soft HO [%] 41.5 41.3 44.2Mean # of mobiles in softer HO [%] 37.1 37.4 41.9Uplink load [%] 31.3 57.6 57.8Other-to-own cell interference 2.135 2.118 1.999DL TX. power [dBm] 33.3 38.8 40.8Throughput [kbps/sector] 205.8 379.5 408.9Noise rise [dB] 1.65 3.81 3.8


If the number of sectors/site grows (in this scenario it is six) the overlapped area

is also bigger. For this reason the number of mobiles in HO is very big when 65 degree

antennas are used. According to the results shown in Figure 5.11, the best configuration

is now 33 degree antenna beamwidth and 25 meters of antenna height and its tendency is

the same than in 3 sectors: narrow and low antennas allow getting better service

5.- SIMULATIONS 77

probability and higher capacity because the interference level is lower and the coverage is

not so bad.

Figure 5.12 shows sector throughput as a function of DL traffic power for


130

180

230

280

330

380

430

480

530

30 32 34 36 38 40 42


SEC

TOR

TH

RO

UG

HPU

T [K

bps/

sect

or]

33_25

33_45

65_25

65_45


When the transmitted power exceeds 40 dBm, the network starts to be saturated in

all cases except for the best configuration (33_25), which seems to grow even if the

network is very high loaded. But this configuration is not immune to interference, which

degrades the service probability as we can see in Figure 5.13, where is depicted the

service probability as a function of sector throughput.

70

75

80

85

90

95

100

130 180 230 280 330 380 430 480


SER

VIC

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OB

AB

ILIT

Y [%

]

33_2533_4565_2565_45


5.- SIMULATIONS 78


2000 T 4000 T 6000 T

33 degree / 25 m


33 degree / 45 m

Service probability [%] 100 99.9 95.1Mean # of mobiles in soft HO [%] 31.4 30.2 29.9Mean # of mobiles in softer HO [%] 3.4 3.3 3.3Uplink load [%] 21.9 43.5 61.1Other-to-own cell interference 0.936 0.944 0.933DL TX. power [dBm] 31.3 35.7 39Throughput [kbps/sector] 152.5 302.6 430.5Noise rise [dB] 1.08 2.52 4.2

65 degree / 25 m

Service probability [%] 99.9 99.6 88.3Mean # of mobiles in soft HO [%] 17.1 16.7 16.6Mean # of mobiles in softer HO [%] 34.9 33 33.8Uplink load [%] 23.4 46.8 62.2Other-to-own cell interference 1.24 1.267 1.236DL TX. power [dBm] 31.6 36.3 39.5Throughput [kbps/sector] 166.3 327.4 437.4Noise rise [dB] 1.17 2.81 4.32

65 degree / 45 m

Service probability [%] 100 99.1 79.6Mean # of mobiles in soft HO [%] 27 26.3 27.4Mean # of mobiles in softer HO [%] 37.9 36.2 39.5Uplink load [%] 27.2 53.9 64.2Other-to-own cell interference 1.633 1.65 1.592DL TX. power [dBm] 32.5 37.6 40.5Throughput [kbps/sector] 183.9 359.6 444.2Noise rise [dB] 1.38 3.41 4.5


In this case the overlapped area is lower (consequence of using higher cell radius)

respect to the case where the spacing between base stations was 1.5 kilometers. For this

reason, when 65 degree antennas are used, the number of mobiles in HO is not as big as it

was in the previous case but it is still big, especially if we do not use narrow antennas.

The best configuration in the capacity point of view is still 33 degree and 25 meters but it

has changed in the service probability aspect: now it is 33 degree and 45 meters because

of higher cell radius means lower overlapped area and this is low interference level.

5.- SIMULATIONS 79



130

180

230

280

330

380

430

480

530

30 32 34 36 38 40 42


SEC

TOR

TH

RO

UG

HPU

T [K

bps/

sect

or]

33_25

33_45

65_25

65_45


In Figure 5.15 is again clearly displayed the saturation area of the network, but in

this case when the transmitted power exceeds 40.2 dBm. Nevertheless, when the best

configurations (33_25 and 33_45) are used, sector throughput grows with the transmitted

power even if the network is very high loaded. From the service probability point of

view, both configurations are the best when the network is loaded, especially the last one,

as shown in Figure 5.16, where is depicted the service probability as a function of sector

throughput.

75

80

85

90

95

100

130 180 230 280 330 380 430 480


SER

VIC

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OB

AB

ILIT

Y [%

]

33_2533_4565_2565_45


5.- SIMULATIONS 80


2000 T 4000 T 6000 T

33 degree / 25 m

Service probability [%] 99.5 99.2 96.3Mean # of mobiles in soft HO [%] 18.9 17.2 17.2Mean # of mobiles in softer HO [%] 4.9 4.7 4.6Uplink load [%] 18.1 36.1 52.7Other-to-own cell interference 0.656 0.673 0.677DL TX. power [dBm] 30 34 37Throughput [kbps/sector] 133.5 265.2 385.9Noise rise [dB] 0.88 2 3.4

33 degree / 45 m

Service probability [%] 100 99.9 96.1Mean # of mobiles in soft HO [%] 24.8 23.9 23.8Mean # of mobiles in softer HO [%] 3.8 3.7 3.7Uplink load [%] 20.2 40.3 58Other-to-own cell interference 0.824 0.837 0.835DL TX. power [dBm] 30.7 34.9 38.1Throughput [kbps/sector] 142.6 283.6 408.9Noise rise [dB] 0.99 2.29 3.88

65 degree / 25 m

Service probability [%] 99.5 98.5 85.4Mean # of mobiles in soft HO [%] 16.4 16.1 16.8Mean # of mobiles in softer HO [%] 32 30.3 31.9Uplink load [%] 23 46 60Other-to-own cell interference 1.243 1.276 1.247DL TX. power [dBm] 31.3 36 39.1Throughput [kbps/sector] 161.6 316.4 418Noise rise [dB] 1.15 2.77 4.11

65 degree / 45 m

Service probability [%] 100 98.7 81.9Mean # of mobiles in soft HO [%] 21.4 20.9 21.9Mean # of mobiles in softer HO [%] 35 33.5 35.8Uplink load [%] 25.5 50.7 62.8Other-to-own cell interference 1.474 1.499 1.456DL TX. power [dBm] 32 37 40Throughput [kbps/sector] 172.2 336.8 427.3Noise rise [dB] 1.29 3.15 4.38


Using maximum spacing between base stations, a reduction of the number of

mobiles in HO (increasing the cell radius decreases the overlapped area) is displayed in

the results. But when widebeam antennas are used, (65 degree) this number of mobiles in

HO is still more than two times bigger with respect to the case where narrowbeam

antennas (33 degree) have been used. In the capacity point of view, the best configuration

is still 33 degree and 25 meters, according to the results shown in Figure 5.17. In the

service probability aspect it is another time 33 degree and 45 meters (like when 2.0

5.- SIMULATIONS 81

kilometers site separation were used), but now the difference compared to the use of 25

meters antenna positions and 33 degree antenna beamwidth is bigger, respect to that case

of 2.0 kilometers site separation.



130

180

230

280

330

380

430

480

530

30 32 34 36 38 40 42


SEC

TOR

TH

RO

UG

HPU

T [K

bps/

sect

or]

33_25

33_45

65_25

65_45


In this case a peculiar event is depicted in Figure 5.18 because the best

configuration, 33_25, which is still giving the best results in capacity aspect, seems to be

saturated when the network load level is high. From the service probability point of view,

33_45 is the best configuration for any state of the network, as shown in Figure 5.19,

where is depicted the service probability as a function of sector throughput.

75

80

85

90

95

100

130 180 230 280 330 380 430 480


SER

VIC

E PR

OB

AB

ILIT

Y [%

]

33_2533_4565_2565_45


5.- SIMULATIONS 82

5.2.3.- Optimum Configurations

Results for the best configuration in 3-sector case are depicted in Figure 5.20. It is

65 degree antenna beamwidth and 25 meters of antenna height. The poorest results are

obtained with 1.5 kilometers between sites because the interference level is higher due to

they are too close to each other. When the site separation is bigger, there is a little fall in

the number of mobiles in HO, because of the smaller overlapped area. For those cases

where the site separation is higher than 1.5 kilometers, capacity level is always better,

particularly for 2.0 kilometers case, which is the best in this aspect, especially when the

network is loaded, because its saturation area begins later. For this load level, it gives

almost 4% more of capacity respect to the case of 2.5 kms (the second one in this aspect).

3-sectored sites with 65 degree antennas and base station antenna height of 25 m.

2000 T 3000 T 4000 T 5000 T 5500T

1.5 kilometers between BTS

Service probability [%] 100 98.7 86.1 70.4Mean # of mobiles in soft HO [%] 18.9 18.5 19.1 19.6Mean # of mobiles in softer HO [%] 4.8 4.7 5 5.3Uplink load [%] 38.6 57.3 66.4 67.9Other-to-own cell interference 0.744 0.751 0.729 0.707DL TX. power [dBm] 34.6 37.8 39.7 40.5Throughput [kbps/sector] 271.9 401.4 470.5 484.1Noise rise [dB] 2.14 3.77 4.81 4.98


Service probability [%] 99.6 98.5 87.8 74.7 68.7Mean # of mobiles in soft HO [%] 16.5 16 16.2 16.2 16.1Mean # of mobiles in softer HO [%] 5.1 5 5.2 5.4 5.5Uplink load [%] 36.3 53.9 63.8 67 67.5Other-to-own cell interference 0.645 0.658 0.63 0.601 0.588DL TX. power [dBm] 34.3 37.4 39.2 40 40.3Throughput [kbps/sector] 266.7 394 469.6 499.6 503.4Noise rise [dB] 2 3.47 4.52 4.9 4.95


Service probability [%] 99.1 97.1 86.1 64.9Mean # of mobiles in soft HO [%] 17.1 16.8 17.5 18.1Mean # of mobiles in softer HO [%] 5 5 5.3 5.7Uplink load [%] 35.9 53.2 62.8 65Other-to-own cell interference 0.672 0.684 0.656 0.61DL TX. power [dBm] 34.2 37.2 39.2 40.3Throughput [kbps/sector] 265.7 390 464.7 486.2Noise rise [dB] 1.98 3.41 4.43 4.66

Figure 5.20 Results of 3-sectored sites with 65 degree antennas and base station antenna height of 25 m.

5.- SIMULATIONS 83


different site separation used.

250

300

350

400

450

500

550

34 35 36 37 38 39 40 41 42


SEC

TOR

TH

RO

UG

HPU

T [K

bps/

sect

or]

1.5 kms

2.0 kms

2.5 kms

Figure 5.21 Sector throughput vs downlink traffic power for the best configuration with 3-sectored sites.

In Figure 5.22 is depicted the service probability as a function of sector

throughput. Also in this aspect, best results are obtained using 2.0 kilometers between

sites but now the worst case is not with a spacing of 1.5 kilometers.

65

70

75

80

85

90

95

100

250 300 350 400 450 500


SER

VIC

E PR

OB

AB

ILIT

Y [%

]

1.5 kms2.0 kms2.5 kms

Figure 5.22 Service probability vs sector throughput for the best configuration with 3-sectored sites.

5.- SIMULATIONS 84

Results for the best configuration in 6-sector case are depicted in Figure 5.23.

Now it is 33 degree antenna beamwidth and 25 meters of antenna height. The poorest

results are again obtained with 1.5 kilometers between sites. They follow the same

tendency, respect to the number of mobiles in HO, capacity and service probability, than

obtained results in 3-sector case when narrow/wide and lower/higher antenna positions

were used. But there are also some significant differences: Figure 5.24 shows that, on the

contrary of the other cases, there is not saturation area when 2.0 kilometers between sites

are used. According to this figure, best cases in the capacity point of view are 2.0 and 2.5

kilometers, both, because capacity levels are the same. When the network is high loaded,

they give more than 3% more of capacity respect to the case of 1.5 kilometers (the worst

one).

6-sectored sites with 33 degree antennas and base station antenna height of 25 m.

2000 T 4000 T 6000 T 8000 T 9000T


Service probability [%] 100 100 96.8 82.2 74.8Mean # of mobiles in soft HO [%] 24.2 23.2 23 23.6 23.6Mean # of mobiles in softer HO [%] 4.1 4 3.9 4 4.1Uplink load [%] 20.1 40.1 58.1 65 66.1Other-to-own cell interference 0.79 0.803 0.801 0.762 0.745DL TX. power [dBm] 30.7 34.9 38.2 39.8 40.2Throughput [kbps/sector] 141.9 281.9 409 464.8 475.5Noise rise [dB] 0.98 2.27 3.89 4.66 4.79


Service probability [%] 99.8 99.7 97.5 85.3 78.9Mean # of mobiles in soft HO [%] 20.5 19.8 19.5 19.1 18.7Mean # of mobiles in softer HO [%] 4.8 4.6 4.5 4.5 4.5Uplink load [%] 18.8 37.4 54.8 63.2 65.2Other-to-own cell interference 0.681 0.696 0.701 0.67 0.651DL TX. power [dBm] 30.4 34.5 37.6 39.1 39.6Throughput [kbps/sector] 137.8 274.3 401.1 465.4 481.8Noise rise [dB] 0.91 2.08 3.57 4.47 4.7


Service probability [%] 99.5 99.2 96.3 78.4Mean # of mobiles in soft HO [%] 18.9 17.2 17.2 17.5Mean # of mobiles in softer HO [%] 4.9 4.7 4.6 4.7Uplink load [%] 18.1 36.1 52.7 63.9Other-to-own cell interference 0.656 0.673 0.677 0.645DL TX. power [dBm] 30 34 37 39.3Throughput [kbps/sector] 133.5 265.2 385.9 472.4Noise rise [dB] 0.88 2 3.4 4.61

Figure 5.23 Results of 6-sectored sites with 33 degree antennas and base station antenna height of 25 m.

5.- SIMULATIONS 85


different site separation used.

130

180

230

280

330

380

430

480

530

30 32 34 36 38 40


SEC

TOR

TH

RO

UG

HPU

T [K

bps/

sect

or]

1.5 kms

2.0 kms

2.5 kms

Figure 5.24 Sector throughput vs downlink traffic power for the best configuration with 6-sectored sites.

Service probability as a function of sector throughput is depicted in Figure 5.25.

Also from this point of view, best results are obtained using 2.0 kilometers between sites.

In this aspect, the worst case is again the same: using a site separation of 2.5 kilometers.

75

80

85

90

95

100

130 180 230 280 330 380 430 480


SER

VIC

E PR

OB

AB

ILIT

Y [%

]

1.5 kms

2.0 kms

2.5 kms

Figure 5.25 Service probability vs sector throughput for the best configuration with 6-sectored sites.

6.- CONCLUSIONS 86

6.- CONCLUSIONS

Coverage and capacity planning of UMTS WCDMA cellular networks cannot be

separated, since they are connected to each other. Furthermore, uplink and downlink

directions should be considered separately due to different (asymmetric) traffic.

Topology planning phase contains definition of key parameters like base station

antenna configuration (antenna beamwidth, antenna height or tilting), number of sectors

used in the sectoring process or description of base station locations: distance between

sites, etc. These elements have great impact on the system performance and they

influence strongly on capacity and service coverage of UMTS networks. All these

parameters should be defined in order to provide good coverage and capacity levels,

fulfiling QoSrequirements with reasonable implementation costs.

UMTS network capacity is interference limited, i.e. it is a soft capacity limited

system, because the interference rise in a cell causes the blocked calls. Interference level

is displayed in the simulation results, in section 5.2, and it decreases when the overlapped

area is smaller. If tilting is not considered (it has not been used in this work), the

capacity is higher when narrow antenna beamwidth and lower antenna positions are used.

Use of high antennas is better supported for the network when the distance between base

stations and/or the number of sectors/site are increased. Thus, when spacing between sites

is 2.5 kilometers, service probability is always better using narrow antennas with higher

antenna positions. This is due to higher antenna positions give larger coverage areas but

also higher interference level to neighbouring cells; nevertheless, when large spacing

between sites is used, the effect of better coverage has greater importance than

interference level. Antenna height affects the signal propagation near the base station and

antenna beamwidth allows to control softer HO areas, i.e. number of softer HOs, which

are needed in UMTS network in order to limit the interference level during the HO

procedure but should be taken into account that too large softer HO areas consumes

limited resources of the base station. Importance of a good choice for the base station

antenna beamwidth grows with the order of sectorisation.

In the aspect of spacing between sites, best results are obtained by using 2.0

kilometers between them, which is a middle value between 1.5 kms (better coverage but

6.- CONCLUSIONS 87

too much interference and bigger number of soft HO connections due to higher

overlapped area) and 2.5 kms (the network needs more transmitted power for the mobiles

located near the cell edges, if they are not in HO area, and also could exist coverage

holes).

In the sectoring point of view, by using a bigger number of sectors/site the

capacity of the network is higher but there is also a drop in the service probability,

although these differences are not much significant. Sectoring increases the number of

softer handover connections in the network when widebeam antennas are used,

decreasing its capacity because there is a greater consumption of the base station limited

resources. Sectoring is used in UMTS networks to increase the system capacity as well as

the service coverage. In macro cellular environment, the best solution for high capacity

requirements is provided by using six-sectored sites.

About the situation when the configuration is not the optimum, in a mixed shape

(narrowbeam and high antennas or low antenna positions combined with wide antenna

beamwidth) and 3-sectored sites, the effect of choosing widebeam antennas is better

supported for the network than the effect of choosing high antenna positions, but in 6-

sectored sites it is on the contrary: results are better by using high than widebeam

antennas. This is because with six-sectored sites overlapped area grows faster with

widebeam antennas than with higher antenna positions, increasing the interference level

of the network. With 3-sectored sites, this use of widebeam antennas is not as critical as it

was when 6 sectors/site were used because cells are bigger and therefore the overlapped

area is smaller.

To conclude, best system configurations in both scenarios (three and six

sectors/site) depending on the network load level, are shown in Table 6.1.

NOT LOADED NETWORK LOADED NETWORK

3-SECTOR CASE 65º - 2.5 kms - 25 m 65º - 2.0 kms – 25 m

6-SECTOR CASE 33º - 2.5 kms – 25 m 33º - 2.0 kms – 25 m

Table 6.1 Best system configurations in three and six sectored sites.

Using 3-sectored sites, a configuration of 65 degree antenna beamwidth, 2.0

kilometers between sites and 25 meters of antenna height gives, when the network is

6.- CONCLUSIONS 88

loaded, a minimum of 17.2 Kbps/sector more of capacity (see Figure 5.20). If

throughput/user is 15 Kbps/user, this configuration allows, with the same QoS level, 65

users more in the network respect to other configurations.

Similarly, if 6-sectored sites are used, repeating the same analysis when the

network is loaded, this situation appears again, but now with 33 degree antennas, 2.0

kilometers between sites and 25 meters of antenna height. That configuration gives a

minimum of 9.4 Kbps/sector more of capacity (see Figure 5.23), which is equivalent to

71 users more in the network compared to other configurations.

In my opinion, in this point it is necessary to study the impact of tilting on

coverage and capacity of WCDMA systems because it has not been used in this work.

Maybe it can change the tendency shown by the results of this thesis, which indicate as

the best configuration for the base station antennas (when tilting is not used) narrowbeam

antennas and low antenna positions.

7.- REFERENCES 89

7.- REFERENCES

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[4] ETSI web site, http://www.etsi.org/.

[5] ITU web site, http://www.itu.int/imt/.

[6] UMTS forum web site, http://www.umts-forum.org/.

[7] 3GPP Technical Specification 23.907, �QoS concept�.

[8] Radio communications group of UPC web site, http://www.gcr.tsc.upc.es/.

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[11] Prasad R., �CDMA for wireless personal communications�, Artech House, 1996.

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7.- REFERENCES 90

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[16] Lee J. S. and Miller L. E., �CDMA systems engineering handbook�, Artech

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[17] Peterson R. L., Ziemer R. E. and Borth D. E., �Introduction to spread spectrum

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[18] Viterbi A. J., �CDMA: principles of spread spectrum communications�, Addison-

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[19] 3GPP Technical Specification 25.213, �Spreading and modulation FDD�.

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[21] Dinan E. H. and Jabbari B., �Spreading codes for direct sequence CDMA and

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[25] 3GPP Technical Report 25.943, Deployment Aspects.

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[29] Holma H. and Toskala A., �WCDMA for UMTS�, John Wiley & Sons Ltd. 2000.

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APPENDIX 94

APPENDIX List of Acronyms

AC Admission Control

ARIB Association of Radio Industries and Businesses

BCCH Broadcast Control Channel

BER Bit Error Rate

BPSK Binary PSK

BS BTS

BTS Base Station

CCPCH Common Control Physical Channel

CDMA Code Division Multiple Access

CIR Carrier to Interference Ratio

CN Core Network

DAS Distributed Antenna Systems

DL Downlink

DPCCH Dedicated Physical Control Channel

DPDCH Dedicated Physical Data Channel

DS Direct Sequence

DTX Discontinuous Transmission

Eb/N0 Bit Energy to Noise Ratio

EIRP Equivalent Isotropic Radiated Power

EMC Electromagnetic Compatibility

ETSI European Telecommunications Standards Institute

FACH Forward Access Channel

FDD Frequency Domain Duplex

FDMA Frequency Division Multiple Access

FFT Fast Fourier Transformation

FH Frequency Hopping

APPENDIX 95

GGSN Gateway GPRS Support Node

GMSC Gateway MSC

GPRS General Packet Radio Service

GSM Global System Mobile

HC Handover Control

HCS Hierarchical Cell Structure

HLR Home Location Register

HM Hybrid Modulation

HO Handover / Handoff

IEEE Institute of Electrical and Electronics Engineers

IMT International Mobile Telephony

IQ In-Phase Quadrature

ISI Intersymbol Interference

IT Information Technologies

ITU International Telecommunication Union

LAN Local Area Network

LC Load Control

LNA Low Noise Amplifier

LOS Line of Sight

LPI Low Probability of Intercept

MC Multicarrier

ME Mobile Equipment

MS Mobile Station

MSC Mobile Services Switching

MSK Minimum Shift Keying

MUD Multi User Detection

NB Narrowband

PC Power Control

PCH Paging Channel

PDF Probability Density Function

PDP Power Delay Profile

APPENDIX 96

PLMN Public Land Mobile Network

PN Pseudo-random Noise-like

PS Packet Scheduling

PSK Phase Shift Keying

QoS Quality of Service

QPSK Quadrature PSK

RNC Radio Network Controller

RNS Radio Network Subsystem

RRM Radio Resource Management

RTT Radio Transmission Technology

RX Receiver

SCH Synchronization Channel

SDU Service Data Unit

SGSN Serving GPRS Support Node

SHO Soft HO

SIR Signal to Interference Ratio

SMS Systems Management Server

SNR Signal to Noise Ratio

SS Spread Spectrum

TDD Time Domain Duplex

TDMA Time Division Multiple Access

TH Time Hopping

TPC Transmission Power Control

TX Transmitting

UE User Equipment

UL Uplink

UMTS Universal Mobile Telecommunications System

USIM UMTS Subscriber Identity Module

UTRAN UMTS Terrestrial Radio Access Network

VCoIP Video Conferencing over IP

VLR Visitor Location Register

APPENDIX 97

VoIP Voice over IP

WB Wideband

WCDMA Wideband CDMA

3GPP 3rd Generation Partnership Project

APPENDIX 98

List of Tables

1.1.- 2G vs 3G ��. pag. 8

2.1.- QoS classes in UMTS��. pag. 12

2.2.- Typical powers for the downlink common channels��.. pag. 19

3.1.- Main parameters WCDMA for UMTS��... pag. 36

3.2.- Path loss exponents according to the environment type��. pag. 38

3.3.- Characteristics for different radio propagation environments�� pag. 40

4.1.- General information of the power budget calculation...��.. pag. 47

4.2.- WCDMA power budget in simulations.............................��.. pag. 51

4.3.- Okumura-Hata model parameters as a function of frequency..............��.. pag. 53

4.4.- Typical maximum allowed path loss of existing GSM and WCDMA

systems........................................................................................................... pag. 54

4.5.- K-values for the site area calculation............................��.. pag. 54

4.6.- Simulation values of the network topology parameters��.. pag. 61

4.7.- Ranges and applications of the different UMTS cell types......��.. pag. 64

5.1.- Advantages and disadvantages of WCDMA simulation methods��.. pag. 66

5.2.- Total number of terminals in the network according to its load level�� pag. 69

6.1.- Best system configurations in three and six sectored sites��.. pag. 87

APPENDIX 99

List of Figures

1.1.- Increase of mobile telephone and Internet users in the last 10 years�� pag. 8

2.1.- UMTS network architecture��. pag. 13

2.2.- Block diagram of the UTRAN and CN��...��. pag. 15

2.3.- Parallel transmission of DPDCH and DPDCCH channels when the data

is present/absent��...�� pag. 16

2.4.- Structure of WCDMA random access burst��. pag. 17

2.5.- Packet transmission on a common channel��.. pag. 20

3.1.- Multiple access schemes��.. pag. 23

3.2.- Principle of spread spectrum technique..��. pag. 24

3.3.- Classification of CDMA types �� pag. 25

3.4.- Despreading of a wideband signal in the presence of a narrowband

interferer��.. pag. 26

3.5.- Example of generation of the CDMA transmitted signal�� pag. 28

3.6.- 2nd example of generation of the CDMA transmitted signal��. pag. 29

3.7.- Basic block diagram of a RAKE receiver in a L � tap channel��... pag. 32

3.8.- Frequency use with WCDMA��. pag. 34

3.9.- Radio propagation environment classes��.. pag. 37

3.10.- Two ray-model in multi path propagation��... pag. 39

3.11.- Channel impulse response of a typical urban channel �� pag. 39

3.12.- Log-normal distribution��.. pag. 41

3.13.- Rayleigh distribution��... pag. 41

3.14.- Frequency response of Rayleigh channel ��.. pag. 42

4.1.- WCDMA radio network planning process�..�� pag. 45

4.2.- Interference degradation margin as a function of load��..�.. pag. 49

4.3.- Path loss as a function of distance by using Okumura-Hata model.��... pag. 53

4.4.- Mutual influence of coverage and capacity in WCDMA networks��.... pag. 55

APPENDIX 100

4.5.- Impact of coverage and capacity on WCDMA network design..�� pag. 56

4.6.- Cell structure for three and six sectors/site��.. pag. 59

4.7.- Coverage vs interference level�� pag. 59

4.8.- A hierarchical cell scenario in UMTS��. pag. 62

5.1.- Digital map of the simulation area�� pag. 68

5.2.- Results of 3-sectored sites, 1.5 km. site separation��... pag. 70

5.3.- Sector throughput vs downlink traffic power with 3-sectored sites,

1.5 km. site separation��.. pag. 71

5.4.- Service probability vs sector throughput with 3-sectored sites, 1.5 km.

site separation��... pag. 71

5.5.- Results of 3-sectored sites, 2.0 km. site separation��.. pag. 72


2.0 km. site separation��. pag. 73


site separation��.. pag. 73
















APPENDIX 101






5.20.- Results of 3-sectored sites with 65 degree antennas and base station

antenna height of 25 m��..... pag. 82

5.21.- Sector throughput vs downlink traffic power for the best configuration

with 3-sectored sites��. pag. 83

5.22.- Service probability vs sector throughput for the best configuration with

3-sectored sites��. pag. 83

5.23.- Results of 6-sectored sites with 33 degree antennas and base station

antenna height of 25 m��. pag. 84

5.24.- Sector throughput vs downlink traffic power for the best configuration

with 6-sectored sites��. pag. 85

5.25.- Service probability vs sector throughput for the best configuration with

6-sectored sites��. pag. 85

APPENDIX 102

Simulation Parameters BS maximum power [dBm] 43

CPICH [dBm] 33

CCCHs [dBm] 33

SCH [dBm] 33

Maximum power per connection [dBm] 33

BS noise figure [dB] 5

UL required Eb/N0 [dB] 5

MS maximum power [dBm] 21

MS dynamic range [dB] 70

Power control step size [dB] 0.5

Required Ec/I0 [dB] -18

MS noise figure [dB] 9

DL required Eb/N0 [dB] 8

Standard deviation of slow fading [dB] 10

UL noise rise [dB] 6

DL orthogonality [%] 60

Handover window [dB] 4

Standard deviation of power control [dB] 0.5

Total number of carriers 1

Carrier frequency [MHz] 2000

UL air interface bit rate [Kbps] 15

UL user bit rate [Kbps] 15

DL air interface bit rate [Kbps] 15

DL user bit rate [Kbps] 15

Voice activity factor [%] 50

APPENDIX 103

UL Eb/N0 [dB] 5

DL Eb/N0 [dB] 8

Propagation model Okumura-Hata

Constant C 44.15

MS height [meters] 1.5

Average area type correction [dB] - 6.7

Standard deviation of interference [dB] 7.5

Simulation resolution [meters] 5

Chip rate [Mcps] 3.84

Intra-site correlation coefficient 0.8

Inter-site correlation coefficient 0.5

ANTENNAS kathrein 33: - 45 degree polarized, system lever position 0 degree

θ-3dB : vertical → 6.0 degree Gain [dBd] 18.85

horizontal → 31.0 degree

APPENDIX 104

kathrein 65: - 45 degree polarized, system lever position 0 degree



kathrein 90: - 45 degree polarized, system lever position 0 degree



impact of antenna beamwidth, propagation slope and ... · propagation slope and coverage...

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