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Cell Planningfor UMTS NetworksCourse Code: MB2005 Duration: 2 days Technical Level: 3

Radio Principles and Planning courses include:

Radio Principles

Principles of Radio Site Engineering

Digital Radio and Microwave Link Planning

Cell Planning for GSM Networks

2G/3G Indoor Coverage Planning

3G Indoor Coverage Planning

Introduction to GSM Optimization

Drive-Test Data Capture and Analysis

Cell Planning for UMTS Networks

Introduction to UMTS Optimization



© wray castle limited

CELL PLANNING FOR

UMTS NETWORKS


First published 2001Last updated May 2004 byWRAY CASTLE LIMITED

BRIDGE MILLS STRAMONGATE

KENDAL CUMBRIALA9 4UB UK

Yours to have and to hold but not to copy

The manual you are reading is protected by copyright law. This means that Wray Castle Limited could take you and

your employer to court and claim heavy legal damages.

Apart from fair dealing for the purposes of research or private study, as permitted under the Copyright, Designs andPatents Act 1988, this manual may only be reproduced or transmitted in any form or by any means with the prior

permission in writing of Wray Castle Limited.




Section 1 UMTS Planning Philosophy

Section 2 Review of UMTS Structure

Section 3 UMTS Air Interface

Section 4 Considerations for CDMA

Section 5 Traffic Analysis

Section 6 Coverage Predictions

Section 7 UMTS Network Planning

Section 8 UMTS Cell Structures

CELL PLANNING FOR UMTS NETWORKS

CONTENTS

iii





SECTION 1

UMTS PLANNING PHILOSOPHY

v





1 The Conventional Cell Planning Loop 1.11.1 Introduction 1.11.2 The Loop 1.11.3 Requirements and Targets for the Plan 1.3

2 Coverage 1.5

2.1 Coverage Requirements 1.52.2 Coverage Definition 1.5

3 Capacity 1.73.1 Traffic Factors 1.73.2 Traffic Types 1.7

4 The Link Between Capacity and Coverage 1.94.1 The Coverage Loop 1.9

5 Cost 1.11

6 Planning Constraints 1.13

7 Section 1 Questions 1.15

SECTION CONTENTS

vii





At the end of this section you will be able to:

• describe how conventional planning philosophy has to be modified for

application to the Universal Mobile Telecommunications System (UMTS)

• describe how planning constraints such as capacity, coverage and quality

are interrelated for UMTS

• justify the use of an iterative approach in the planning process for UMTS

OBJECTIVES

ix





MB2005/S1/v6.21.1 © wray castle limited

1.1 Introduction

The term cell planning refers to a collective series of processes designed to producea network plan that will meet a predefined set of cost and performance targets. Itwould, however, be wrong to think of planning as a finite process which ends atsome point when a particular target is met. It is iterative, and each additional stepmay result in a re-evaluation of the existing plan.

1.2 The Loop

The planning process is probably best considered as a loop. The loop involves targetsetting, initial planning, assessment and re-evaluation at all stages. This is animportant concept, which can be applied both to individual planning processes and tothe system plan as a whole.

Figure 1 shows a loop which would be considered typical when applied to a second-generation system. A key feature of this is that the initial plan is an estimate whichcan be refined once the network has been built and has become live. Third-generation systems are much more sensitive to errors in the planning process, thismaking subsequent optimization more difficult. There is a heightened need to planeffectively prior to network build and operation.

1 THE CONVENTIONAL CELL PLANNING LOOP




1.2© wray castle limitedMB2005/S1/v6.2

Re-evaluate and Optimize the Plan

Testing, Monitoring and Analysisof Network Performance

Build the Network

Improve/Modify the

Network Plan

Produce an Initial Plan

Analyze the Requirements

for the Network Plan

Tests and Surveys

Figure 1

The Conventional Planning Loop





1.3 Requirements and Targets for the Plan

Before any plan can be started, a set of design criteria must be set out. These willdefine where and how the completed system should operate.

In general, the criteria will describe five factors:

• coverage – initial wide area coverage is unlikely

• capacity – determining traffic capacity will be more difficult to analyze andpredict

• Quality of Service (QoS) – will impact both coverage and capacity• timescale – may be dictated by the licence conditions or finance

• cost – there will be a strict budget to work to

Each of these factors will consist of a series of individual requirements, some of which may be essential and some simply desirable. The requirements of each factor will probably need to be balanced against those of others.

An example of an essential requirement may be that the terms of the licence dictatethat 80% of a country’s population is covered within five years. The desired

requirement may be to meet that target within four years.



1.4© wray castle limited

Requirements forNetwork Plan

Coverage

Capacity

Quality ofService

Timescale Cost

Desired Essential

xxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxx

xxx xxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxx

Figure 2

Network Plan Requirements

MB2005/S1/v6.2






2 COVERAGE

2.1 Coverage Requirements

The driving force for coverage will usually be competitive advantage, but in manycases the licence agreement will itself stipulate a coverage requirement within agiven timeframe. It is important that any coverage requirements set should berealistic, i.e. 100% coverage will be impossible.

Because of the nature of a Code Division Multiple Access (CDMA) radio interface, itwould be impossible to predict and to guarantee with absolute certainty any givenfigure for coverage. As a result of this, coverage requirements can only be expressedas desirable with percentage reliability.

2.2 Coverage Definition

Percentage population coverage is probably the most important driver as it is likely tobe one of the terms of the licence. There is perhaps little point striving for blanketgeographical coverage when there is already GSM coverage, which may be used for backup.

The power budget will impact on coverage and this will need to be carefully plannedtaking into account that signal strength requirements will vary from service to service

and the effect of cell loading will cause cell breathing.

Path loss at 2 GHz will be greater than at 900 MHz resulting in much smaller cellsizes and a greater cell density than for a traditional 900 MHz network. Cell densitieswill be more in line with traditional 1800 MHz networks, though this will depend uponservice types.

Small macro cells and micro cells are most likely to be employed in built-upenvironments, with pico cells being used in hotspot areas where high-bit-rateservices are needed.

Voice traffic will be the most dominant along roads and motorways, but high-bit-ratedata services may be popular along railways, for business commuters andentertainment.

High-bit-rate data services may be required in buildings as well as meeting specialrequirement needs such as providing video links at a motor racing event.





Coverage

Requirements

% Geographical

Power Budget Path Loss

Signal Strength

LicenceAgreement

In-buildingCoverage

% Population Area/ClutterTypes

SpecialRequirements

RailwaysRoads/Motorways

Figure 3

Coverage Requirements for Each Traffic Type





3.1 Traffic Factors

The specification of traffic capacity requirements for the network cannot be exact.The traffic requirement itself will only be an estimate and may not accurately reflectthe traffic that occurs on the completed network. Traffic load and distribution is likelyto vary a great deal in the completed network, but the network is planned on thebasis of an estimated snapshot. This should be taken into account when settingrealistic targets within the planning criteria. Any large variations from this which showup once the network begins operation should result in re-evaluation and optimization.

3.2 Traffic Types

To plan a multimedia network it is important to know the total volume of trafficexpected. This can then be broken down into the different traffic types. These typeswill include voice traffic, which has been the most dominant traffic type in 2Gnetworks. This could be handled by an existing GSM infrastructure, leaving the 3Gnetwork to support the high-bit-rate data services.

Data services will be divided into circuit-switched services offering constant bit ratesdesirable for real-time applications such as videoconferencing, and packet-switchedservices offering high-bit-rate non-real-time applications. This is seen as the most

important traffic type and it is important to identify QoS levels and ensure they aremet.

Message services will also be an important traffic type and will include text, voiceand video. There will also be a need to support messaging for SupplementaryService (SS) activities.

Many of the new services will be based on lifestyle, so it is important to define user profiles, detailing the behaviour of subscribers and incorporating demographicinformation.

The available spectrum will have an impact upon capacity. The number of carriers anoperator has may vary from one to three Frequency Division Duplex (FDD) carriersand possibly one Time Division Duplex (TDD) carrier.

Finally, a decision about the percentage blocking level for circuit-switchedconnections must be made and will impact traffic capacity. For packet operationdelay criteria will influence the QoS targets.

3 CAPACITY




Capacity

VoiceVideo Telephony

DataPS/CS

SMS/SSMessaging

Spectrum

TotalVolume

UserProfiles

% Blocking Demographics

Figure 4

Traffic Factors

MB2005/S1/v6.2






Conventional planning practices deal with capacity and coverage as fundamental but

independent processes. This approach is not applicable for a CDMA-based system.UMTS is both CDMA based and it provides multimedia support, hence capacitycalculations cannot be separated: any tool used to simulate and plan a UMTSnetwork must link these calculations.

4.1 The Coverage Loop

The link budget is a normal starting point for any coverage estimate. However, in aCDMA-based system the link budget must account for interference levels. The

interference level for a cell can be calculated if the capacity of a cell is known. If traffic distribution and traffic types are known, then cell capacity can be calculated for a given coverage. In order to calculate cell coverage it is necessary to calculate alink budget.

To establish an initial entry point to this loop, an assumed capacity is used, allowingan iterative process to begin. This will ultimately converge on a solution.

4 THE LINK BETWEEN CAPACITY AND COVERAGE





Coverage

LinkBudget Capacity

Figure 5

The Coverage Loop





Almost every aspect of the planning process will have an impact upon cost. In most

cases, cost will be the main constraint in the design process. The aim will always beto provide the best overall performance at the least cost. Careful planning,particularly at the roll-out stage of a network, can make a big difference in thisrespect.

5 COST





Costs

Radio AccessHardware

Masts/Antennas

Licence

Fee

Ground Rent NetworkInfrastructureand Switching

OptimalFeatures

TransmissionEquipment/

Leasing

Figure 6

Cost Factors





It is impossible to produce a plan which will fully satisfy all requirements all of the

time; there has to be a compromise between conflicting requirements. A decision willneed to be made about how best to balance these conflicting requirements andwhich, if any, are higher priorities.

For example, almost all requirements will need to be balanced against the initial costof the rollout. However, if strict adherence to budget results in poor coverage or capacity, then there will be a long-term reduction in revenue from the network.

This brings us back to the concept of the planning loop. Any major and unresolvableconflicts between requirements should result in re-evaluation before planning evenbegins. The aim should be to make targets ambitious, but realistic.

6 PLANNING CONSTRAINTS





ServiceRequirements

Cost Licence

Capacity Quality of

Service

?

Figure 7

Overall Constraints on the Network Plan





1 In conventional planning, after the production of an initial plan, in which order

would the follow up activities be carried out in relation to the planning loop?

a Re-evaluate and optimize then build the networkb Build the network then improve/modify the planc Perform tests and surveys and then build the networkd Perform tests and surveys and modify the plan

2 Conventionally, when considering the traffic capacity requirements, which of thefollowing should be taken into account?

a PS and CS data requirementsb Cell size and numbersc User profilesd % blocking

3 Conventionally, when taking into account the coverage requirements, which of the following should be considered?

a Volume of SMS traffic

b In-building coveragec Licence agreementd Area/clutter types

4 In UMTS, both capacity and coverage together are part of the planningprocess. This is because:

a UMTS is both CS and PS orientedb UMTS uses CDMAc UMTS operates at higher frequencies than GSM

d Interference levels are very low

5 Which of the following do you consider not to be a major constraint whenplanning a UMTS network?

a Costb Licencec Capacityd Transmit frequency

7 SECTION 1 QUESTIONS




SECTION 2

REVIEW OF UMTS STRUCTURE

i





1 The Third Generation (3G) Concept 2.11.1 The Movement Towards Third Generation Mobile 2.11.2 The UMTS Vision 2.31.3 Service Aims for UMTS 2.51.4 UMTS Data Rates 2.7

2 Spectrum Allocation 2.92.1 International Spectrum Allocations 2.9

3 Air Interface Technologies 2.113.1 Major Technology Options – ETSI Activity 2.11

4 Radio Network Architecture 2.154.1 The UMTS Radio Environment 2.154.2 Network Hierarchy 2.15

5 UTRAN Architecture 2.17

5.1 Key Components of the UTRAN 2.175.2 Node B 2.175.3 Radio Network Controller (RNC) 2.175.4 Radio Network Subsystem (RNS) 2.17

6 UTRAN Interfaces 2.196.1 Required Connections 2.196.2 Interface Protocols 2.19


SECTION CONTENTS

iii






• describe the origins of UMTS technology

• name the two physical layer types defined for the UMTS air interface, FDD

and TDD

• state the general aims for UMTS performance and service provision

• state the spectral requirements for UMTS radio carriers and the UMTS

operational bands

• characterize macro, micro and picocellular architectures in respect of UMTS

• describe the functional elements within the UMTS Terrestrial Radio Access

Network (UTRAN)

• state the general functions of the Radio Network Controller (RNC) and the

Node B

OBJECTIVES

v





1.1 The Movement Towards Third Generation Mobile

Mobile telephone networks first began to enter commercial service in the early 1980s,initially in America and Scandinavia. They spread rapidly across the remainder of Europe and the rest of the developed world.

The first generation of systems was based on an analogue air interface, hence theywere only suitable for voice and very low-speed data. The number of additionalservices was limited, and security was poor.

Second generation (2G) systems began to appear during the early 1990s. Several2G systems have evolved, most of them either Japanese or American, but twostandards have dominated the market: the European Global System for Mobilecommunications (GSM), and the American National Standards Institute (ANSI)-basedIS-95, known as cdmaOne™.

2G systems are still predominantly based upon voice and low data-rate services,although these services are a significant improvement upon the first generation. Moreimportantly, security was greatly improved; indeed, such has been the success of theGSM security system that many of its principles are being directly migrated to UMTS.

The current generation of mobile phone technology, known as Generation 2.5, or

2.5G, has seen the introduction of packet data services and increased data rates,with the development of High Speed Circuit Switched Data (HSCSD), the GeneralPacket Radio Service (GPRS), and Enhanced Data-rates for Global Evolution(EDGE) technology.

While 3G systems are designed to be compatible with 2G, they offer a major stepforward in service offerings. Much higher user data rates (up to 2.048 Mbit/s peak)may be offered, together with full support for multimedia services. The system isdata-optimized and will ultimately transfer all information as packet data. Also, for thefirst time in mobile communication, bandwidth-on-demand is supported.

Nonetheless, the third generation – known in Europe as the UMTS – has a complexevolution path, as Figure 1 shows.

1 THE THIRD GENERATION (3G) CONCEPT






First Generation

1980s

AMPS TACS NMT

Second Generation

1990s

TDMA PDCGSM cdmaOne™

Third Generation2001+

UMTS CDMA2000™ EDGE

2.5 Generation2000+

GPRS HSCSD EDGE

digitaldata-optimizedCS + PShigh data ratesbandwidth on demandfull multimedia supportenhanced security

higher dataratespacket datasupportpossiblemultimediasupport

digitalvoice-optimizedlow-speed databetter security

analoguevoice-optimizeddata via modempoor security

Figure 1

UMTS Evolution Path




1.2 The UMTS Vision

The International Telecommunication Union’s (ITU) vision of UMTS was that of athird generation of mobile telecommunications technology which would:

• become an international standard, adopted by all ITU member countries

• be a catalyst for the convergence of fixed and mobile telephony

• support wideband and multimedia services, up to 2 Mbit/s

• support network-independent innovative devices

Following the allocation of the 3G spectrum (at around 2 GHz) by the World RadioConference (WRC) in 1992, the ITU Radiocommunications Sector (ITU-R) begandefining a standard for third-generation technologies known as International MobileTelecommunications 2000 (IMT-2000). The initial aim was to achieve a single,international standard which would be endorsed by the ITU.

To this end, several candidate technologies were submitted to the ITU for consideration. This took place before the end of June 1998. Unfortunately, however,political and commercial constraints have prevented a single standard frombecoming a reality. IMT-2000 now represents several different but harmonized

standards based upon 2.5G and 3G technologies. UMTS is being developed andspecified under the auspices of the 3rd Generation Partnership Project (3GPP).

Standards will be deployed largely upon areas of political influence, but it is hopedthat handset technologies will evolve far enough and quickly enough to support all of the recognized standards.

More spectrum was identified for 3G operation at the World Radio Conference of 2000 (WRC2000). This spectrum encompasses existing 800, 900 and 1800 MHzsegments currently in use for 1G, 2G and 2.5G systems. It also identifies newspectrum around 2500 MHz.





TIAETSI ETSI ARIB

CDMA2000™(cdmaOne™

based)

UMTS WCDMA

3G Family

EDGE(2.5G)(GSM based)

3GPPUMTS

Figure 2

Radio Access Technology (RAT) Convergence

MB2005/S2/v6.2






1.3 Service Aims for UMTS

UMTS has been designed to offer true mobile multimedia for the mass market, withan air interface that will support wideband and multimedia services.

Voice has been the dominant traffic type in second-generation technology. However,because of the high-data-rate capability of the air interface (data rates of up to 2Mbit/s are proposed), new services are expected to be developed. These servicesshould be innovative and network-independent.

They could include:

• Internet access

• remote file transfer

• database access

• e-mail

• Web browsing

• high-quality audio

• video telephony

• multimedia

• customized supplementary services

Specifications for services and the methods of carrying these applications over thenetwork have been kept flexible, allowing operators to differentiate their servicesfrom those of their competitors.

As many different service classes will be developed for UMTS, an increasedemphasis on careful service and user interface design and service availability isneeded. Most applications, especially multimedia, will require very careful network

design with a particular emphasis upon QoS parameters.



2 . 6

©

wr a y c a s t l el i mi t e d

MB 2 0 0 5 / S 2 / v 6 .2

W r a y C a s t l e B r o w s e r

I n te rn et Se ar ch : h t t p // w w w.

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4 5

6

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Designed formultimediaapplications

Service specificationsare loosely defined

Increased emphasisupon QoSparameters

Voice is the dominain the second ge

Many new serviceswill be innovative

and networkindependent

F i g ur e 3

S er vi c eA

i m sf or UMT S




1.4 UMTS Data Rates

UMTS aims to offer the user a range of data rates that will depend upon the servicerequirements at any time. The ability to support any given data rate is determined bya number of environmental factors, including:

• location

• speed

• cell usage (Eb/No)

• cell capacity

3GPP has specified three maximum theoretical rates as network rollout targets. Upto 144 kbit/s, in a (rural) outdoor environment with a maximum speed of 500 km/h; upto 384 kbit/s, in a (suburban) outdoor environment with a maximum speed of 120km/h; and up to 2 Mbit/s in an indoor environment (or low-range outdoor) with amaximum speed of 10 km/h.

Each of the peak bit rates has associated Bit Error Rate (BER) and delayrequirements.





Operating Environment Bit Rate User Speed

Rural Outdoor 144 kbit/s 500 km/h

Urban/suburbanoutdoor 384 kbit/s 120 km/h

Indoor/low rangeoutdoor

2048 kbit/s 10 km/h

Figure 4

WCDMA Data Rates

MB2005/S2/v6.2





2.1 International Spectrum Allocations

2.1.1 World Radio Conference (WRC)

The WRC proposed international spectrum allocations for all three ITU regionsduring 1992. A uniform spectrum allocation was designed to simplify mobility and thecoordination of spectrum between the satellite and terrestrial elements of IMT-2000.

Unfortunately, it is not possible to implement a global plan because of existingspectrum allocations and the logistic and financial difficulties of spectrum refarming.

In 2000, the WRC reached general agreement on three new bands for third-generation operation:

• 806–960 MHz

• 1710–1885 MHz

• 2500–2690 MHz

2.1.2 Region 1 – Europe

This is probably the least troubled region. The only major issue here is the spectrumthat is allocated to Digital Enhanced Cordless Telephony (DECT), from 1880–1900MHz. However, because of the DECT radio interface and service capabilities, it isprobable that DECT and a future IMT-2000 system could coexist.

2.1.3 Region 2 – USA

This region has by far the most troublesome issues. The recently-allocated PCS1900bands in North America completely overlap the lower part of the IMT-2000 spectrum.This problem can only be solved if the technology chosen for IMT-2000 is compatibleto the extent that it can coexist with the current second-generation PersonalCommunication Systems (PCS).

2.1.4 Region 3 – Japan

The potential problems in this region are similar to those of Region 1.

2 SPECTRUM ALLOCATION




2 .1 0

©


1700 1750 1800 1850 1900 1950 2000 2050 2100

GSM 1800

Downlink

DE

CT

Satellite

Uplink

EUROPE

Re

WRC-92

USA

PHS JAPAN

Licensed

Downlink

Licensed

Uplink

Satellite

Uplink

GSM 1800

Uplink

F i g ur e 5

C ur r en t S p e c t r um U s a g

ei n t h eI T UW or l d R e gi on

s

MB 2 0 0 5 / S 2 / v 6 .2





3.1 Major Technology Options – ETSI Activity

The European Telecommunications Standard Institute (ETSI) working group SMG5selected two Radio Access Technologies (RAT) for the UTRAN: Wideband CDMA(WCDMA) and Time Division CDMA (TD-CDMA). WCDMA, operating in FDD mode,will be used in the paired spectrum, primarily for wide area coverage; TD-CDMA,operating in TDD mode, will be utilized in the unpaired spectrum, principally for low-mobility indoor applications.

3.1.1 UMTS Terrestrial Radio Access (UTRA)/FDD

UTRA/FDD is designed to operate in either of three paired bands, as illustrated inFigure 6a. Bands I and III are intended for use in ITU Region 2. Twelve additionalchannels are specified and may be offset 100 kHz to the normal 200 kHz raster.

The 200 kHz raster runs across the entire UMTS spectrum and acts as marker pointsfor the channels. Each channel is identified by a UMTS Absolute Radio FrequencyChannel Number (UARFCN). These are illustrated in Figure 6b. The nominalchannel band spacing is taken to be 5 MHz.

Duplex separation must be flexible, but Figure 6c shows the typical duplex distances

applicable to the three bands.

3 AIR INTERFACE TECHNOLOGIES





Operating Band

I

II

III

UL Frequencies

1920–1980 MHz

1850–1910 MHz

1710–1785 MHz

Operating Band

I

II

III

TX-RX Frequency Separation

190 MHz

80 MHz

95 MHz

DL Frequencies

2110 – 2170 MHz

1930 – 1990 MHz

1805 – 1880 MHz

a) UTRA/FDD Frequency Bands

b) UARFCNs

c) Duplex Distance

UARFCN = DL Freq or UL Freq in MHz x 5

Operating Band

I

II

III

Uplink

9612 to 9888

9262 to 9538

and

12, 37, 62, 87, 112, 137,

162, 187, 212, 237, 262, 287

8562 to 8913

Downlink

10562 to 10838

9662 to 9938

and

412, 437, 462, 487, 512, 537,

562, 587, 612, 637, 662, 687

9037 to 9388

Figure 6

UTRA/FDD




3.1.2 UTRA/TDD

UTRA/TDD is intended to operate in one of five unpaired frequency bands asillustrated in Figure 7a. Bands b and c are intended for use in Region 2.

The same 200 kHz raster applies to the TDD spectrum as for FDD and acts asmarker points for the channels. Each channel will be identified by its UARFCN, asillustrated in Figure 7b. Channel spacing will be 5 MHz if the system chip rate is 3.84Mcps, but in the case where the chip rate is 1.28 Mcps channel spacing will be 1.6MHz.





Region

1

2

Frequency Bands

1900 – 1920 MHz

2010 – 2020 MHz

1850 – 1910 MHz

1930 – 1990 MHz

1910 – 1930 MHz

a) UTRA/TDD Frequency Bands

b) UTRA/TDD ARFCNs

UARFCN = 3.84 Mcps TDD

Region

1

2

Frequency Range

1900 – 1920 MHz

2010 – 2025 MHz

1850 – 1910 MHz1930 – 1990 MHz

1910 – 1930 MHz

UARFCN

9512 to 9588

10062 to 10113

9262 to 95389662 to 9938

9562 to 9638

UARFCN = 1.28 Mcps TDD

Region

1

2

Frequency Range

1900 – 1920 MHz

2010 – 2025 MHz

1850 – 1910 MHz

1930 – 1990 MHz

1910 – 1930 MHz

UARFCN

9504 to 9596

10054 to 10121

9254 to 9546

9654 to 9946

9554 to 9646

Figure 7

UTRA/TDD

MB2005/S2/v6.2






4.1 The UMTS Radio Environment

The UMTS environment is deemed to comprise a number of individual domains:

• macrocellular

• microcellular

• picocellular

Macro cells give public wide-area coverage and support rapidly moving terminals.Micro cells give localized coverage, providing higher bit rates to slower terminals in

areas where traffic density is likely. Pico cells can be either publicly or privatelyoperated systems, serving homes and offices and other commercial areas.

4.2 Network Hierarchy

The domains need to combine to form a very strictly defined network hierarchy,which will be split between:

• public wide area networks

• public microcellular networks• public/private picocellular networks

The defined interaction between these network domains is a critical part of thenetwork design process. The importance of this is particularly applicable whenconsidering demographics and traffic modelling.

4 RADIO NETWORK ARCHITECTURE





Macro cell

Macro Micro PicoHigh Mobility Local Area Indoor/Low Range Outdoor

Wide Area Voice Voice

Voice High Data <384 kbit/s Very High Data >384 kbit/s

Low Data <144 kbit/s Public Low Mobility

Public Scattered Sites

Public/Private

Micro cell

Pico cell

Figure 8

The UMTS Radio Environment





5.1 Key Components of the UTRAN

The UMTS Terrestrial Radio Access Network (UTRAN) constitutes the part of anoperator’s network that enables users to access the services provided by the CoreNetwork (CN) via radio in a mobile environment. In this context there will be two mainroles: radio provision and the control of the radio channel resource. Two functionalelements have been defined to carry out these roles, the Node B and the RadioNetwork Controller (RNC).

These functions and the interfaces between them are only logical descriptions, their physical implementations are open to vendors’ interpretations. However, a likelyinterpretation would be to implement them as physical elements. This would lead toan architecture similar to that used in 2G systems, and thus a potentially simpler migration route.

5.2 Node B

The Node B contains radio transmitters, receivers, baseband functions, antennasand feeders for one or more cells. The Node B only acts as a relay between the radiointerface on the User Equipment (UE) side, and the terrestrial interface on thenetwork side. In this role it only has lower-layer functionality. A Node B may be able

to support one or more of the radio access modes.

5.3 Radio Network Controller (RNC)

Control of functionality for a number of Node Bs is performed by the RNC. The RNCterminates signalling and control between the UE and the UTRAN. In this role it hasfunctionality up to layer 3 of the air interface protocol stack. The RNC has control of the radio channel resource and handles local mobility in the context of macrodiversity.

5.4 Radio Network Subsystem (RNS)

Radio Network Subsystem (RNS) is a collective term for one RNC and its associatedNode Bs. An UTRAN may contain one or more RNS.

5 UTRAN ARCHITECTURE





Node BRadio Network

Controller (RNC)

Radio

Network

Subsystem

(RNS)

modulation/demodulation

transmission/reception

CDMA physical channel coding

micro diversity

error protection

closed loop power control

broadcast signalling

radio resource control

admission control

channel allocation

power control thresholds

open loop power control

handover control

macro diversity

segmentation/reassembly

ciphering

Figure 9

UTRAN Architecture





6.1 Required Connections

There are four defined logical interfaces that interconnect the functional elements of the UTRAN and connect the UTRAN to other network domains. Two of theseinterfaces, the Iu and Uu, are external interfaces. One of the interfaces, the Iub, isinternal only, and one, the Iur, will usually be internal, but could be external for somenetwork architectures.

The interfaces used are as follows:

• Iu RNC – Core Network

• Uu Node B – User Equipment

• Iub RNC – Node B

• Iur RNC – RNC

6.2 Interface Protocols

The interfaces are described in terms of layered protocols broadly in line with theprinciples of the Open Systems Interconnect (OSI) Seven-Layer Model. All theinterfaces are used to carry both signalling and traffic and therefore the protocolstacks are divided into separate planes: the control plane and the user plane.

6 UTRAN INTERFACES





Core Network

UTRAN

Node B

Node B

Node B

Node B

Iu-CS

Iu-PS

Iu-PSIu-CS

Iur

IubIub

Iub

Iub

Figure 10

UTRAN Interfaces




1 The ability to support high-data-rates in UMTS is dependent upon which of the

following?

a The modulation schemeb The transmit frequencyc The cell capacity and its locationd The application being served

2 Which of the following bit rates is correct for UMTS?

a Rural outdoor – 384 kbit/sb Rural outdoor – 2048 kbit/sc Indoor – 384 kbit/sd Rural outdoor – 144 kbit/s

3 In Europe, which part of the WRC-92 spectrum allocation is already in use?

a 1880–1900 MHzb 1710–1885 MHzc 2500–2690 MHz

d 806– 960 MHz

4 Which air interface mode of operation is likely to be used for low-mobility indoor applications?

a WCDMA in FDD modeb WCDMA in TDD modec TD-CDMA in TDD moded TD-CDMA in FDD mode

5 Identify the incorrect interface.

a RNC – Core Network = Iub RNC – RNC = Ir c Node B – UE = Uud Node B – RNC = Iub






SECTION 3

UMTS AIR INTERFACE

i





1 General Protocol Structure 3.11.1 Access Stratum (AS) 3.11.2 Non-Access Stratum (NAS) 3.11.3 The AS on the Air Interface 3.31.4 Logical and Transport Channels 3.3

2 Protocol Termination Within the UTRAN 3.52.1 Termination Nodes 3.52.2 Variations for Protocol Termination 3.5

3 UMTS Channel Types and Functions 3.73.1 Logical Channels 3.73.2 Logical Channel Types 3.73.3 Transport Channels 3.93.4 Transport Formats 3.93.5 Transport Channel Types 3.11

4 Downlink (DL) Physical Channels 3.134.1 Introduction 3.134.2 Physical Channels for Common Packet Channel (CPCH) Access 3.17

5 Uplink (UL) Physical Channels 3.195.1 Physical Random Access Channel (PRACH) 3.195.2 Dedicated Physical Channel (DPCH) 3.195.3 Physical Common Packet Channel (PCPCH) 3.19

6 FDD Access Mode Channel Mapping 3.216.1 Logical to Transport Channel Mapping 3.216.2 Transport to Physical Channel Mapping 3.216.3 Mapping for the Uu Interface 3.21


SECTION CONTENTS

iii






• define the division between the Access Stratum (AS) and the Non-Access

Stratum (NAS) in respect of the UMTS air interface

• characterize the term physical channel as applied to the UMTS air interface

• describe the logical and transport channels used on the UMTS air interface

• relate the mapping of logical transport and physical channels for typical UE

operational states

OBJECTIVES

v





Isolation of radio-related functions from the data networking functions is achieved by

splitting the air interface into two distinct areas: the Access Stratum (AS) and theNon-Access Stratum (NAS).

1.1 Access Stratum (AS)

The AS provides communication between the UE and the UTRAN, managing theUMTS radio interface and providing services, called Radio Access Bearers (RAB), tothe NAS.

The AS can be considered as being layers 1–2 of the OSI Seven-Layer Model, withsome layer 3 functionality.

The main AS functions are:

• provision of physical channels

• control of physical channels

• link establishment and clearing

• channel coding

• some security functions

1.2 Non-Access Stratum (NAS)

The NAS provides communication between the UE and the CN. The NAS actstransparently through the UTRAN and can be considered as being carried by, rather than being, the air interface.

The NAS can be considered as being layers 3–7 of the OSI Seven-Layer Model.

1 GENERAL PROTOCOL STRUCTURE






L7

L3AccessStratum

Non-Access Stratum

UTRAN

Core NetworkUEOSI Layers

L3

L1

Uu Iu

Relay

Figure 1

UTRAN Architecture




1.3 The AS on the Air Interface

The AS covers functionality from layers 1–3. At layer 1, signalling and traffic data iscarried across the air interface in physical channels that are defined in terms of either code set and frequency for FDD mode, or code, timeslot and frequency for TDD mode.

Layer 2 is divided into two sublayers. The lower sublayer is the Medium AccessControl (MAC) layer. It is responsible for a wide range of functions including randomaccess procedures, physical link control, multiplexing and channel mapping to thephysical layer. The upper sublayer is the Radio Link Control (RLC) layer, which isresponsible for Logical Link Control (LLC), and acknowledged and unacknowledgeddata transfer. Ciphering may be provided by either RLC or MAC.

Layer 3 in the AS provides only the lower part of layer 3 in the control plane. This isknown as the Radio Resource Control (RRC) layer. It is responsible for thecoordination and control of a range of functions including bearer control, monitoringprocesses, power control processes, measurement reporting, paging and broadcastcontrol functions.

1.4 Logical and Transport Channels

There is a complex array of user and signalling requirements. In order to define aprocess for each type of information, sets of logical channels mapping into transportchannels and ultimately physical channels are defined. Logical channels are definedbetween RLC and MAC. Transport channels are defined between MAC and thephysical layer.





Control Plane Signalling

Radio Resource

Control(RRC)

Radio LinkControl

(RLC)

Medium Access

Control

(MAC)

Physical Layer

Transport

Channels

LogicalChannelsL2

L3

L1

User Plane Information

Figure 2

AS on the Air Interface

MB2005/S3/v6.2





wr a y c as t l e Bro ws er

In te rn e tS e a rc h: ht t p://w w w.

X XX X X X X X x xx X X

X X X x X X X X X

X X X X X X XX X X X X

X X X Xx x x xx X X X X

X x X X XX X X XX

X X X X X X X

Node B

Uu

Iub

UserEquipment

Physical

MAC

RLC

RRC

Radio

Network

Controller

Physical

MAC

RRC

RLC

Figure 3

Protocol Termination

MB2005/S3/v6.2





3.1 Logical Channels

The MAC layer provides transfer services via a set of logical channels. A logicalchannel is defined for each different transfer requirement. Each logical channelrelates to particular kinds of information that need to be transferred. Some relate tosignalling information, and some to traffic information.

The logical channels are used for the transfer of signalling information in FDD modeare the Broadcast Control Channel (BCCH), Paging Control Channel (PCCH),Common Control Channel (CCCH) and Dedicated Control Channel (DCCH).

The logical channels used for the transfer of user information in FDD mode are theDedicated Traffic Channel (DTCH) and the Common Traffic Channel (CTCH).

3.2 Logical Channel Types

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

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

network does not know the location cell of the UE, or the UE is using sleep modeprocedures.

Common Control Channel (CCCH)This is a bidirectional channel carrying control information between the network andthe UE. It is used when the UE has no RRC connection with the network.

Dedicated Control Channel (DCCH)This is a point-to-point bidirectional channel carrying dedicated control informationbetween the network and the UE. It is used when a dedicated connection has beenestablished through RRC connection set-up procedures.

Dedicated Traffic Channel (DTCH)The DTCH is a dedicated point-to-point channel carrying user information betweenthe network and the UE. It may be used in both the uplink and downlink directions.

3 UMTS CHANNEL TYPES AND FUNCTIONS





Medium Access Control (MAC)

Control Channels from RLC

Traffic Channels from RLC

BCCH PCCH CCCH DCCH

DTCH CTCH

Figure 4

Logical Channel Types

MB2005/S3/v6.2






3.3 Transport Channels

Information is transferred from the MAC layer and mapped into the physical channelsvia a set of transport channels. Transport channels can be classified into two groups:common channels and dedicated channels. Information in common channels willrequire in-band identification of the UE. For dedicated channels the UE’s identity isassociated with the channel allocation.

The common transport channels for FDD mode are:

• Random Access Channel (RACH)

• Common Packet Channel (CPCH)

• Forward Access Channel (FACH)

• Downlink Shared Channel (DSCH)

• Broadcast Channel (BCH)

• Paging Channel (PCH)

The dedicated transport channel for FDD mode is the Dedicated Channel (DCH)

3.4 Transport Formats

Each transport channel has an associated transport format. This is defined as acombination of encoding, interleaving, bit rate and mapping into physical channels.For some transport channels this may be variable within a set of transport formats.





Physical Layer

Common Channels from MAC

Dedicated Channelsfrom MAC

RACH DSCHCPCH FACH BCH PCH

DCH

Figure 5

Transport Channel Types





3.5 Transport Channel Types

Random Access Channel (RACH) A contention-based channel in the uplink direction, the RACH is used for initialaccess or non-real-time dedicated control or traffic data.

Common Packet Channel (CPCH)This channel is only used in FDD mode. It is a contention-based channel used for the transmission of bursty traffic data in a shared mode. Fast power control is used.

Forward Access Channel (FACH)The FACH is a common downlink channel without power control. It is used for relatively small amounts of data.

Downlink Shared Channel (DSCH) A downlink channel used in shared mode by several UEs, the DSCH is used to carrycontrol or traffic data.

Broadcast Channel (BCH)This is a downlink broadcast channel used to carry system information across awhole cell.

Paging Channel (PCH)The PCH is a downlink broadcast channel used to carry paging and notificationmessages across a whole cell.

Dedicated Channel (DCH)The DCH is used in the uplink or downlink direction to carry user information to or from the UE.




Physical Layer

Common Channels from MAC

Dedicated Channelsfrom MAC

RACH DSCHCPCH FACH BCH PCH

DCH

Figure 5 (repeated)

Transport Channel Types

MB2005/S3/v6.2






4.1 Introduction

In the DL direction there are a number of channels carrying higher-layer informationand a large number having control and synchronization functions associated withlayer 1.

The DL physical channels carrying higher-level information are:

• Primary Common Control Physical Channel (PCCPCH)

• Secondary Common Control Physical Channel (SCCPCH)

• Physical Downlink Shared Channel (PDSCH)• Dedicated Physical Data Channel (DPDCH)

The DL channels carrying control and synchronization are:

• Synchronization Channel (SCH)

• Common Pilot Channel (Primary and Secondary) (CPICH)

• Dedicated Physical Control Channel (DPCCH)

• Acquisition Indicator Channel (AICH)

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

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

• CPCH – Status Indicator Channel (CSICH)

• Paging Indicator Channel (PICH)

4 DOWNLINK (DL) PHYSICAL CHANNELS





PICH DPCCH

DPCH

DPDCH

DCH

PCCPCH

BCH

SCCPCH

FACH PCH

PDSCH

DSCH

SCHCPICHAICHAP-AICHCD/

CA-ICHCSICH

Transport Channels

Layer 2Layer 1

Physical Channels

Figure 6

Downlink Physical Channel




4.1.1 Physical Downlink Shared Channel (PDSCH)

This is a DL channel used to carry the DSCH. It is shared by multiple users by way of code multiplexing. The PDSCH is always associated with one or more DL DedicatedPhysical Channels (DPCHs).

4.1.2 Secondary Common Control Physical Channel (SCCPCH)

The SCCPCH is used to carry the transport channels PCH and FACH in the DLdirection. There may be one or more SCCPCHs, and if an SCCPCH is only carryingthe FACH, it may be transmitted over only part of the cell using beam-formingantennas.

4.1.3 Primary Common Control Physical Channel (PCCPCH)

This is used in the DL direction to broadcast the BCH across a cell. There will beonly one of these on each cell.

4.1.4 Dedicated Physical Data Channel (DPDCH) and Dedicated Physical

Control Channel (DPCCH)

The DPDCH is a bidirectional channel used to carry higher-layer information from thetransport channel DCH. It is multiplexed with the DPCCH that provides the layer 1control and synchronization information. Once multiplexed, the two are referred to asa DPCH. One DPCCH may be associated with one or more DPDCHs

4.1.5 Paging Indicator Channel (PICH)

This DL channel is used to carry Paging Indicators (PI). These are used to enable

discontinuous reception of the PCH being carried on an associatedSCCPCH.

4.1.6 Synchronization Channel (SCH)

This is a DL channel used during cell search. It consists of primary and secondarysubchannels, and conveys information to the UE concerning the time alignment of acell’s codes and frame structures.





PICH DPCCH

DPCH

DPDCH

DCH

PCCPCH

BCH

SCCPCH

FACH PCH

PDSCH

DSCH


CA-ICHCSICH

Transport Channels

Layer 2Layer 1

Physical Channels

Figure 6 (repeated)


MB2005/S3/v6.2





4.1.7 Common Pilot Channel (CPICH)

This channel is used to provide the phase reference for the SCH, PCCPCH, AICHand the PICH. It may also be the default phase reference for all the other DLchannels. There will be only one Primary CPICH in a cell. It is an option to have oneor more Secondary CPICHs in a cell. If present, the Secondary CPICHs would act asthe phase reference for SCCPCH, and potentially DPCH.

4.1.8 Acquisition Indicator Channel (AICH)

This DL channel carries Acquisition Indicators (AI). These are used to acknowledgeUE random access attempts, and grant permission for a UE to continue with itsrandom access transmission.

4.2 Physical Channels for Common Packet Channel (CPCH) Access

These channels carry information used for the CPCH access procedure and do notcarry transport channels.

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

This channel carries AP acquisition indicators which correspond with the APsignature transmitted by the UE. It is also used to acknowledge the random accesspreambles, which are then followed by a collision detection preamble.

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

The CD/CA-ICH is used to acknowledge the collision detection access preamble.

4.2.3 CPCH – Status Indicator Channel (CSICH)

The CSICH uses the unused part of the AICH channel to indicate CPCH physicalchannel availability so that access is only attempted on a free channel.





PICH DPCCH

DPCH

DPDCH

DCH

PCCPCH

BCH

SCCPCH

FACH PCH

PDSCH

DSCH


CA-ICHCSICH

Transport Channels

Layer 2Layer 1

Physical Channels

Figure 6 (repeated)


MB2005/S3/v6.2





In the UL direction there are four types of physical channel:

• Physical Random Access Channel (PRACH)

• Dedicated Physical Data Channel (DPDCH)

• Dedicated Physical Control Channel (DPCCH)

• Physical Common Packet Channel (PCPCH)

5.1 Physical Random Access Channel (PRACH)

This UL channel is a contention-based channel used to carry higher-layer information in the form of the RACH.

5.2 Dedicated Physical Channel (DPCH)

The DPCH is ultimately used to carry the transport channel DCH. However, inaddition to this it carries layer 1 information in the form of the pilot, Transmit Power Control (TPC), and Transport Format Combination Indication (TFCI) bits. As such,the DPCH can be considered as two subchannels: the DPDCH, which is used tocarry DCH; and the DPCCH, which is used to carry the layer 1 information. These

two subchannels are time division multiplexed together to form the DPCH.

5.3 Physical Common Packet Channel (PCPCH)

The PCPCH carries the common packet transport channel, which comprises accesspreambles, collision detection preamble, power control preamble and a messagepart.

5 UPLINK (UL) PHYSICAL CHANNELS





CPCH

PCPCH PRACH

RACH

Transport Channels

Layer 2

Layer 1

Physical

ChannelsDPCCH

DPCH

DPDCH

DCH

Figure 7

Uplink Physical Channel

MB2005/S3/v6.2





6.1 Logical to Transport Channel Mapping

Before its transmission across the air interface, information presented in logicalchannels must be mapped into transport channels. This mapping process is veryflexible, and for some logical channels there are several options, depending on thefunction and the type of information being transferred.

6.2 Transport to Physical Channel Mapping

The physical layer applies error protection and maps and multiplexes transportchannels into physical channels.

It should be noted that some unidirectional channels, i.e. PICH, CPICH and AICH,which perform some kind of indication to the receiving element are derived at thephysical layer, since the information carried in these channels is of no interest tohigher layers.

6.3 Mapping for the Uu Interface

The directions of arrows shown in Figure 8 reflect the mapping process as seen from

the UTRAN side. For the channels carrying broadcast information, mapping is directfrom BCCH to BCH and from PCCH to PCH.

For the other control and traffic-carrying channels, mapping is more flexible. For example, DL DCCH can be mapped either to FACH or to DSCH, depending oninformation requirements. In the UL direction DCCH may take information fromCPCH, RACH, USCH or DCH. The logical channel DTCH is similar, in that it hasaccess to a range of transport channels. However, the CCCH is simple: it uses onlyRACH and FACH for bidirectional communication.

6 FDD ACCESS MODE CHANNEL MAPPING




3 .2 2

©


BCCH PCCH DCCH CCCH CTCH

BCH PCH CPCH RACH FACH DSCH

PCCPCH SCCPCH PCPCH PRACH PDSCH

F i g ur e 8

F DD

M o d e C

h ann el M a p pi n g

MB 2 0 0 5 / S 3 / v 6 .2




1 Which of the following is not a function of the UMTS access stratum?

a Link establishment and clearingb Provision of physical channelsc Channel codingd Modulation of the radio channel

2 UMTS air interface channels in the FDD mode are defined in terms of:

a Code set and frequencyb Timeslot and frequencyc Code set and timeslotd Code set, timeslot and frequency

3 Which of the following transport channels are not mapped to the DTCH logicalchannel?

a PCHb FACHc RACH

d DSCH

4 Which transport channel is used only in the FDD mode, uses fast power control, and is a shared contention-based channel?

a DSCHb RACHc CPCHd FACH

5 Within layer 2 of the access stratum, there are two sublayers. These are the:

a RRC and MACb RRC and LLCc MAC and RLCd RLC and LLC






SECTION 4

CONSIDERATIONS FOR CDMA

i





1 Advantages of CDMA 4.11.1 Introduction 4.11.2 The Key Advantages 4.1

2 Code Types 4.32.1 DL Code Requirements 4.3

2.2 General DL Code Organization 4.92.3 Uplink Code Requirements 4.112.4 Code Planning 4.152.5 Code Interference 4.17

3 Radio Considerations 4.193.1 The Cocktail Party Effect 4.193.2 The Near–Far Effect 4.193.3 The Need for Fast Power Control 4.213.4 Open Loop Power Control 4.233.5 Adjacent Channel Interference Blocking 4.27

3.6 Cell Breathing 4.313.7 Example Cell Breathing Simulation 4.333.8 Cell Dead Spots 4.413.9 Multi-Service Coverage 4.43

4 Handover 4.454.1 Soft Handover 4.454.2 Hard Handover 4.474.3 Example of a Soft Handover 4.49

5 Handover Measurements 4.515.1 Measurement Process 4.515.2 Measurement Types 4.535.3 Modes for Measurements 4.535.4 Reporting of Measurement Results 4.53


SECTION CONTENTS

iii






• justify the use of CDMA in a third-generation system

• state the code types and their application on the UMTS air interface

• describe how codes relate to the description of physical channels in the UL

and DL directions

• describe typical radio carrier and physical channel allocations for a UMTS

cell

• describe how codes may be planned and applied to a typical cell

configuration

• describe considerations for code performance and limitations

• describe the near–far effect and relate this to capacity and coverage

• outline the problems that can occur through adjacent channel interference in

a CDMA-based system

• explain the application of fast power control and its influence on capacity and

coverage

• relate different service types and quality requirements to coverage

• explain the application of soft handover and its influence on capacity and

coverage

• describe the measurement procedures necessary to support handover

OBJECTIVES

v





1.1 Introduction

The use of CDMA as the access technique for UMTS introduces many newchallenges to the radio planner. It is reasonable to expect that it should be easily justifiable in terms of clear benefits to the operator and the user. In practice this is notthe case.

Traditional spread spectrum systems (from which the CDMA concept originates),were used primarily because of good anti-jamming and privacy performance.However, conventional CDMA systems exhibit neither of these properties. In publicCDMA systems the spreading codes are in the public domain; security comes fromencryption as it would with any other multiple access technology. Anti-jamming is lostbecause the interference margin is translated as far as possible into capacity.

1.2 The Key Advantages

The main advantages of using CDMA must ultimately be related to revenuegeneration for an operator. This is reflected in three key areas:

• increased spectral efficiency

• improved flexibility for multimedia• suitability for the application of advanced features

Most system simulations and channel modelling suggest that CDMA offers a way (intheory) to approach the Shannon limit for capacity in a channel more closely thaneither Frequency Division Multiple Access (FDMA) or Time Division Multiple Access(TDMA). If this proves to be the case in practice then spectral efficiency should result.The ability to change spreading factors smoothly provides a variable-rate channelwell suited to a multimedia system. CDMA is inherently a mathematical process. Thisitself leads to significant improvements in channel processing techniques that

promise much higher data rates and the prospect of software radio in the future.

1 ADVANTAGES OF CDMA





increased spectral efficiency

improved flexibility for multimedia

suitability for the application of advanced features

Figure 1

Advantages of CDMA

MB2005/S4/v6.2





© wray castle limited MB2005/S4/v6.24.3

2.1 DL Code Requirements

There are three code types utilized in the UMTS DL direction. Each of these codetypes maps to one of the key DL requirements: synchronization, cell resolution, andphysical channel resolution. Different code types are chosen for these functions sothat they match in terms of code characteristic.

Synchronization requires short, highly orthogonal codes. Therefore, hierarchicalGolay codes are used in conjunction with Hadamard codes.

Cell resolution requires noise-like spectral characteristics and good cross-correlationcharacteristics; consequently, Gold code segments are used. The codes used for cellresolution are referred to as cell scrambling codes.

For channel resolution, maximal orthogonality is required, which is provided throughthe use of an orthogonal code set in a code tree. The codes used for channelresolution are referred to as spreading codes.

2.1.1 Synchronization Codes

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

codes. All the codes are potentially available on all cells. The single primary code willalways be present in all cells. In addition, each cell will be broadcasting one of 64sequences consisting of 15 secondary codes.

The combination of primary code and secondary code sequences provides initialsynchronization information for the UE. It will be able to acquire slot, frame and cell-scrambling code alignment. By identifying the sequence number for the secondarycode sequence, the UE will also have acquired the cell scrambling code groupnumber. This enables a trial-and-error search for the cell’s scrambling code within aset of eight possible codes.

2 CODE TYPES





Cell ScramblingCode Group Secondary Codes in Frame Sequence

0

1

2

63

1

1

1

9

1

1

2

12

2

5

1

10

8

16

15

15

9

7

5

13

10

3

5

14

15

14

12

9

8

16

16

14

10

3

6

15

16

10

11

11

2

5

2

11

7

12

16

13

15

14

11

12

7

12

15

16

16

10

12

10

Primary SCH Code Cp

Secondary SCH Codes CS1 CS2 CS3 CS4 . . . . . . . . . . . . .CS16

Figure 2

Synchronization Codes




2.1.2 Cell Scrambling Codes

The cell scrambling codes are complex-valued 10 ms segments of Gold codes.There are 512 primary cell scrambling codes; each cell will be allocated one of these. The allocated code will be unique to a cell within its immediate geographicarea, i.e. these codes are planned as if in a frequency plan.

The set of 512 primary codes is organized into 64 groups of 8. These 64 groups mapto the secondary synchronization code sequences.

Each of the 512 primary cell scrambling codes is also associated with 15 additionalsecondary cell scrambling codes. Thus there are a total of 8192 cell scramblingcodes defined. These secondary scrambling codes could be used to subdivide a cellinto subcells, thus providing a means of increasing capacity in a cell, or dealing withtraffic hotspots.





PrimaryCodes

Secondary

Codes

0 1 2 8 97 15 16 504 510 511

1

2

3

4

5

15

Downlink Scrambling Codes

Gold Codes

Group 0

Complex values

10 ms segments

38400 chips

512 codes in 64 groups of 8

Group 1 Group 63Group 2

... ... ... ... ...

... ... ...

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Figure 3

DL Scrambling Code Organization

MB2005/S4/v6.2





2.1.3 DL Spreading Codes

A set of Orthogonal Variable Spreading Factor (OVSF) codes in the form of a codetree is defined for spreading and channel resolution in the DL direction. The use of the code tree enables orthogonal codes to be applied across the length of onecomplete baseband symbol for a range of different possible baseband rates. Thus atlow rates with long-duration baseband symbols, long codes from the top of the treecan be selected. At high rates with short-duration baseband symbols, codes from theroot of the tree can be selected. The result is the maintenance of good orthogonalitybetween DL channels running at either the same or different rates.

Codes from different levels of the tree may be used simultaneously. There are somelimitations, however. Firstly, a code may only be used if no other code on the path tothe root of the tree is already in use. Secondly, once a code is in use no other codederived from it may be used.





1

1,1

1,–1

1,1,1,1

1,1,1,1,1,1,1,1

1,1,1,1,–1,–1,–1,–1

1,1,–1,–1,1,1,–1,–1

1,1,–1,–1,–1,–1,1,1

1,–1,1,–1,1,–1,1,–1

1,–1,1,–1,–1,1,–1,1

1,–1,–1,1,1,–1,–1,1

1,–1,–1,1,–1,1,1,–1

1,1,–1,–1

1,–1,1,–1

1,–1,–1,1

SF = 1

SF = 2

SF = 4

SF = 8

Figure 4

OVSF Codes

MB2005/S4/v6.2





2.2 General DL Code Organization

Figure 5 shows how a typical UMTS cell may be configured in the DL direction. Inthis case it is assumed that the cell is operated with a single radio carrier.

The cell will contain a single PCCPCH. This channel carries the BCH transportchannel, which in turn carries system information messages. Phase synchronizationfor this physical channel is provided by the CPICH. The OVSF codes used to spreadthese two channels are defined and are common to all cells. These channels willalways be scrambled by the cell-specific primary scrambling code. The two channelswill be time-aligned in terms of scrambling code and frame structure, this timingbeing indicated by the Primary SCH (P-SCH) and Secondary SCH (S-SCH).

The cell will contain one or more SCCPCHs. These are used to carry the FACH andPCH as required. These are variable-rate channels that, in the case of FACH, maycontain a mixture of signalling and traffic. Each SCCPCH will be spread by one of theavailable OVSF codes. Either the primary or one of the secondary scrambling codesallocated to the cell may used to scramble the SCCPCHs. Their time alignment maybe different from that of the PCCPCH. SCCPCHs may contain associated pilotinformation for the maintenance of phase synchronization; alternatively, secondaryCPICHs could be provided.

There are several types of physical channels with which a cell may be provisionedthat carry only physical layer signalling. Two of these are shown in Figure 5: the AICH, which is used to acknowledge random access probes, and the PICH, which isused to support a discontinuous reception function for the PCH. Each of thesechannels will be spread with an appropriate OVSF code and scrambled by either theprimary or one of the secondary scrambling codes allocated to the cell.

There are likely to be multiple DPCHs and PDSCHs in operation on the cell. Theseare variable-rate channels that may carry signalling or traffic. Each of these channelswill be spread with an appropriate OVSF code and scrambled by either the primaryor one of the secondary scrambling codes allocated to the cell. Their time alignment

may be different from that of the P-CCPCH. Each DPCH contains associated pilotinformation for the maintenance of phase synchronization. A DSCH has no pilotinformation and thus will always be associated with an existing DPCH.





Common pilotsymbols

BCH

CPICH

P-SCH

S-SCHΣ Σ

OVSF P-SCRAMB

PCCPCH

OVSF P-SCRAMB

FACH SCCPCH

OVSF P/S SCRAMB

PCH SCCPCH

OVSF P/S SCRAMB

AICH

OVSF P/S SCRAMB

PICH

OVSF P/S SCRAMB

DCH DPCH

orPDSCH

OVSF P/S SCRAMB

DCH DPCH

orPDSCH

OVSF P/S SCRAMB

Figure 5

DL Physical Channels on a Cell

MB2005/S4/v6.2





2.3 Uplink Code Requirements

In the UL direction there are three physical channel types with slightly different coderequirements. The PRACH and the PCPCH are always directed at a single cell; softhandover is not a feature of these channels. As a result, the codes used can be cell-specific. Since multiple users exhibiting variation in propagation delay may transmitsimultaneously, good cross correlation characteristics are required. Gold codes areused to fulfil this requirement; in this application they provide both channel resolutionand target cell resolution. In the case of the PCPCH, short S(2) codes are also anoption.

The DPCH also uses either Gold codes or the shorter S(2) codes, but in this casethey are only used for user resolution. This is because the DPCH may be operated insoft handover, requiring that the allocated codes be non-cell specific. A large pool of UL scrambling codes is thus available across the network.

The UL physical channels make use of In-phase/Quadrature (I/Q) multiplexing for the combination of higher-layer and physical layer information. In this respect,orthogonal codes are used to separate the I and the Q streams. In the case of theDPCH, additional orthogonal codes may be used to add additional physical channelsand thus extra capacity for the UE’s UL transmission.





RACH

Physical

LayerControl

PRACH

OVSF

PRACH-SCRAMB

OVSF

CPCH

PhysicalLayerControl

PCPCH

OVSF

PCPCH-SCRAMB

OVSF

DCH

PhysicalLayer

Control

DPCH

OVSF

UE-SCRAMB

OVSF

DCH

V

Figure 6

UL Code Options

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2.3.1 UL Scrambling Codes

There are two options for UL scrambling codes, complex-valued 10 ms segments of Gold codes, or complex-valued S(2) codes. While similar in structure andcharacteristic, the UL Gold code segments are from a different and much larger setof codes than that used in the DL direction. In total there are 16,777,216 codesavailable.

The Gold code segments are sometimes referred to as ‘long’ codes. From the set of Gold code segments, the first 8192 codes are reserved for PRACH operation and thenext 32,768 codes are reserved for PCPCH operation. In both these cases groups of codes taken from these sets will be allocated to particular cells within the planningprocess. The remainder of the Gold code segments are available for DPCHoperation and are not part of the planning process.

The Gold code segments may optionally be replaced with S(2) codes for use in thePCPCH and DPCH only. The S(2) codes are sometimes referred to as short codes.The set of S(2) codes is the same size as that of Gold codes and there is a directmapping from one to the other. The S(2) codes will be used if the Node B equipmentsupports Multi-User Detection (MUD).

2.3.2 UL Spreading Codes

UL spreading is performed using the same set of OVSF codes as is used in the DLdirection for channel resolution. However, in the UL direction a pair of OVSF codeswill be allocated to a physical channel in order to differentiate between I and Qinformation flows.





10 ms Gold Codesegments

38,400 chips

PRACH512 groups of 16

maps to cellprimary

scrambling

PCPCH512 groups of 64

maps to cellprimary

scrambling

DPCHNon-cellspecific

S(2) Codes256 chips

0

1

2

8191

8192

40959

40960

16,777,215

N/A

8192

40959

40960

16,777,215

Figure 7

Scrambling Code Options

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2.4 Code Planning

Code planning in a CDMA system can be seen as analogous to frequency planningin a TDMA or FDMA system. However, for UMTS there is a large number of codesavailable for planning, which results in a relatively straightforward process, as shownin Figure 8.

The basic code type that needs to be planned is the primary cell scrambling code. Itshould be noted that the allocation of a primary scrambling code brings with it 15additional secondary scrambling codes, 16 UL RACH codes, and 64 UL CPCHcodes. Although all these codes are associated with each primary scrambling code itis not necessarily the case that they will all be used. The number provisioned willdepend on the expected cell traffic load and traffic profile.

Some operators may also choose to reserve some scrambling codes for assignmentto temporary or future sites.





P1 Primary Scrambling+ 15 Secondary Scrambling+ 16 UL RACH Scrambling+ 64 UL CPCH Scrambling

P1

P2P3

P4

P5P6

P10

P11P12

P7

P8P9

Figure 8

Code Planning

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2.5 Code Interference

The codes defined for UMTS operation have characteristics well suited to their particular applications, but all CDMA code types have some limitations. This meansthat it is not possible to assume that they will provide full orthogonality under allconditions. Some of the codes used will be non-optimal even in ideal conditions. Ineither the UL or DL directions, codes entering a receiver from different channels or different sources will be subject to varying degrees of time and amplitude variation.These variations occur through the unpredictable nature of propagation delay andmultipath propagation.

2.5.1 Scrambling Codes

The scrambling codes defined for UMTS are chosen because they have good crosscorrelation properties. These cross correlation properties should ensure that differentcodes arriving at a receiver can be independently despread irrespective of their timealignment on arrival. However, both Gold codes and S(2) codes are non-optimal,thus some interference between channels on the same radio carrier is to beexpected. This interference must be allowed for when estimating total interferencelevels as part of a power budget. Since it would be almost impossible to model theeffect precisely, it is usual to allow a weighting in the calculation.

2.5.2 Spreading Codes

The OVSF spreading codes are perfectly orthogonal within their set. The use of thecode tree ensures this orthogonality is maintained even when codes of differentlength are used simultaneously. However, orthogonality is only maintained if thecorrect time alignment is used. In the UL direction this not usually a problem sincetime-variant channels arriving at the Node B are separated using Gold or S2scrambling codes. In the DL direction, user and channel separation is provided onlyby the OVSF codes. A DL transmission that has been subjected to multipath

propagation could present different channels at a UE’s receiver input, exhibiting timevariation between the received OVSF codes. Figure 9 shows what happens whendifferent code lengths are used. Again this effect is impossible to model exactly andmust be accounted for through the use of a weighting in the power budgetcalculation.





Correlation = 0

Correlation = 0 Correlation = 0

ALIGNED

NON-ALIGNED

1 0 1 0 0 1 0 1

1 1 0 0 1 1 0 0

Correlation = 0

Correlation = 2 Correlation = –2

1 0 1 0 0 1 0 1 1

0 1 1 0 0 1 1 0 0

Figure 9

Requirement for Time Alignment of OVSF Codes

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3.1 The Cocktail Party Effect

CDMA requires a complex and very accurate power control system, which is a keyfactor for the system capacity and proper operation.

The analogy of a cocktail party is often used to help describe the problem: if somebody starts speaking louder, they disturb the other conversations. To be able tounderstand each other, the other groups will also need to start speaking louder. If toomany people are present (or if too many people talk too loudly), it becomesimpossible to understand anything.

The same problem occurs in CDMA systems. Although in theory each user’s signalshould be distinguishable by the use of different codes, thus eliminating interference,in practice, due to propagation characteristics and their effect on the orthogonality of code sequences, this is not the case.

Ostensibly, there is no limit to the number of users that can access a CDMA system,unlike TDMA and FDMA systems. However, as the number of users increases, theSignal to Noise Ratio (SNR) will drop below acceptable levels and the pressure onresources will start to degrade quality. Hence users start to ‘shout’, i.e. transmit morepower, in order to make themselves heard, thereby monopolizing resources andreducing everyone else’s ability to transmit effectively. Hence, in UMTS systems, the

need for effective power control.

3.2 The Near–Far Effect

The imbalance in UE power consumption is exacerbated by the user’s location inrelation to the base station. This is called the near–far effect , and is illustrated inFigure 10.

It can be seen that the cell has two active users, mobile A and mobile B. Mobile A ismuch closer to the serving base station than mobile B, and without uplink power

control, both mobiles would transmit the same power (P1).

Because of the difference in distance, the power received at the base station frommobile A would be much greater than the received power from mobile B. As bothmobiles are transmitting on the same frequency, there is a significant probability thatthe base station will be unable to decode mobile B’s transmission as the SNR is toolow.

3 RADIO CONSIDERATIONS





3 km

30 m

Node B

UE A

3

0.03

Power Ratio with Square Law Propagation

= 1002

= 10,000

Interference Margin Required = 40 dB

UE B

wr ay cas tl e Bro ws er

I nt ern e t S ea rc h: h ttp//w w w.

X X X X XX X X x x x X X

X X X x X X X X X

X X X X X X X X X X X X

X X X X x x xx x X X X X

X x X X X X X X X X

X X X XX X X

wr a y cas tl e Bro ws er

I n tern e t S e arc h: h ttp//w w w.

X XX X X X X X x x xX X

X X X x X X X X X


X X X X xx x x x X X X X

X x X X X X X X X X

X X X X X X X

= 100Distance Ratio

Figure 10

Near–Far Effect

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3.3 The Need for Fast Power Control

Dynamic power control is common in all cellular systems. In FDMA and TDMAsystems, where frequency planning is used, power control commands can beinfrequent, and coarse power steps can be used. This is because the transmission of too much power has less effect on other users in either the serving cell or inneighbour cells.

In a CDMA system it is important that the power contribution from each user into theNode B is carefully balanced. If any user’s UE transmits too much power, even for ashort period of time, then it will degrade the communications of all other users in thecell and probably those of some users in neighbour cells also.

Corner effect and movement out of multipath fades are a particular problem. Veryfrequent power commands are required to control this, typically several hundred per second. More frequent power commands should increase capacity, particularly inurban areas.





Building

A

A

B

UE needs to

transmit highpower in shadow

As UE A comes out of

shadow power must be reduced

quickly to avoid degradation ofUE B signal.

Node B

wra y c as t le Bro ws er

Int e rne t Sea r ch: h tt p// ww w.

X X X XX X X X x xx X X

X X X x X X X X X

X XX X X X X X X X X X

X X X X x x x x x X X X X

X x X X XX X X X X

X XX X X X X

wra y c as tle Bro ws er

In te rne t Se ar ch: h t tp// ww w.

X X X XX X X X x xx X X

X X X x X X X X X



X x X X X X X X X X

X X X X X X X

wra y c ast le Bro ws er

Inte r net S ea rc h: ht t p// w w w.

X X X X X X X X x x x XX

X X X x X X X X X

X X X X X X X XX X X X

X X X X x xx x x X X X X

X x X X X X X X X X

X X X X X X X

Figure 11

Need for Fast Power Control

MB2005/S4/v6.2





3.4 Open Loop Power Control

Open loop power control is used to provide a coarse initial assessment of path losswhen a mobile first attempts to establish a connection. This method of power controlis too inaccurate to control the uncorrelated UL and DL.

3.4.1 Closed Loop – UL Power Control

The base station performs regular estimates of the received Signal to InterferenceRatio (SIR). If the measured SIR is higher than the target value, the mobile istransmitting more power than it needs, and the base station commands the mobile toreduce its transmit power by one step.

Similarly, if the SIR is lower than the target SIR, the mobile is transmitting too littlepower, and the base station commands the mobile to increase its transmit power byone step.

This measure–compare–adjust cycle is repeated up to 1500 times per second,allowing the mobile transmit power to accurately follow the changes in path loss.

3.4.2 Implications for the Planning Tool

There are two key parameters that are likely to be entered into a planning tool.These are the step size and the dynamic range supported by the UE. The UE isrequired to support 1 dB, 2 dB and 3 dB step sizes and for a 0.5 W (27 dBm) UE, thedynamic range is required to be at least 77 dB.





Node B

U L T r a n s m i s s i o n

D L P o w e r C o n t r o l C o m m a n d s

UE

wr a y c as t le Bro ws er

In ter net Se arc h: h t t p// w w w.

X X X X X X X X x x x X X

X X X x X X X X X



X x X X X X X X X X

X X X X X X X

Measures SIR Step size→ 1 dB, 2 dB, and 3 dB

Class 2 UE → 0.5 W (27 dBm)

77 dB dynamic range

Figure 12

Power Control

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3.4.3 Closed Loop – DL Power Control

The requirement for adjustments in DL power is assessed by the UE. This is alsobased on SIR measurement and performed 1500 times per second. However, theimplementation differs from UL power adjustment.

In the DL direction, total maximum transmit power available from the highly linear power amplifier can be considered constant. This power is shared between allchannels. DL power control is implemented through the adjustment of the weightedsum of the DL channels. Broadcast and common control channels are likely to beallocated a fixed proportion of the power available. The remainder of power is thenshared between users. The weighting may be used to vary proportions to each user dependent on path loss, interference and required quality of service. If not all thechannels are allocated then not all the power is transmitted.

Therefore, if the downlink is employing fewer channels than the maximum number possible, all transmit power will not be used.





DL Ch. 1

DL Ch. 2

DL Ch. n

G1

G2

Gn

DL Physical Channels

Σ

Modulation

and Linear

Power Amplifier

Distant User

Currently unused

margin of power

Both allocatedrelatively low power

Relatively high power

Cell

EIRP

(max)

Current

Total

EIRP

0

Nearby UserNearby User

SCCPCH

PCCPCH

Common Pilot

Figure 13

Implementation of DL Power Control

MB2005/S4/v6.2





3.5 Adjacent Channel Interference Blocking

3.5.1 Adjacent Channel Performance

In both the UL and DL, adjacent channel interference performance is determined bythe performance of the mobile. UL interference is largely caused by power amplifier non-linearities causing out-of-band radiation. In the DL, receiver selectivity of theadjacent channel is the limiting factor.

Adjacent channel interference blocking is best described by considering the followingscenario.

Consider two network operators, operator A and operator B. Operator B’s spectrumallocation is immediately above operator A’s. Channel N (operator A) is adjacent toChannel N+1 (operator B). Mobile A is being served by base station A, a distantmacro cell (operator A). Mobile B is being served by base station B, a small microcell (operator B). Both operators use power control.

3.5.2 UL Adjacent Channel Interference Blocking

Mobile A is transmitting on full power (set by UL power control by base station A) and

is close to base station B, which is receiving mobile B’s transmission on the adjacentcarrier. If the received signal from mobile A by base station B is sufficiently strong,there is a probability that all calls served by base station B will be dropped. Morelikely, however, base station B will power up mobile B; this in turn increases the totalinterference within the cell and hence reduces cell coverage.

Ideally, when planning a UMTS radio network, simulations should be performed tounderstand the magnitude of the problem. It must be noted, however, thatsimulations need to model both the adjacent operator case described here, and alsointra-system adjacent channel interference from an operator causing adjacentchannel interference to his own network through a poorly designed network.





BS BChannel N+1Operator B

BS AChannel NOperator A

Mobile BChannel N+1

Mobile AChannel N

w r a y c a s t l e B r o w s e r

I n t e r n e t S e a r c h : h t t p / / w w w .


X X X x X X X X X



X x X X X X X X X X

X X X X X X X

w r a y c a s t l e B r o w s e r

I n t e r n e t S e a r c h : h t t p / / w w w .

X X X X X X X X x x x X X X X X x X X X X X

X X X X X X X X X X X X X X X X x x x x x X X X X

X x X X X X X X X X X X X X X X X

Figure 14

Adjacent Channel Interference Blocking

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3.5.3 DL Adjacent Channel Interference Blocking

Mobile A is receiving adjacent channel interference from base station B, and due toits poor front end selectivity, this interference has a cumulative effect upon the totalinterference level perceived by mobile A. It is likely that the call will be droppedbefore the mobile gets too close to base station B.

The call drop should be considered preferable to mobile A causing interference to allof base station B’s UL traffic. Where possible, mobile A will have performed a hardhandover to the operator’s other carrier, thus eliminating the adjacent channelinterference effects and maintaining the call.

As with the UL case, simulations should be performed to understand the magnitudeof the problem and to find engineering solutions prior to building the network.

3.5.4 Possible Solutions

Although the UE and Node B are required to conform with Adjacent ChannelLeakage Ratio (ACLR) requirements illustrated in Figure 15, adjacent channelinterference problems can also be reduced by other techniques. Keeping Node Bantennas high will reduce the effects produced by nearby UEs. Similarly, for smaller

cells (e.g. micro/pico cells), Node B receiver sensitivity could be deliberatelyreduced. Wider guard channels between operators can be produced by adjustingradio carrier frequencies on the 200 kHz raster as shown in Figure 15. Also, co-location of antennas belonging to different operators helps to reduce adjacentchannel interference.





–y dB

f – 2c f + 2cf – c f + cf

–x dB –y dB –x dB

f = transmission frequency c = channel nominal spacing

FDD

3.84 Mcps

UE Node B

5 MHzc 5 MHz

33 dBx 45 dB43 dB

> 5 MHz < 5 MHz

Enhanced Guard Channel

e.g. 5.2 MHz

Operator A Operator B

e.g. 4.8 MHz

y 55 dB

5 MHz 5 MHz

33 dB 45 dB43 dB 55 dB

1.6 MHz 1.6 MHz

33 dB 40 dB43 dB 50 dB

UE Node B UE Node B

3.84 Mcps 1.28 Mcps

TDD

Figure 15

ACLR Requirements and Guard Channels

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3.6 Cell Breathing

3.6.1 Eb/No Requirements

Eb/No is defined as the energy per bit, divided by the noise density. Where Eb = S/R,signal power divided by bit rate and No = KT, Boltzmanns Constant multiplied byabsolute temperature. The Eb/No ratio in simple terms is equivalent to the SNR inanalogue systems.

The Eb/No ratio is usually quoted with reference to a required BER. So to provide aservice with a required QoS the ratio interface must be engineered to give thecorrect Eb/No ratio.

In practical terms, because the No value is constant the only parameter which maybe engineered is the signal power for a given bit rate.

In a CDMA system, because all mobiles are transmitting on the same frequency theSNR is more accurately expressed at Eb/No + Io where Io represents the noisepower contributed by the other mobiles. As more mobiles become active in the cellthe background noise will increase, a phenomenon known as noise rise. This willdegrade the performance of the system.

3.6.2 UL Cell Breathing

As the number of active mobiles in a cell increases the load on the cell is said toincrease. The interference will grow to the extent that distant mobiles will be droppeddue to the poor signal-to-noise ratio, effectively causing the cell to shrink. As mobileconnections are terminated the interference reduces and the cell size increases. Thisis known as cell breathing.

3.6.3 DL Cell Breathing

Downlink cell breathing also occurs as the cell becomes loaded. However, this iscaused by the fact that the base station employs a linear power amplifier. As moreconnections are established in the cell each mobile will be given proportionally lesspower, causing the range of the cell to reduce. With fewer connections each mobilemay be apportioned more power, effectively increasing the cell range.





Small Cell Load

Heavy Cell Load

w r a y c a s t l e B r o w s e r I n te r ne t Se a rc h: ht t p / /w w w .

X X X X X X X X x x x X X X X X x X X X X X X X X X X X X X X X X X X X X X x x x x x X X X X X x X X X X X X X X

X X X X X X X

w r a y c a s t l e B r o w s e r I n te r ne t Se a rc h: h t t p / /w w w .

X X X X X X X X x x x X X X X X x X X X X X X X X X X X X X X X X X X X X X x x x x x X X X X


w r a y c a s t l e B r o w s e r In t e r ne t Se a rc h: h t t p / /w w w .


X X X X X X X X X X X X X X X X x x x x x X X X X X x X X X X X X X X

X X X X X X X

w r a y c a s t l e B r o w s e r I n te r ne t Se a rc h: h t t p / /w w w .

X X X X X X X X x x x X X X X X x X X X X X X X X X X X X X X X X X X X X X x x x x x X X X X


w r a y c a s t l e B r o w s e r In t e rn e t Se a rc h : h t t p/ / w w w .


X X X X X X X X X X X X X X X X x x x x x X X X X X x X X X X X X X X X X X X X X X

w r a y c a s t l e B r o w s e r I nte rne t Se a rc h: h t tp //w w w .


X X X X X X X X X X X X X X X X x x x x x X X X X X x X X X X X X X X

X X X X X X X

w r a y c a s t l e B r o w s e r I nt e rn e tS e a r c h : h tt p // w w w .

X X X X X X X X x x x X X X X X x X X X X X X X X X X X X X X X X X X X X X x x x x x X X X X X x X X X X X X X X X X X X X X X

w r a y c a s t l e B r o w s e r Int e rn e t S e a r c h : h tt p // w w w .


X X X X X X X X X X X X X X X X x x x x x X X X X X x X X X X X X X X X X X X X X X

UE out of range

Figure 16

Cell Breathing

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3.7 Example Cell Breathing Simulation

3.7.1 Jersey Sites

Figure 17 shows a small system comprising 26 sectorized sites. All sites are on 25 mmasts using three 85° antennas with 2° downtilt. The area in view is about 20 km by12 km.





Figure 17

Jersey – Site Locations

MB2005/S4/v6.2





3.7.2 Radio Coverage

All sites have an Effective Isotropic Radiated Power (EIRP) of 50 dBm and thepropagation model is adapted from one used for GSM 1800 in open areas. Coverageis indicated in areas with a predicted signal level above –98 dBm. Given a suitablelink budget this could be considered a reasonable prediction of coverage for a GSMsystem.





Figure 18

Jersey – Radio Coverage

MB2005/S4/v6.2





3.7.3 CDMA Coverage with Heavy Traffic

Figure 19 shows a simulation for the system taking into account inter- andintra-cell interference. In this case traffic was used at 12.2 kbit/s with around 70users per cell. A Monte Carlo simulation ran and 10,000 drops were used to producethe image. The dark areas near the Node Bs show coverage likelihood above 80%.





3.7.4 CDMA Coverage with Light Traffic

Figure 20 shows the same system simulated under light traffic conditions. In thiscase, load was reduced to around ten users per cell. Coverage above 80% is notcontiguous but patches can be seen at much greater ranges from the Node Bs.





3.8 Cell Dead Spots

In order to maximize cell capacity the power control algorithm must balance theinterference contribution from all UEs in a cell. It is therefore important that dynamicrange for power adjustment at the UE is sufficient to account for the range of pathloss variations in a cell. If this is not the case, dead spots can occur near to a cell.

This happens when traffic load is high and UEs near to a cell are asked to reducepower such that UEs nearer the cell edge can be retained. A UE which does nothave enough dynamic range to reduce power sufficiently may be refused access byadmission control at the cell. Thus a mobile near to the cell may not receive servicebecause it is not capable of transmitting a low enough power. This results in a similar effect to cell breathing, except that it works from the cell site outwards.





Dead Zone near Node B.

UE A access is barred.

Node BUE A

wr ay cas tl e Bro ws er

I nt ern e t S ea rc h: h ttp//w w w.

X X X X XX X X x x x X X

X X X x X X X X X


X X X X x x xx x X X X X

X x X X X X X X X X

X X X XX X X UE B

wr a y c as tl e Bro ws er

In te rn et Se a rch: h t tp//w w w.


X X X x X XX X X

X X X X X XX X X X X X


X x X X X X X X X X

X X X X X X X

Figure 21

Dead Spots

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3.9 Multi-Service Coverage

The UMTS air interface, unlike GSM, has been designed to carry different types of services and data rates simultaneously. These different services will be characterizedby:

• user bit rate

• activity factor (in UL and DL)

• traffic model

• radio quality requirements (UL and DL) in terms of Eb/No

• maximum mobile transmit power per service class

Each one of these factors has an impact on cell size; higher data rates result in alower spreading factor, therefore a greater Eb/No requirement, hence reduced cellsize.

In practice this means that each service type has a different cell radius, despite beingtransmitted from the same base station. It may, therefore, be desirable to plancoverage on a service-by-service basis.





Medium Data Rate

High Data Rate

Voice andLow Data Rate

Figure 22

Multi-Service Coverage

MB2005/S4/v6.2





4.1 Soft Handover

When a mobile is in an area of overlapping coverage from two or more cells it maybe placed in a state of soft handover. In soft handover the mobile will becommunicating with a number of Node Bs simultaneously. In the downlink directionthis is made possible by using individual rake fingers to despread traffic from anumber of cells, aided by the fact each cell has its own scrambling code. In theuplink direction, traffic from the mobile will be received by a number of Node Bs,which can then be combined.

Figure 23a shows a mobile in soft handover between two Node Bs connected to thesame RNC. Traffic will be carried over two Iub interfaces to the RNC where it will becombined.

In Figure 23b a mobile is in soft handover between two Node Bs attached to twoseparate RNCs. Once again, traffic will be carried over two Iub interfaces, but thedrift RNC will relay the traffic over the Iur interface to the serving RNC, where it willbe combined. It can be seen that mobiles engaged in soft handover will demandextra capacity on the backhaul circuits. From IS-95 experience 30 to 40% of mobilesmay be involved in soft handover at any one time.

One of the benefits of soft handover is that the parallel communication channels give

an improvement in receive performance. This is known as soft handover gain. Thiscan be as much as 4 dB and may be included in the link budget calculation.

4.1.1 Softer Handover

Figure 23c shows a mobile in soft handover between two cells controlled by thesame Node B. Here the traffic will be combined locally in the Node B. No extrabackhaul capacity will be required and the combining process in the Node B willprovide a slightly greater soft handover gain of 5 dB. This process is commonlycalled ‘softer handover’. From IS-95 experience 5 to 15% of mobiles may be

engaged in a softer handover.

Both soft handovers and softer handovers are also known as Diversity Handovers(DHO).

4 HANDOVER





Node B

a) Soft Handover, two Node Bs, one RNC

b) Soft Handover, two Node Bs, two RNCs

c) Softer Handover

Cell

Node B

RNC

Cell Cell

Iub

wra y c as t le Bro ws er

I nt ernet Se arch: ht tp// ww w.

XX X X X XX X xx x XX

X XX x XX X X X

X X XX X X X XX X XX

X XX Xx x xx x XX XX

Xx X X X XX XX X

X X X X XX X

wr a y c as tle Bro wser

In terne t S earch: h ttp//w ww.

X X XX X X X Xx x xX X

X XX xX X XX X

X X X X XX X X X XX X

XX X Xx x xx x XX X X

Xx X X XX X X X X

X XX XX X X

Node B

RNC

Iub Iub

Node B

wra y cas tl e Bro ws er

Inter ne t Sear ch: htt p//ww w.

X XX X XX XX x xx X X

XX X xX XX X X

X XX XX X XX XX X X

X X XX x xx x xX X X X

X x XX X X X X XX

XX X X X X X

Node B

Iub Iub

SRNC DRNC

Figure 23

Soft Handover

MB2005/S4/v6.2





4.2 Hard Handover

When a mobile is in soft handover it will be power-controlled by all Node Bs involvedin the handover. This is imperative to control the interference in a CDMA system.However, when a mobile is in coverage by two cells on different frequencies it maybe desirable to perform a hard handover. But before the handover is executed amobile may contribute adjacent channel interference to the neighbouring cell.Consider Figure 24.

Mobile UE1, though nearer to base station B2 than to B1, is still power-controlled byB1. Similarly, UE2 is controlled by B2.

For simplicity, also assume that the condition for a mobile to be correctly received bya base station is that the SIR received by this base station is greater than unity.Then, B1 does not receive UE1 correctly, since the interference that B1 receivesfrom UE2 is greater than the signal received from UE1. Therefore, B1 asks UE1 toraise its transmission power. But this increases the interference seen by B2 and, as aconsequence, B2 asks UE2 for an increase of transmission power. Clearly, we havea regenerative effect that ends only when the two mobiles have reached their maximum transmission power.





Possible instability of power control

Node B 1 Node B 2UE 1

UE 2 w r a y c a s t l e B r o w s e r In ter ne t S ea rc h: h tt p / /w w w .


X X X x X X X X X


X x X X X X X X X X X X X X X X

X

w r a y c a s t l e B r o w s e r In te rn et Se ar ch : h tt p //w w w .




Figure 24

Hard Handover

MB2005/S4/v6.2





4.3 Example of a Soft Handover

The example is simplified for clarity and involves a UE monitoring three Node Bs.The diagram shows the relative quality levels of the Node Bs’ CPICHs as the UEmoves through the system.

Over the period of time shown on the diagram, the UE starts with an active setcontaining only cell A. In this case it is assumed that the active set is limited to twocells.

1 At this point, the quality measurement for cell B has reached the additionalthreshold for macro diversity. This is reported to the RNC and, subject to therequirements of access control and the expiry of a wait timer, the UE is sent ahandover command. This message instructs the UE to add cell B to the activelist and includes the required code and timing information.

2 At this point, the difference between the quality of cell A and cell C has fallenbelow the replacement hysteresis threshold. This is reported to the RNC and,subject to the requirements of access control and the expiry of a wait timer, theUE is sent a handover command. This time the handover command instructsthe UE to remove cell A from the active list and replace it with cell C.

3 At this point, the quality measurement for cell C has fallen below the removalthreshold for macro diversity. This is reported to the RNC and if this situation ismaintained beyond the expiry of the appropriate timer, a handover command issent to the UE. This message instructs the UE to remove cell C from the activeset, leaving only cell B.




4 . 5 0

©


Quality

Cell A

Cell B

Cell C

Timer

TimerMacro

Add

Threshold

Macro

Replacement

Threshold

Macr

Remo

Thresh

1. 2.

F i g

ur e2 5

E x am pl e of a S of t H an d ov er

MB 2 0 0 5 / S 4 / v 6 .2




RRC procedures relating to measurements are used by the UTRAN to set up the

measurement process, and by the UE to provide requested measurements.

5.1 Measurement Process

The purpose of this procedure is to set up, modify or release one or moremeasurements that are being, or will be, performed by a UE. It is applicable for a UEin any of the RRC-connected mode states. The UTRAN transmits the MeasurementControl message to the UE using the established RRC connection. This messagewill contain a number of parameters.

Included in this message are the following.

Measurement TypeThis indicates to the UE the type of quantity which is to be measured.

Measurement Identity Number This is used by the UTRAN to identify the measurement, should it need to bemodified subsequently.

Measurement Command

This is used to set up, modify or release.

Measurement ObjectsThis is neighbour cell information.

Measurement QuantityThese are specific details on the indicated quantities to be measured.

Reporting QuantitiesThese are the quantities to be reported.

Measurement Reporting CriterionThis is the criterion that will trigger a report generation.

Reporting ModeThis is the acknowledged or unacknowledged mode for RLC.

5 HANDOVER MEASUREMENTS





UE

Node B

Iub

Uu

M e a s u r e m

e n t C o n t r o l

measurement type

measurement identity number

measurement command

measurement objects

measurement quantity

reporting quantities

measurement reporting criteria

reporting mode


I nt er n et S ea r ch: h t tp//w w w.

XX X X X X X X xx x X X

X X X x X X X X X


X X XX x x x xx X X X X

X x X X X X X X X X

X X X X X X X

RRC

Figure 26

Measurement Control

MB2005/S4/v6.2





5.2 Measurement Types

There are seven categories for measurement types. The UTRAN will indicate to theUE which types are to be included in its measurement process, and specific detailsrelating to that type. The types are:

• intra-frequency measurements

• inter-frequency measurements

• inter-system measurements

• uplink traffic volume measurements

• downlink quality measurements

• UE internal measurements

• measurements for location services

5.3 Modes for Measurements

The measurement process is applicable for UEs in all modes of operation, and theytherefore require instruction from the UTRAN on the measurements to be made. The

Measurement Control message is only used for UEs in the CELL_DCH state. For UEs in idle mode or in one of the other connected states, the instructions for measurements to be made are included in the System Information Blocks (SIBs)being broadcast on the BCCH.

5.4 Reporting of Measurement Results

Reporting of measurement results is only performed by UEs in the CELL_DCH state.The UTRAN instructs the UE about its reporting requirements.

Reporting is normally performed using the Measurement Report message. However,the UTRAN may instruct a UE to append radio link related measurements to other uplink messages including RRC Connection Request, Direct Transfer and CellUpdate.





UE

Downlink

Quality

Uplink

Traffic

Volume

RLC

Buffer

Internal – TX Power

– RSSI

Location Measurement

Node BIntra-frequency

Intra-

frequencyInter-

frequency

Inter-

system


In t er ne t S ea rc h: h t tp//w w w.

X X X X X X X X xx x X X

X X X x XX X X X

X X X XX X X X X X X X

XX X X x x xx x X X X X

X x X X X X X X X X

X X X X X X X

Node B

GSM

BTS

Node B

Micro

Figure 27

UE Measurements

MB2005/S4/v6.2





1 From an operator’s point of view, which of the following would not be regarded

as an advantage of using CDMA?

a It allows for multimedia featuresb It has an increased spectral efficiencyc It is suitable for applications with advanced featuresd It requires a greater number of cell sites than 2G systems

2 The number of downlink scrambling codes available is:

a 384b 16c 512 sets of 16d 512

3 Which of the following indicates to the UE that access to the network isavailable?

a AICHb PICH

c DPCHd FACH

4 The Cocktail Party Effect results in which of the following?

a Slurred speechb Slanted antennas and slant polarizationc The whole system falling downd The need for power control

5 When using closed loop power control the power level can be adjusted howmany times per second?

a 384b 1500c 77d 200






SECTION 5

TRAFFIC ANALYSIS

i





1 Traffic Characteristics 5.11.1 High-Level Call Characteristics 5.11.2 Detailed Call Characteristics 5.11.3 Quality of Service (QoS) 5.31.4 QoS – Human Factors 5.5

2 Data Usage 5.72.1 UMTS Call Characteristics 5.72.2 User Profiles 5.92.3 Data Symmetry 5.11

3 Traffic Modelling 5.133.1 Traditional Methods 5.133.2 Packet Data Modelling 5.15


SECTION CONTENTS

iii






• relate QoS to UMTS service capabilities

• state the general UMTS service aims in respect of the radio environment

• describe traffic types likely to be available in a UMTS system and relate them

to QoS

• discuss possible UMTS user profiles and relate these to demographic

distribution

• discuss appropriate traffic modelling for UMTS systems

• describe the impact on capacity and coverage of the operation of contention-

based physical channels in the UL direction and shared channels in the DL

direction

OBJECTIVES

v





1.1 High-Level Call Characteristics

Primarily, UMTS will provide customers with two different types of service: CircuitSwitched (CS) and Packet Switched (PS).

1.1.1 Circuit Switched (CS)

A specific data rate is chosen at the start of the call, based upon user requirementsand service category. This rate may be renegotiated during the call. The allocatedresources are solely for the use of that customer. Charging is generally based on thetype of service selected and the duration of use.

CS communications are needed for applications which are sensitive to delay, such asvoice and videoconferencing.

1.1.2 Packet Switched (PS)

With PS communications there is no permanently established end-to-end connection.Network resources are allocated to users in bursts to deliver packets as they aregenerated. The network is a shared resource, so at one instant a user may be using

the whole channel capacity and at the next none at all.

Packets may be delivered with a required QoS that may influence delay. Charging isgenerally based on volume rather than time.

Typical packet-based applications include e-mail, file transfer and WWW pagedownload. These applications are delay tolerant.

1.2 Detailed Call Characteristics

Within the general terms of packet- and circuit-switched traffic, a number of traffictypes, each with their own agreed set of characteristics, can be described in terms of:

• data rate

• symmetry (whether more data is transferred in one direction than another)

• typical usage (duration in terms of switched call, average data transfer volumefor packet services)

• delay as perceived by the user.

1 TRAFFIC CHARACTERISTICS






Circuitswitched

Packetswitched

No permanent connection

Resources allocated in bursts

Shared resources

Charge based upon volume

Delay-tolerant applications

Fixed data rate, set at start of call

Dedicated resource for call duration

Charging is generally based upon:

Delay-sensitive applicationsHigh-level callcharacteristics

Detailed call

characteristics

Sub-category 2

-

--

Sub-category n

Sub-category 1

Type of service

Duration

Data rate

Symmetry

Typical usage

Delay

wra y cas t le bro wser

In te rne t Sea rc h: ht t p:/ /w w w. wra y ca s tle.com

X X X X X X X X xx x X X

X X X x X X X X X



X X X X x x x x xX X X X

X x X X X X X X X X

X X X X X X X

X X X

X X X

X X X

X X X

X X X

X X X

X X X

X X X

1 2

3

4 5

6

7 8

0

9

Callcharacteristics

Figure 1

Call Characteristics




1.3 Quality of Service (QoS)

Services are generally defined as being either circuit switched or packet switched.

Currently, in terms of QoS, these may be treated differently. For CS systems, QoS isconsistent and guaranteed. On packet networks, however, congestion leads toincreased delays and therefore reduced (and variable) QoS.

Longer term it may be more appropriate to view all services as being delivered by apacket-based network. In this case it must be assumed that adequate QoS guaranteesand resource reservations are built into packet-based transmission protocols. To helpidentify suitable levels of QoS, three factors must be considered for each service type:data rates, average usage and delay.

1.3.1 Data Rates

For CS data, the data rate offered to a user is fixed unless renegotiated during the call.

In the packet data context, a guaranteed data rate will need to be offered; this could bea fixed percentage of the maximum nominal rate of data transfer. In this case, the user would subscribe to a minimum guaranteed QoS that must be maintained during

periods of congestion. However, under lighter traffic conditions better performancewould be expected.

1.3.2 Average Usage

To determine a circuit or network Grade of Service (GoS), it is necessary to know theaverage usage for each type of customer/service.

For CS services, average call duration is needed, whereas for the packet-basedservices the average file size is needed, which must take into account overheads

incurred by the radio interface or protocol headers. The distribution of these inputsalso needs to be known or assumed, i.e. a standard Poisson distribution.

1.3.3 Delay

It is reasonable to assume that customers will be increasingly sensitive to delay, andthat QoS demands will increase. For packet-based services, delay targets should beachieved for a percentage of customers. Delay is not just service-sensitive, but UE-sensitive also. For example, Internet radio stations do not deliver a complete file

before audio playback begins; sufficient buffering on the terminal device will enableplayback of the file as soon as enough of the file has been received to satisfy theseQoS demands.





Data Rate

CS

fixed

rate may

be negotiated

PS

guaranteed rate

nominal rate

rate may be

exceeded

CS

none

PS

service sensitive

UE sensitive

delay ranges for

percentage of customers

CS

average call duration

PS

average file size and protocol

overhead

Delay

Average Usage

QoS

Figure 2

QoS

MB2005/S5/v6.2





1.4 QoS – Human Factors

1.4.1 Data Services

Internet-based services currently provide a best-effort QoS. For applications such asfile access, file download and WWW browsing, users require a QoS that they deemto be acceptable. Perceived quality in this situation, where applications are not highlysensitive of QoS, is subjective.

It is possible to define recommended and maximum response times for a number of applications and services that will suit the majority of users. Given that the amount of data to be transferred in a given time is known, the required bandwidth can becalculated. However, in some situations it may not be necessary for all the data to betransferred in order for the user to perceive a satisfactory response, for examplewhere later parts of a WWW page continue to be downloaded while the user isreading the page.

1.4.2 Voice Services

As with data, there is a wide range of acceptable delays for voice-based services.Perceived quality depends not only on the actual delay in the network, but also

whether echo cancellation techniques are used. The ITU makes recommendationsfor one-way transmission delays where echo is controlled; these values concerninternational links, which may be appropriate in the UMTS global context.





Example Recommended Maximum

Simple service Select page from menu, 0.5 seconds 2 seconds

select hyperlink

Complex service Send message, process data, < 5 seconds 5 seconds

return, e.g. WWW-based

database enquiry

Loading data Loading of programs and data, < 15 seconds 60 seconds

e.g. file download for use with

helper application, Java Applet

The ITU recommendations for one way transmission delay where echo

is controlled:

0–150 ms delay acceptable for most applications

150–400 ms provided that degradation in quality is acceptable(applies to international links with a satellite component)

over 400 ms is unacceptable but may be necessary under some circumstances, e.g. multiple satellite hops

Figure 3

QoS – Human Factors

MB2005/S5/v6.2





2.1 UMTS Call Characteristics

Prior to understanding usage patterns, service types and their associatedcharacteristics need to be defined. Seven service types are characterized:

• voice

• fax

• interactive

• high-quality interactive

• messaging

• medium multimedia

• high multimedia

Clearly, there are many sub-categorizations below this top level.

2 DATA USAGE




5 . 8

©


MediumMultimedia(small file)

100kbyte

90%Packet64 k

LAe-matt

< 2 sec < 1 sec n/a

Service

Voice

Fax(Low-speed data)

Interactive

High-QualityInteractive

Messaging

High Multimedia(large file)

7.8 kbit/s 2 min.

3 min.

25 min.

40 min.

1 kbyte

2 Mbyte

< 30 ms

200 ms

200 ms

200 ms

BestEffort

< 2 sec

50%Stream

50%Stream

50%Stream

50%Stream

80%Packet

90%Packet

28.8 kbit/s

64 kbit/s(wide area)

384 k(wide area)

2 Mbit/s(in pico cell)

200 k

guaranteedminimum

inbusy hour

Data Rate Symm AV Use Delay(2005)

Delay(2010)

Grade ofService

Co

< 20 ms

n/a

100 ms

100 ms

BestEffort

< 1 sec

1%

2%

5%

5%

n/a

n/a

Dedisec

Suby

80int200

20int200

No

Reonstran

F i g ur e4

UMT S C al l C h ar a c t er i s t i c s

MB 2 0 0 5 / S 5 / v 6 .2




2.2 User Profiles

2.2.1 Usage Patterns and Traffic Statistics

In order to develop realistic assumptions for user profiles, these should include:

• call holding times

• typical data volumes

• data rates

• types of service

• time of day when services are used

• locations where services are used

Data from a number of sources needs to be investigated. This can then be used tocompare traffic levels seen today with proposed traffic characteristics for UMTS.

2.2.2 Circuit Switched (CS)

It may be possible to estimate future demand for UMTS streaming-based services byanalyzing current demand for CS services on PSTN and ISDN networks. Data onanalogue modem and ISDN traffic is available from a wide range of sources.

2.2.3 Packet Switched (PS)

It is far more difficult to find information on Internet usage patterns since, historically,traffic profiles are generally recorded on a per-network basis. There is little regardgiven to the amount of traffic generated per user. This makes it difficult to validate theassumed average and maximum file sizes for UMTS.





20

18

16

14

12

10

8

6

42

01 30 60

Percentage of calls

Holding time (minutes)

Holding time (minutes)

Application Mean duration(minutes)

Videoconferencing 42

Private circuit back-up 29

Remote LAN access 26

Desktop conferencing 25

Internet access 23

High-quality audio 22

Complex file transfer 21

LAN interconnection 20

Database access 17

Security/surveillance 15

Voice 6

Short file transfer 5

Fax 3

Card verification 0.3

Figure 5

User Profiles

MB2005/S5/v6.2





2.3 Data Symmetry

The development of UMTS is based on a number of environments, ranging fromthose found in the Central Business District (CBD) of a town or city through to thosefound in rural areas. For any defined UMTS service group the degree of asymmetryin the traffic being generated will vary. This is because the service people requirevaries in different environments.

For example, for high multimedia, in the CBD some business/professional users maywant to upload large files (especially images from remote information gathering) justas often as they want to download files (database, intranet, etc.).

However, in the suburban and rural areas, people in their leisure activities maygenerally be seeking to download Internet pages, hobby-related data or educationalinformation.

The trends in transactional and therefore net asymmetry will vary depending on themarket environment. This could have an impact on the net asymmetry in spectrumrequirements between the UMTS macro cell and micro cell layers, and/or betweenurban, suburban and rural macro cells.





Node B

U L T r a f f i c

D L T r a f f i c

UE


I nte rne t S ea rch: h t tp// w w w.


X X X x X X X X X



X x X X X X X X X X

X X X X X X X

Voice

Video Telephony

Messaging

Audio/Video streaming

Web Browsing

E-mail

Symmetric

Symmetric

Asymmetric

Asymmetric

Asymmetric

Asymmetric

50:50

50:50

60:40

Heavy DL

Heavy DL

60:40

Figure 6

Data Symmetry

MB2005/S5/v6.2





3.1 Traditional Methods

First- and second-generation systems have relied on traditional traffic modellingtechniques, which were developed for fixed telephony networks. There are severalreasons why these models are not really suited to a mobile environment, althoughthey are generally considered to be close enough to be usable.

3.1.1 Inclusion of Data

Second-generation systems have seen the introduction of data and messaging. Evenwith these in place, a simple Erlang B model can still be applied. Data is largelycircuit switched and can thus be modelled as a telephone call with modifiedcharacteristics, i.e. call rate and call duration. Similarly, SMS can be treated as atelephone call of very short duration.

3 TRAFFIC MODELLING





BTS S M S

P o i n t - t o - P

o i n t C i r c u

i t - S w i t c h e

d D a t a

V o i c e T r a f f i c

MS

Erlang B

Average Call Duration

Average Call Arrival Rate


In te r ne t S e ar ch: h tt p//w w w.


X X X x X X X X X



X x X X X X X X X X

X X X X X X X

Figure 7

Traditional Traffic Modelling

MB2005/S5/v6.2





3.2 Packet Data Modelling

The modelling of packet data involves a far greater level of complexity than that of circuit-switched data. It must take into account packet size, throughput rate,retransmission rate and packet activity. The wide range of services that are likely torely on packet data will probably require a range of different packet traffic types to bedefined, each with unique characteristics. The chosen modelling tool must be able toaccommodate and combine these varied traffic types.

3.2.1 Characterizing Packet Traffic

Figure 8 illustrates an example of packet data traffic and represents what mayhappen whilst web browsing. The following parameters characterize the packet datatraffic.

A session is a period of time that a user is accessing resources via a packetconnection, i.e. web browsing. A session can be divided into a number of calls withperhaps five calls per session. Each call would be initiated by a user selecting ahyperlink or menu option.

The number of packets in a call will depend upon content and packet size. The

average packet size is typically 500 bytes with 25 packets in a call. The inter-arrivaltime of packets in a call is typically 2 ms.

There is usually a longer interval between calls, known as the call interval. This istaken as being the time a user reads the downloaded content before selectinganother option. This so-called reading time is often taken to be about 400 seconds.

This information will be needed for each packet-based service and may be differentin the uplink and downlink directions.

Knowing the bit rate for the defined service, the packet characteristics and assuming

a Poisson packet arrival distribution for all users it is possible to determine thecapacity and load placed on a cell.





Total number of

calls in session

Packets in call

Packet interval Packet size Call interval

call and session arrival assumed to follow a Poisson process

Figure 8

Packet Characterization

MB2005/S5/v6.2





3.2.2 Transport for Packet Data

For successful system simulation, the model should ideally account for the differentmechanisms for packet data transfer on the UMTS air interface. In particular, accountneeds to be taken of the inclusion (or otherwise) of fast power control in the usedchannel. A channel without power control will represent more interferencecontribution. In addition, the support of soft handover must be accounted for sincethis will also impact on interference and capacity.

These effects must be modelled accurately for reliable predictions to be obtained.





Node B D C H

D S C H

C P C H

FA C H

RA C H

UE


Int ern et Sea rc h: h t t p//w w w.


X X X x X X X X X



X x X X X X X X X X

X X X X X X X

Transport

Channel

RACH/FACH

CPCH/FACH

DSCH

DCH

Rapid set-upSmall amountsBursty applications

Share channelHigh or low bit ratesMultiple CPCH/cellFast power controlSmall/medium amounts of data

Sharing OVSF codesFast power controlMedium/large amounts of dataSoft H/O

Fast power controlSoft H/OLess interferenceHigh bit ratesHigh data volumes

Few RACH/FACH pairsNo fast power controlNo soft H/OGenerates more noise

No soft H/O

Not suited to bursty trafficSlower set-up time

Advantage Disadvantage

Figure 9

Packet Transport

MB2005/S5/v6.2





1 Cell breathing has which of the following effects?

a It allows more users into the cell coverage areab It removes the need for open loop power controlc It results in the cell varying in sized It prevents high capacity users accessing the Node B

2 Which of the following is a feature of a packet-switched call?

a No permanent connectionb Uses a dedicated resourcec Is suitable for delay-sensitive applicationsd Charging is based upon call duration

3 Which of the following would not be regarded as a user profile?

a Call holding timeb Class of UE in usec Time when service is usedd Locations where services are used

4 When assessing data symmetry, which of the following would be regarded assymmetric?

a Voiceb Messagingc Web browsingd E-mail

5 When modelling for packet data, which of the following may be ignored?

a Packet sizeb Throughputc Retransmission rated SMS traffic






SECTION 6

COVERAGE PREDICTIONS

i






• state typical radio parameters applicable to coverage prediction in UMTS

• suggest appropriate propagation models and prediction techniques for

UMTS coverage planning

• describe multipath effects and receiver characteristics in respect of CDMA

operation

• discuss link budgets for different traffic types and loads to allow for cell

breathing

• state the significance of noise rise and load factor

• relate traffic characteristics to a typical UMTS link budget

• estimate approximate range from link budget

OBJECTIVES

v





1.1 Introduction

Although UMTS introduces a very different air interface structure to that of GSM, itmay not need a fundamental change in radio propagation prediction. However, thereare several points that may require consideration:

• shift in frequency

• emphasis on microcellular not macrocellular models

• wideband channel

• lack of UL and DL correlation

1.2 Current Models

Research into propagation models has been extensive since the introduction of second-generation systems. Most are based on an empirical format and range from abasic Okumura Hata model to more complex offerings resulting from COST 231.Most of these models are more suited to the macrocellular environment and aresupplemented by diffraction loss and clutter loss weightings. Some of the moreadvanced models may need very little adaptation for UMTS.

There are some microcellular and picocellular models in use, both empirical and raytracing based. It is likely that more effort will be required in this area to developmodels better suited to UMTS channel characteristics.

1 PROPAGATION MODELLING






shift in frequency

microcellular rather than macrocellular

wideband channel

lack of UL and DL correlation

Figure 1

Considerations for UMTS Propagation Models




1.3 Frequency Change for UMTS

The degree to which the change to a new frequency band for UMTS affectspropagation modelling may depend on the operator in question. A GSM 900 operator may see the introduction of new propagation models. It is likely that a GSM 1800operator will only initially need to modify existing models. In either case, most modelsused for GSM 900 and GSM 1800 could be adapted for use with UMTS.

Models could be recalibrated for UMTS using measurement information gatheredfrom the UE. Additionally, drive test logging could also be used.

1.4 Emphasis on Microcellular Models

Many factors suggest a much smaller cell size than has been the case for second-generation systems. There is already a trend to reduce cell size for increasedcapacity and this continues for UMTS. Thus there will be a great deal of interest inmicrocellular models. There are two modelling approaches of interest, a statisticalmodel and a deterministic model.

1.4.1 Statistical Models

Statistical models are based on mathematical analysis of a statistically significant setof field measurements. The precise approach varies, but often takes the form of apower law model with modifications for the local environment. Figure 2 shows ageneral form for such a model.





The general form of a Power Law model:

Lp(d) = L(do) + 10n Log10 (d/do) + x dB

Lp(d) = path loss in dB

L(do) = free space path loss at 1m reference point (38.5 dB at 2 GHz)

n = path loss exponent

x = location-specific factors of fade margins

Figure 2

Power Law Micro Cell Model

MB2005/S6/v6.2





1.4.2 Deterministic Models

A deterministic model attempts to predict propagation through the application of thefirst principles of physics and detailed knowledge of the local environment. The mostwell-known technique is Ray Tracing. This is an attempt to predict the precise pathfrom transmitter to receiver. A detailed knowledge of buildings and terrain is required,and, as a result, this type of model is very limited in its application.





Node B

wr a y c as t le Bro ws er

In t ern et S ea rch: h tt p// w w w.


X X X x X X X X X



X x X X X X X X X X

X X X X X X X

Figure 3

Ray Tracing

MB2005/S6/v6.2





190 MHz

5 MHz 5 MHz

Non-correlated channel

Non-correlated UL and DL

Figure 4

Effects of the Wideband Channel

MB2005/S6/v6.2





A link budget would normally be a function of accounting for link losses and

requirements in order to ascertain an acceptable path loss. For CDMA-basedsystems, the power budget must also take account of the interference level and QoSrequirements. These in turn will be a function of system load.

2.1 Load Factor (L j)

The load factor is an indicator of how close a link is operating in respect of itstheoretical maximum capacity. Given that loading will reduce coverage, it isundesirable to plan a system for a very high load factor. Ideally, the system should bedimensioned such that cells operate with a load factor allowing a margin of safety.

2.2 Noise Rise

The noise rise is a measure of the increase in noise caused by the interference levelin the cell. The interference in question includes both intra-cell and inter-cell sources.The noise rise can be calculated from serving and neighbour cell operating loadfactors. Thus a higher load factor results in a higher noise rise.

2 LINK BUDGET





Load Factor Noise Rise

Radio Parameters

Link Budget

InterferenceMargin

Figure 5

Link Budget Inputs

MB2005/S6/v6.2





2.3 Interference Margin

The interference margin is a factor in the link budget that is used to account for predicted noise rise. As part of the planning process an assessment of operatingload factor will indicate a noise rise. The interference margin should be set such thatthe link budget is valid for the required noise rise. However, in setting interferencemargin, hence link budget, the cell size is determined. This in turn will affect thepredicted load factor, leading to a reassessment. Thus an iterative process isrequired to arrive at suitable parameters for system planning and simulations.





OfferedTraffic

LoadFactor

NoiseRise

RadioParameters

InterferenceMargin

LinkBudget

Coverage

Figure 6

Setting Interference Margin

MB2005/S6/v6.2





The total load factor for a cell is simply the sum of all the individual load factors (L j)

for all UEs which have influence in a cell. A typical way to find this is to calculate L j

for all UEs in a single cell and then allow a weighting for neighbour cells.

3.1 Individual UL Load Factor

Refer to Figure 7.

3 CALCULATION OF LOAD FACTOR





The load factor for an individual UE (L j) is the ratio of wanted signal power (P j) againsttotal interference power (Itotal

) for that UE.

P j

Itotal

L j =

P j is a function of required Eb/No, processing gain, activity factor (ν

i) and the ratio

signal power to total power in the channel. Starting from an expression for Eb/No

for user j, (Eb/No) j:

where:

(Eb/No) j = (Processing gain)

j

(Signal power) j

Total receive power

excluding that of user j

(Eb/No) j =

W P j

ν j R

j Itotal

– P j

Solving this for P j gives:

W is the chip rate

R j is the bit rate for user j.

P j =

1

WItotal

(Eb/No) j . R

j . ν

j

1+

1

W

(Eb/No) j . R

j . ν

j

1+

Substituting for P j in the expression for L

j gives:

L j =

Figure 7

Individual UL Load Factor

MB2005/S6/v6.2






3.2 UL Cell Load Factor (ηUL)

The load factor for the cell (ηUL) is the sum of all the individual load factors (L j) of theUEs in the cell. It is then necessary to add a weighting for UEs in neighbour cells.This can be expressed as:

neighbour cell weightingi=

neighbour cell interference

serving cell interference

The load factor for a cell serving N users can be expressed as:

substituting for L j

( )

=

+= ∑N

j

i

1

L jUL1η

( )

( )=+

+= ∑N

j

i

11

1

j j

j

UL

νR /NE

W1

ob

η





( )

( )=+

+=

∑

N

j

i

11

1

j j j

UL

νR /NE

W1

ob

η

ULη = UL load factor

= neighbour cell interference factor

= an individual UE

= number of UEs in the cell

= chip rate

= energy per bit

= noise spectral density

= bit rate for UE j

= activity factor for UE jν j

R j

No

Eb

W

N

j

i

Figure 8

UL Load Factor





3.3 DL Load Factor (ηDL)

A similar process can be used to arrive at an expression for DL load factor. However,there are two important differences. Firstly, the UL has multiple transmit sources andone receiver, whereas the DL has one (main) transmitter with secondary interferencesources and receivers in multiple locations. The result is that the effect of neighbour cell interference must be considered independently for each UE, i.e. the factor ibecomes i j.

Secondly a new factor, α j, is introduced to account for DL orthogonal codeperformance in a multipath channel. In theory this should be independently set for each UE, but in practice it may be set for the cell and based on its environment.Typically this may lie between 0.4 and 0.8.

( )=+

=∑N

j

+ i j

11

1

j j

j

DL

νR /NE

W(( ) )−α j 1

ob

η





( )=

+=∑

N

j

+ i j

11

1

j j j

DL

νR /NE

W(( ) )−α j1

ob

η

DLη = DL load factor

= an individual UE

= activity factor for UE jν j

= orthogonality factorα j

= bit rate for UE jR j

= noise spectral densityNo

= energy per bitEb

= chip rateW

= number of UEs in the cellN

j

= neighbour cell interference factori j

Figure 9

DL Load Factor





3.4 Load Factor and Noise Rise

The load factors (η) in either the UL or DL directions are related to noise rise in thefollowing way:

Noise rise =1

1 – η

Noise rise (dB) = –10 log10 (1 – η)

An important consequence of this is that as the load factor approaches unity, the

noise rise tends to infinity. It can be seen that attempts to dimension a system withvery high load factors will result in the requirement for an impossibly largeinterference margin. Since such a margin would be impractical, the resulting systemplan would give very poor coverage.





Load Factor (η)

NoiseRise

1

1

Figure 10

Noise Rise and Load Factor





4.1 Introduction

The key radio parameters in a UMTS link budget are as they would be for a second-generation system. Thus transmit and receive powers, antenna gains, feeder losses,equipment noise figures and fade margins are still relevant. The new factors for UMTS are processing gain and interference margin.

Another change for UMTS is the need to perform multiple link budgets reflecting therange of different services that may need to be supported.

4.2 UL 12.2 kbit/s Speech

Figure 11 shows a possible link budget for the Adaptive Multi-Rate (AMR) voiceservice. The margins allowed are suitable for an in-car user travelling at up to120 km/h.

The interference margin of 3 dB relates to expected noise rise.

The processing gain is: 10 log3.84 x 106

= 25 dB12.2 x 103

The log-normal fade margin provides the required probability of coverage.

4 LINK BUDGET EXAMPLES





Mobile (TX)

Maximum Transmit Power

Antenna Gain

Body Loss

EIRP

Thermal Noise Density

Receiver Noise Figure

Receiver Noise Power over 4.8 MHz

Interference Margin

Effective Noise and Interference

Processing Gain

Required Eb/No

Receiver Sensitivity

Antenna Gain

Feeder Loss

Fast Fade Margin

Log Normal Fade Margin

Soft Handover Gain

In-Car Loss

dBm

dBi

dB

dBm

dBm/Hz

dB

dBm

dB

dBm

dB

dB

dBm

dBi

dB

dB

dB

dB

dB

dB

21

0

3

18

– 174

5

– 102.2

3

– 99.2

25

5

– 119.2

18

2

0

7.3

3

140.9

8

Node B (RX)

Maximum Path Loss

A

B

C

D = A –

C

G = E + F + 10 log 4.8 x 106

H

I = G + H

J

E

F

M

N

O

P

Q

R

S = D + M – N – O – P + Q – R – L

K

L = I – J + K

Figure 11

UL 12.2 kbit/s Speech





Mobile (TX)


Antenna Gain

Body Loss

EIRP




Interference Margin


Processing Gain

Required Eb/No


Antenna Gain

Feeder Loss

Fast Fade Margin


Soft Handover Gain

Indoor Loss

dBm

dBi

dB

dBm

dBm/Hz

dB

dBm

dB

dBm

dB

dB

dBm

dBi

dB

dB

dB

dB

dB

dB

24

2

0

26

– 174

5

– 102.2

3

– 99.2

14.3

1.5

– 112

18

2

4

4.2

2

132.8

15

A

B

C

D = A –

C

E

F

G = E + F + 10 log 4.8 x 106

H

I = G + H

J

K

L = I – J + K

M

N

O

P

Q

S = D + M – N – O – P + Q – R – L

R

Node B (RX)

Maximum Path Loss

Figure 12

UL 144 kbit/s Data





4.4 384 kbit/s Data

This budget assumes a low-mobility user in an urban outdoor environment. Softhandover is not supported.

Once again, the 2 dB antenna gain and absence of body loss suggest a PC card or stand-alone data terminal.

The processing gain is 10 log3.84 x 106

= 10 dB3.84 x 103





Mobile (TX)


Antenna Gain

Body Loss

EIRP




Interference Margin


Processing Gain

Required Eb/No


Antenna Gain

Feeder Loss

Fast Fade Margin


Soft Handover Gain

Indoor Loss

dBm

dBi

dB

dBm

dBm/Hz

dB

dBm

dB

dBm

dB

dB

dBm

dBi

dB

dB

dB

dB

dB

dB

A

B

C

D = A + B

E

F

G = E + F + 10 log 4.8 x 106

H

I = G + H

J

K

L = I – J + K

M

N

O

P

Q

R

S = D + M – N – O – P + Q – R – L

24

2

0

26

– 174

5

– 102.2

3

– 99.2

10

1

– 108.2

18

2

4

7.3

0

138.9

0

Node B (RX)

Maximum Path Loss

Figure 13

UL 384 kbit/s Data




4.5 Translating Pathloss to Range

Pathloss can be translated to range using an appropriate pathloss model. As yet, nopathloss model has been formally identified for UMTS but the COST-231 Hata model(originally developed for GSM1800/1900) is often used.

For a base station antenna height of 15 m and operating frequency of 2000 MHz,these models can be simplified to:

Pathloss (Metropolitan Area) = 144.95 + 37.2 log d

Pathloss (Urban Area) = 141.95 + 37.2 log d

Pathloss (Suburban Area) = 129.68 + 37.2 log d

Pathloss (Quasi-open Area) = 114.44 + 37.2 log d

Pathloss (Open Area) = 109.44 + 37.2 log d

in each case, d = range in km.

For example, for a 12.2 kbit/s speech service in a metropolitan area the range can beestimated as follows:

Pathloss (Metropolitan Area) = 144.95 + 37.2 log d

140.9 = 144.95 + 37.2 log d

37.2 log d = 140.9 – 144.95

log d =140.9 – 144.95

37.2

d = antilog

140.9 – 144.95

37.2

d = 0.778 km


( )




12.2 kbit/s

high mobility

Open

Area

Quasi-open

Area

Surburban

Area

Urban

Area

Metropolitan

Area

144 kbit/sindoor

384 kbit/s

outdoor,

low mobility

7 km

4.25 km

6.19 km

5.14 km

3.12 km

4.54 km

2 km

1.2 km

1.77 km

940 m

570 m

830 m

780 m

470 m

690 m

Figure 14

Estimated Ranges

MB2005/S6/v6.2





5.1 Soft Handover Regions

The soft handover region represents the area in which a UE would be involved ineither a soft or a softer handover. It is the responsibility of the planner to ensureappropriate handover parameter setting for optimal soft handover regions. It issuggested that an ideal figure for soft handover region would be between 30% and40% of coverage area. If the soft handover region is too large it will become anexcessive burden on system capacity. If the soft handover region is too small it mayaffect quality and, in turn, coverage. However, it is important to bear in mind theeffects of mixed traffic types and cell breathing.

5.1.1 Mixed Traffic in Soft Handover

Different traffic types will have differing coverage footprints for any given cell. Thus,even in static traffic load conditions, there will be a number of different soft handover regions for different traffic types. If the planner optimizes soft handover region for one particular traffic type to the exclusion of all others, the resulting soft handover regions will be non-optimal for other traffic types. Setting of parameters will need tobe a compromise weighted towards key traffic types. In addition, different sets of parameters may be applied to UEs in different traffic states.

5 HANDOVER REGIONS AND CELL BREATHING





Soft handover region

for voice

Soft handover regionfor high-rate data

Figure 15

Soft Handover Regions

MB2005/S6/v6.2





5.2 Consideration of Cell Breathing

As cell capacity increases, the coverage footprint of the cell will shrink. If this is nottaken into account when setting coverage overlap between cells, the cell breathingeffect could result in coverage holes at periods of high traffic demand. This is mostlikely to occur in high-priority coverage areas since these will be the areas most likelyto present high traffic demand.

Again, a compromise must be found between the general need to control softhandover regions and the need to prevent the occurrence of coverage holes. Asimple way to achieve this is to ensure larger overlap between adjacent cell cover areas. At times this will mean the soft handover regions could be very large, but thiswill only occur when traffic load is light. At such times the inefficiency resulting fromlarge soft handover regions is tolerable. When traffic load increases, the effect of cellbreathing will reduce cell overlap and increase capacity efficiency.





SECTION 7

UMTS NETWORK PLANNING

i





1 The UMTS Radio Planning Process 7.11.1 Introduction 7.1

2 Coverage Requirements 7.32.1 Coverage Scenarios 7.5

3 Capacity Requirements 7.73.1 Capacity Issues 7.9

4 QoS Requirements 7.134.1 Call Set-up Quality 7.154.2 Call Quality 7.17

5 Planning Constraints 7.195.1 Spectrum Availability 7.195.2 Emission Limits 7.195.3 Site Locations 7.19

5.4 Antennas 7.195.5 Radio Link Budget 7.215.6 Costs 7.21

6 Forming the Overall Radio Network Plan 7.23

7 Design Process in Detail 7.257.1 Monte Carlo Simulation 7.257.2 Simulation Process 7.27

8 Border Regions 7.298.1 Border Region Problem 7.298.2 Border Strategies 7.31


Annex:Cell Dimensioning for Full and Concentric Coverage Scenarios 7.36

SECTION CONTENTS

iii






• state the key factors required as inputs to the UMTS planning process

• explain the cyclical nature of UMTS planning

• describe the link between planning constraints and the system architecture

• discuss QoS and coverage target-setting for application to UMTS systems

• discuss the importance of usage patterns for UMTS users and services

• explain the significance and derivation of traffic type and load distribution

• relate coverage requirements, QoS and traffic within the planning loop

• outline the consideration for UMTS system dimensioning

• relate traffic, coverage and QoS requirements along with UL and DL power

budgets to derive coverage estimates in a UMTS system

• consider how coverage may be described for a UMTS system

• characterize considerations for control of coverage and coordination of

handovers in border regions

OBJECTIVES

v





1.1 Introduction

The UMTS radio planning process can be divided into three broad areas comprisingInput Requirements, Dimensioning and Output Results.

The Input Requirements will detail coverage requirements in terms of percentage of population or geographical area, the choice of macro, micro, pico or hierarchical cellstructures; capacity requirements based on the types of traffic and services withsubscriber growth information; QoS detailing area location probability, blockingprobability and service availability.

The Dimensioning deals with the capacity and coverage calculations and radionetwork dimensioning and will take into account a number of constraints that may beforced upon the planning process.

The Output Results will give an operator the basic facts to begin building a UMTSradio network in terms of the number of sites, locations, configurations, cell-specificparameters, number of RNCs, capacity and coverage analysis and QoS analysis.

For an existing GSM operator existing sites are likely to be used for UMTS. This maynot always be an ideal solution, but offers considerable cost savings as well asminimizing the site acquisition process. Data from the existing GSM network can be

used, including traffic density information which may identify traffic hot spots. GSMmay be used to extend coverage in outlying districts leaving UMTS to target high-bit-rate services in areas where they are needed. However, co-siting GSM with UMTSmay constrain the network plan.

A new operator will have the advantage of starting with a clean slate but will bedisadvantaged because rollout of a new network will include radio network planning,transmission planning, site acquisition, CN planning, construction work,commissioning and integration. It may be possible for a new entrant to use theservices of third parties for such tasks as site acquisition.

1 THE UMTS RADIO PLANNING PROCESS






Input

Requirements coverage

capacity

QoS

site selection

number of sites

configuration of

sitescell-specific

parameters

number of RNCs

capacity and

coverage analysis

QoS analysis

Dimensioning

Constraints

Output

Figure 1

UMTS Radio Planning Process




An operator may aim to provide 99% coverage fo r a populated area wh ile

maximizing geographical coverage. However, a 3G licence may dictate that only80% of the population is covered within five years of launch. Even 80% coveragemay not be necessary in the first years of operation, so an operator may plan tolaunch with 50% coverage. So, starting in the areas of major population an operator may roll out a network in three stages: 50%, 80% and finally 99%.

An existing GSM operator will already have potential subscriber density informationallowing coverage planning to be focused on areas of existing subscriber density. Anew entrant may not have that luxury, and will therefore have to rely on populationdensity information and potential market penetration figures to identify key areas of radio coverage.

Figure 2a shows the relationship between percentage population and percentagegeographical area. 50% of the population is likely to be located in 10% of thelandmass. To provide 80% coverage, only 30% of the land mass needs radiocoverage. 99% coverage equates to 84% of the landmass.

Using morphology distribution information as illustrated in Figure 2b, it is possible toidentify what percentage of landmass is covered by different clutter types such asdense urban, urban, commercial/industrial, suburban, forest and open. Theseproportions will aid in estimating the number of sites.

This type of information is also available for radio planning tools in the form of clutter data. Such data overlaid onto terrain height data will quickly allow potential sites tobe located.

When planning coverage using a radio planning tool, information will be requiredconcerning power levels in different environments; dense urban, suburban, etc. Thepower levels chosen will depend upon the service being planned for and the pathloss and penetration losses that can be expected.

With this information the planning tool can then statistically analyze and display

whether the target signal level has been achieved.

2 COVERAGE REQUIREMENTS





2.1 Coverage Scenarios

Design philosophy for CDMA can be based on two scenarios for coverage.

2.1.1 Full Coverage Scenario

In this case it is assumed that the aim is to provide the same coverage for allservices within a given target area. This implies that services using higher bit ratesmust operate at higher power because of their lower spreading factor.

2.1.2 Concentric Coverage Scenario

This scenario assumes only one service is offered across the whole cell area (ingeneral the lowest data rate service), whereas the remaining services are onlyoffered across a reduced area nearer to the base station.

It can be assumed that the area of the service with the lowest data rate correspondsto the cell area. The coverage radii of all other services, with higher data rates, aresmaller. This results in a series of concentric service areas. Potential users of thehigher-data-rate service will not be served in the outer zones of the cell.

Since the coverage is not homogeneous for all services throughout the system, user distribution has to be determined for each service. Mobile transmit power is thenassumed to be set to maximum for each service.





Full CoverageScenario

Concentric Coverage

Scenario

Range forlowest datarate service

Range forall services

Highdatarate

service

Mediumdatarate

service

Figure 3

Coverage Scenarios

MB2005/S7/v6.2





Capacity and coverage are strongly interlinked and cannot be planned separately as

with 2G networks. What will be required is a good long term plan from the start,which means predicting traffic levels five years hence.

It is difficult to say what the uptake of 3G services will be, or what services maybecome available, but it may be possible to predict the potential number of subscribers from a number of growth forecast assumptions.

Figure 4 illustrates subscriber growth over a 14-year period for 2G networkssupporting speech only and 3G networks supporting a mix of speech and data.

The table assumes that 3G services are launched in Year 3. After that date therewould be a steady decline in the number of subscribers using voice only services on2G networks. After launch of 3G voice and data services it is anticipated there will bean initial surge in the number of subscribers but after 5 years this will level out at asteady growth.

The figures are not representative of any particular network but illustrate potentialsubscriber growth.

3 CAPACITY REQUIREMENTS





Subscribers (millions)

Year

2G voice

3G voice + data

Total

Year 1

0.75

0

0.75

Year 2

1.0

0

1.0

Year 3

1.209

0.3

1.2

Year 4

0.6

0.7

1.3

Year 5

0.4

1.0

1.4

Year 6

0.3

1.2

1.5

Year 7

0.2

1.4

1.6

Year

2G voice

3G voice + data

Total

Year 8

0.15

1.5

1.65

Year 9

0.1

1.6

1.7

Year 10

0.05

1.7

1.75

Year 11

0.05

1.75

1.8

Year 12

0

1.75

1.75

Year 13

0

1.8

1.8

Year 14

0

1.85

1.85

Figure 4

Subscriber Growth

MB2005/S7/v6.2





3.1 Capacity Issues

In order to quantify capacity requirements it is important to identify key demographicsand usage patterns.

3.1.1 Demographics

Accurate demographic information is critical to 3G planning. Many of the advancedservices to be offered are targeted on the basis of lifestyle. This means simple dataon population density is insufficient on its own, it must include information on activity:

• Where do people spend their leisure?

• Where do people travel?

• Where do people work?

• Where do people live?





3.1.2 Usage Patterns

The way subscribers will use their UMTS terminals can only be guessed at today.Operators will almost certainly target one or more market segments. Their understanding of their subscribers’ usage patterns will be essential, not only for maintenance of the network, but also during the network design process.

Usage patterns can be defined in terms of:

UsageHigh data/high voiceHigh data/low voiceLow data/high voiceLow data/low voice

TimeCall durationsTime of usage

LocationHigh-riseDense city

TownResidentialJourneys

MobilityHigh mobilityLow mobilityFixed line replacement

From these categorizations, it is possible to build up standard usage tables to helpplan radio network capacity.





usage

time

location

mobility

Figure 6

Usage Patterns

MB2005/S7/v6.2





QoS cannot be treated in isolation because it is closely interlinked with coverage and

capacity. With a UMTS network it will no longer be a case of ‘Is the coverage goodenough in this location?’ but of ‘Is the quality good enough?’. But coverage will havea huge impact on quality. It may be desirable to identify location probabilities indifferent environments for the various types of service to be supported. See Figure 7.

The UMTS QoS guidelines offer the operator the ability to set up a wide variety of QoS levels. The levels are set by parameter values, which are wide ranging.Because it is the end user that will perceive the quality of the network it is importantto identify factors affecting quality from the user’s point of view. These can bebroadly divided into Call Set-up Quality and Call Quality.

4 QoS REQUIREMENTS





Bearer Service Coverage Probabilities

Area

DenseUrban

Urban

Industrial/

Commercial

Suburban

Open

64 kbit/s

CS

Indoor95%

Indoor

95%

Indoor

90%

Indoor

90%

In-car

90%

144 kbit/s

CS

Indoor95%

Indoor

95%

Indoor

95%

Indoor

90%

In-car

90%

64 kbit/s

PS

Indoor95%

Indoor

95%

Indoor

95%

Indoor

90%

In-car

90%

144 kbit/s

PS

Indoor95%

Indoor

95%

Indoor

95%

Indoor

90%

In-car

90%

384 kbit/s

PS

Indoor

95%

Indoor

95%

Indoor

90%

–

–

Figure 7

Coverage Probabilities

MB2005/S7/v6.2





4.1 Call Set-up Quality

This is what the user sees when attempting to set up a call in a UMTS network. Itcan be characterized by Accessibility, Call Blocking Probability and Call Set-upDelay.

4.1.1 Accessibility

This defines how easy it is for a user to access services on the network and will beinfluenced by:

• lack of coverage

• cell barring

• equipment failure

• signalling failure

In terms of network reliability, equipment failure rate should be less than 0.01%,which equates to less than ten seconds in any 24-hour period.

4.1.2 Call Blocking Probability

This is the probability of a call not being processed because of lack of resources onthe air interface or on a transmission line. For circuit-switched traffic the blockingprobability would typically be between 1–3%.

4.1.3 Call Set-up Delay

This is the end-to-end delay the user sees when accessing a service. This will

depend on what that service is. Figure 8 illustrates suggested call set-up times for avariety of UMTS services.





Call Type

Switched

Voice Call

Circuit-Switched

Video Call

Voice Call

IP Based

Real-Time

IP Streaming

InteractiveIP Web Browsing

Background

e.g. e-mail

Set-up Time

< 3s

< 3s

< 4s

< 10s

< 4s

N/A

Figure 8

Call Set-up Delay

MB2005/S7/v6.2






4.2 Call Quality

Call quality can be defined in terms of the user’s perception once the call isestablished. It can be categorized by:

• delay variation

• service interruption

• call drop probability

4.2.1 QoS Classes

The QoS will vary from service to service and need not be constant across the entirenetwork. It may therefore be useful for an operator to create a number of QoSprofiles as illustrated in Figure 9.

There are four broad classes of profile; conversational, streaming, interactive andbackground. An example of a conversational service would be speech or videoconferencing characterized by delays of less than one second. Streaming audio or video would have longer delays, but less than ten seconds. Interactive servicesinclude web browsing with delays of approximately one second. Background

services would include email and fax transmission where delays may exceed tenseconds. Profiles, however, would also specify other QoS parameters as illustratedin Figure 9.




5 PLANNING CONSTRAINTS


There are a number of factors that must be taken into account in the planning process

that are not adjustable. These parameters will constrain the network plan.

5.1 Spectrum Availability

Most UMTS licences are for three WCDMA carriers. In several countries, however,some operators have only been allocated two carriers. This places severe limitationson the design of the network architecture and may restrict capacity enhancement.

A further complication is spectrum usage from adjacent operators, who can causesignificant adjacent channel interference and thus create dead zones around anoperator’s base station.

5.2 Emission Limits

Most countries have their own standard emission limits for radio base stations. Theselimits are usually broken into public exposure limits and occupational limits.

In the United Kingdom, the National Radiological Protection Board (NRPB) hasdefined these limits. Throughout the European Union, new, tighter emission limits

defined by the International Committee for Non-Ionizing Radiation Protection(ICNIRP) are being introduced. Maximum EIRP is also limited by the license terms.

5.3 Site Locations

Site acquisition is becoming increasingly difficult with most prime sites already takenfor 2G installations. A 2G operator will be forced to use many of the existing sitesbecause of cost. These sites may not always be the most suitable for 3G services. Anew entrant may be forced into site sharing. Site location will therefore become asignificant input into the planning process rather than an output, as would be ideal.

5.4 Antennas

In the early stages of UMTS roll-out similar antennas to those used in 2G networkswill be utilized. Later, more capacity could be found by using beamforming or adaptiveantennas. There are increasingly more multiband antennas entering the market.These fall into one of two categories: wideband and dual/triband antennas. Suchantennas may be ideal for an operator co-siting GSM with UMTS because of their lowvisual impact, but may constrain the network plan.





5.5 Radio Link Budget

Different link budgets will be required for different traffic types. In a CDMA system,link budgets should be considered as dynamic rather than static.

5.6 Costs

Experience from many GSM networks would suggest that radio planning andeconomic planning are two separate functions that frequently clash. However, theymust be considered as two inputs with a common goal if a quality network is to bebuilt and to survive.





spectrum availability

emission limits

site locations

antennas

radio link budget

costs

Figure 10 (repeated)

Planning Constraints




6 FORMING THE OVERALL RADIO NETWORK PLAN


An eff ective overall plan requires coordinated consideration of coverage

requirements, traffic density and QoS targets. Regarding these as three input layers,they must be geographically referenced onto a map to allow each geographic area tobe associated with an architectural option suiting its needs. This will includecoverage requirements on a service-by-service basis, QoS requirements on aservice-by-service basis, spectrum usage and hierarchical layers.

The resulting architectural output forms the basis of the radio network plan.





Resulting NetworkMap/Architecture

QoS Targets

CoverageRequirements

Traffic DensityMapping (Raster)

Figure 11

Forming the Overall Radio Network Plan





A radio planning tool will be used to create a detailed plan on the UMTS network. The

flow chart in Figure 12 illustrates the basic steps.

To create a nominal cell plan the following information will be required:

• carriers – for interference evaluation

• services – to characterize bearers, e.g. packet or circuit switched, bit rates,required Eb/No values, QoS values

• terminals – detailing transmit power levels and fast power control parameters

• cells – locations in the area to be planned

• cell parameters – antenna height, gains, transmit power, codes, channels

• prediction model – macro cell model or micro cell model

• traffic – detailing terminal density

The nominal plan will allow the planner to see if there is adequate coverage in theareas of interest, for example that power levels are high enough to offer indoor coverage. Once satisfied with the nominal plan the next step is to simulate thebehaviour of a WCDMA network

7.1 Monte Carlo Simulation

In first- and second-generation networks coverage was determined by the link budgetwith margins added to take into account fading problems. Fast fading has a Rayleighdistribution and slow fading a log-normal distribution allowing fading margins to beadded to the link budget based upon statistical probabilities. This process was alsodone in early CDMA networks with gains added to the budget to account for softhandovers. However, this approach could not take into account intra- and inter-cellinterference. From an uplink point of view, this would be caused by mobiles in theserving cell and neighbouring cells. The extent of this interference would depend

upon the mobiles’ transmit powers and relative positions. Using statistics to derive amargin gives misleading results; what is required is some means of simulating therandom behaviour of mobiles. Monte Carlo algorithms can be used to simulate thisrandomness and provide a good balance between accuracy and practicality.

The mobile terminals are randomly distributed across the network and tested for probability of satisfactory service support. The terminals are redistributed randomlyand tested again. This process is repeated over and over again and accounts for therandom behaviour of the mobiles and radio environment. The snapshots are thenused to obtain measurement information giving an indication of the networkperformance. If the design criteria are met a final plan may be produced, otherwisethe initial plan needs to be reassessed.

7 DESIGN PROCESS IN DETAIL





Start

ProduceNominalCell Plan

Simulation

AdjustInputs

AnalyzeProblems

DesignCriteriaMet?

ProduceFinal Plan

Stop

No

Yes

Figure 12

Design Process Details




7.2 Simulation Process

Figure 13 details the Monte Carlo simulation process.

Set Initial ConditionsFirstly the mobile terminals are given a random priority level and will be tested inorder of priority. This is to ensure there is no biasing of the results. The terminals arethen placed in statistically determined positions before having their transmit powersinitialized. The power levels are set to fulfil the Eb/No requirement at the base stationtaking into account the base station sensitivity, data rate and the path loss. These willbe adjusted by considering the soft handover gain and activity factor.

The base station power is also initialized in a similar way to ensure all mobilesreceive an adequate signal level. By initializing the transmit powers in the cell, theinitial noise rise can be determined.

Creating a SnapshotThe first terminal in the list is tested for satisfactory performance. If it fails it is placedto outage and the next terminal is chosen. If it does not fail then its transmit power and that of the base station are modified, simulating power control. Potentialhandover cells are tested for handover. If a handover is possible, mobile and basestation powers are adjusted accordingly. Then the next terminal in the list is chosen.

Once all of the terminals have been tested the simulator returns to the first terminaland repeats the process until there is little change in the noise rise. The results arethen said to have converged.

Typically only a few iterations are needed before convergence is reached and theresults of the snapshot can be appended to the overall simulation.

RedistributionThe simulator will then redistribute the terminals to represent the random behaviour of terminals and the simulation is repeated. After many thousands of iterations, theresults of the simulation can be analyzed. Arrays can then be created quantifying the

probability of satisfactory performance.





Start

Randomly prioritize terminals

Place terminals in statistically

determined positions

Initialize cell and mobile

transmit powers

Assess Performancefor all user terminals

Haveresults stabilized

(converged)

Analyzeresults of simulation

No

No

Yes

Yes

Snapshot or drop

Redistributeuser terminals

Produce final plan

Analyzeproblems, implement

corrections andre-run simulation

Satisfactoryperformance

?

Figure 13

Monte Carlo Simulation

MB2005/S7/v6.2





8.1 Border Region Problem

In any cellular system where there has been international cooperation regardingspectrum allocation, there will be potential interference problems in border regions.This is because in these regions there will be neighbouring operators utilizing thesame spectrum allocation.

This is usually dealt with by common agreement for restricted spectrum use in theseregions, i.e. each operator agrees to use different subsets of their total spectrumallocation. This limited amount of cooperation between operators is sufficient toprevent serious problems. In principle a similar approach could be taken in a CDMA-based system, particularly for second-generation systems. However for third-generation systems, such as UMTS, the width of a radio channel results in limitedscope for such spectral cooperation. An operator may have only two or three FDDcarrier pairs, in some cases they may have only one. In addition, radio carrier centrefrequencies are not fully standardized. The result is that spectral cooperation maynot be sufficient to prevent serious interference problems in border regions.

8 BORDER REGIONS





International

Border

w r a y c a s t l e B r o w s e r I n t e r n e t S e a r c h : h t t p // w w w .


X X X x X X X X X



X X X X x x x x x X X X X X x X X X X X X X X

X X X X X X X



1

2

3 4

5

6 7

8

0 9

F1

F1

F1

F1

F1

F1

?

Figure 14

Border Regions

MB2005/S7/v6.2





8.2 Border Strategies

Although spectral cooperation may not be the whole solution, there is still somescope for its use. Where bordering operators have more than one radio carrier available and where their centre frequencies are the same, agreement could bereached on limited use. This would limit capacity in border regions, but in manycases these are not areas likely to present high traffic load and thus it may be anacceptable compromise. In some cases an operator may be able to absorb some of the loss in UMTS capacity by handing down to GSM/GPRS. However, there will beareas where a reduction in capacity will not be acceptable; in these areas a moreradical solution is required.

8.2.1 Inter-System Handover

If operators cannot tolerate the loss in capacity that would be associated withspectral cooperation, co-channels will need to be allocated in neighbouring, or inextreme cases, co-sited cells. These cells would be separated by code, but in order to meet the stringent requirements for power control, soft handover must beprovisioned between cells. Thus inter-system handover will be required betweenoperators in border regions.

The implications of this are considerable. Some are listed below:

• interconnection of CN

• interconnection of the UTRAN

• cooperation on handover parameter setting

• cooperation over service provision

• cooperation over UL code allocation

• cooperation over radio resource management

• cooperation over admission control





w r a y c a s t l e B r o w

s e r

I n te r n e t S e a r c h: h tt p/ /w

w w.

X X X X X X X X

x x x X X

X X X x X X X X

X

X X X X X X X X

x x x X X

X X X X X X X X

X X X X

X X X X x x x x x

X X X X

X x X X X X X

X X X

X X X X X X X

X X X

X X X

X X X

X X X

X X X

X X X

X X X

X X X

1 2

3

45

6

78

0

9

UE

External

Networks

Inter-operator

links

Inter-operator

links

CoreNetwork

Operator 1

CoreNetwork

Operator 2

UTRANOperator 1

UTRANOperator 2

Figure 15

Border Strategies

MB2005/S7/v6.2





1 In relation to an initial UMTS radio planning model, which of the following

statements is incorrect?

a Coordination of code usage is required at international boundariesb Cell breathing does not affect soft handoversc Link symmetry impacts on cell ranged Coverage is affected by the number of active users in a cell

2 In relation to a planning philosophy, which of the following statements is true?

a QoS is not constant everywhereb Coverage, quality and capacity are not necessarily relatedc A planning model is considered as having three inputs: requirements,

standard inputs and constraintsd QoS is constant everywhere

3 When determining a subscriber’s profile which of the following may bedisregarded?

a The user’s speed

b The user’s priorityc The user’s locationd The user’s antenna

4 When assessing possible usage patterns, which of the following can beignored?

a A user’s mobilityb The time a user is likely to require network servicesc A user’s location

d The user’s type of user equipment






ANNEX TO SECTION 7

CELL DIMENSIONING FOR FULL

AND

CONCENTRIC COVERAGE

SCENARIOS

7.36





DETAILED PROCESS


1 The first step of the dimensioning process consists of fixing the cell loading

assumption for the UL. The initial value of XUL is chosen arbitrarily according tothe planner’s experience.

2 Calculate the mobile transmit powers for the full coverage scenario and theconcentric coverage scenarios.

3 Calculate the pole (theoretical absolute maximum) capacities for both links.

4 When the cell loading has been fixed for the UL, the number (NkUL ) of mobiles

using service k within the UL of one cell, for all services (k), can be derived,which is only valid for the assumed UL loading factor.

5 The DL loading factor XDL has to be modified in order to achieve the samenumber of users for service k in UL and DL. Since the loading factor of one linkconstitutes a percentage of its pole capacity, the ratio between the loadingfactors x = XUL/XDL leading to an equal number of users in both links isreciprocal to the ratio of the corresponding pole capacities.

6 The assumption of a UL cell load therefore directly implies a DL cell load. Theratio x = XUL/XDL between the UL and the DL loading has to remain constant inorder to maintain the equilibrium on the links in terms of number of users for a

given service k in one cell.

7 Calculate the receiver sensitivity and the Maximum Allowable Path Loss(MAPL) for the UL for the different services. In the full coverage scenario, theMAPL is the same for all the services, because the mobile transmitting powershave been fixed to fulfil the condition of same service radii for all services,which are directly related to the MAPL by the propagation model. In theconcentric coverage scenario, there will be one MAPL for each service.

8 In order to balance UL and DL, the UL MAPL results are taken as input for theDL budget, adding a margin for the PCCPCH and the synchronization.

9 Fixing the MAPL derives the DL transmission power share Ti,k for eachconnection i of service k. Summing up all service power shares determines thetotal transmission power Ttotal. This sum of all output powers must not exceedthe maximum DL transmission power. If this occurs, the system is DL-limitedand the UL powers will have to be reduced accordingly.





Choose Dimensioning Scenario

Assume Uplinkcell load xUL

Cell Count Cell Count

Calculate MobileTransmit Power values

(includes ii0 calculation)

Calculate number of usersNk for all services k

andDerive downlink cell load

xDL

Calculate Pole CapacitiesNUL

pole and NDLpole

Fix MAPLULk=MAPLDL

k andmax(MAPLUL

k)+marg=MAPLDLcc

to derive the total transmitted

DL power Ttot

Calculate the MAPLUL

and the cell radius r

Calculate the cell radiusand determine cell area

Calculate number nk

area of users for eachservice k located within the cell area Calculate number nk

area of users for each service klocated within the corresponding service area

Calculate the service radii and determineservice areas per cell

Calculate MAPLULk and

service area radius rk foreach service k

reduce max.mobile

transmitpowers

keeping theratios

between allpower pairs

Assumesmallercell loadxUL andrestart

process

Assumehigher

cell loadxUL andrestart

process

Assumehigher

cell loadxUL andrestart

process

Assumesmallercell loadxUL andrestart

process

Calculate number of usersN

k

for all services kand

Derive downlink cell loadxDL

Calculate Pole CapacitiesNUL

pole and NDLpole

Calculate User Percentages P'kfor all services k (includes ii0

calculation)

Full Coverage Scenario Concentric Coverage Scenario

Fix MAPLUL=MAPLkDL for all

services k andMAPLDL+marg=MAPLDL

cc toderive the total transmitted

downlink power Ttot

NOTDL

tot<Tmax

?

TDLtot<Tmax

?

NO

YES YES

nkarea≈Nk

with

nkarea<Nk

for all k

nkarea≈Nk

with

nkarea<Nk

for all k

nkarea<<Nk

for all k

nkarea<<Nk

for all k

nkarea>Nk

for all k

nkarea>Nk

for all k

reduce max.mobiletransmitpowers

1

2 2

3 3

4

5

6

4

5

6

7 7

8 8

9 9

10 10

11

Figure A1

Design Process





10 Once the cell radius and the service radii are calculated, the absolute number

nkarea of simultaneous users in session for each service k located in the servicecoverage area of a cell can be derived from the users’ densities yk for allservices k.

11 This number is then compared to the number of users of each service in thecell area derived from pole capacity and cell load assumption. There are threeoutcomes, which will lead to different actions:

The number of simultaneous users of each service is approximately equal to thenumber of users of each service in the cell area derived from pole capacity and cellload assumptions.

The cell load assumptions for UL and DL correspond to the number of users within acell. The calculated cell radius can be used to perform the cell count, using standardcellular dimensioning procedures.

The number of simultaneous users of each service is much less than the number of users of each service in the cell area derived from pole capacity and cell loadassumptions.

The cell load assumptions have been too high, lower cell loads should be chosen,

maintaining the ratio x = XUL/XDL between the UL and DL cell load. The processhas to be performed again using the new cell loads.

The number of simultaneous users of each service is much greater than the number of users of each service in the cell area derived from pole capacity and cell loadassumptions.

The cell load assumptions are too low. Higher cell loads should be chosen,maintaining the ratio x = XUL/XDL between the UL and DL cell load.




SECTION 8

UMTS CELL STRUCTURES

i





1 UMTS Cell Structures 8.11.1 Introduction 8.11.2 Choice of Antenna 8.3

2 Radio Frequency (RF) Requirements 8.52.1 Introduction 8.5

2.2 Transmitter Noise/Spurious Emissions 8.72.3 Receiver Blocking 8.112.4 Intermodulation 8.15

3 Antenna System Options 8.253.1 Dual Band Sites 8.253.2 Triple Band Sites 8.29

4 Masthead Amplifiers (MHA) 8.31

5 Additional Cell Site Requirements for UMTS 8.33

6 RF Emission Limits and Safety 8.356.1 Introduction 8.356.2 ICNIRP Guidelines 8.356.3 Occupational and Public Exposure 8.356.4 Assessing Compliance with Reference Levels 8.376.5 Calculating Compliance 8.376.6 Exposure to Multiple Sources 8.39


SECTION CONTENTS

iii






• discuss UMTS/GSM co-siting issues

• compare and contrast antenna options

• describe principal RF requirements in terms of transmitter noise, spurious

emissions, receiver blocking and intermodulation

• suggest techniques which help to meet principal RF requirements

• describe the benefits of masthead amplifiers

• list additional cell site requirements for UMTS

• describe factors related to RF emission limits and safety

• calculate compliance with current guidelines issued by the International

Commission on Non-Ionizing Radiation Protection (ICNIRP)

OBJECTIVES

v





1.1 Introduction

In many cases, UMTS will be rolled out as an overlay to existing GSM networks.

Even in the case of a new operator, without the GSM spectrum this same assumptionapplies as most new entrants have the right to roam onto existing GSM networks, atleast for the first few years of operation. Site sharing, which already accounts for half of all GSM sites, will become standard for UMTS. Providers operating GSM systemscannot afford simply to add new sites for the new systems. The existing base has tobe reused.

In addition, a new sort of business within the mobile industry is emerging: tower management. It is in the interests of these companies to rent their sites to as manyoperators as possible, resulting in co-location of different communication systems.

In order to avoid serious mutual impacts between the co-located mobile systems,careful site engineering is required. A point of major importance is antennaengineering.

The demand for increasingly environmentally-friendly base sites is in directcontradiction with the need to maximize coverage area per site.

Four types of antenna need to be considered:

• single band: UMTS

• dual band: GSM 900 with UMTS

• dual band: GSM 1800 with UMTS

• triple band: GSM 900/GSM 1800 dual-band with UMTS

1 UMTS CELL STRUCTURES






UMTS overlaid onto GSM 900/1800

site sharing standard practice

rise in tower management companies

precise site engineering vital

antennas of critical importance

antenna options:

Bands:

GSM 900

(incl. E-GSM)

GSM 1800UMTS (TDD)

UMTS (FDD)

880–915

1710 – 17851900 – 1920

1920 – 1980

925 – 960

1805 – 18801900 – 1920

2110 – 2170

Uplink (MHz): Downlink (MHz):

single band UMTS

dual band GSM 900/UMTS

dual band GSM 1800/UMTStriple band/broadband GSM 900/1800/UMTS

new entrant has right to roam onto

existing GSM/GPRS networks

Figure 1

UMTS Cell Deployment




1.2 Choice of Antenna

An integrated, multiband antenna offers a relatively compact and low-cost solution.Low visual impact, together with ease of installation and relatively low ongoingmaintenance, make it a popular choice. Wind loading is also low.

However, such antennas confine the operator to using the same azimuth bearingand downtilt for both GSM and UMTS (within current antenna design limits).Separate upgrade and optimization cannot be carried out. These factors maypersuade operators to deploy separate antennas for UMTS, although this is bound tobe an unpopular choice for planning approval and so may be limited to specificcases.





Low visual impact

Low cost

Low wind loading

Low maintenance

Rapid fitting

Different azimuths

Different downtilts

Separately optimized

Separately upgraded

Consideration Type of UMTS Antenna

Separate Integrated/Multiband

(Broadband)

Current multiband antenna products provide the

same azimuth and tilt angles for all bands

Figure 2

UMTS Antenna Considerations

MB2005/S8/v6.2






2.1 Introduction

Co-location of systems may cause interference resulting in performancedegradation. In order to minimize this performance degradation to an acceptabledefined level, decoupling between the systems is required.

The most important interference mechanisms are:

Transmitter Noise/Spurious EmissionsThe transmitter noise floor or transmitter spurious emissions of system A within thereceive band of system B causes interference of system B’s receiver and vice versa.This could be avoided by increasing the stopband attenuation of system A’s antennanetwork in the transmit path for the receive band of system B, or by increasingdecoupling between the two systems, either the air decoupling or the decouplingprovided by the diplexer.

Receiver BlockingTransmit signals of system A are blocking the receiver of system B and vice versa.This could be avoided by increasing the stopband attenuation of system B’s antennanetwork in the receive path for transmit frequencies of system A, or by increasing thedecoupling between the two systems (air or diplexer decoupling).

Intermodulation ProductsIntermodulation products are interfering with the receivers of one or both systems.Significant intermodulation products are generated in non-linear devices (especiallymixers and amplifiers but also connectors), if two or more strong signals are applied.In our case the strong signals could be different transmit carriers either from system A or from system B or a combination of system A’s and B’s transmit carriers.

2 RADIO FREQUENCY (RF) REQUIREMENTS





transmitter noise and spurious emissions

receiver blocking

intermodulation products

Figure 3

Interference Mechanisms




2.2 Transmitter Noise/Spurious Emissions

2.2.1 Currently Specified Equipment

On sites where GSM and UMTS base stations are co-located, out-of-band spuriousemissions from one service must not be allowed to adversely affect the performanceof the other. This means that the strength of any spurious emission must be strictlycontrolled such that, with normal antenna decoupling (>30 dB), the spurious signal isreceived at a level well below the sensitivity threshold.

GSM 900/1800 equipment manufactured to the latest 3GPP specification must notproduce spurious emissions stronger than –96 dBm in the UMTS bands. This falls to –126 dBm (assuming 30 dB isolation between antennas) at the input to the Node B,well below the reference sensitivity of –121 dBm (12.2 kbit/s channel).

Similarly, any spurious output from a Node B must be limited to –98 dBm in GSMbands, producing a nominal –128 dBm at the GSM BTS input (reference sensitivity –104 dBm).

Given also that reference sensitivity is quoted for the RX input and not BTS/Node Binput, it can be seen that a 30 dB antenna isolation is perfectly adequate.





–96 dBm –126 dBm

–128 dBm –98 dBm

Antenna System

Isolation = 30 dB

UMTS

Node

B

GSM

BTS

GSM UMTS

Antenna System

Isolation = 30 dB

UMTS

Node

B

GSM

BTS

GSM UMTS

Figure 4

UMTS ↔GSM Spurious Emissions Limits

MB2005/S8/v6.2





2.2.2 Older GSM Equipment

However, co-locating UMTS Node B and older GSM 900 or especially GSM 1800equipment requires additional isolation measures. This is because older GSMequipment was not required to suppress out-of-band spurious emissions to the samedegree. In the UMTS band, it is required only that spurious emissions be kept to lessthan –30 dBm. Unless additional isolation is provided, the normal 30 dB of antennaisolation would result in a –60 dBm input to the Node B – with disastrousdesensitization resulting. The effective uplink range of the Node B would be severelyreduced.

It may be impractical to increase the isolation by antenna spacing alone, as a further 60 dB+ are required. One solution would be to include an in-line bandpass filter inthe output from the GSM BTS, with a steep roll-off characteristic. Such filters willintroduce a small (1–2 dB) additional downlink loss for the GSM cell, causing a smallreduction in range unless more BTS output power can be obtained from the TRXs(thus maintaining EIRP).

This assumes the filter is placed in the GSM transmit branch, i.e. between thecombiner and duplex filter (if fitted).





–30 dBm

older equipment Node B desensitized

–60 dBm

< –120 dBm

Node B not

desensitizedolder equipment

filter included only

in GSM transmit branch

> 60 dB

attenuation inUMTS band

Antenna System

Isolation = 30 dB

UMTS

Node

B

GSMBTS

GSM UMTS

–30 dBm

Antenna System

Isolation = 30 dB

UMTSNode

B

GSM

BTS

GSM UMTS

BandpassFilter

GSM UMTS

Figure 5

Increasing GSM ↔ UMTS Isolation

MB2005/S8/v6.2





2.3 Receiver Blocking

The blocking characteristic of a receiver is a measure of its ability to receive a signalon its assigned channel frequency in the presence of an unwanted interferer, whilestill maintaining its reference performance.

For co-located GSM 900 and UMTS installations, the Node B must be able to handle900 MHz signals up to 16 dBm and the BTS must be able to handle 2000 MHzsignals up to 8 dBm as a blocking limit.

Figure 6 illustrates that this requirement can be met with 30 dB antenna isolation.

Assumed link budgets:

UMTS Node B output 43.0 dBm

UMTS feeder and connector loss –3.0 dB

Assumed antenna decoupling –30.0 dB

GSM 900 feeder and connector loss –2.0 dB

UMTS input to GSM BTS 8.0 dBm (on limit)

GSM 900 BTS output 43.0 dBm


Assumed antenna decoupling –30.0 dB

UMTS feeder and connector loss –3.0

GSM 900 input to UMTS Node B 8.0 dBm (within limit)





Antenna SystemIsolation = 30 dB

43 dBm

Feeder/Connector

loss = 2 dB

Feeder/Connector

loss = 3 dB

UMTS

Node

B

GSM 900

BTS

8 dBm

Antenna SystemIsolation = 30 dB

43 dBm

Feeder/Connector

loss = 2 dB

Feeder/Connector

loss = 3 dB

UMTS

Node

B

GSM 900

BTS

8 dBm

Figure 6

GSM 900 ↔ UMTS Receiver Blocking

MB2005/S8/v6.2





For co-located GSM 1800 and UMTS installations, the blocking limit for the Node B

remains at 16 dBm but the blocking limit for the BTS is only required to be 0 dBm.

With 30 dB antenna isolation, GSM 1800 to UMTS blocking is unlikely to cause aproblem (as discussed for the GSM 900 to UMTS case). However, unless additionalfiltering is used to increase the out-of-band rejection for the GSM 1800 BTS input,there is likely to be a problem with blocking of the GSM 1800 receiver by signalsfrom the Node B.

Such a filter would be required to offer at least 8 dB attenuation of UMTS signals tomeet the blocking requirement of 0 dB for the GSM 1800 BTS.

Assumed link budget:

UMTS Node B output 43.0 dBm

UMTS feeder and connector loss –3.0 dB

Antenna isolation (decoupling) –30.0 dB


Bandpass filter attenuation (mix) –8.0 dB

UMTS input to GSM 1800 BTS 0 dBm (on limit)





filter included only

in GSM receive branch

> 8 dB

attenuation

in UMTS

band

Feeder/Connector

loss = 2 dB

Feeder/Connector

loss = 3 dB

< 0 dBm

GSM1800

UMTS

43 dBm

Antenna System

Isolation = 30 dB

UMTS

Node

B

GSM 1800

BTS

GSM UMTS

BandpassFilter

Figure 7

UMTS →GSM 1800 Receiver Blocking

MB2005/S8/v6.2






2.4 Intermodulation

Intermodulation, also called non-linear distortion, is generated in non-linear devices.The transfer characteristic of such devices, e.g. the V-I characteristic of asemiconductor diode or the output versus input power characteristic of an amplifier,is non-linear. At high power levels, even connectors exhibit non-linear effects.

At low input levels, the output signal is almost a linear function of the input signal.With increasing input level, the output level will be less than expected and eventuallybe limited to the saturated output power of the amplifier, e.g. due to power supplyconstraints.

The output signal of a non-linear device will not have the same shape as the inputsignal. Its frequency spectrum will have more components than the input signal. Thenew frequency components are either harmonics of the input frequencies or acombination of the input components (mixing). These new frequencies are calledintermodulation products.

Figure 8 shows an output spectrum with intermodulation products up to third order.The frequencies ƒ1 and ƒ2 are the original two tones at the input of the amplifier.

The level of a specific intermodulation component depends on the coefficients of the

power series contributing to this component, and the input power level applied to thenon-linear device. Typically, high-order intermodulation products have lower levelsthan low-order intermodulation products.

Because of the higher-order power series terms from which the intermodulationproducts will be generated, the levels of the intermodulation products will rise morethan linear with the input signal level, e.g. third-order terms will rise by 3 dB if theinput signal is raised by 1 dB. This is why intermodulation products are not a problemat low input power levels for a given device, but at high-input levels they may be. Theratio of wanted signal to intermodulation product decreases with increasing inputsignal level.

Problems can occur if intermodulation products (generated by a combination of transmitted signals in a non-linear medium) fall within the uplink band of a receiver,causing interference and even receiver blocking.

In general, the most troublesome are third-order subtractive (2ƒ2 – ƒ1 or 2ƒ1 – ƒ2)products.





50

45

40

35

30

25

– 20 – 15 – 10 – 5

Input power in dBm

0 5 10 15

O u t p u t p o w

e r i n d B m

ƒ 2 –

ƒ 1

2 ƒ

1 –

ƒ 2

ƒ

S(ƒ)

Two tone output spectrum with intermodulation products up to third order

Non-linear transfer characteristic of a power amplifier

ƒ 1 + ƒ

2

ƒ 1

ƒ 2

2 ƒ

2 –

ƒ 1

3 ƒ

1

2 ƒ

1 + ƒ

2

2 ƒ

2 + ƒ

1

3 ƒ

2

2 ƒ

1

2 ƒ

2

Figure 8

Intermodulation




A typical co-located system is illustrated in Figure 9. Separate GSM and UMTS

antennas or dual-band antennas using diplexers could be deployed. It is assumedthat TX/RX duplexing is being carried out in the Antenna Network Combiner (ANC)and that each system (GSM and UMTS) fulfils all intermodulation requirements in itsown right as a stand-alone system. This restricts problems to intermodulationbetween the two systems.

When co-located, problems can be caused if intermodulation of transmitted carriersproduces intermodulation products falling within an uplink channel of either system

e.g. GSM signal at 1850 MHz (ƒ1)UMTS signal at 1900 MHz (ƒ

2

)

2f 1 – ƒ2 = 1800 MHz2f 2 – ƒ1 = 1950 MHz

1800 MHz does not lie in any cellular band but may interfere with other services.However, 1950 MHz lies in the UMTS FDD uplink band and may cause severeinterference if the channel is used by a co-located Node B.

Intermodulation can occur in transmitters, receivers or other devices such asdiplexers and ANC equipment.





GSM BTS

Feeder Feeder

TX/RX TX/RX TX/RX TX/RX

Antennas Dual-band antenna

UMTSNode B

Air decoupling

Diplexer decoupling

GSM BTS UMTSNode B

Diplexer

Diplexer

ANC

TRX TRX

ANC

TRX TRX

ANC

TRX TRX

ANC

TRX TRX

Air decoupling (left side) and diplexer decoupling (right side) for co-located sites

Upper diplexer not required if the dual-band antenna has a single RF input(internal combining)*

*

Figure 9

Typical Co-located System

MB2005/S8/v6.2






2.4.1 Intermodulation in the Transmitters

A transmit signal of another TRX (either within the same BTS or from the co-locatedBTS) is reverse fed to the power amplifier of a TRX module. This happens becauseof finite decoupling within the ANC modules or finite air/diplexer decoupling. Thepower amplifier reacts with the generation of intermodulation products.

These intermodulation products could be coupled to a receiver within the same BTSor to a receiver within the co-located BTS. If they fall on a used receive channel, theywill degrade the receiver performance provided their level is not well below thereference sensitivity of the interfered receiver (signals 15 to 20 dB or more below thereference sensitivity will cause only a few tenths of a dB degradation).

A possible measure against this kind of intermodulation degradation could be carefulfrequency planning, so that no low-order intermodulation product falls inside a usedreceive channel. Another solution may be to increase the stopband attenuation of theinterfering system’s transmit filter in the receive band of the interfered system. Thisminimizes coupling of the generated intermodulation products to the receiver. If thestopband attenuation of the interfering system’s transmit filter is increased in thetransmit band of the co-located system, coupling between the transmitters isminimized, hence the generated intermodulation products in the transmitters will belower. Finally, it may be possible to increase the decoupling between the systems.

This also minimizes coupling between the transmitters.





Antenna System

ANC

TRX TRX

ANC

TRX TRX

F1F2

2F2 – F1

F1

2F1 – F

2

GSMBTS

UMTSNode B

orGSMBTS

UMTSNode B

or

Figure 10

Intermodulation in a Transmitter





2.4.2 Intermodulation in the Receivers

Transmit signals from the co-located system or a combination of own and co-locatedtransmit signals are fed to a receiver and generate intermodulation products in thereceiver which may fall on the used receive channel.

Possible measures against intermodulation generated in the receivers are carefulfrequency planning, so that no low order intermodulation product falls inside a usedreceive channel; increasing the receive filter’s stopband attenuation for theinterfering transmit frequencies, so that the levels of these transmit signals arelowered below the critical value; and increasing the decoupling between the systemsin order to lower the interfering signal from the co-located system.





Antenna System

ANC

TRX TRX

ANC

TRX TRX

F2

F2F

1

GSMBTS

UMTSNode B

orGSMBTS

UMTSNode B

or

2F2 – F

1

2F1 – F

2

Figure 11

Intermodulation in a Receiver





2.4.3 Intermodulation within the Diplexers or within the ANC Duplex Filters

Intermodulation in these modules is critical, as the generated intermodulationproducts fall inside the receive band and will follow the same path as the wantedreceive frequencies.There are no means of filtering the generated IM products.

Measures against intermodulation within the diplexers or within the ANC duplexfilters are careful frequency planning, so that no low-order intermodulation productfalls inside a used receive channel, and careful design of the diplexers and ANCmodules.

2.4.4 Intermodulation in Antenna Systems

Non-linear characteristics at any point in the antenna system can generateintermodulation products. Corroded elements or connections are a common sourceof such problems and it is especially important to guard against the increase of moisture with appropriate weather protection.





Antenna System

ANC

TRX TRX

ANC

TRX TRX

F1

F2

F1

GSMBTS

UMTSNode B

orGSMBTS

UMTSNode B

or

2F2 – F

1

2F1 – F

2

Figure 12

Intermodulation in the ANC




Co-located antenna systems can be composed of multiple, single-band antennas.

This offers maximum flexibility in engineering terms (different azimuths, tilts, heights,etc.) but is visually poor and offers higher wind loading, installation and cost. The useof multiband, integrated antennas (dual or triple band) reduces the number of physical antenna structures on the tower, mast or building.

Similarly, co-located antenna systems will tend to increase the antenna feeder count,possibly to six antennas per sector for a co-located GSM 900/1800/UMTS site. Thiscan be reduced using diplexers, but these increase system losses, which may resultin reduced coverage.

The design and planning of co-located systems must include these considerationsand trade-offs.

3.1 Dual Band Sites

These can be implemented using either multiple single-band antennas or by usingintegrated dual-band (or broadband) assemblies.

Figure 13 illustrates the use of single-band antennas with air decoupling. A horizontalseparation (typically at least 2λ) or vertical separation (typically at least 0.5λ)

ensures adequate isolation, especially critical for GSM 1800/UMTS operation.

3 ANTENNA SYSTEM OPTIONS





GSMBTS

GSM

GSM

UMTS

UMTS

GSM 1800 antenna

Feeder

UMTS antenna

Feeder

UMTSNode B

Air decoupling

dh

dv

Single-band antennasusing air decoupling

Horizontal and verticalseparation of antennasFront

elevation

Sideelevation

Figure 13

Dual-Band Site using Single-Band Antennas

MB2005/S8/v6.2





Figure 14 illustrates the use of dual-band antennas.

These can be used with or without diplexing, as shown. Consideration must be givento the trade-off between feeder count and the additional losses resulting from thediplexers.

Broadband antennas are available, covering GSM 900/1800/UMTS and GSM1800/UMTS. These reduce the feeder count and the need for some diplexing.

However, in all cases, isolation between GSM and UMTS services needs to bemaintained to avoid blocking and intermodulation problems.





GSMBTS

Dual-band antenna

GSMBTS

UMTSNode B

UMTSNode B

UMTSNode B

GSMBTS

Diplexer

Diplexer

Diplexer

Feeder

Feeder

Broadbandantenna

Diplexer and broadband antenna

Without Diplexer With Diplexer

Feeder Feeder

Dual-band antenna

Figure 14

Dual-Band Antenna and Broadband Antenna Options

MB2005/S8/v6.2





3.2 Triple Band Sites

The options for a co-located, triple-band site are:

• separate single-band antennas

• a mixture of single- and dual-band antennas

• a multiband or broadband antenna covering all bands required

Separate single-band antennas can be fed separately or via diplexing or triplexingarrangements, as shown in Figure 15. This could also be adopted for triple-band

antennas with separate input connections for each band. Another possibility, alreadyseen, is the use of a GSM 900/1800/UMTS antenna with triplexing.

Final choice of antenna system depends on a number of factors including theevolution path from 2G to 3G, the trade off between antenna count and the ability tooptimize each band separately and the trade off between feeder count and theadditional losses caused by diplexing or triplexing.






Feedersystem

Feeder

system

Antennasystem

BTSsystemsGSM 900 GSM 1800 UMTS

Triple-bandantenna

Diplexer

Triplexer

GSM 900 GSM 1800 UMTS

Diplexer

Diplexer Triplexer

GSM 900 GSM 1800 UMTS

Diplexer

Diplexer Triplexer

Diplexer

GSM 900

GSM 1800 UMTS

Triplexer application

Triple-bandantenna

Diplexer

Diplexer

GSM 900

GSM 1800 UMTS

GSM 1800/UMTS diplexing at triple-band site

Broadbandantenna

Possible triple-band or single-band antenna connections

* *

*

MB2005/S8/v6.2

Figure 15

Triple-Band Site Antenna Options




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

1800/1900 installations and helps to ensure a balanced cell where uplink range ismatched to downlink. In most cellular systems, the uplink tends to be the weaker of the two. This can be established by calculating the uplink and downlink power budgets and then choosing an LNA whose performance is just adequate to correctthe difference.

The best site for the LNA is as close to the antenna feedpoint as possible. The LNAwill require power for its operation and will also have internal switching to shuntdownlink power around the amplifier to the common antenna. The additionaldownlink loss may need adding to the downlink losses overall and could reduce therange slightly.

The LNA will also, in the case of CDMA, bring capacity benefits because it will lower the noise level at the input to the Node B, which is equivalent to lowering the overallinterference level.

4 MASTHEAD AMPLIFIERS (MHA)





UMTS

Node

B

NodeB

Feeder

Power

Antenna

LNA

D o w n l i n k

U p l i n k w i t h o u t LN A

MA P L = 1 3 5 d B ( e

. g. )

M AP L = 13 2 d B ( e .g . )

MAPL = MaximumAllowable

Path loss

SeveraldB

improvement

Backgroundnoise and interference

without LNA

UMTS Radio Channel (Bandwidth = 5 MHz)

LNA must make

up this diference

ƒc

Figure 16

Masthead Amplifier (MHA)

MB2005/S8/v6.2





To upgrade existing GSM/GPRS sites to include UMTS, consideration must be given

to physical space, transmission link capacity and availability of power.

More space will be required for the additional equipment. This will include one or more cabinets for the Node B radio equipment. To satisfy the requirement for ATM inthe UTRAN, equipment for either a switched or point-to-point ATM link must beaccommodated. Antenna diplexing equipment may need to be included. If the NodeB is microwave-linked to the RNC, this equipment will also require space. Additionalantennas will require space and cable trays may need upgrading for the extrafeeders. In some cases, towers or masts may need upgrading.

Transmission link requirements are considerable, given the high user data ratesoffered by UMTS. The equivalent of an E1 (2.048 Mbit/s) link will be required for each TRX at a Node B site, as a minimum requirement. For highly-equippedsectored sites, for example 2 + 2 + 2, the requirement would be equivalent to 6 x E1links.

Main and backup power supplies at the co-located site must also be considered for upgrade. Backup power is often included in the form of batteries within equipmentcabinets.

5 ADDITIONAL CELL SITE REQUIREMENTS FOR UMTS





Additional Space:AntennasEquipment cabinets for Node B

ATM equipmentTransmission equipment

Transmission Link Capacity:E1 link per TRX2 + 2 + 2 site requires 6 x E1 links

Power Supplies:Possible upgrade of mains supply

Backup power may be within equipment

Figure 17

Additional Cell Site Requirements for UMTS

MB2005/S8/v6.2






6 RF EMISSION LIMITS AND SAFETY

6.1 Introduction

The level of RF emission from a site is governed by two factors: licence conditionsand safety considerations. The operator’s licence will limit the EIRP per RF channel,e.g. 53 dBm. In some countries, the operator may also be legally obliged todemonstrate that emissions from the site comply with guidelines for limiting humanexposure to the time-varying Electromagnetic Fields (EMF) emitted from theantennas. In the UK, there is currently no such legal obligation, but in practice localauthorities expect any installation to comply with current recommendations. The UKNational Radiological Protection Board (NRPB) published a statement in 1993(NRPB Volume 4, number 5) detailing recommended limits. However, following theStewart report in 2000 regarding mobile phone safety, the NRPB agreed to adopt therecommendations of the ICNIRP.

6.2 ICNIRP Guidelines

At the frequencies used by cellular systems, the guidelines define basic restrictionson exposure, based on Specific Absorption Rate (SAR) in Watts per kilogram (Wkg-1)of body tissue. These can be equated to reference levels, for the purpose of compliance testing, in terms of E-field strength in volts per metre (Vm -1), H-fieldstrength in Amperes per metre (Am-1), magnetic flux density (µT) and plane wave

power density (s) in Watts per square metre (Wm-2). If measurement indicates thatlevels are below the reference level, then the basic restrictions are being met. If measured levels exceed the reference level, it does not automatically follow that thebasic restrictions are being exceeded, and further investigation is necessary.

6.3 Occupational and Public Exposure

The basic restrictions and reference levels for exposure of the general public are fivetimes lower (in terms of power density) than the levels for exposure of groupsexposed as part of their occupation. This is based on factors such as the potentially

poorer health of the general public (e.g. older age profile) and the vulnerability of babies and children. Also, occupational groups are more aware of health and safetyprecautions to be employed.

Figure 18 shows how these values relate to GSM 900, GSM 1800 and UMTS bands.



8 . 3 6

©


MB 2 0 0 5 / S 8 / v 6 .2

ICNIRP Reference Levels for 400 MHz to 300 GHz

ƒ measured in MHzaveraged over any six minute periodunperturbed rms values.

averaged over any six minute periodunperturbed rms values

400 – 2000 MHz E = 3ƒ½ Vm – 1S = ƒ /40 Wm – 2

E = 1.375ƒ½ Vm – 1S =ƒ /200 Wm – 2

Occupational Exposure General Public Exposure

OccupationalExposure

PublicExposure

ƒ MHz

E Vm – 1

S Wm – 2

E Vm – 1

S Wm – 2

880

Uplink Downlink Uplink Downlink Upli

P-GSM + E-GSM 900 GSM(DCS)1800

89

22

40.8

4.4

90.8

915

22.9

41.6

4.6

91.2

925

23.1

41.8

4.6

93

960

24

42.6

4.8

124.1

1710

42.8

56.9

8.6

126.7

1785

44.6

58.1

8.9

127.5

1805

45.1

58.4

9

130.1

1880

47

59.6

9.4

131.5

1920

48

60.3

9.6

E = 137 Vm – 1

S = 50 Wm – 2

E = 61 Vm – 1

S = 10 Wm – 22000 – 300 GHz

F i g

ur e1 8

I C NI RP

R ef

er en c eL ev el s





6.4 Assessing Compliance with Reference Levels

At the planning stage, compliance can be verified by calculation. Established sitescan be verified by direct measurement of the E field or power density usingcalibrated equipment.

6.5 Calculating Compliance

For a single TRX, and assuming the worst case of continuous radiation (e.g. for aGSM BCCH TRX or UMTS FDD TRX), then from the EIRP it is possible to calculateE field strengths and power densities along the bearing of strongest radiation at adistance d from:

S =EIRP

Wm –2

4πd2

E = 120πS Vm –1

where:

EIRP is in Watts

d is in metresE is in Volts per metre (Vm –1)S is in Watts per metre (Wm –2)

If the EIRP is in dBm, then:

EIRP (Watts) =antilog (dBm/10)

1000

Also, at a range of d metres from the antenna:

E =30 EIRP

Vm –1

d2

and for a given E:

d =30 EIRP

Wm –2

E2





GSM 900 cell sited in a public place

1 TRX fitted, assigned to ARFCN 3 (FDL = 935.6 MHz)

EIRP = 53 dBm

ICNIRP Reference level for Public Exposure

at 935.6 MHz is given by E = 1.375 ƒ½

and s = ƒ /200

E = 1.375 x 935.6½ = 42.1 Vm – 1

S = 935.6/200 = 4.7 Wm – 2

In Watts, the EIRP is:

The distance in metres where E = 42.1 Vm – 1

(the reference level) is:

At a distance of 5 m from the antenna:

Which is 37% of the reference level

Example

EIRP =

d =

= 200 Watts

= 1.84 metres

Averaged over any six-

minute period

antilog1000

53

10

30 x 200

42.12

E = = 15.5 Vm – 130 x 200

52

Figure 19

GSM 900 Example





6.6 Exposure to Multiple Sources

If an installation has multiple RF sources, for example a GSM BTS with multipleTRX, then a worst-case approach should be taken. This assumes the fields areadditive in their effects. For analysis, it should also be assumed that all TRX areactive at all times.

For relative simplicity, it is prudent to sum the powers of the individual transmissionsand base any exclusion zone dimensions on the reference levels for the lowestfrequency in use (because that will have the lowest reference level).

Figures 20–23 illustrate a number of examples, assuming siting in a public place:

• Figure 20 – GSM 900 BTS

• Figure 21 – GSM 1800 BTS

• Figure 22 – GSM 900 Micro BTS

• Figure 23 – UMTS FDD Node B





GSM 900 sector with 2 TRX and EIRP = 53 dBm

ƒ1 = 935.6 MHz ƒ

2 = 937.8 MHz,

Reference level for lowest frequency = 1.375 x 935.6½

There are two transmitters, so total power

= 2 x 200 W = 400 W

The distance at which the reference level of

42.1 Vm – 1

is met is:

For 3 TRX, total power = 3 x 200 W = 600 W

and:

For 4 TRX, total power = 800 W

and:

Example

EIRP in Watts =

d =

= 200 W

= 2.6 m

antilog

1000

53

10

30 x 400

42.12

d = = 3.2 m30 x 600

42.12

d = = 3.7 m30 x 800

42.12

= 42.1 Vm – 1

Figure 20

GSM 900 Multiple Source Example




8.41 © wray castle limited MB2005/S8/v6.2

Example

GSM 1800 sector with 1 TRX and EIRP = 53 dBm

ƒ = 1869.4 MHz

Reference level = 1.375 x 1869.4½ = 59.5 Vm – 1

The distance at which the reference level is met is:

For 2 TRX, total power = 400 W and:

EIRP in Watts =

d =

= 200 W

= 1.3 m

antilog

1000

5310

30 x 200

59.52

d = = 1.8 m30 x 400

59.52

For 3 TRX, total power = 600 W and:

d = = 2.3 m30 x 600

59.52

Figure 21

GSM 1800 Multiple Source Example





GSM 900 micro cell with 2 TRX and EIRP = 33 dBm

ƒ1 = 940.2 MHz, ƒ

2 = 950.4 MHz,

Reference level for lowest frequency = 1.375 x 940.2½

There are two TRX, so total output = 4 W


Example

EIRP in Watts =

d =

= 2 W

= 0.26 m

antilog

1000

33

10

30 x 4

42.22

= 42.2 Vm – 1

Figure 22

GSM 900 Micro Cell Example




8.43 © wray castle limited MB2005/S8/v6.2

Example

Reference level = 61 Vm – 1

UMTS FDD Node B with 1 TRX and EIRP = 47 dBm

ƒ = 2120 MHz


For an EIRP of 50 dBm (100 W), this is:

EIRP in Watts =

d =

= 50 W

= 0.64 m

antilog

1000

47

10

30 x 50

612

d = = 0.9 m30 x 100

612

For an EIRP of 53 dBm (200 W), it becomes:

d = = 1.27 m30 x 200

612

Figure 23

UMTS FDD Node B Example




1 Which of the following statements is incorrect?

a Site sharing is standard practiceb UMTS cells should not overlay GSM cellsc Antennas are of critical importanced Dual band GSM 1800/UMTS antennas may be used

2 GSM equipment manufactured to 3GPP specifications must not producespurious emissions in the UMTS band stronger than:

a –96 dBmb –121 dBmc –98 dBmd –126 dBm

3 The blocking limit for co-located GSM 1800 and UMTS installations at the NodeB is:

a 0 dBmb 30 dBm

c 8 dBmd 16 dBm

4 Which of the following statements is true?

a An LNA should be mounted at the RX inputb An LNA ensures the DL is greater than the ULc An LNA is only used in co-located sitesd An LNA can balance a cell

5 ICNIRP guidelines are based on measurements using the specific absorptionrate. This is measured in:

a W/kgb mW/kgc µW/kgd MW/kg





MB2005/Glossary G.1© wray castle limited

2.5G Generation 2.5

2G Second Generation3G Third Generation3GPP 3rd Generation Partnership Project

ACLR Adjacent Channel Leakage Ratio AI Acquisition Indicator AICH Acquisition Indicator Channel AMR Adaptive Multi-Rate ANC Antenna Network Combiner ANSI American National Standards Institute AP-AICH Access Preamble – Acquisition Indicator Channel ARIB Association of Radio Industries and Businesses AS Access Stratum ATM Asynchronous Transfer Mode

BCCH Broadcast Control ChannelBCH Broadcast ChannelBER Bit Error RateBTS Base Transceiver Station

CBD Central Business District

CCCH Common Control ChannelCD-CA-ICH Collision Detection/Channel Assignment Indicator ChannelCDMA Code Division Multiple AccessCN Core NetworkCPCH Common Packet ChannelCPICH Common Pilot ChannelCS Circuit SwitchedCSICH Status Indicator ChannelCTCH Common Traffic Channel

DCCH Dedicated Control Channel

DCH Dedicated ChannelDECT Digital Enhanced Cordless TelephonyDHO Diversity Handover DL DownlinkDPCCH Dedicated Physical Control ChannelDPCH Dedicated Physical ChannelDPDCH Dedicated Physical Data ChannelDSCH Downlink Shared ChannelDTCH Dedicated Traffic Channel




MB2005/GlossaryG.2 © wray castle limited

Eb/No Energy per bit divided by noise spectral density

EDGE Enhanced Data rates for Global EvolutionEIRP Effective Isotropic Radiated Power E-GSM Extended GSMEMF Electromagnetic FieldsETSI European Telecommunications Standards Institute

FACH Forward Access ChannelFDD Frequency Division DuplexFDMA Frequency Division Multiple Access

GoS Grade of ServiceGPRS General Packet Radio ServiceGSM Global System for Mobile communications

HSCSD High Speed Circuit Switched Data

I/Q In phase/QuadratureICNIRP International Committee for Non-Ionizing Radiation ProtectionIMT-2000 International Mobile Telecommunications 2000ISDN Integrated Services Digital NetworkITU International Telecommunication Union

ITU-R International Telecommunication Union – Radiocommunicationsector

LLC Logical Link ControlLNA Low Noise Amplifier

MAC Medium Access ControlMAPL Maximum Allowable Path LossMHA Masthead Amplifier MSC Mobile Switching CentreMUD Multi-User Detection

NAS Non-Access StratumNMT Nordic Mobile TelephoneNRPB National Radiological Protection Board

OSI Open Systems InterconnectOVSF Orthogonal Variable Spreading Factor




MB2005/Glossary G.3© wray castle limited

PCCH Paging Control Channel

P-CCPCH Primary Common Control Physical ChannelPCH Paging ChannelPCPCH Physical Common Packet ChannelPCS Personal Communications SystemPDSCH Physical Downlink Shared ChannelPI Paging Indicator PICH Paging Indicator ChannelPRACH Physical Random Access ChannelPS Packet SwitchedP-SCH Primary Synchronization ChannelPSTN Public Switched Telephone Network

QoS Quality of Service

RAB Radio Access BearersRACH Random Access ChannelRAT Radio Access TechnologyRF Radio FrequencyRLC Radio Link ControlRNC Radio Network Controller RNS Radio Network Subsystem

RRC Radio Resource ControlRX Receive

SAR Specific Absorption RateS-CCPCH Secondary Common Control Physical ChannelSCH Synchronization ChannelSGSN Serving GPRS Support NodeSIB System Information BlockSIR Signal to Interference RatioSMS Short Message ServiceSNR Signal to Noise Ratio

SS Supplementary ServicesS-SCH Secondary Synchronization Channel


cell planning for umts networks

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