umts rnp guideline ed01

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ED 01 RELEASED CONFIDENTIAL 23-Feb-2001

MCD UMTS_RNP_Guideline_ed01.doc 3DF 00902 UA10 VAZZA 2/2

REVIEW

Edition Date Review Report Identification

HISTORY Edition Date Reason of change

01 19.01.2001 Creation of document

01 23.01.2001 Draft 01

01 07.02.2001 Proposal 01

Short description of significant changes to previous edition:

Edition Changes

INTERNAL REFERENCED DOCUMENTS

Not applicable

FOR INTERNAL USE ONLY Not applicable

IDDL - ALCATEL-INTERNAL DOCUMENT DISTRIBUTION LISTPCS ISC Manager BR Operation Manager

Documentation Management Systems : DIAMS

EDDL - ALCATEL-EXTERNAL DOCUMENT DISTRIBUTION LIST

END OF ALCATEL INTERNAL PART OF THE DOCUMENT


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UMTS RADIO NETWORK PLANNING GUIDELINE

CONFIDENTIALGuideline

TABLE OF CONTENTS

REFERENCED DOCUMENTS..................................................................................................................... 6

RELATED DOCUMENTS............................................................................................................................. 6

PREFACE ........................................................................................................................................................ 6SCOPE.............................................................................................................................................................. 6

INTRODUCTION ........................................................................................................................................... 61 RNP P ROCESS DESCRIPTION ........................................................................................................................ 82 WCDMA F UNDAMENTALS AND UMTS A IR INTERFACE ........................................................................... 92.1 UMTS NETWORK ARCHITECTURE ............................................................................................................... 92.1.1 UE ( User Equipment) .............................................................................................................................. 92.1.2 UTRAN (UMTS Radio Access Network) .............................................................................................. 102.1.3 CN (Core network) ................................................................................................................................. 102.1.4 External networks................................................................................................................................... 102.1.5 Interfaces ................................................................................................................................................ 112.1.6 Logical roles of the RNC........................................................................................................................ 112.1.6.1 CRNC .................................................................................................................................................. 112.1.6.2 SRNC & DRNC................................................................................................................................... 112.1.7 Mapping between GSM and UMTS....................................................................................................... 122.2 S TANDARDS AND USED FREQUENCY SPECTRUM ........................................................................................ 122.3 M OBILE CLASSES ....................................................................................................................................... 142.4 B ROADBAND PROPAGATION CHANNEL AND WCDMA BASIC CONCEPT ................................................... 142.4.1 Multiple Access Techniques................................................................................................................... 142.4.2 Broadband signal and Coherence bandwidth.......................................................................................... 152.4.3 Multipath propagation and RAKE receiver ............................................................................................ 162.5 S PREADING , SCRAMBLING AND MODULATION .......................................................................................... 162.5.1 Spreading................................................................................................................................................ 162.5.2 Despreading ............................................................................................................................................ 172.5.3 Codes used.............................................................................................................................................. 182.5.3.1 Channelization codes........................................................................................................................... 182.5.3.2 Scrambling codes................................................................................................................................. 192.5.4 Example for scrambling code allocation: Cell Search Process............................................................... 212.5.5 Spreading, scrambling and modulation .................................................................................................. 212.5.5.1 Uplink part ........................................................................................................................................... 212.5.5.2 Downlink part ...................................................................................................................................... 222.6 U SER DETECTION MECHANISMS (QUICK OVERVIEW )................................................................................. 232.7 P OWER CONTROL IN UMTS FDD.............................................................................................................. 232.7.1 General Power Control in UMTS........................................................................................................... 23

2.7.1.1 Outer Loop Power Control .................................................................................................................. 24

01 010123 Draft 01 C. Brechtmann, PCS PCS/NPL/METHODSOA, UB, AG, MH, LSP, MG

ED DATE(YYMMDD)

CHANGE NOTE APPRAISAL AUTHORITY ORIGINATORS


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2.7.1.2 Inner Loop Power Control for dedicated channels .............................................................................. 242.7.1.3 Open Loop Power Control................................................................................................................... 262.7.1.4 Site selection diversity transmit power control.................................................................................... 262.8 HO TYPES & EVENTS ................................................................................................................................. 272.8.1 Hard handover ........................................................................................................................................ 272.8.2 Soft handover.......................................................................................................................................... 272.8.3 Softer handover....................................................................................................................................... 292.8.4 Power control in soft(er) handover ......................................................................................................... 292.8.4.1 Downlink PC in SHO .......................................................................................................................... 292.8.4.2 Uplink PC in SHO ............................................................................................................................... 302.8.5 Reporting events for Soft Handover and measurement reports .............................................................. 302.8.6 Filtering E C/N0 measures out of raw measures....................................................................................... 312.9 R ECEIVE & T RANSMIT DIVERSITY ............................................................................................................. 312.9.1 Receiver diversity mechanisms .............................................................................................................. 322.9.1.1 Uplink receiver diversity ..................................................................................................................... 322.9.1.2 Downlink receiver diversity ................................................................................................................ 322.9.2 Downlink Transmit diversity mechanisms ............................................................................................. 332.9.2.1 Open loop downlink transmit diversity ............................................................................................... 342.9.2.2 Closed loop downlink transmit diversity for DPCH transmission....................................................... 352.10 CODEC S SUPPORTED BY UTRAN .......................................................................................................... 352.10.1 Fixed Rate CODECs............................................................................................................................. 362.10.2 Adaptive Multi Rate CODECs ............................................................................................................. 363 C HANNEL T YPES AND R ADIO R ESOURCE M ANAGEMENT ........................................................................ 383.1 O VERVIEW ON CHANNEL TYPES AND NAMES ............................................................................................ 393.1.1 Physical channels.................................................................................................................................... 393.1.2 Transport channels.................................................................................................................................. 403.1.3 Logical channels..................................................................................................................................... 423.1.4 Mapping between different channel types .............................................................................................. 433.2 T HE PHYSICAL CHANNELS ......................................................................................................................... 433.2.1 The physical channels in Uplink............................................................................................................. 43

3.2.1.1 DPCH (DPDCH & DPCCH) in UL..................................................................................................... 433.2.1.2 PRACH................................................................................................................................................ 443.2.1.3 PCPCH................................................................................................................................................. 463.2.2 The physical channels in DL .................................................................................................................. 473.2.2.1 Downlink DPCH.................................................................................................................................. 483.2.2.2 CPICH Common Pilot channel......................................................................................................... 493.2.2.3 PCCPCH Primary Common Control Physical Channel ................................................................... 493.2.2.4 SCCPCH Secondary Common Control Physical Channel ............................................................... 503.2.2.5 SCH Synchronization Channel......................................................................................................... 513.2.2.6 PDSCH Physical Downlink Shared Channel.................................................................................... 513.3 R ADIO RESOURCE MANAGEMENT FUNCTIONS ........................................................................................... 523.3.1 Radio Admission Control ....................................................................................................................... 54

3.3.1.1 Admission control for uplink............................................................................................................... 543.3.1.2 Admission Control for Downlink ........................................................................................................ 554 UMTS S ERVICES AND T RAFFIC M ODELING ............................................................................................. 574.1 I NTRODUCTION .......................................................................................................................................... 574.2 UMTS S ERVICES ....................................................................................................................................... 584.3 T RAFFIC MODELLING ................................................................................................................................. 594.3.1 Microscopic Traffic Models ................................................................................................................... 604.3.2 Macroscopic Traffic Models................................................................................................................... 604.4 S ERVICE DEFINITION ................................................................................................................................. 604.4.1 Circuit Switched Services....................................................................................................................... 604.4.1.1 Bit rate: ................................................................................................................................................ 614.4.1.2 Radio Quality and QoS........................................................................................................................ 62


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4.4.1.3 Grade of Service (GoS) ....................................................................................................................... 624.4.1.4 Microscopic Traffic Model.................................................................................................................. 624.4.2 Packet Switched Services ....................................................................................................................... 634.4.2.1 Bit rates................................................................................................................................................ 644.4.2.2 QoS and Radio Quality ........................................................................................................................ 654.4.2.3 Grade of Service .................................................................................................................................. 654.4.2.4 Microscopic Traffic Models ................................................................................................................ 654.4.2.5 The Page-Oriented Web-Browsing Model .......................................................................................... 654.5 M ACROSCOPIC TRAFFIC MODEL FOR LINK BUDGET A NALYSIS ............................................................... 674.5.1 Concept................................................................................................................................................... 674.5.2 Acceptance Step ..................................................................................................................................... 684.5.2.1 Circuit Switched Model....................................................................................................................... 684.5.2.2 Packet Switched Model ....................................................................................................................... 704.5.2.3 Number of Emitting Channels per Service as Random Variable ........................................................ 734.5.3 Outage Step............................................................................................................................................. 754.5.3.1 Uplink Load as Random Variable ....................................................................................................... 754.5.3.2 Downlink Total Power as Random Variable ....................................................................................... 764.6 ANNEX A: R EQUIRED EB/N0 FOR SPEECH SERVICE ................................................................................. 784.6.1 Speech 8 kbit/s........................................................................................................................................ 784.6.2 Speech 12.2 kbit/s................................................................................................................................... 784.7 ANNEX B: R EQUIRED EB/N0 FOR CIRCUIT SWITCHED SERVICES ............................................................. 794.7.1 CS 64 kbit/s ............................................................................................................................................ 794.7.2 CS 144 kbps............................................................................................................................................ 794.7.3 CS 384 kbit/s .......................................................................................................................................... 804.8 A NNEX C: R EQUIRED EB/N0 FOR PACKET SWITCHED SERVICES ............................................................... 814.8.1 PS 64 kbit/s............................................................................................................................................. 814.8.2 PS 144 kbit/s........................................................................................................................................... 814.8.3 PS 384 kbit/s........................................................................................................................................... 824.9 ANNEX D: P ROBABILITY GENERATING FUNCTIONS AND PROPERTIES ................................................... 834.9.1 Random Sum of Random Variables ....................................................................................................... 83

4.9.2 Sum and Products ................................................................................................................................... 834.9.3 Useful Combinations .............................................................................................................................. 844.10 A NNEX E: D ERIVATION OF PROBABILITY DENSITY FUNCTIONS ............................................................. 855 L INK BUDGET AND INITIAL NETWORK DESIGN ........................................................................................ 875.1 C ONTEXT .................................................................................................................................................... 875.2 M ULTISERVICE LINK BUDGET .................................................................................................................... 875.2.1 Uplink Analysis ...................................................................................................................................... 885.2.1.1 Uplink Iteration Process ...................................................................................................................... 895.2.2 Downlink Analysis ................................................................................................................................. 925.2.2.1 Downlink Iteration Process.................................................................................................................. 925.3 L INK BUDGET PARAMETERS ...................................................................................................................... 975.3.1 Input Parameters for Link Budget Process ............................................................................................. 97

5.3.1.1 Service Inputs ...................................................................................................................................... 975.3.1.2 Additional traffic modeling inputs....................................................................................................... 995.3.2 Transmission Parameters........................................................................................................................ 995.3.3 UE specific parameters......................................................................................................................... 1005.3.4 Node B Specific Parameters ................................................................................................................. 1005.3.5 Exemplary Link Budget........................................................................................................................ 1026 C ELL P LANNING WITH PLANNING TOOL .................................................................................................. 1066.1 I NTRODUCTION ........................................................................................................................................ 1066.2 W ORKAROUND FOR UMTS CELL PLANNING ........................................................................................... 1066.3 D ESCRIPTION OF THE WORKAROUND USING THE EXAMPLE OF OSTRAVA ............................................... 1066.3.1 Introduction and Process Description................................................................................................... 1066.3.2 Input Data ............................................................................................................................................. 107


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6.3.2.1 Databases........................................................................................................................................... 1076.3.2.2 Traffic ................................................................................................................................................ 1086.3.3 A955 planning step............................................................................................................................... 1096.3.4 ILBT4RNP planning steps.................................................................................................................... 1106.3.4.1 Propagation model............................................................................................................................. 1116.3.4.2 Input parameters ................................................................................................................................ 1116.3.4.3 ILBT4RNP output ............................................................................................................................. 1126.3.5 Comparison of the intermediate results ................................................................................................ 1136.3.6 Results & Conclusion of the workaround............................................................................................. 1146.4 C ODE PLANNING INSTEAD OF FREQUENCY PLANNING ............................................................................. 1147 A NTENNA E NGINEERING ........................................................................................................................... 1167.1 I NTRODUCTION ........................................................................................................................................ 1167.2 A NTENNA TILT ......................................................................................................................................... 1167.3 D IVERSITY ASPECTS ................................................................................................................................ 1167.3.1 RX Diversity......................................................................................................................................... 1167.3.2 TX STTD Diversity Gain ..................................................................................................................... 1187.4 ANXU (A NTENNA NETWORK FOR UMTS)............................................................................................. 1197.4.1 Single Carrier Configuration with Transmit Diversity ......................................................................... 1207.4.2 Dual Single Carrier Configuration........................................................................................................ 1217.5 MHA (M AST HEAD AMPLIFIER ).............................................................................................................. 1217.6 GSM AND UMTS/FDD C O-LOCATION .................................................................................................... 1237.6.1 RF Requirements .................................................................................................................................. 1237.6.1.1 Interference Mechanism .................................................................................................................... 1237.6.1.2 Decoupling requirements................................................................................................................... 1247.6.1.3 Receiver blocking .............................................................................................................................. 1277.6.1.4 Intermodulation ................................................................................................................................. 1307.6.1.5 Summary on the required decoupling................................................................................................ 1377.6.2 Antenna System Solutions.................................................................................................................... 1377.6.2.1 Dual Band Sites ................................................................................................................................. 1377.6.2.2 Feeder Sharing................................................................................................................................... 146

7.6.2.3 Triple Band Sites ............................................................................................................................... 1477.6.3 Outlook to the future: Smart antennas (beam-forming)........................................................................ 1558 P RODUCTS AND M IGRATION STRATEGIES ............................................................................................... 1568.1 I NTRODUCTION ........................................................................................................................................ 1568.2 ROADMAP: RADIO ACCESS NETWORK EVOLUTION.................................................................. 1578.2.1 RELEASE 1: UMTS OVERLAY NETWORK.................................................................................... 1578.2.2 RELEASE 2: UMTS/GSM NETWORK INTEGRATION.................................................................. 1598.2.3 RELEASE 3GR3: UNIFIED RAN ARCHITECTURE ....................................................................... 1608.2.4 What is GERAN? ................................................................................................................................. 1618.2.5 Interoperability in a multi-vendor environment.................................................................................... 1628.3 PRODUCTS ............................................................................................................................................ 1628.3.1 Evolium Node B (MBS V1) ................................................................................................................. 162

8.3.1.1 Possible configurations within one cabinet ....................................................................................... 1638.3.1.2 Baseband board capabilities .............................................................................................................. 1638.3.1.3 Radio performance values of MBS V1.............................................................................................. 1648.3.1.4 Iub interface to RNC.......................................................................................................................... 1658.3.2 Evolium MBS V2 ................................................................................................................................. 1658.3.3 RNC V1 ................................................................................................................................................ 1658.3.4 RNC Evolution ..................................................................................................................................... 1668.3.5 OMC ..................................................................................................................................................... 1668.3.5.1 OMC V1 ............................................................................................................................................ 1668.3.5.2 OMC V2 ............................................................................................................................................ 1688.4 MIGRATION STRATEGIES RECOMMENDED BY ALCATEL........................................................ 1688.4.1 Migration strategy recommended for incumbent operators.................................................................. 168


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8.4.2 Migration strategy recommended for greenfield operators .................................................................. 1718.5 A NNEX A.................................................................................................................................................. 1728.6 A NNEX B.................................................................................................................................................. 1748.7 A NNEX C.................................................................................................................................................. 1758.8 A NNEX D.................................................................................................................................................. 1769 D ENSIFICATION STRATEGIES .................................................................................................................... 1779.1 I NTRODUCTION ........................................................................................................................................ 1779.2 D ENSIFICATION STRATEGIES .................................................................................................................... 1789.2.1 Adding carriers ..................................................................................................................................... 1799.2.2 Sectorization ......................................................................................................................................... 1799.2.3 Adding cells .......................................................................................................................................... 1809.2.4 Microcells ............................................................................................................................................. 1819.2.4.1 Microcells and macrocells on the same channel................................................................................ 1829.2.4.2 Microcells and macrocells on different channels .............................................................................. 18210 M ULTI OPERATOR ENVIRONMENT ......................................................................................................... 18410.1 I NTRODUCTION ...................................................................................................................................... 18410.2 A DJACENT CHANNEL INTERFERENCE IN CASE OF UMTS FDD-FDD CO-EXISTENCE ........................... 18410.2.1 Capacity Loss due to adjacent operators co-existence ...................................................................... 18510.2.1.1 Uplink case ...................................................................................................................................... 18510.2.1.2 Downlink case ................................................................................................................................. 18610.2.1.3 How can it be avoided?.................................................................................................................... 18710.2.2 Dead zones.......................................................................................................................................... 18711 M EASUREMENTS ...................................................................................................................................... 18911.1 M EASUREMENTS FOR PREDICTION MODEL CALIBRATION .................................................................... 18911.2 M EASUREMENTS OF CELL COVERAGE .................................................................................................. 19011.2.1 Coverage of Pilot Channel in DL Compared to GSM BCCH Channel.............................................. 19011.2.2 Impact of Service Type on Coverage ................................................................................................. 19011.2.3 Investigation on HO Gain................................................................................................................... 19111.2.3.1 Soft Handover Gain ......................................................................................................................... 19111.2.3.2 Softer Handover Gain ...................................................................................................................... 192

11.2.3.3 Influence of the UE Speed............................................................................................................... 19311.2.3.4 Influence of the Interference Level.................................................................................................. 19311.2.4 Investigation on Power Control .......................................................................................................... 19311.2.4.1 Open Loop Power Control............................................................................................................... 19311.2.4.2 Closed Loop Power Control ............................................................................................................ 19311.2.4.3 Influence of the Propagation Environment ...................................................................................... 19411.2.4.4 Influence of the UE Speed............................................................................................................... 19511.3 I NTERFERENCE MEASUREMENTS ........................................................................................................... 19511.3.1 Dead zones.......................................................................................................................................... 19511.3.2 Influence of the Interference Level..................................................................................................... 19611.4 T RIAL MEASUREMENTS ......................................................................................................................... 19711.4.1 Co-Siting with GSM........................................................................................................................... 197

11.4.2 Code Multiplex ................................................................................................................................... 19811.4.2.1 Test COD1: Orthogonality of Scrambling Codes on Downlink (Intercell)..................................... 19811.4.2.2 Test COD2: Orthogonality on Spreading Codes on DL (Intracell) ................................................. 19811.5 N ETWORK ACCEPTANCE PROCEDURE ................................................................................................... 20011.6 Q OS M EASUREMENTS ........................................................................................................................... 20111.7 R ECOMMENDED MEASUREMENT TOOLS FOR AIR I NTERFACE MEASUREMENTS .................................. 20111.8 P OSSIBLE MEASUREMENTS .................................................................................................................... 202

GLOSSARY/TERMINOLOGY................................................................................................................. 205

LIST OF ABBREVIATIONS..................................................................................................................... 205


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REFERENCED DOCUMENTS

Document references are given in the chapters![21.905] 3GPP specification TS21.905 V3.10 Release 1999

Useful document with explanations for UMTS abbreviations

RELATED DOCUMENTS

These documents give a good overview on the UMTS system.

[WCDMA] WCDMA for UMTS, Harri Holma & Antti Toskala, John Wiley & Sons, LTDPublished January 2000, ISBN 0471720518

[INTRO] Memorandum Introduction to UMTS Ref.: MCD/TD/BDC/JVPA/UMTS/2000/01

PREFACE

This document gives information required by radio network planning engineers to understand andplan a UMTS network.

SCOPE

This guideline is giving an introduction to the radio network planning related topics of the UMTSsystem. It is shown what input parameters are required to dimension and plan a UMTS radionetwork, how the dimensioning and planning is done and what kind of measurements are ofinterest.

INTRODUCTIONUMTS is the 3G mobile communication system specified by 3GPP. It is part of the IMT-2000standard provided by the ITU and consists of a WCDMA system based on FDD. A future TDD part isnot yet specified by 3GPP, thus not included in this document.

The guideline is intended to provide all necessary information required for planning a UMTSnetwork in FDD mode. It is assumed that the reader has already experience in planning othermobile communication systems, e.g. GSM.

Each chapter of this document contains its own introduction explaining the aim of the chapter. Findhereafter a short summary of contents of all chapters of the guideline:

1 RNP Process Description

This chapter deals with the overall RNP process. This process is valid for GSM and UMTS. The differentsteps of radio network planning are given together with input, output and interfaces.

2 WCDMA Fundamentals and UMTS Air Interface

This chapter gives an overview on the WCDMA technology used within UMTS. Power control andhandovers are explained in more detail.


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3 Channel Types and Radio Resource Management

The different layers and their according channels used in FDD UMTS are explained in this chapter.Furthermore some aspects of Radio Resource Management like Radio Admission Control aredescribed.

4 UMTS Services and Traffic Modeling

Contrary to GSM a high variety of services with different requirements are possible in UMTS. Theseservices can be transmitted simultaneously. This requires a deeper understanding of services and trafficmodeling to be able to plan a UMTS network accurately.

5 Link Budget and Initial Network Design

Before doing the final cell planning, a rough dimensioning of the network is done. Therefore alinkbudget tool is used, which is presented in more detail in this chapter.

6 Cell Planning with planning tool

Starting with an initial design, methods to find a network layout which can be implemented, are givenin this chapter.

7 Antenna EngineeringThings to keep in mind when doing antenna engineering for UMTS with and without co-location ofGSM sites are presented in this chapter.

8 Products and Migration strategies

What products are currently available from Alcatel and what is the Alcatel strategy to migrate existingnetworks to 3G networks? Here you find the answer.

9 Densification strategies

There are different strategies possible to increase the capacity of an existing network. They areexplained in this chapter.

10 Multi operator environmentHaving more than one UMTS operator in the same area may cause interference problems. How todeal with these problems is explained in this chapter.

11 Measurements

Measurements are necessary for a lot of different purposes, e.g. to test the QoS or the propagationconditions of a network. In the early phase of UMTS they are also important to understand thealgorithms used for HO. What is interesting to measure and how we can do it is described in thischapter.


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1 RNP PROCESS DESCRIPTION

The RNP process description gives answers on the question what is radio network planning (RNP).The main tasks included in RNP are bundled in packets. The inputs, contents, outputs and interfacesof each packet are given and explained. In addition the relation of each packet to the existing AIOmodules are shown.

As this process is the same for UMTS and GSM, a separated document has been created for theRNP process. This document can be found either in the PCS intranet or on DIAMS.

Document reference: RNP Process Description 3DF 00902 UA00 DEZZA

Intranet: http://aww.rcd.alcatel.com/PCS


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2 WCDMA FUNDAMENTALS AND UMTS AIR INTERFACE

Referenced Documents

[UTRA] UMTS Terrestrial Radio Access 3DF 009955 0004 UAZZA

[25.213] Spreading and modulation (FDD) (Release 1999) 3GPP 25.213 V3.3.0

[25.214] Physical layer procedures (FDD) (Release 1999) 3GPP 25.214 V3.4.0

[25.101] UE Radio Transmission and Reception (FDD) (Release 1999)3GPP 25.101 V3.4.1

[25.331] RRC Protocol Specification (Release 1999) 3GPP 25.331 V3.4.1

[26.103] Speech CODEC List for GSM and UMTS 3GPP 26.103 V3.0.0

[WFI] 3 Day UMTS training held for ALCATEL in August 2000

[INTRO] Memorandum Introduction to UMTS

Ref.: MCD/TD/BDC/JVPA/UMTS/2000/01[WCDMA] WCDMA for UMTS, Holma & Toskala, John Wiley & Sons 2000,

ISBN 0 471 72051 8

[OPNET] Study of soft handover with OPNET system simulations,Ref: MCD/TD/SYT/PBL/200816

[SysDesign] UTRAN System Design Document Ed.7, 3BK 10240 0005 DSZZA

2.1 UMTS network architec ture

The UMTS network includes not only the air interface of an UMTS network, but also the fixednetwork part with its connection to the core networks (packet and circuit switched). All main elementsof an UMTS network and the connection to the external networks are shown in Figure 1.

USIM

ME

Cu

UE

Node B

Node B

Iur

UTRAN

RNC

RNC

Node B

Node B

Iub

Uu

MSC/VLR

CN

GMSC

GGSN

HLR

SGSN

Iu

PLMN, PSTN,ISDN, ...

Internet

External Networks

RNS

RNS

Iu-CS

Iu-PS

Figure 1: Structure of the UMTS network [WCDMA]

The elements shown in Figure 1 are explained hereafter.

2.1.1 UE ( User Equipment)

The UE consists of two parts:


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The mobile equipment (ME) is the radio terminal used for radio communication over theUu interface

The UMTS Subscriber Identity Module (USIM) is the equivalent smartcard to the SIM inGSM. It holds the subscriber identity, performs authentication algorithms, storesauthentication and encryption keys, etc.

2.1.2 UTRAN (UMTS Radio A ccess Network)

The UTRAN consists of one or several Radio Network Subsystems (RNS) each containing one RNCand one or several Node B:

Node BThe Node B is the correspondent element to the BTS in GSM. Within Alcatel this part ofthe network is called the Multi-standard Base Station (MBS), as it is possible to integrateGSM modules as well (not in the early versions!)

RNCThe Radio Network Controller (RNC) owns and controls the radio resources of the

connected Node Bs. The RNC can have three different logical roles: CRNC, SRNC,DRNC. See more details in chapter 2.1.6.

2.1.3 CN (Core network)

HLR The Home Location Register is a database located in the users home system that storesthe master copy of the users service profile.

MSC/VLR The Mobile Services Switching Center and Visitor Location Register are the switch (MSC)

and database (VLR) serving the UE in its current location for circuit switched services.

GMSCThe Gateway MSC (GMSC) is the MSC at the point where the UMTS PLMN is connectedto external circuit switched networks.

SGSNThe Serving GPRS Support Node (SGSN) is the counterpart of the MSC/VLR for the packetswitched part of the network.

GGSNThe Gateway GPRS Support Node (GGSN) is the counterpart of the GMSC in the packetswitched domain.

2.1.4 External networks

The UMTS network is connected to two kinds of external networks:

Circuit switchedExamples for CS networks are: Existing telephone service, ISDN, PSTN

Packet switchedBest example today for a packet switched network is the Internet


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2.1.5 Interfaces

It is important to know, that all external UMTS interfaces are open interfaces. This means thattheoretically equipment of different vendors can be mixed if it fulfills the standards.

Cu interfaceThe Cu interface is a standard interface for smartcards. In the UE it is the connection

between the USIM and the UE. Uu interface

The Uu interface is the WCDMA radio interface within UMTS. It is the interface throughwhich the UE accesses the fixed part of the network. This interface is the most importantone to understand for RNP issues.

Iu interfaceThe Iu interface connects the UTRAN to the core network and is split in two parts. The Iu-CS is the interface between the RNC and the circuit switched part of the core network.The Iu-PS is the interface between the RNC and the packet switched part of the corenetwork.

Iur interfaceThis RNC-RNC interface was initially designed in order to provide inter RNC soft HO, butmore features were added during the development. Four distinct functions areprovided now:

1. Basic inter-RNC mobility

2. Dedicated channel traffic

3. Common channel traffic

4. Global resource management

Iub interface

The Iub interface connects the Node B and the RNC. Contrarily to GSM, this interface isfully open in UMTS and thus more competition is expected.

2.1.6 Logical roles of the RNC

2.1.6.1 CRNC

For each Node B the RNC to which the Node B is connected is the Controlling RNC (CRNC).

2.1.6.2 SRNC & DRNC

The Serving RNC (SRNC) for a certain connection is the RNC providing the Iu connection to the corenetwork. When the UE is in inter-RNC soft HO, more than one Iub and at least one Iur connection isestablished. Only one of the RNCs (the SRNC) is providing the Iu interface to the core network, allother ones are just routing information between Iub and Iur interface. These RNCs are called DriftRNC (DRNC). Figure 2 illustrates the logical role of SRNC and DRNC.


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UE

Node B

Node B

Iur

SRNC

DRNC

Node B

Node B

Iub

MSC/VLR

SGSN

Iu

RNS

RNS

Iu-CS

Iu-PS

UE

Node B

Node B

Iur

SRNC

DRNC

Node B

Node B

Iub

MSC/VLR

SGSN

Iu

RNS

RNS

Iu-CS

Iu-PS

Figure 2: Logical role of SRNC and DRNC

2.1.7 Mapping between GSM and UMTS

For easy understanding of the new notations within a UMTS network, the correspondent parts of theGSM network are given in the table below.

Table 1: Mapping of notations between GSM and UMTS

GSM/GPRS UMTS

MS Mobile Station ME Mobile Equipment

SIM Subscriber Identity Module USIM UMTS SIM

- - UE User Equipment (USIM+ME)

Um Air interface Uu

BTS Base Station Node B Node B

Abis Iub

BSC Base Station Controller RNC Radio Network ControllerBSS Base Station Subsystem RNS Radio Network Subsystem

- Iur

A Iu-CS

Gb Iu-PS

MSC Mobile Switching Center MSC Mobile Switching Center

SGSN Serving GPRS Support Node SGSN Serving GPRS Support Node

OMC Operation & MaintenanceCenter

OMC dito

In this chapter, the air interface (Uu) part and its terminating devices UE and Node B areinvestigated in more detail.

2.2 Standards and used fr equency spectrum

The ITU-R has produced high-level documents covering the performance, service type, and inter-working requirements for IMT-2000. Various international standards bodies such as the EuropeanTelecommunications Standards Institute (ETSI) are responsible for the detailed technicalspecifications of the equipment required to provide an IMT-2000 compatible service. A number of


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different standards are likely to emerge; but they are expected to have sufficient inter-workingcapability to allow an integrated IMT-2000 service for subscribers. IMT-2000 networks will supportfive interface standards:

IMT-DS UMTS Frequency Division Duplex (FDD)

IMT-MC US CDMA 2000 standard

IMT-TC UMTS Time Division Duplex (TDD) IMT-SC GSM EDGE (IS-136) standard

IMT-FT DECT standard

The four Technical Specification Groups (TSGs) of the ETSI-supported 3 rd Generation PartnershipProject (3GPP) have approved the detailed specification parts of their submission to the ITU-R for theIMT-2000 radio interface standard. This is a terrestrial radio interface specification known as theUniversal Terrestrial Radio Access Network (UTRAN). The UTRAN is based on a Wide-band CodeDivision Multiple Access (WCDMA) air interface.

Figure 3: IMT 2000 frequency spectrum compared to existing PLMN systems

In this document we are focusing on the FDD-WCDMA part of the IMT2000 system, the so calledFDD-UMTS. For this part, the following band is reserved:

UL: 1920 1980 MHz

DL: 2110 2170 MHz

As the UMTS carrier spacing is 5 MHz, the available bandwidth for the FDD part provides 12different channels. Depending on the country these 12 available licenses are given to differentoperators. An operator gets typically 2 or 3 licenses for paired (UL and DL) frequency bands. Thissmall amount of frequencies is due to the frequency reuse of 1 applied within a UMTS system.

The nominal channel spacing is 5 MHz, but this can be adjusted to optimize performance in aparticular deployment scenario. The channel raster is 200 kHz, which means that the centerfrequency must be an integer multiple of 200 kHz. The carrier frequency is designated by the UTRA

Absolute Radio Frequency Channel Number (UARFCN). The value of the UARFCN in the IMT2000band is defined as follows [25.101]:


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t

tt0

t1

t1

t0

Figure 5: Delay spreads of broad band (upper) and narrow band (lower) channels

2.4.3 Multipath propagation and RAKE receiver

One big advantage of the UMTS system is its capability to benefit from a multipath environment. Inthe upper part of Figure 4 we can see the delay spread of a broadband channel as used in UMTS.The received energy from the different multipaths of one signal overlaps much less than in thenarrow band case. Thus, the different multipaths can be combined by a special receiver technique,called RAKE receiver, to one improved signal. A RAKE receiver has several input paths (called RAKEfingers), where the signal can be delayed by an adjustable time. Selecting the delay time on eachfinger in that way, that the different multipaths entering the receiver at the same time, the signalscan be combined and thus an improved summary signal can be generated.

The delay time on each RAKE finger is determined automatically. The number of RAKE fingers is notfix and depends on the considered product.

Conclusion:

The UTRA system can take advantage from a multipath environment, e.g. dense urban areas.

2.5 Spreading, scrambling and modulation

2.5.1 Spreading

The UTRA system uses direct sequence (DS) spreading for both FDD and TDD mode. The principleconsists of multiplying the bipolar data signal b i(t) with a bipolar, broad band carrier signal s i(t). Thissignal is user specific and therefor called signature waveform of the user i. The multiplication in thetime domain corresponds to a convolution in the frequency domain, so that the transmitted signal isalso broadband. The spreading factor S P describes the widening of its spectrum. The equivalent low-pass of the transmitted signals consists of chips, i.e. bipolar impulses of the duration T c. One databit of the duration T b=S P x Tc corresponds to SF chips during transmission.


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data signal consists of bipolar "bits"

signature signal consists of bipolar "chips"

chiprate = spreading factor bitrate

data signal b i(t)

PN signature signal s i(t)

spread signal g i(t)=b i(t) si(t)

t

t

t

1

-1

1

1

-1

-1

Figure 6: Principle of spreading

Before the data signal b i can be spread, it has to be generated out of the user bits u i and thechannel coding bits. The channel coding bits are added to the data bit rate b i. Knowing the data bitrate b i, e.g. 960 kbit/s for the 384kbit/s data channel, the spreading factor is calculated. In this

example the spreading factor would be (3840kbit/s bandwidth)/(960kbit/s data rate) = 4.Due to this spreading the signal can be recovered out of the noise and interference at the receiverby de-spreading (auto-correlation). The received signal energy increase compared to the noise andinterference in dB is called the processing gain: PG [dB] = 10 x log SF.

Thus the processing gain can vary between 6 (SF = 4) and 24 (SF = 256).

2.5.2 Despreading

What is the sense of spreading the data signal onto the whole available channel bandwidth? Tworeasons we have seen in chapter 2.4.3 Multipath propagation and RAKE receiver:

1. Less fading sensible channel

2. Takes advantage from multipath environment

The main reason for spreading the data signal over the whole bandwidth is the ability to extract atthe receiver the wanted signal out of the total received power (interference, noise and useful signal)by doing correlation with the known user specific code. This is the main principle of Direct SequenceCDMA (DS-CDMA).

Principle:

timecode

channel bandwidth

timecode

channel bandwidth

Autocorrelation withknown code of channel 1

channel 1

Figure 7: Extracting the useful signal out of the overall noise


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The overall received power consists of lots of overlaid transmitted channels using different codes.The wanted signal is extracted by correlating the whole received signal with the known code of thewanted signal. Due to correlation, the part of the total received signal using the same code as thecode used for correlation, will have increased power. At the same time signals using codes differentfrom the one used for correlation will be suppressed. This is leading in the ideal case to animproved SIR in the range of the processing gain PG.

2.5.3 Codes used

The spreading of the data signal onto physical channels is done in two steps:

1. ChannelizationChannelization codes transform every data bit into a number of chips. The number of chips perdata bit is the so called spreading factor SF.

2. ScramblingDuring the scrambling operation a complex scrambling code (real part for the I branch andimaginary part for the Q branch) is applied to the spread signal.The scrambling code is used to identify in UL the mobile and in DL the cell.

As this scrambling codes change very often between 1 and 1, they are responsible for increasingthe bandwidth. The channelization codes spread the signal to the chip rate of 3.84 Mbit/s, but donot really increase the required bandwidth of the signal to 3.84 MHz. A chiprate of 3.84 Mbit/s isonly leading to an required bandwidth of 3.84 MHz in case of altering the sign on a chip by chipbasis.

2.5.3.1 Channelization codes

Orthogonal Variable Spreading Factor (OVSF) codes are used as channelization codes, whichensure that a number of mobiles can share the same RF channel (frequency) without causing

unacceptable interference. These codes allow Code Division Multiple Access (CDMA) to the sharedRF channel (frequency).

These spreading codes are of variable length and therefore offer spreading factors between 4 and256. In that way, different user bit rates can be realized. The codes are mutually orthogonal eventhough of different length, if they are synchronized. As synchronization is not possible betweendifferent mobiles, the orthogonal OVSF codes are not leading to orthogonal signals in UL. In DLthey are fully orthogonal assuming a ideal propagation channel, but due to multipaths in realenvironments, the signals using the codes are not fully orthogonal.

Figure 8 shows the OVSF code tree, which is generated by applying at each branch split the rule:Cnew,upper_branch = +C old+C old and C new, lower_branch = +C old-C old


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SF = 1 SF = 2 SF = 4

c1,1 = (1)

c2,1 = (1,1)

c2,2 = (1,-1)

c4,1 = (1,1,1,1)

c4,2 = (1,1,-1,-1)

c4,3 = (1,-1,1,-1)

c4,4 = (1,-1,-1,1)

Figure 8: Code tree for generating OVSF codes

The code tree defines the code length used to provide the specified spreading factor. The higheruser data rate services use shorter codes and hence lower spreading factors (and associated de-

spreading gain). A given mobile cannot use all channel codes simultaneously. A channel code canonly be used by a mobile if no other code on the path from the specific code to the root of the codetree, or in the sub-tree below the specific code, is used by any mobile. Thus the number of availablechannel codes is not fixed, but depends on the data rate and associated spreading factor of eachphysical channel used.

For each call, the mobile is allocated at least one uplink channel code, for an uplink DPCCH (seeexplanation on channel types in chapter 3). Usually, at least one further uplink channel code isallocated for an uplink DPDCH. Additional uplink channel codes may be allocated if the mobileneeds more DPDCHs. All channel codes used for the DPDCH must be orthogonal to the channelcode used for the DPCCH.

As each mobile using the same RF channel uses a unique uplink scrambling code, no co-ordinationof the allocation of uplink channel codes to mobiles is needed. They are allocated in a predefinedorder that exploits the design of the scrambling codes used by the mobile transmitter.

The mobile and the network may negotiate the number and length (spreading factor) of the channelcodes needed for the call, and the network allocates the necessary codes.

2.5.3.2 Scrambling codes

For the scrambling, there is the choice between short scrambling codes and long scrambling codes.The first option is used if there is multi user detection in the base station in order to simplify thecorrelation matrix computations. In case of single user detection, the second option is applied, for

improving the cross correlation properties and to assure a uniform distribution of the interference.The short scrambling code is a complex code c scramb = c I+jc Q , where c I and c Q are two differentcodes from the extended Very Large Kasami set of length 256. The long scrambling codes constituteof segments of 10ms (=38400 chips) of a set of Gold sequences with period 2 41 -1. What longscrambling code to use is directly given by the short scrambling code.

Currently only single user detection is done within the Node Bs, thus long scrambling codes areused. Multi user detection is just an option for the future.


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Downlink:

Each cell is allocated one and only one primary scrambling code. The primary CCPCH and primary CPICH are always transmitted using the primary scrambling code. The other downlink physicalchannels can be transmitted with either the primary scrambling code or a secondary scramblingcode from the set associated with the primary scrambling code of the cell.

There is a one-to-one mapping between each primary scrambling code and 15 secondary scrambling codes in a set such that ith primary scrambling code corresponds to ith set ofsecondary scrambling codes.

Hence, according to the above, scrambling codes k = 0, 1, , 8191 are used.

The set of primary scrambling codes is further divided into 64 scrambling code groups, eachconsisting of 8 primary scrambling codes. The jth scrambling code group consists of primary scrambling codes 16*8*j+16*k, where j=0..63 and k=0..7.

Uplink:

The UL scrambling code is the scrambling code used by UE. Every UE has its specific UL scramblingcode. The network decides the uplink scrambling code (UL scrambling code number 0..2 24-1). No

explicit allocation of the long scrambling code is thus needed.Depending on the channel type, different scrambling codes are used, but for all of them there is onerelation valid:

The UL scrambling codes of PRACH and PCPCH preambles are subdivided into 512 code groups,having a one-to-one correspondence to the scrambling code used by the downlink. An overview onspreading and scrambling code usage is given in Figure 9.

Node B

SpreadingOVSF

(User identifier)

ScramblingPN

(Cell identifier)

UE

Descrambling Despreading

SpreadingOVSF

(User identifier)

ScramblingPN

(User identifier)DescramblingDespreading

1 2

34

1 As the codes are sync. within the Node B, Orthogonal Codes are used to providesmall crosscorellation

2 To provide a small crosscorellation to unsyncronized codes (from other Node Bs orfrom UEs), PN codes are used for scrambling in DL. One code for one cell !!!

As the UL isnt syncronized, the OVSF codes arent used for spreading because oftheir orthogonality, but because of their easy generation for different req. lengths!

To provide a small crosscorellation to unsyncronized codes (from other UEs orNode Bs), PN codes are used for scrambling

3

4

DL

UL

Figure 9: Overview on spreading and scrambling code usage


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2.5.4 Example for scrambling code allocation: Cell Search Process

During the cell search, the UE searches for a cell and determines the downlink scrambling code andframe synchronization of that cell. The cell search is typically carried out in three steps:

Step 1: Slot synchronization

During the first step of the cell search procedure the UE uses the SCHs primary synchronizationcode to acquire slot synchronization to a cell. This is typically done with a single matched filter (orany similar device) matched to the primary synchronization code which is common to all cells. Theslot timing of the cell can be obtained by detecting peaks in the matched filter output.

Step 2: Frame synchronization and code-group identification

During the second step of the cell search procedure, the UE uses the SCHs secondary synchronization code to find frame synchronization and identify the code group of the cell found inthe first step. This is done by correlating the received signal with all possible secondary synchronization code sequences, and identifying the maximum correlation value. Since the cyclicshifts of the sequences are unique the code group as well as the frame synchronization isdetermined.

Step 3: Scrambling-code identification

During the third and last step of the cell search procedure, the UE determines the exact primary scrambling code used by the found cell. The primary scrambling code is typically identified throughsymbol-by-symbol correlation over the CPICH with all codes within the code group identified in thesecond step. After the primary scrambling code has been identified, the Primary CCPCH can bedetected. And the system- and cell specific BCH information can be read.

If the UE has received information about which scrambling codes to search for, steps 2 and 3 abovecan be simplified.

2.5.5 Spreading, scrambling and modulation As demodulation is the reciprocal of modulation, only the modulation is explained in more detailhere.

The UTRA system uses QPSK modulation. This means, that one transmitted symbol consists of twobits, one is transmitted with 0 phase shift (I branch, or real part) and the other one with 90 phaseshift (Q branch or imaginary part).

2.5.5.1 Uplink part

Concerning the uplink physical channels, one can distinguish between the two dedicated physical

channels (Dedicated Physical Control Channel, DPCCH and Dedicated Physical Data Channel,DPDCH) and the Physical Random Access Channel (PRACH) which carries the random access burst.

For the QPSK modulation, the DPDCH bits are mapped to the in-phase (I) branch while the DPCCHbits belong to the quadrature (Q) branch. The spreading is done separately for each branch by twodifferent spreading codes c D and c C, which are called channelization codes. Both are then scrambledby the same mobile specific complex scrambling code c scramb which is therefore the signature of themobile in uplink direction. The in-phase part I and quadrature part Q are then separated again andmodulated with the signals cos( t) and sin( t) respectively (see Figure 10). The modulationfrequency is of course the center frequency of the used 5MHz band.


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2.6 User detection mechanisms (quick overview)

In Figure 12 the proposed multi user detection ,mechanisms for the UTRA system are shown. Today only the single user detection (SUD) is implemented in the Node Bs. This is due to the hugecalculation capacity required for performing multi user detection. More information about userdetection mechanisms can be found in [UTRA].

Single User Detection(SUD)

Interference Cancellation(IC)

Joint Detection(JD)

Multi User Detection(MUD)

CDMA Receiver

Figure 12: Possible multi user detection mechanisms in the UTRA system

2.7 Power Control in UMTS FDD

Find detailed information on power control in [25.214]. Summary in [WFI] or [INTRO]. This chapteris in accordance with [SysDesign]. This chapter is divided into 3 parts:

General Power Control

Uplink PC

Downlink PC

2.7.1 General Power Control in UMTS

Evaluation of measurement reports and sending of power control commands is done by the servingradio network controller SRNC.

Unlike in GSM, the power control mechanism in UMTS is not based on selecting appropriate powerlevels to be used in the transmitter. Instead, the power control mechanism is based on a quality level(the Signal to Interference Ratio) that has to be achieved by transmitting with an appropriate powerlevel.

CDMA is very sensitive for what concerns power control: for the proper functioning of UMTS, it is ofvital importance to have a good power control mechanism: the signal to interference ratio (SIR) hasto be kept at a certain level. If the SIR is too low, the signal of a UE can not be de-spreaded andreconstructed any more. Since all users are transmitting simultaneously, the noise level depends(among others) on the number of users.

-> The more interference, the more a cell is congested

This means that interference (transmit power of other links) determines the usage and thusavailability of free radio resources. A good power control algorithm will optimize the usage of radioresources and thus increase the availability of radio resources.


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Another very important goal (maybe the most important goal) of power control is to maintain thesignal quality on a radio link. Once a radio link has been established, we try to maintain it.

There are 2 types of power control:

power control for common channels: Open Loop Power control

power control for dedicated channels DPCCH/DPDCH and downlink shared channel DSCH:

Closed Loop Power controlClosed loop power control is intended to reduce interference in the system by maintaining thequality of a UE-UTRAN communication (i.e. radio link) as close as possible to the minimum quality required for the type of service requested by the user. Closed loop power control is relevant for thephysical layer channels that support dedicated transport channels (DCH) and for those that supportshared transport channels (DSCH).

Closed loop power control consists of two parts an inner loop and outer loop. This chapter isdivided into subsections related to outer loop and inner loop power control for dedicated channelsfollowed by open loop power control for common channels.

2.7.1.1 Outer Loop Power Control

The parameter used by layer 1 for making inner loop power control decisions are determined by theouter loop power control algorithm. The outer loop control function manages the inner loop processby setting the SIR target parameter and the power up/down step sizes.

In general, the algorithm for generating the TPC bits can be described with the following rules:

SIR est >= SIR target TPC command = power down one step

SIR est < SIR target TPC command = power up one step

The frequency of the outer loop power control is typically in the range of 10 100 Hz.

2.7.1.2 Inner Loop Power Cont rol for dedicated channels

The inner part of closed loop power control is also called fast power control (1500 Hz) since it isintended to respond to fast variations in propagation characteristics of the radio link (e.g. fast fadingat slow or medium speeds) as well as rapidly changing interference conditions. The power controlloop is closed because the receiver of the radio signal communicates commands back to the senderto adjust its transmitted power. Fast power control is considered to be part of the physical layer ofthe UTRA and is performed in the Node B and the UE.

The structure of the air interface enables power control commands called Transmit Power Control(TPC) command bits to be sent once per slot. TPC bits can tell the remote end of the loop to eitherpower up by a step or to power down by a step. The decision to power up or down is based on anestimate of the signal to interference ratio (SIR) of the channel. Since SIR is related to the quality ofthe radio link, the principle of managing the quality of the link is achieved.

As closed loop power control is slightly different for UL and DL, more details are given in chapters2.7.1.2.1 for uplink and 2.7.1.2.2 for downlink.

2.7.1.2.1 Uplink closed loop power control

Uplink power control in a CDMA system is very important because of the necessity of suppressingthe near-far effect. Assuming all mobiles transmitting with the same power, a mobile close the


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receiver (Node B) would interfere the signal received from a mobile at the cell edge very strong,while the mobile at the cell edge doesnt interfere the one close to the Node B. This effect is harmingall communications of mobiles having another mobile between themselves and the Node B. This isthe so called Near-Far-Effect.

The uplink inner-loop power control adjusts the UE transmit power in order to keep the receiveduplink signal-to-interference ratio (SIR) at a given SIR target.

The serving cells (cells in the active set) estimate signal-to-interference ratio SIRest of the receiveduplink DPCH. TPC commands are generated in the serving cells and transmitted once per slotaccording to the following rule:

SIRest > SIRtarget then the TPC command to transmit is "0"

SIRest < SIRtarget then the TPC command to transmit is "1"

Upon reception of one or more TPC commands in a slot, the UE derives a single TPC command(TPC_cmd) for each slot, combining multiple TPC commands if more than one is received in a slot.Two algorithms are supported by the UE for deriving a TPC_cmd. Which of these two algorithms isused is determined by a UE-specific higher-layer parameter, "PowerControlAlgorithm", and is under

the control of the UTRAN. If "PowerControlAlgorithm" indicates "algorithm1", then the layer 1parameter PCA shall take the value 1 and if "PowerControlAlgorithm" indicates "algorithm2" thenPCA shall take the value 2.

If PCA has the value 1, Algorithm 1 shall be used for processing TPC commands.

If PCA has the value 2, Algorithm 2 shall be used for processing TPC commands.

(Algorithm 1 and 2 are described in section 5.1.2.2.2 and 5.1.2.2.3 in 3GPP TS25.214 V3.3.0.)

The step size TPC is a layer 1 parameter which is derived from the UE-specific higher-layerparameter "TPC-StepSize" which is under the control of the UTRAN. If "TPC-StepSize" has the value"dB1", then the layer 1 parameter TPC shall take the value 1 dB and if "TPC-StepSize" has the value"dB2", then TPC shall take the value 2 dB. The step size for the UL power control is thus 1 or 2 dB.

After deriving of the combined TPC command TPC_cmd using one of the two supported algorithms,the UE shall adjust the transmit power of the uplink DPCCH with a step of DPCCH (in dB) which isgiven by:

DPCCH = TPC* TPC_cmd.

Node B

Outer loop

Open loop

Inner loop

Closed Loop = Inner Loop + Outer Loop

Figure 13: Different UL power control mechanisms


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2.7.1.2.2 Downlink closed loop power control

In Downlink both the inner and outer loop of the closed loop power control are performed in theUE. The UE generates TPC commands to control the network transmit power and send them in theTPC field of the uplink DPCCH. The UE checks the downlink power control mode (DPC_MODE)before generating the TPC command:

DPC_MODE = 0: The UE sends a unique TPC command in each slot and the TPC commandgenerated is transmitted in the first available TPC field in the uplink DPCCH

DPC_MODE = 1: The UE repeats the same TPC command over 3 slots and the new TPCcommand is transmitted such that there is a new command at the beginning ofthe frame. This mode is also called Slow Power control. Its advantage is ahigher precision of the TPC command.

Note: DPC_MODE=1 shall not be used in 3GR1.1 because 3GPP specs are not finalized.

The DPC_MODE parameter is a UE specific parameter controlled by the UTRAN.

The power control step size TPC can take four values: 0.5, 1, 1.5 or 2 dB. It is mandatory for

UTRAN to support TPC of 1 dB, while support of other step sizes is optional.In case of congestion (commanded power not available), UTRAN may disregard the TPC commandsfrom the UE.

2.7.1.3 Open Loop Power Control

The open loop power control is relevant for physical channels that support common transportchannels. In the definition of TS 25.214 V3.3.0 this is the UL PRACH. This physical channel is usedby the UE for establishing a connection to the network or sending small amounts of data. The OpenLoop Power control consists in setting the transmit power by measuring the path loss of the directlink and adding the interference level of the node B and a constant value.

Method:

On the BCCH, the node-B will indicate the transmit power of the PCCPCH (and also the requiredSIR). By measuring the received power-level, the UE can find the downlink pathloss including fading.From this path loss estimation and the knowledge of the uplink interference level and the requiredSIR, the transmit power needed on the PRACH channel can be determined.

2.7.1.4 Site selection diversity transmit power control

Site selection diversity transmit power control (SSDT) is another macro diversity method in softhandover mode. This method is optional in UTRAN.

Operation is summarized as follows. The UE selects one of the cells from its active set to beprimary, all other cells are classed as non primary. The main objective is to transmit on thedownlink from the primary cell, thus reducing the interference caused by multiple transmissions in asoft handover mode. A second objective is to achieve fast site selection without network intervention,thus maintaining the advantage of the soft handover. In order to select a primary cell, each cell isassigned a temporary identification (ID) and UE periodically informs a primary cell ID to theconnecting cells. The non-primary cells selected by UE switch off the transmission power. Theprimary cell ID is delivered by UE to the active cells via uplink FBI field. SSDT activation, SSDTtermination and ID assignment are all carried out by higher layer signaling


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2.8 HO types & events

Definition: The list of cells involved in the soft/softer HO is called Active Set. The maximum size ofthe active set can be defined.

2.8.1 Hard handover

The hard handover (HO) is comparable to the HO procedure of GSM. The mobile is alwaysconnected to only one base station (Node B). When performing the HO to another Node B, theconnection to the former Node B is released.

All connections using a FACH channel (Fast Allocation CHannel, without power control and only forshort packages) or a DSCH (Downlink Shared CHannel, best channel for packet switched services)must use the hard HO. They can not benefit from soft HO gains.

Other hard HO:

Inter-system HO between e.g. UTRA and GSM

Inter-frequency HO between different UTRA carriers Within 3GR1.1 no compressed mode is possible, which is necessary for hard handover. Hardhandover and support of DSCH are not included in 3GR1.1. This release is also not offering Inter-RNC cell reselection in idle mode.

2.8.2 Soft handover

Packet switched communications using a DCH channel and all circuit switched communications areable to perform a soft HO. Soft HO means, that the mobile receives the same signal from morethan one Node B and its transmitted signal is processed by more than one Node B. The number of

Node Bs to which the UE is connected is called the Active Set. This is increasing the number ofreceived multipaths in UL and DL and thus is leading to diversity gain (see chapter 2.8.4). If a NodeB is put into the active set of a mobile is depending on the pilot E c/I0. The general scheme of SHOcan be seen in Figure 14.

For the description of the exemplary Soft Handover algorithm presented in this section the followingparameters are used (AS means Active Set):

AS_ThThreshold for macro diversity (max difference for best signal in AS and candidate signal)

AS_Th_HystHysteresis for the above threshold AS_Th

AS_Rep_HystReplacement Hysteresis

TTime to Trigger

AS_Max_SizeMaximum size of Active Set

The following figure describes this Soft Handover Algorithm.


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Meas_Sign > Best_Ss As_Th

as_Th_Hyst for a period of T

Yes

No(Event 1B)

Remove Worst_Bs inthe Active Set

Meas_Sign > Best_Ss As_Th+ as_Th_Hyst

for a period of T

No

Yes(Event 1A)

Add Best_Bs in the ActiveSet

Best_Cand_Ss > Worst_Old_Ss +As_Rep_Hyst

for a period of T

Yes(Event 1C)

No

Active Set Full

NoYes

Add Best BS in ActiveSet and Remove WorstBs from th Active Set

Begin

Figure 15: Flowchart of an simple SHO algorithm

2.8.3 Softer handover

A softer HO is a soft HO between cells of the same Node B, thus sectors of the same site. As this isnot improving the multipath conditions as much as soft HO does, the diversity gain is smaller.

2.8.4 Power control in soft(er) handover

In SHO, the UE has established more than one radio link. This requires special power controlfunctionality to identify the correct power control command.

2.8.4.1 Downlink PC in SHO

This is leading to the reception of more than one Power Control command in downlink (one fromeach Node B in the active set). If at least one of the Node Bs in the active set is sending a powerdown command, the UE will reduce its output power. It is enough, if one of the Node Bs is receivedcorrectly.


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2.8.4.2 Uplink PC in SHO

In uplink, the UE is transmitting only one power control command for all connected Node Bs,leading to the same power up/down steps of all connected Node Bs. If at least one link has goodquality (the SIR target is met), the UE sends a power down command.

2.8.4.2.1 Power driftingDue to UL transmission errors it is possible, that not all Node Bs in the active set receive the samepower control command. This is leading to power drifting: some Node Bs perform a power up,some a power down. This is degrading the performance of the SHO and should be avoided. Mainreason is that the Node Bs detect the PC commands independently and no MRC or selectioncombining can be done (would cause to much delay). Thus the error rate for PC commands can behigher than for transmitted user data.

2.8.5 Reporting events for S oft Handover and measurement reports

To find out the best cell or cells within UMTS, the UE measures the CPICH of all received neighborcells. The UE is told by UTRAN witch reporting events shall force the mobile to generate ameasurement report and sent it to the SRNC. This is different from GSM, where a measurementreport was generated at fixed time intervals (480 ms). So by using less reporting events within thehandover algorithms is leading to less measurement reports sent over the air interface.

In this chapter all HO events defined in 3GPP for intra-frequency measurements are listed. The HOalgorithms using this events are not standardized, but have to use reporting events out of the poolgiven by 3GPP [25.331].

Intra frequency reporting events

1A A primary CPICH enters the reporting range- A measured CPICH stronger than the best CPICH minus the reporting range

- Periodically reporting possible if cell is not added to active set due to any reason (cell additionfailure)

1B A primary CPICH leaves the reporting range

1C A nonactive primary CPICH becomes better than an active primary CPICH

- Non-active means, not in active set yet

- Periodic reporting possible if weakest cell is not removed from active set (cell replacement failure)

1D Change of best cell

1E A primary CPICH becomes better than an absolute threshold

1F A primary CPICH becomes worse than an absolute threshold


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To additionally reduce the number of sent measurement reports, the system can apply two differentfeatures for each of the triggering events separately:

A hysteresis value

Time-to-trigger (the event condition must be fulfilled for a certain time before the event itselfis triggered)

For each cell an individual offset can be applied to force or delay a the event triggering by adding/subtracting the offset to the measured CPICH level at the UE.

2.8.6 Filtering E C/N 0 measures out of raw measures

According to [OPNET] and [25.331] the E C/N 0 measurements taken by the UE every timeslot (15times per 10ms) on the CPICH of a neighbor cell are filtered by the following form