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UMTS

UTRAN Optimization

UMTS-04.03

401-382-810R04.03 Issue 1 August 2007 Alcatel-Lucent - Proprietary

This document contains proprietary information of Alcatel-Lucent and is not to be disclosed or used except in accordance with applicable agreements.

Copyright © 2007 Alcatel-Lucent Unpublished and Not for Publication

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Alcatel, Lucent, Alcatel-Lucent and the Alcatel-Lucent logo are trademarks of Alcatel-Lucent. All other trademarks are the property of their respective owners.

The information presented is subject to change without notice. Alcatel-Lucent assumes no responsibility for inaccuracies contained herein. Copyright © 2007 Alcatel-Lucent. All Rights Reserved.

Notice

Every effort was made to ensure that the information in this Information Product (IP) was complete and accurate at the time of printing. However, information is subject to change.

Ordering information

The order number for this information product is 401-382-940R04.03. To order documentation from an order entry representative, use one of the following numbers:

Within the United States, call +1-888-582-3688, or send email to cicorders@alcatel-lucent.com (to fax an order, call 1-800-566-9568). Within Canada, call +1 317 322 6616, or send email to cicorders@alcatel-lucent.com.

International, call +1 317 322 6616, or send email to intlorders@alcatel-lucent.com (to fax an order, call +1 317 322 6699).

Technical support

For initial technical assistance, please call one of the following numbers: North America, Central and Latin America and Asia Pacific regions:

Customer Technical Assistance Management (CTAM) center: +1 630 713 0488 Europe, Middle East and African regions:

International Customer Management Center (ICMC): +353 1692 4579

Information product support

For non-technical questions or comments regarding this information product, please call one of the following numbers: North America, Central and Latin America and Asia Pacific regions:

Customer Technical Assistance Management (CTAM) center: +1 630 713 0488 Europe, Middle East and African regions:

International Customer Management Center (ICMC): +353 1692 4579

See notice on first age

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Contents

About this information product

Purpose ... xixi

Reason for reissue ...xixi

Intended audience ...xiixii How to use this information product ...xiixii

Conventions used ...xiixii Systems supported ...xiixii Related documentation ...xiixii Related training ...xiixii How to comment ...xiiixiii

Part I: Optimization concepts 1 Introduction to optimization

Overview ...1-11-1 What is optimization? ...1-21-2 Why optimize a network ? ... 1-41-4 When to optimize a network ? ... 1-61-6

2 Information sources and tools Gathering information

Overview ...2-12-1

Key Performance Indicators ...2-22-2 ...

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Drive test ... 2-32-3 Customer complaints... 2-62-6 OMC-UPS tools ...2-72-7

Analyzing information

Overview ...2-92-9

Data analysis software ... 2-102-10

Optimization and design tools ...2-132-13

3 Common optimization problems and their solutions

Overview ...3-13-1 RF coverage problem ...3-23-2 Cell breathing problem ...3-43-4 Pilot pollution problem ...3-63-6 Near-far problem ... 3-83-8 Around-the-corner problem ... 3-93-9 Handover problem ...3-103-10

Missing neighbors problem ...3-113-11

4 UTRAN Signaling

Overview ...4-14-1

Protocol architecture of the air interface

Overview ...4-34-3 Protocols of the air interface ... 4-44-4 Radio interface protocol architecture ...4-64-6 Service access points ...4-84-8 Air interface channels

Overview ...4-124-12 Physical channels ...4-134-13

Contents

...

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Transport channels... 4-204-20 Logical channels ... 4-244-24 Air interface protocols

Overview ...4-264-26

Medium Access Control ... 4-274-27

Radio Link Control ... 4-314-31

Packet Data Convergence Protocol (PDCP) ... 4-344-34

Radio Resource Control ... 4-354-35 RRC State Machine ... 4-384-38 RRC Connection and Signaling Connection ... 4-394-39 Signaling radio bearers ... 4-404-40 Radio bearer establishment ...4-444-44 UTRAN protocols

Overview ...4-484-48 Iub protocol structure ... 4-494-49

Protocols of the Iub interface ... 4-514-51

Iur interface ... 4-544-54 Iu-cs interface ... 4-564-56

Part II: Optimization process 5 Optimization process

Overview ...5-15-1

Network lifecycle ... 5-25-2

Optimization process phases ...5-45-4

Planning and preparation (site readiness) ...5-75-7

Drive test optimization before live traffic... 5-95-9

Information gathering ...5-115-11

Contents

...

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Information analysis ...5-125-12

6 Drive testing

Overview ...6-16-1

Drive test optimization process ...6-26-2

Planning and preparation (site readiness) ...6-46-4

Optimization planning ... 6-66-6

Perform cluster optimization ... 6-86-8

Perform system verification ... 6-116-11

Part III: Optimization and troubleshooting 7 UTRAN key performance indicators

Overview ...7-17-1

Performance Counters and Key Performance Indicators ...7-27-2

KPI example - CS IRAT HO success rate (UMTS -> GSM) ...7-67-6

CS IRAT HO success rate (UMTS -> GSM) ...7-77-7 Performance counter trigger event basis ...7-87-8 Parameter trigger event basis ... 7-107-10 Parameter setting ...7-127-12 Parameter discussion ... 7-137-13

8 Call availability optimization and troubleshooting

Overview ...8-18-1 Call availability

Overview ...8-38-3

Call availability ... 8-48-4

Determination of accessibility problem ...8-68-6

Accessibility

Overview ...8-78-7

Contents

...

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Access preliminary procedures ... 8-88-8 Cell re-selection failures... 8-98-9 RACH access procedure failures ...8-118-11

RRC connection establishment analysis

Overview ...8-158-15

Introduction to RRC connection establishment ... 8-168-16

Call admission control failures ... 8-198-19

Radio link setup analysis ... 8-218-21 RRC connection setup failure ... 8-238-23 Paging failures ... 8-248-24 RAB establishment analysis

Overview ...8-268-26 RAB establishment ...8-278-27 Dynamic bearer control failures ... 8-308-30 Radio bearer establishment failures ... 8-328-32

No answer from UE ...8-338-33

9 Call reliability optimization and troubleshooting

Overview ...9-19-1

Dropped calls analysis ... 9-29-2

Radio link failures analysis due to synchronization issues ...9-69-6 Dropped RAB analysis due to congestion ... 9-99-9

10 Call quality optimization and troubleshooting

Overview ...10-110-1 Quality KPIs ... 10-210-2

11 Call mobility optimization and troubleshooting

Overview ...11-111-1

Contents

...

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Soft/Softer handover and troubleshooting

Overview ... 11-311-3 Soft/softer handover procedure ... 11-411-4

Average active set size ... 11-711-7

Soft handover troubleshooting ... 11-911-9

No Node B resources available ...11-1211-12

No transport resources available ... 11-1311-13

No UE answer ...11-1411-14 UE reject ...11-1511-15 Unlisted set cells ...11-1611-16 CS Voice UMTS to GSM (inter-RAT) handover and troubleshooting

Overview ...11-1811-18 CS Voice UMTS to GSM (inter-RAT) handover procedure ...11-1911-19 CS Voice relocation preparation procedure troubleshooting ...11-2311-23 CS Voice IRAT handover procedure troubleshooting ...11-2511-25

CS Voice GSM to UMTS (inter-RAT) handover and troubleshooting

Overview ...11-2611-26

CS Voice GSM to UMTS (inter-RAT) handover procedure ...11-2711-27

Relocation resource allocation procedure troubleshooting ...11-3011-30

Handover procedure troubleshooting ...11-3211-32 PS UMTS to GSM (inter-RAT) Cell Change Order and troubleshooting

Overview ...11-3311-33 PS UMTS to GSM (inter-RAT) Cell Change Order procedure ... 11-3411-34 PS UMTS to GSM (inter-RAT) Cell Change Order troubleshooting ...11-3711-37 Serving HS-DSCH Cell Change

Overview ...11-3911-39

Contents

...

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Serving HS-DSCH Cell Change procedure ...11-4011-40 Serving HS-DSCH Cell Change troubleshooting... 11-4311-43 Inter-frequency hard handover and troubleshooting

Overview ...11-4411-44

Inter-frequency hard handover procedure ...11-4511-45

Hard handover troubleshooting ... 11-5011-50

No Node B resources available ...11-5311-53

No transport resources available ... 11-5411-54 UE reject ...11-5511-55 Inter-system directed retry

Overview ...11-5611-56 Inter-system directed retry procedure ...11-5711-57 Inter-system directed retry troubleshooting ...11-6011-60

12 Throughput optimization and troubleshooting

Overview ...12-112-1 Throughput optimization ... 12-212-2 Glossary Index Contents ... 401-382-810R04.03 Alcatel-Lucent - Proprietary ix

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About this information product

About this information product

Purpose

This document describes the methods to perform an optimization of the UTRAN Network based on performance indicators and drive tests. These include:

• identification of sources of performance data,

• description of drive testing equipment, methods and tool

• identification of performance data and traffic measurements to locate trouble spots • solution proposals for improving the performance

• evaluation of the effectiveness of counter measures.

Use of this document, or the information it contains, with any configuration other than the ones above may not be valid.

The UMTS UTRAN optimization manual is specific to the optimization of UMTS networks and does not cover other aspects of network management or network engineering.

Reason for reissue

This is the first issue of this Information Product (IP) for UMTS Release 04.03. Updates for the addition of new information and corrections in subsequent document issues will be summarized in this notice.

Reason for reissue:

Issue Reason for reissue

0.1 Preliminary version for FOA

1 Final version for GA

...

401-382-810R04.03 Issue 1, August 2007

Alcatel-Lucent - Proprietary

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Intended audience

Alcatel-Lucent assumes that anyone using the information in this manual has a general familiarity with UMTS networks, and has specific experience working with, and operating, the Alcatel-Lucent UMTS system.

Therefore, the audience for this manual consists of: • Network operators

• Field support personnel • RF engineers

• Network planners

• Systems engineers who work with the Alcatel-Lucent UMTS network and need to know how to plan and expand a UMTS network using network statistics.

How to use this information product

Use this documentation as a guidance for the preparation of optimization tasks in the UTRAN Network. Use it in combination with the latest user documentation.

Conventions used

The term “FIMS-UT” is a generic term to describe any local maintenance terminal (LMT) for any UTRAN network element.

The terms “RMT” and “Node B RMT” are used to describe the Node B Remote Maintenance Tool application.

The term “OMC” is a generic term to describe the Operation and Maintenance Center entities which control the UTRAN network elements.

Acronyms are explained on their first appearance in the text. Systems supported

This document applies to the Alcatel-Lucent UMTS System Release 04.03. Related documentation

The following related documentation is available:

Performance Measurements Definitions Manual, UMTS-04.03/IMS 5.0,

401-382-803R04.03 Related training

The following related courses are available: • UMTS System Introduction, UM1001UMTS Hardware Overview, UM1911

About this information product

...

xii Alcatel-Lucent - Proprietary

See notice on first page

401-382-810R04.03 Issue 1, August 2007

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UMTS UTRAN Signaling and Parameters, UM4302UTRAN Processes and Parameters, UM4305

UTRAN Optimization, UM4801.

How to comment

To comment on this information product, go to the Online Comment Form

(http://www.lucent-info.com/comments/enus/) or e-mail your comments to the Comments Hotline (comments@alcatel-lucent.com).

About this information product

...

401-382-810R04.03 Issue 1, August 2007

Alcatel-Lucent - Proprietary

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Part I: Optimization concepts

Overview

...

Purpose

This document part provides an introduction to the concepts of UTRAN optimization, information on tools and sources that are used to gather the information for the optimization process, a short description of typical areas for optimization problems, and an overview over UTRAN signaling.

Contents

Chapter 1, Introduction to optimization 1-1

Chapter 2, Information sources and tools 2-1

Chapter 3, Common optimization problems and their solutions 3-1

Chapter 4, UTRAN Signaling 4-1

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1

1

Introduction to optimization

Overview

...

Purpose

This chapter provides an introduction to the concepts of optimization. It explains what optimization is, why optimization is performed and when optimization must be

performed. Contents

What is optimization? 1-2

Why optimize a network ? 1-4

When to optimize a network ? 1-6

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What is optimization?

...

Definition

Optimize To make as effective, perfect, or useful as possible. Optimizing a UMTS network

For a UMTS network, optimization means getting the entire UMTS network to operate according to the requirements of an operator.

Optimizing a UMTS network consist of optimizing: • RF network

• Transmission network.

Most of the optimization takes place in the RF network. The transmission network does not have many parameters or variables that can be changed to increase the effectiveness of the network.

Requirements

By optimizing a network, an operator tries to find the best configuration and use of the network. This strongly depends on the requirements that an operator has and the

priorities an operator assigns to these requirements. Requirements can relate to:

• Quality of service

• Traffic expectations and predictions • Coverage area

• Capacity

• Current and future business strategies (network expansion, market shares, profitability levels).

Requirements and costs

An operator weighs the requirements against the costs that are involved to meet the requirements and the priorities of the requirements. An operator could probably meet many requirements, but the costs involved would be very large.

Therefore the financial cost is a very important issue to decide: • Which requirements can be met

• Which solutions can be implemented to meet a requirement. Introduction to optimization

...

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Finding compromises

Requirements for a network often contradict each other. Improving a network to meet one requirement can introduce a problem for another requirement. Optimization therefore usually involves finding a compromise (or trade-off) between different requirements. When an engineer makes a choice for implementing a solution, all requirements an operator has must be kept in mind.

Example of finding compromises An operator wants:

• RF coverage over a large area • Minimal interference.

Increasing transmit power increases RF coverage but at the same time increases

interference. An operator must decide what is more important and implement a solution that reflects that decision.

What is not optimization

Optimization does not include all actions that make a network work better. Fault management actions, such as replacing a circuit pack, is not network optimization. Fault management only ensures the network operates as it is supposed to operate. The starting point for optimization is a network that does not have errors. Before starting the optimization of a network or trying to solve an optimization problem, an engineer must ensure that a problem is not caused by an error or fault.

Introduction to optimization What is optimization?

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Why optimize a network ?

...

Goal of optimization

The goal of optimization is to fine-tune an existing network to meet the requirements of an operator in the most efficient way.

Important! Optimization of an existing network must not be used to correct a bad network design.

Reasons for optimization

Optimization is needed because a network is never perfect. It never fully complies to the requirements of an operator.

Optimization is needed because of:

Reason Example

Deviations from (planning) assumptions Changes in subscriber behavior (increased

use of a service or a cell)

Changes in operator requirements Increased market share, introduction of

new service

Changes in environment New buildings, snowfall, trees

Most of these reasons can not be prevented or can only be prevented partially. Good models (for example for traffic behavior and forecasts) can help predict changes and thus help in designing and optimizing networks.

Consequences of not optimizing

Not optimizing a network means the goals of optimization are not met and the network does not “meet the requirements of an operator, in the most efficient way.”

Of course a network must meet the requirements of an operator, but not meeting these requirements in the most efficient way costs an operator money. By optimizing the network, the same requirements could be met with fewer resources.

Not optimizing the network will cost money, related to:

• Subscribers, in missed revenue because of blocked calls or subscribers changing to other operators

• Operational and maintenance costs. Introduction to optimization

...

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Subscribers

In a network that is not optimized, subscribers can experience: • Blocked calls

• Dropped calls

• Smaller RF coverage area • Lower voice quality • Lower data rates.

Blocked calls are a direct loss of revenue for an operator. Poor network quality can be a reason for existing subscribers to change to another operator and for potential

customers to subscribe to competitors. Operational costs

A network that is not optimized is more expensive to operate. The equipment is not used effectively, so more equipment is needed. The extra equipment increases maintenance and operational costs.

Also more errors and problems can be expected in a network that is not optimized. This increases the costs of fault management.

Result of optimization

An optimized network increases network coverage and network capacity. This directly translates into:

• Lower operational and maintenance costs • Higher number of voice and data users • Higher average data throughputs

• Higher Quality of Service for voice and data users.

Introduction to optimization Why optimize a network ?

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When to optimize a network ?

...

Phases when optimization takes place

Optimization during the network life cycle:

Optimization is performed:

• Before a commercial network launch • In a live, operational network.

Before a commercial network launch, typical optimization includes: • Network design optimization

• Optimization based on drive testing.

This document covers in service optimization in a live, operational network, even though optimization methods and tools are similar during both phases.

Always

The environment in which a network operates is always changing, so the network itself must always change too, adapting to the changes that take place. There are always reasons for optimization, therefore optimization in a live network never stops.

Network design In service optimization Optimization Planning Live network Implementation Network design & implementation Y N Acceptance criteria met? Introduction to optimization ... 1-6 Alcatel-Lucent - Proprietary 401-382-810R04.03

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Optimization is always needed because there are always: • Deviations from (planning) assumptions

• Changes in subscriber behavior • Changes in operator requirements • Changes in environment.

Introduction to optimization When to optimize a network ?

...

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2

2

Information sources and tools

Gathering information

Overview

...

Purpose

This section provides information on tools and information sources that are used to gather information that is used in the optimization process.

This section describes the use of: • Customer complaints

• Drive testing

• Key Performance Indicators.

Other tools

Protocol analyzers can also be used to gather performance data. Protocol analyzers can be used to monitor and count messages on interfaces in the network. Protocol analyzers are available from many different vendors.

Contents

Key Performance Indicators 2-2

Drive test 2-3

Customer complaints 2-6

OMC-UPS tools 2-7

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Key Performance Indicators

...

Use of Key Performance Indicators

Key Performance Indicators (KPI) are calculated using measurements that are gathered by the OMC-UPS. The KPIs are used to determine if the network complies to the levels of performance that are needed.

Key Performance Indicators (KPI) play an important role in detecting (optimization) problems. Changes in values of the key performance indicators, especially reaching thresholds, are often the first indication of a problem that can be an issue for optimization.

A KPI value can change suddenly, or gradually, but both types of change can be an indication that optimization will be needed.

Available KPIs

KPIs that can be indication of a performance problem, that needs optimization, are: • Handover failure rates

• Channel occupancy rates • Dropped RRC connections rate • RAB failure rates

• Radio link dropping rates.

For detailed information on all the available KPIs, refer to UMTS Performance

Measurement Definitions Manual, 401-382-803R04.03.

Detected problems

KPIs can be useful in detecting all the problems that were mentioned, such as: • RF coverage gaps

• Cell breathing • Pilot pollution • Near-far problems

• Around-the-corner problems

• Handover problems (failures or ping-ponging) • Missing neighbor cells in the neighboring cell list. Information sources and tools

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Drive test

...

Purpose

Drive tests are performed to measure: • RF spectrum coverage and interference

• UTRAN parameters (mobile measurements, protocol messages) • Network quality (call completion, hand over, data rates, voice quality)

When to perform

Drive test are performed during network deployment and in a live network. During network deployment drive tests are used to check basic cell operation and to ensure clusters and the network meets customer requirements.

During optimization in a live network, drive tests recheck cell performance. During these test, neighboring cells must be operational, so cell selection, interference measurements and hand overs can be performed and tested.

After implementing a solution to correct an (optimization) problem, a drive test can be performed to check if the problem is solved.

Regular drive tests are also a method for preventive maintenance to detect areas where services are degrading.

Components

Components of a typical drive test system (picture provided courtesy of Agilent Technologies):

Information sources and tools

...

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Components of a drive test system are: • UMTS scanner/receiver

• UMTS antenna

• PC with software for logging the data • UMTS terminal

• Vehicle with location/positioning equipment (for example GPS).

Detecting problems

Drive testing can be useful in detecting most problems that occur: • RF coverage gaps

• Cell breathing • Pilot pollution • Near-far problems

• Around-the-corner problems

• Hand over problems (failures or ping-ponging) • Missing neighbors in a neighboring cell list. Drive testing can also detect:

• Poor voice reception quality • Poor data rates.

Information sources and tools Drive test

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Analyzing drive test data

Data that is gathered during a drive test can be displayed in real time or stored on the PC for off-line analysis.

The information must be analyzed to check for performance problems, that can be solved by network optimization.

Automated tools are needed because a large volume of information is collected. Automated tools help to sort out the information and draw conclusions from the information.

Analysis tools can project the collected data on a map that includes characteristics of the terrain. On the map, details are shown such as coverage strength, and locations where handovers, cell reselections or dropped calls occur.

This information is used to identify problems and the locations where the problems occur.

Information sources and tools Drive test

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Customer complaints

...

Use of customer complaints

Customer complaints can provide an indication of problems. Especially if multiple complaints can be related to one source. Customer complaints can point to a problem on a specific location, time or related to a resource.

A customer complaint can be the trigger for further investigation using KPIs or drive testing.

Trouble tickets

Customer complaints are typically documented as trouble tickets. The form of trouble tickets (electronic, paper) and the way trouble tickets are stored and handled differs between operators.

Trouble ticket information

Trouble tickets typically contain the following information: • UE type and model

• Type of problem (for example dropped call, poor quality) • Time and place of the problem.

Example

Customers complain regularly about dropped calls in a certain location. Dropped calls can be an indication of an RF coverage gap or a neighboring cell list problem. So further investigation of the problem is needed.

Further investigation can determine that the dropped calls always occur when there is a lot of traffic in the cell. The problem can be the result of an RF coverage gap because of cell breathing.

Detected problems

Although customer complaints are often not very specific, they can be helpful to detect problems that may be an issue for optimization.

Information sources and tools

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OMC-UPS tools

...

OMC-UPS tools

The OMC-UPS offers the following tools that can be used in gathering information for optimization:

• RF call trace • OCNS.

RF call trace

RF call trace gathers radio related information associated to one or more cells. RF call trace collects signaling messages on the Uu, Iub and Iu interfaces.

When a RF call trace is activated for a UE, information about calls established by that UE is collected, as long as the UE is connected to the tracing RNC. The information is composed of measurements performed at the UE, the NodeB and the RNC. All

measurements are stored at the RNC until the OMC-UPS requests a transfer to the OMC-UPS.

Use of RF call trace

The operator can use information from RF call traces to: • Verify call establishment

• Check performance and maintenance of radio links • Check radio link quality and coverage.

OCNS

Orthogonal Channel Noise Simulator (OCNS) is a tool that is activated on the OMC-UPS and generates downlink interference to simulate traffic.

The OMC-UPS administrator can define characteristics of the simulated traffic such as mode of operation (voice or data), number of users and average power of users. Use of OCNS

OCNS is a tool that is normally used in a network without traffic. OCNS simulates traffic during testing before a network is live.

OCNS can also be used to generate additional traffic in a live cell, simulating heavier traffic loads.

Detected problems

RF Call trace can be useful to detect all problems that may be an issue for optimization.

Information sources and tools

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OCNS can be useful to detect Cell breathing.

Information sources and tools OMC-UPS tools

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Analyzing information

Overview

...

Purpose

This section provides information about tools that can be used during optimization. Contents

Data analysis software 2-10

Optimization and design tools 2-13

Information sources and tools

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Data analysis software

...

Need for data analysis software

Data analysis software is needed to process data, because a large volume of

information is collected. The software helps to sort out the information, present it to an engineer and helps the engineer to draw conclusions.

The software also allows an operator to show the consequences of changes that are made to the network.

Data analysis software is used in: • Network design optimization

• Live network performance optimization.

Inputs for analysis software tools

Data analysis tools can project the collected data on a map that includes characteristics of the terrain. On the map, details are shown such as coverage strength, and locations where handovers, cell reselections or dropped calls occur.

To show and analyze information, inputs are needed such as: • Maps (with terrain features and roads)

• Location and orientation of sites

• Parameter settings for cells, antennas and sites (power, antenna tilts) • Drive test data

• Performance measurements.

Benefits of data analysis software

Data analysis software helps an engineer to: • Identify and locate a problem

• Determine the source of a problem • Find solutions

• Predict the effects of implementing a solution.

Predict effect of changes

Optimization software predicts the effects of changes (for example in power level or antenna tilt). An engineer can easily try different options. This helps an engineer to determine what is the best solution to correct an optimization problem.

Information sources and tools

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Output of analysis tools

Data analysis tools can provide output on performance in different forms, but most commonly used are outputs in tables and graphical outputs. Especially graphical output clearly shows problem areas in a network.

Typical output from data analysis software and illustrates a network before and after optimization:

The dark lines indicate areas that have no coverage. Changes in the shade of the antennas indicate changes in antenna tilt.

Analysis tool availability

Many tools are available for analyzing information. The main input for many

commercially available analysis software tool is drive test data. But also other inputs can be used.

Before optimization Optimizated design

Information sources and tools Data analysis software

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Besides commercially available software tools also many proprietary tools are available.

Key capabilities

To be able to handle the large volumes of data from many sources with different formats, data analysis tools must support key capabilities such as:

• Interfaces to different vendors of drive test equipment, protocol analyzers and measurement programs

• Open interfaces • Multiple technologies

• Interfaces to databases to retrieve and store data

• Synchronization of data from different sources to remove timing variations • Database querying and filtering to reduce data volumes.

Information sources and tools Data analysis software

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Optimization and design tools

...

This topic gives an overview of tools, developed by Alcatel-Lucent, that are used in optimization and design of 3G networks.

LCAT

LCAT is the Lucent Cells Application Tool. It is a tools that allows an engineer to define cells and sectors.

LCAT information as input for LDAT and SPAT3G. LDAT3G

Lucent Data Analysis Tool for 3G (LDAT3G) is an application for performing RF analysis of drive test data for IS-95, 3G CDMA, 1xEV-DO, and UMTS systems. Used for initial optimization of deployed network.

Drive test data, RF Call Trace, Cell Diagnostic Monitor, Packrat, and WINDS are supported.

SPAT3G

Service Performance Analysis Tool for 3G (SPAT3G) is a tool that can be used to quickly troubleshoot and improve network performance. It gives you easy access to a wealth of information at the system, cell, face, and carrier level that can be displayed graphically or in tabular formats. SPAT3G is used to optimize a live network and not during initial optimization.

SPAT3G:

• Displays of performance metrics for all network entities at different report levels (ECP, Cell, Face, Carrier, and IWF/PCF).

• Provides data trending for a metric or multiple metrics in a single chart per system, cell, face, and carrier. SPAT3G also provides peg trending at the system, cell, face, and carrier levels, allowing more detailed analysis.

• Provides ROP Analysis, Metric and Service Measurement Trending, or Service Measurements data, as well as FCIAlert, Handoff Matrix, and UNL data by right clicking on a cell site.

• Displays handoff matrix data on a map display showing handoff relationships between sites.

AirPro

AirPro is an RF planning tool that is used to design wireless systems. AirPro can be used in the designs of new wireless networks, networks migrating from older

generation to newer generation and existing network optimization. AirPro includes RF Information sources and tools

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propagation analysis, interference prediction, RF optimization, and utilities that help you create and manage system designs for mobile systems in diverse operating environments

Ocelot®

Ocelot® is used to optimize tilt, azimuth and power levels of antennas in a scenario to

get best coverage and capacity from the network. The benefit of using Ocelot® for

optimization is reduced dependence on drive testing required for calibrating the design parameters and post deployment optimization using service measurements.

In post deployment optimization, Ocelot® is used in:

• Moving traffic from heavily-loaded sectors to more lightly-loaded sectors (“traffic balancing”)

• Reducing the amount of soft- and softer-handoff traffic • Reducing the average power per user.

Information sources and tools Optimization and design tools

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3

3

Common optimization problems

and their solutions

Overview

...

Purpose

This chapter describes typical problem areas that can be addressed by optimization and provides possible solutions for the problem.

For each problem, the topic provides:

• Description and definition of the problem • How the problem shows itself in a network • Consequences for the network and the users • Useful tools and information sources

• Possible solutions.

Since optimization usually is a trade-off, keep in mind that the possible solutions that are given may solve that particular problem, but at the same time may introduce a problem elsewhere.

Contents

RF coverage problem 3-2

Cell breathing problem 3-4

Pilot pollution problem 3-6

Near-far problem 3-8

Around-the-corner problem 3-9

Handover problem 3-10

Missing neighbors problem 3-11

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RF coverage problem

...

Definition

The RF coverage area is the area where two conditions are met: • Pathloss < maximum allowed pathloss

• Ec/Io > minimum signal-to-noise ratio.

Pathloss and Ec/Io depend on the services and quality that is defined for a network and can be checked using drive tests. The user equipment receive power is not an accurate measure of pathloss for spread spectrum technologies. The user equipment may have strong receive power due to many overlapping sectors but no pilot fulfills the above mentioned coverage conditions. Therefore the Ec/Io ratio and the Ec signal strength (connected to the pathloss) of the Primary Common Pilot Channel are used as an accurate measures for the RF coverage.

Optimization goal

The goal is to close RF coverage gaps and maximize RF coverage. Or to be more precise, maximize RF coverage, while continuing to comply to other requirements. Because increasing RF coverage must not mean other requirements such as interference levels can not be met anymore.

If RF coverage gaps can not be closed, it may be possible to move an RF coverage gap from an area with high traffic volumes to an area with low traffic volumes. This does not solve the RF coverage problem itself, but lowers the impact of a gap. Detection of the problem

There are several ways in which RF coverage problems show themselves in the network.

These include: • Dropped calls • Failed handovers.

Information sources

The following information sources are used to detect RF coverage problems: • Drive test

• Key performance indicators • Customer complaints. Common optimization problems and their solutions

...

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Possible solutions

Possible solutions for RF coverage problems are: • Antenna tilt or reorientation

• Power increase

• New antenna or new cell site.

Common optimization problems and their solutions RF coverage problem

...

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Cell breathing problem

...

Definition

Cell breathing is the growing and shrinking of an RF coverage area, depending on the network load.

An increase of the network load increases network interference. Higher interference lowers the quality of service especially at the initial cell coverage border and thus the coverage area shrinks. To remain connected, power levels must increase. When power can not be increased further, a handover is needed.

A low network load leads to low network interference, which increases the cell

coverage. This can result in neighboring cells not being used because the mobiles stay connected to the original cell and no handovers occur.

Cell breathing:

Traffic needed during optimization

Cell breathing occurs when the network is loaded, so RF optimization must be performed on a loaded network. The network can be loaded with live traffic or simulated traffic.

To simulate (additional) traffic on the downlink, the Orthogonal Channel Noise Simulator (OCNS) can be activated on the OMC-UPS to generate downlink

interference. On the uplink, an attenuator attached to the user equipment simulates the loading.

Cell at 30 % capacity Cell at 60 % capacity Common optimization problems and their solutions

...

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Optimization goal

The goal is to ensure that high load situations do not lead to RF coverage gaps. At the same time, low load situations should not create large overlaps in cell coverage, which may lead to pilot pollution or unwanted handover behavior.

In both high and low load situations, the network must have sufficient coverage and the network must be used efficiently.

Detection of the problem

There are several ways in which cell breathing problems show themselves in the network.

These include: • Dropped calls

• Poor quality, especially at cell edges (during high traffic loads) • Appearance of RF coverage gaps (during high traffic loads) • Failed handovers

• No handover to neighboring cells (during low traffic loads) • Excessive or unexpected handovers (during high traffic loads) • Pilot pollution (during low traffic loads).

Information sources

The following information sources are used to detect cell breathing problems: • Drive tests

• Key performance indicators • Customer complaints.

Possible solutions

Possible solutions for cell breathing are: • Increase coverage area:

– Antenna downtilt or reorientation – Power increase.

– New antenna or new cell site. • Change handover parameters • Change neighboring cell list.

Common optimization problems and their solutions Cell breathing problem

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Pilot pollution problem

...

Definition

Pilot pollution is interference caused by overlapping pilots with similar signal strengths.

The lack of a dominant pilot causes low Ec/Io ratios. Problem areas with low Ec/Io ratios may be misinterpreted as pilot pollution areas and lead to iterative drive testing and unnecessary parameter changes in attempts to establish a dominant pilot.

If a pilot has:

• Insufficient Ec signal strength (extensive pathloss), the problem area is considered as a RF coverage hole

• Sufficient Ec signal strength (low pathloss), the problem area has pilot pollution. An optimization engineer needs to determine whether the Ec/Io ratio is poor due to excessive pathloss or pilot pollution.

Pilot pollution is also considered if the number of present pilots is greater than the actual active set size of the user equipment. Present pilots which cannot be added into the active set cause interference.

Another aspect for interference is multipath reception. Each received pilot is accompanied by 2-3 strong multipaths. The user equipment uses a rake receiver to exploit multipath reception. Since the rake receiver has a limited number of fingers, unused multipaths act as interference. Consequently, a six-finger rake receiver is fully occupied when receiving three pilots (each with 2 multipaths). Any additional pilots and multipaths are interference. Common trouble spots are bridges, upper floors in buildings, elevated highways, street intersections, and large bodies of water.

Optimization goal

The goal is to minimize pilot pollution. Coverage of the dominant pilot must be increased and coverage of the weaker pilots (which cause interference) must be decreased. At the same time, continuous coverage through the soft handover must be ensured.

Detection of the problem

There are several ways in which pilot pollution problems show themselves in the network.

These include: • Dropped calls • Handover failures Common optimization problems and their solutions

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• Increased interference • Decreased capacity.

Information sources

The following information sources are used to detect pilot pollution problems: • Drive tests.

Possible solutions

Possible solutions for pilot pollution problems are: • Antenna tilt and azimuth rotation

• P-CPICH channel power changes • Change neighboring cell lists.

Common optimization problems and their solutions Pilot pollution problem

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Near-far problem

...

Definition

Near-far problems occur when user equipment near the cell site transmits on high power. This creates excessive interference for user equipment that is located far away from the cell site.

Optimization goal

The goal of the cell site is to receive all user equipment at equal signal strengths. Therefore power control must be tightly controlled. Fast closed loop power control is needed to direct mobiles to power up or power down very quickly. The optimization goal is to ensure that all power control algorithms are working properly. Power control parameters are tuned only when there are obvious power control failures.

Detection of the problem

There are several ways in which near-far problems show themselves in the network. These include:

• High interference

• Node B always transmits on full power despite satisfying block error rates

• User equipment always transmits on full power despite satisfying block error rates.

Information sources

The following information sources are used to detect near-far problems: • Drive test

• Key performance indicators • Customer complaints.

Possible solutions

Possible solutions for near-far problems are: • Changing power control parameters. Common optimization problems and their solutions

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Around-the-corner problem

...

Definition

Around-the-corner problems occur when user equipment travels beyond an obstruction and if there is significant downlink interference from a new sector with low pathloss. The downlink degrades momentarily until the handover is performed or the downlink power control reacts to compensate the interference.

When the user equipment goes into handover with the new cell site, fast power control is needed to quickly reduce cell site transmit power.

The around-the-corner problem is a continual and unavoidable issue. Known trouble spots are elevated highways and street intersections.

Optimization goal

The goal is to optimize the power control mechanism. The optimization goal is similar to the near-far goals. Detection of the problem

There are several ways in which around-the-corner problems show themselves in the network.

These include: • High interference

• Unusual handover behavior.

Information sources

The following information sources are used to detect around-the-corner problems: • Drive tests

• Key performance indicators.

Possible solutions

Possible solutions for around-the-corner problems are: • Changing power control parameters

• Changing handover parameters. Common optimization problems and their solutions

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Handover problem

...

Definition

Unnecessary delays in handovers may cause uplink/downlink interference. Quick handovers are required when there are rapid changes in pathloss between the user equipment and the sector due to fading. Also, unnecessary handovers due

non-contiguous UMTS coverage or pilot pollution lead to excessive handover activity. Optimization goal

The goal is to optimize the handover performance by careful selection of thresholds and timers.

Handovers require signaling resources, and increase downlink interference, so

excessive handover activity must be minimized. Time delays due to resource allocation (channel units, transmission links to RNC, OVSF codes) degrade call quality and reduce the throughput of data calls.

Detection of the problem

There are several ways in which handover problems show themselves in the network. These include:

• Dropped calls (because of handover failure)

• Ping-ponging (frequent handovers between 2 cells).

Information sources

The following information sources are used to detect handover problems: • Drive test

• Key performance indicators.

Possible solutions

Possible solutions for handover problems are: • Adjust handover parameters

• Change the neighboring cell list. Common optimization problems and their solutions

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Missing neighbors problem

...

Definition

A neighboring cell list contains the cell identifiers to which a handover is allowed. The list is kept in the RNC and is transmitted to the UE. The UE measures signals only from the neighboring cell list and uses these measurement for power control and handovers. A handover can therefor only occur to a cell that is in the neighboring cell list of a UE, so setting up proper neighboring cell lists is very important.

Missing neighbors are pilots that are not in the neighboring cell list. When pilots are received that are not in the neighboring cell list, these pilots cannot be added to the active set and thus these pilots will cause interference. It is important that all received UMTS sectors are either eliminated or declared in the neighboring cell list.

Optimization goal

The goal is to optimize the neighboring cell lists. Received pilots must either be eliminated or declared in the neighboring cell list. They must not be ignored. Detection of the problem

There are several ways in which missing neighbor problems show themselves in the network.

These include:

• Dropped calls (when neighboring cell list is too short and UE can not handover to another cell)

• High interference levels (UE transmits at high power levels to serving cell, because it can not handover to another cell)

• Unusual handover behavior (no handovers are performed from on cell to another cell).

• Uneven traffic distribution (UE stay with a cell and are not handed over to a neighboring cell).

Information sources

The following information sources are used to detect missing neighbors problem: • Drive test

• Key performance indicators • Customer complaints. Common optimization problems and their solutions

...

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Possible solutions

Possible solutions for missing neighbor problems are:

• Updating the neighboring cell list to include or exclude a pilot.

• Change RF coverage, so pilots are not received anymore or pilot reception is improved:

– Adjust power levels

– Change antenna orientation or tilt.

Common optimization problems and their solutions Missing neighbors problem

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4

4

UTRAN Signaling

Overview

...

Purpose Contents

Protocol architecture of the air interface 4-3

Protocols of the air interface 4-4

Radio interface protocol architecture 4-6

Service access points 4-8

Air interface channels 4-12

Physical channels 4-13

Transport channels 4-20

Logical channels 4-24

Air interface protocols 4-26

Medium Access Control 4-27

Radio Link Control 4-31

Packet Data Convergence Protocol (PDCP) 4-34

Radio Resource Control 4-35

RRC State Machine 4-38

RRC Connection and Signaling Connection 4-39

Signaling radio bearers 4-40

Radio bearer establishment 4-44

UTRAN protocols 4-48

Iub protocol structure 4-49

Protocols of the Iub interface 4-51

...

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Iur interface 4-54

Iu-cs interface 4-56

UTRAN Signaling Overview

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Protocol architecture of the air interface

Overview

...

Purpose

The purpose of this section is:

• to describe the protocols of the air interface

• to match these protocols to their correct layer in the protocol architecture of the air interface

• to explain how the layers communicate with one another by the use of channels.

Contents

Protocols of the air interface 4-4

Radio interface protocol architecture 4-6

Service access points 4-8

UTRAN Signaling

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Protocols of the air interface

...

Logical structure of the air or Uu interface (PS example)

The following illustration shows the UTRAN protocol architecture (for DCH) with the protocols of the Uuhighlighted.

Description

The following table lists the protocols of the Uu and introduces the functions each performs.

Part Description

Radio Resource Control The RRC controls the connection between UE and

UTRAN (setup, maintenance and teardown). Secondly, RRC provides the means for the transmission of NAS signaling. Finally, it is used by the Radio Resource Management algorithms.

Packet Data Convergence Protocol

The PDCP provides header compression and

decompression of IP data streams. It also transmits user data from the non-access stratum to the RLC layer and vice versa.

RANAP

SSCOP

Uu Node B Iub RNC Iu-ps

MTP3-b SGSN SSCF UE -N SCCP PMM SM PMM -ATM U STM AAL5 1 IP GTP UDP -SM MAC Phy-up PHY RRC IP PDCP RLC ATM E1/ STM-1 AAL2 AAL5 NBAP PHY ALCAP SSCOP STC.2 SSCF-UNI FP SSCOP NBAP AAL5 AAL2 SSCOP MTP3-b SSCF-N SCCP RANAP RRC ATM STM-1 GTP-U UDP PDCP ALCAP STC.2 SSCF-UNI IP RLC MAC Phy FP -up AAL5 User plane Control plane UTRAN Signaling ... 4-4 Alcatel-Lucent - Proprietary 401-382-810R04.03

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Part Description

Radio Link Control The RLC provides functions related to data transfer, such

as segmentation and reassembly, in-sequence delivery, error-correction and flow control. Three modes are provided: transparent, acknowledged and

unacknowledged.

Medium Access Control The MAC prepares transport blocks for most efficient

transfer over the air. The functions include scheduling, multiplexing, channel type switching, UE identification (on common channels) and transport format selection on a frame-by-frame basis.

The MAC is responsible for mapping logical channel onto the appropriate transport channel.

UTRAN Signaling Protocols of the air interface

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Radio interface protocol architecture

...

A layered architecture

The radio protocol architecture in the UTRAN is layered.

• The top layer (layer 3) is the network layer and includes the RRC and the user traffic

• below that is layer 2 or the data link layer, Layer 2 is split into the following sub-layers: – Medium-Access Control (MAC)

– Radio Link Control (RLC)

– Packet Data Convergence Protocol (PDCP) – Broadcast/Multicast Control (BMC).

• the bottom layer is the physical layer (layer 1).

Layer 3 and the RLC are divided into Control (C) and User (U) planes. The PDCP and the BMC exist in the U plane only.

In the C plane, Layer 3 is partitioned into sub-layers where the lowest sub-layer which is called the Radio-Resource Control (RRC), interfaces with Layer 2 and terminates in the UTRAN.

Higher-layer signaling, such as Session Management (SM)Mobility Management (MM) and Call Control (CC), belongs to the non-access stratum, is not terminated in the UTRAN and thus not discussed in this topic.

Structure of radio protocol architecture

The following figure illustrates the logical structure of the radio protocol architecture: UTRAN Signaling

...

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Explanation of overall protocol structure

Each block in the previous figure represents an instance of the respective protocol. Service Access Points (SAP) for peer-to-peer communication are marked with ovals at the interface between sub-layers. The SAP between the MAC and the physical layer provides the transport channels. The SAPs between the RLC and the MAC sub-layer provide the logical channels. In the C-plane, the interface from RRC to higher layers (CC, MM) is defined by the General Control (GC), Notification (Nt) and Dedicated Control (DC) SAPs.

The connections between the RRC and the MAC as well as the RRC and L1 provide local inter-layer control services.

Equivalent control interfaces exist between: • The RRC and the RLC sub-layer

• The RRC and the PDCP sub-layer • The RRC and the BMC sub-layer.

These interfaces allow the RRC to control the configuration of the lower layers. For this purpose separate Control SAPs are defined between the RRC and each lower layer (PDCP, RLC, MAC and L1).

Physical Layer (PHY) Medium Access Control (MAC) RLC RLC RLC RLC RLC RLCRLC RLC BMC PDCP DCP control control GC Nt DC

Radio Resource Control (RRC) control Layer 3 L2/PDCP L2/BMC L2/RLC Logical Channels L2/MAC Transport Channels L1 Physical Channels C-plane signaling U-plane information

UTRAN Signaling Radio interface protocol architecture

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Service access points

...

Service access points

The layers provide services to the layer above, and use the services of the layer below. These services are provided through Service Access Points, which provide different kinds of channels for communications. The channels are divided into four broad categories, depending on which layer interface provides them. These categories are: • Radio Bearers provided by the RLC

• Logical Channels provided by the MAC to the RLC • Transport Channels provided by the PHY to the MAC • Physical Channels provided to the PHY.

The SAPs and their position between the layers are illustrated in the following figure.

What are the different channels for?

The different channels provide the following different services.

• The logical channel service contains the type of information that is transferred over the radio link. For example, the DTCH carries the actual user data; the BCCH provides system information to all users in a cell.

• The transport channel service defines how and with what characteristics (with which QoS) data is transferred over the radio link. Every transport channel has a transport format assigned to it which contains information such as channel coding, interleaving and rate matching.

• The physical channel service provides the means by which the UE is radio-linked with the Node B.

SAPs Medium Access Control (MAC)

L2

Radio Resource Control (RRC) L3

Radio Link Control (RLC) L2 SAPs SAPs Physical Layer L1 L a y e r M a n a g e m e n t Air SAPs UTRAN Signaling ... 4-8 Alcatel-Lucent - Proprietary 401-382-810R04.03

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Channel mapping

For each of the channel categories, there is a number of types, each with different characteristics. The Radio Bearers map directly to the Logical Channels; the Logical Channels map to the Transport Channels; and the Transport Channels map to the Physical Channels.

The following illustration shows the relationships between channels linking different protocol layers.

UTRAN Signaling Service access points

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Transport channels are mapped to physical channels as shown in the illustration above. There are many physical channels which do not carry higher-layer traffic; some are associated with traffic-carrying channels, while others are necessary for cell discovery by the UE and channel estimation.

S-SCH S-CPICH P-CPICH PICH PRACH S-CCPCH P-CCPCH DPDCH HS-DPCCH DPCCH HS-SCCH E-DPCCH E-DPDCH HS-PDSCH AICH BCH FACH PCH DCH E-DCH HS-DSCH RACH PCCH BCCH CTCH DTCH DCCH CCCH DPCH P-SCH E-AGCH E-HICH E-RGCH

Logical channels Transport channels

Physical channels Uplink Downlink Bidirectional Data transfer Association Fixed channels

UTRAN Signaling Service access points

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Multiple transport channels can be multiplexed onto a single physical channel, or conversely, one transport channel can be transferred over multiple physical channels (multicode). PCH and FACH can be multiplexed onto the same S-CCPCH or can each be transferred over separate S-CCPCHs.

Associated channels are used as follows:

• PICH indicates in an efficient manner that information for a mobile will shortly be transferred on the PCH transport channel

• AICH indicates that an access preamble has been received, and that the UE can stop ramping up its power, or (for PCPCH) that a collision detect preamble has been received and resolved

• DPCCH carries power control information for associated channels as well as TFC indication for DPDCH and PDSCH, and pilot and feedback information. The shared channels are power controlled, so a UE which uses them must also have a dedicated channel set up and associated with them. This DCH can be of very low bandwidth compared to the shared channel, and may well carry the DCCH. • HS-SCCH is used for UE addressing for HSDPA, that is, indicating a specific UE

that data packets are being sent on the HS-PDSCH, and provides the UE with necessary information to decode the data packets.

• The HS-DPCCH carries the UE feedback information used for link adaptation and the Hybrid Automated Repeat request (HARQ) process.

UTRAN Signaling Service access points

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Air interface channels

Overview

...

Purpose

The purpose of this section is:

• to describe the channels of the air interface

• to map these channels to their layer of the air interface • to explain the function of the channels.

Contents Physical channels 4-13 Transport channels 4-20 Logical channels 4-24 UTRAN Signaling ... 4-12 Alcatel-Lucent - Proprietary 401-382-810R04.03

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Physical channels

...

Overview

In this section, we will look at each of the physical channels that link the UE with the Node B and consider their mapping relationships to the transport channels.

We shall consider the following groups of physical channels: • Common downlink physical channels.

• Dedicated downlink physical channels • Common uplink physical channels • Dedicated uplink physical channels

Introduction

In the Node B, physical channels are created out of either related transport channels or out of Node B control data. In the latter case, the information in the physical channel does not carry higher-layer traffic but is pure layer 1 control data created by the Node B, e.g. SCH or CPICH.

Multiple transport channels can be multiplexed onto a single physical channel, or conversely, one transport channel can be transferred over multiple physical channels (multicode). For example, PCH and FACH can be multiplexed onto the same

S-CCPCH or can each be transferred over separate S-CCPCHs.

Transport channels are mapped to physical channels as shown in the illustration. UTRAN Signaling

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Channel mapping

The DCHs are coded and multiplexed and the resulting data stream is mapped sequentially directly to the physical channel(s).

S-SCH S-CPICH P-CPICH PICH PRACH S-CCPCH P-CCPCH DPDCH HS-DPCCH DPCCH HS-SCCH E-DPCCH E-DPDCH HS-PDSCH AICH BCH FACH PCH DCH E-DCH HS-DSCH RACH PCCH BCCH CTCH DTCH DCCH CCCH DPCH P-SCH E-AGCH E-HICH E-RGCH Logical channels Transport channels

Physical channels Uplink Downlink Bidirectional Data transfer Association Fixed channels

UTRAN Signaling Physical channels

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The mapping of BCH and FACH is equally straightforward where the data stream, after coding and interleaving, is mapped sequentially to the Primary and Secondary CCPCH respectively.

Also for the RACH, the coded and interleaved bits are sequentially mapped to the physical channel, in this case the message part of the random access burst on the PRACH.

The mapping of the PCH to the Secondary CCPCH is more complex to allow for an efficient sleep mode.

The mapping of the HS-DSCH to the HS-PDSCH is done by mapping the data stream sequentially directly to the physical channel.

Common downlink physical channels

The following is a list of the common downlink physical channels: Common

downlink physical channels

Description

P-CCPCH The Primary Common Control Physical Channel is a fixed rate (32

kbps, SF=256) downlink physical channels used to carry the BCH.

S-CCPCH The Secondary Common Control Physical Channel is used to carry

the FACH and PCH. It is of constant rate. However, in contrast to the Primary CCPCH, the rate may be different for different

secondary CCPCH within one cell and between cells, in order to be able to allocate different amount of FACH and PCH capacity to a cell. The rate and spreading factor of each secondary CCPCH is broadcast on the BCH. The set of possible rates is the same as for the downlink DPCH.

The FACH and PCH can be mapped to separate secondary CCPCHs.

The main difference between the Primary and Secondary CCPCH is that the Primary CCPCH has a fixed predefined rate while the Secondary CCPCH has a constant rate that may be different for different cells, depending on the capacity needed for FACH and PCH.

UTRAN Signaling Physical channels

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Common downlink physical channels

Description

P-SCH The Synchronisation Channel (SCH) is a downlink signal used for

cell search. The SCH consists of two sub channels, the Primary and Secondary SCH. Along with the CPICH, the SCH channels provide information that enables the UE to camp on, search for and select a cell.

During the first step of the initial cell search procedure, the UE uses the Primary Synchronisation Channel (P-SCH) to acquire slot synchronisation to the strongest cell. The Primary Synchronisation Code in the P-SCH is the same for every cell in the system.

S-SCH During the second step of the initial cell search procedure, the UE

uses the secondary SCH to find frame synchronisation and identify the code group of the cell found in the first step.

P-CPICH The Primary Common Pilot Channel is a fixed rate (30 kbit/s, SF =

256) downlink physical channel.

This channel is coded with the scrambling code of the cell that it belongs to, therefore the UE can use this channel to determine the received signal strength of this particular cell. Furthermore the P-CPICH is also used as a phase and power reference for the other downlink physical channels.

The downlink common control channels have to reach all UEs in the cell and should not be too loud to disturb other cells. As the cell size is often adjusted, it may occur that the power level of all control channels must be readjusted. To simplify this, the power level of all control channels are expressed in relation to the power that is used by the Pilot Channel of a cell. That is, when the power of P-CPICH is reduced, the power of all other common channels is reduced by the same factor.

S-CPICH The Secondary Common pilot Channel may be transmitted over the

entire cell or a part of the cell. There may be zero, one or several S-CPICH per cell. An S-CPICH may be the phase reference for the secondary CCPCH and the downlink DPCH. If this is the case, the UE is informed about this by higher layer signaling.

PICH The Paging Indicator Channel informs the UE that paging

information will shortly be available for that mobile over the S-CCPCH. This is an efficient process which saves the UE from having to permanently listen in on the S-CCPCH.

UTRAN Signaling Physical channels

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Common downlink physical channels

Description

AICH The Acquisition Indicator Channel is a common downlink physical

channel which works closely together with the uplink PRACH. Upon reception of an access preamble from a UE, the Node B uses the AICH to acknowledge the success of the transmission and to inform the UE that it can stop ramping up its power.

PDSCH The Physical Downlink Shared Channel is shared by several users

based on code multiplexing.

HS-PDSCH The High Speed Physical Downlink Shared Channel (HS-PDSCH)

carries the data traffic in the form of MAC-hs Packet Data Units (PDUs). It has a fixed spreading factor of 16. This allows for up to 15 parallel channels. The transmit power is set by the scheduler, that is, it is constant during one transmit time interval.

HS-SCCH The High Speed Shared Control Channel (HS-SCCH) transmits the

information about the configuration to be used next on the

HS-PDSCH channel. It has a fixed spreading factor of 128. The UE can monitor up to four HS-SCCH channels.

Dedicated downlink physical channels

The following is a list of the dedicated downlink physical channels: Dedicated

downlink physical channels

Description

DPCH There is only one type of downlink dedicated physical channel, the

Downlink Dedicated Physical Channel (downlink DPCH).

Within one downlink DPCH, dedicated user data generated at layer 2 and above (from MAC and above at the RNC) and control

information generated at layer 1 (known pilot bits, TPC commands, and an optional TFCI) are multiplexed at the Node B and

transmitted together over the Uu interface. The downlink DPCH can

thus be seen as a time multiplex of a downlink DPDCH and a downlink DPCCH.

E-HICH The E-DCH HARQ Indication Channel (E-HICH) carries the

ACK/NACK information from the E-DCH Active Set cells that a packet was received and retrieved successfully. This channel uses a spreading factor of 128.

UTRAN Signaling Physical channels

...

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