qos and qoe managemaent in umts cellular systems

QoS and QoE Managementin UMTS Cellular Systems QoS and QoE Management in UMTS Cellular Systems Edited by David Soldani, Man Li and Renaud Cuny © 2006 John Wiley & Sons, Ltd... 7 Service

QoS and QoE Management

in UMTS Cellular Systems

QoS and QoE Management in UMTS Cellular Systems Edited by David Soldani,

Man Li and Renaud Cuny © 2006 John Wiley & Sons, Ltd ISBN: 0-470-01639-6

QoS and QoE

Management in UMTS Cellular Systems

Edited by

David Soldani

Nokia Networks, Nokia Group, Finland

Man Li

Previously Nokia Research Center, Nokia Group, Boston, USA

Currently JumpTap, Inc., Cambridge, USA

Renaud Cuny

Nokia Networks, Nokia Group, Finland

Copyright # 2006 John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester,

West Sussex PO19 8SQ, England Telephone (þ44) 1243 779777 Email (for orders and customer service enquiries): cs-books@wiley.co.uk

Visit our Home Page on www.wiley.com

All Rights Reserved No part of this publication may be reproduced, stored in a retrieval

system or transmitted in any form or by any means, electronic, mechanical, photocopying,

recording, scanning or otherwise, except under the terms of the Copyright, Designs and

Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency

Ltd, 90 Tottenham Court Road, London W1T 4LP, UK, without the permission in writing of the Publisher Requests to the Publisher should be addressed to the Permissions Department, John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex PO19 8SQ,

England, or emailed to permreq@wiley.co.uk, or faxed to (þ44) 1243 770620

Designations used by companies to distinguish their products are often claimed as trademarks All brand names and product names used in this book are trade names, trademarks or registered trademarks of their respective owners The Publisher is not associated with any product or vendor mentioned in this book.

This publication is designed to provide accurate and authoritative information in regard to the subject matter covered It is sold on the understanding that the Publisher is not engaged

in rendering professional services If professional advice or other expert assistance is

required, the services of a competent professional should be sought.

Other Wiley Editorial Offices

John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA

Jossey-Bass, 989 Market Street, San Francisco, CA94103-1741, USA

Wiley-VCH Verlag GmbH, Boschstr 12, D-69469 Weinheim, Germany

John Wiley & Sons Australia Ltd, 42 McDougall Street, Milton, Queensland 4064, Australia John Wiley & Sons (Asia) Pte Ltd, 2 Clementi Loop #02-01, Jin Xing Distripark, Singapore 129809 John Wiley & Sons Canada Ltd, 6045 Freemont Blvd, Mississauga, Ontario, Canada L5R 4J3

Wiley also publishes its books in a variety of electronic formats Some content that appears

in print may not be available in electronic books.

British Library Cataloguing in Publication Data

Acatalogue record for this book is available from the British Library

ISBN-13 978-0-470-01639-8 (HB)

ISBN-10 0-470-01639-6 (HB)

Project management by Originator, Gt Yarmouth, Norfolk (typeset in 10/12pt Times).

Printed and bound in Great Britain by Antony Rowe Ltd, Chippenham, Wiltshire.

This book is printed on acid-free paper responsibly manufactured from sustainable forestry

in which at least two trees are planted for each one used for paper production.

Preface xiii

Noman Muhammad, Davide Chiavelli, David Soldani and Man Li

Renaud Cuny, Man Li and Martin Kristensson

2.2.10 Presence 25

Anna Sillanpa¨a¨ and David Soldani

David Soldani and Paolo Zanier

4.3.2 Protocol architecture 125

David Soldani, Paolo Zanier, Uwe Schwarz, Jaroslav Uher,

Svetlana Chemiakina, Sandro Grech, Massimo Barazzetta and

5.3.9 Flow control algorithm in Node B and RNC handling of

Renaud Cuny, Heikki Almay, Luis Alberto Pen˜a Sierra and Jani Lakkakorpi

7 Service and QoS Aspects in Radio Network Dimensioning and Planning 239David Soldani, Carolina Rodriguez and Paolo Zanier

David Soldani, Man Li and Jaana Laiho

David Soldani, Davide Chiavelli, Jaana Laiho, Man Li, Noman Muhammad,Giovanni Giambiasi and Carolina Rodriquez

9.2 QoE monitoring framework 319

David Soldani, Giovanni Giambiasi, Kimmo Valkealahti, Mikko Kylva¨ja¨,

Massimo Barazzetta, Mariagrazia Squeo, Jaroslav Uher, Luca Allegri and

Jaana Laiho

10.4 QoS optimisation in core and backbone networks 416

Wireless mobile networks have come a long way from providing voice-only services tooffering a proliferation of multimedia data services Mobile data services are rapidlybecoming an essential component of mobile operators’ business strategies and aregrowing very quickly alongside traditional voice services For example, in the secondquarter of 2005, total average data revenue per month from leading US operatorsreached $575 million – more than double the amount for the same period in 2004.With the spread of WCDMAand EGPRS, availability of new services, functionality-richhandsets and convergence of various technologies, this trend is poised to gain pace in thefuture According to a Yankee Group study, US mobile data revenue streams in 2009 areexpected to reach $15.9 billion

Mobile office applications, browsing and multimedia messaging services (MMS) areexpected to be the major contributors together with many small contributions from othercurrent and future applications The following list covers some of the revenue generatingdata services available today and some to come in the near future:

As the requirements for different applications vary, this growth of non-voice services hasposed a new challenge to managing their performance in more effective ways This isessential in order to provide best-of-class services to the end-user without overdimension-ing precious network resources.

‘Quality of experience’ (QoE) is the term used to describe user perceptions of theperformance of a service Quality of service (QoS), on the other hand, is the ability of thenetwork to provide a service at an assured service level In order to provide the best QoE

to users in a cost-effective, competitive and efficient manner, network and service viders must manage network QoS and service provisioning efficiently and effectively.Enterprises and network providers that provide superior QoE enjoy a significantcompetitive advantage, while companies that ignore the importance of QoE may sufferunnecessary costs, lost revenue and diminished market perception Asurvey by a famousconsulting firm suggests that around 82% of customer defections (‘churning’ to thecompetition) are due to frustration over the product or service and the inability of theprovider/operator to deal with this effectively Moreover, this leads to a chain reaction,because, on average, 1 frustrated customer will tell 13 other people about their badexperience An operator cannot afford to wait for customer complaints to assess the level

pro-of its service quality Surveys have shown that for every person who calls with a problem,there are another 29 who will never call About 90% of customers will not complainbefore defecting – they will simply leave (churn) once they become unsatisfied This churndirectly affects the profitability and image of the operator, especially if it happens in theearly stage of their induction So, the only way to prevail in this situation is to devise astrategy to constantly manage and improve QoE and QoS

QoE and QoS management can be classified in four interdependent categories:network planning, service and QoS provisioning, QoE and QoS monitoring and opti-misation There has been rich research and development in this field, and the purpose ofthis book is to introduce the principles, practices and research undertaken in these fourareas The book is intended for both academic and professional audiences

We would like to acknowledge the contributions and time invested by our colleaguesworking at Nokia Apart from the editors, the contributors were Anna Sillanpa¨a¨, PaoloZanier, Giovanni Giambiasi, Carolina Rodriguez, Jaana Laiho, Kimmo Valkealahti,Davide Chiavelli, Jaroslav Uher, Heikki Almay, Noman Muhammad, Uwe Schwarz,Massimo Barazzetta, Martin Kristensson, Luis Alberto Pen˜a Sierra, Mariagrazia Squeo,Mikko Kylva¨ja¨, Sandro Grech, Svetlana Chemiakina, Jani Lakkakorpi and LucaAllegri

We would like to express our gratitude to our employer, Nokia, for general permission,support and encouragement, and for providing some illustrations In particular, LauriOksanen is acknowledged for giving us the opportunity to spend several years in dealingwith QoE and QoS management issues in UMTS cellular systems, and for letting uscollect a part of the attained results in this manuscript

The publishing team at John Wiley & Sons, Ltd, led by Mark Hammond, has done anoutstanding job in the production of this book We are especially grateful to SarahHinton and Jennifer Beal for their patience, support, guidance and assistance.Ultimately, we would like to dedicate this book to our families for their love, patienceand assistance during this endeavour

The editors and authors welcome any comments and suggestions for improvement orchanges that could be implemented in possible future editions

David Soldani, Man Li and Renaud CunyEspoo, Finland and Boston, Massachusetts, USA

16QAM 16 Quadrature Amplitude Modulation

BCS Block Check Sequence

CRF Charging Rules Function

EQoS Enhanced Quality of Service

LLC Logical Link Control protocol

NM Network Manager

PM Performance Monitoring or Management

RNSAP Radio Network Subsystem Application Part protocol

SPASelf Provided A pplications

TSG Technical Specification Group

Introduction

Noman Muhammad, Davide Chiavelli, David Soldani and Man Li

Browsing through the literature, one may find many different definitions for quality ofend-user experience (QoE) and quality of service (QoS) Some try to define the termsfrom a business perspective whereas others do so from a technical perspective In thecontext of this book, QoE is the term used to describe the perception of end-users on howusable the services are QoS, on the other hand, describes the ability of the network toprovide a service with an assured service level In order to provide the best QoE to users

in a cost-effective, competitive and efficient manner, network and service providers mustmanage QoS and services in proper and appropriate ways

QoS and QoE are so interdependent that they have to be studied and managed with acommon understanding, from planning to implementation and engineering (optimisa-tion) In short, the aim of the network and services should be to achieve the maximumuser rating (QoE), while network quality (QoS) is the main building block for reachingthat goal effectively QoE, however, is not just limited to the technical performance of thenetwork, there are also non-technical aspects, which influence the overall user perception

to a great deal Figure 1.1 shows an example of technical and non-technical factorsaffecting the QoE This book will only deal with the technical aspects of QoE in detail

In subsequent chapters of this book, the relationship between QoS and QoE and theirmanagement is discussed in length Although the specific focus of the discussion is onUniversal Mobile Telecommunication System (UMTS) cellular networks, many of thecovered concepts are generic in nature and, as such, they are effectively applicable toother types of fixed and cellular networks

1.1 QoE value chain

The overall QoE depends on how well the operator orchestrates the entire value chain asseen by the user This value chain comprises the following:

audio, portals, etc

QoS and QoE Management in UMTS Cellular Systems Edited by David Soldani,

Man Li and Renaud Cuny © 2006 John Wiley & Sons, Ltd ISBN: 0-470-01639-6

Service and network providers – that is, mobile network operators (MNOs), mobilenetwork virtual operators (MVNOs) and mobile Internet service providers (ISPs),which are often owned by the operators themselves and transmit the content to theuser.

by the user, enable the above three components in the value chain

The QoE value chain is depicted in Figure 1.2

Although everyone in the mobile data service value chain should focus on optimisingthe experience, it is the MNO who has the main stake Ignoring QoE, when designing asystem/service, and waiting for users to vote with their loyalty is expensive and can haveeven worse consequences

Mobile operators sit in the middle of this chain and orchestrate all four of thesecomponents in order to provide an overall ‘experience’ to the user At the same time theyhave the highest stakes in ensuring an excellent QoE

Technical factors (mainly QoS):

• E2E network quality

• Network/service coverage

• Handset functionality

Non-technical (subjective) factors:

• Ease of service setup

• Service content

• Pricing

• Customer support

Quality of end-user experience (QoE)

Figure 1.1 QoE is affected by the technical (QoS) and non-technical aspects of service

Network vendors and system integrators

Although not seen by the end-user, they enable the above

three entities of the value chain

Mobile content providers and contents

Mobile content providers and originators, websites, WAP sites, games, video, audio, portals, etc.

Figure 1.2 QoE value chain

As already pointed out, QoE and QoS are integral parts of each other and no cussion on QoE would be complete without referring to QoS These two terms have beendescribed in different ways in different forums, leading to confusion for some readers inmany cases It is very important to understand their interaction – as discussed in the nextsection An effort has been made to present various definitions and view points to come to

dis-a common understdis-anding Throughout this book, the terms ‘QoS’ dis-and ‘QoE’ will be used

in the context described in the following section

1.2 QoS and QoE

This section defines and explains the differences between QoS and QoE This will help us

to understand the requirements of the operator and of the end-user:

level QoS encompasses all functions, mechanisms and procedures in the cellularnetwork and terminal that ensure the provision of the negotiated service qualitybetween the user equipment (UE) and the core network (CN)

she is with a service in terms of, for example, usability, accessibility, retainability andintegrity of the service Service integrity concerns throughput, delay, delay variation(or jitter) and data loss during user data transmission; service accessibility relates tounavailability, security (authentication, authorisation and accounting), activation,access, coverage, blocking, and setup time of the related bearer service; serviceretainability, in general, characterises connection losses

The term ‘QoE’ refers to the perception of the user about the quality of a particularservice or network It is expressed in human feelings like ‘good’, ‘excellent’, ‘poor’, etc

On the other hand, QoS is intrinsically a technical concept It is measured, expressed andunderstood in terms of networks and network elements, which usually has little meaning

to a user QoE and QoS concepts are shown in Figure 1.3

Although a better network QoS in many cases will result in better QoE, fulfilling all thetraffic QoS parameters will not guarantee a satisfied user An excellent throughput in onepart of a network might not help if there is no coverage a short distance away

As far as measures are concerned, these statistics tell an operator very little aboutthe level of customer satisfaction Flawless transmission of garbled packets does notmake for happy users So, the inference that QoE is improved because QoS mechanismsare used to reduce jitter or average packet delivery delay may not be accurate in allcircumstances What is important is good user experience or QoE, and the goal of QoSshould be to deliver a high QoE

Delivering high QoE depends on gaining an understanding of the factors contributing

to the user’s perception of the target services, and applying that knowledge to define theoperating requirements This top-down approach reduces development costs and therisks of user rejection and complaint, by ensuring that the device or system will meet userrequirements

QoS is often treated as a bottom-up process, consisting of a concatenation of point performance differentiation methodologies with little consideration for whathappens on an end-to-end basis The top-down approach is based on the premisethat it is the end-user who is the ultimate beneficiary of QoS In order to meet end-user expectations, the implementation of QoS in actual networks must be focused on theend-user perspective and provide the service performance levels necessary for a high QoEfor the user In practice, this means focusing on the customer – that is, the person whopays the bill – understand end-user expectations for QoS performance (QoE), and usethese to drive requirements for specific QoS mechanisms (functions) for individualnetwork domains such as UE, access, core, backbone and external packet datanetworks, and corresponding interfaces The conceptual models of end-to-end QoEand QoS adopted in this book are illustrated in Figure 1.4.

point-to-There are many different end-to-end scenarios for delivering end-to-end QoS that mayoccur from a UE connected to a UMTS cellular network The network architecture forthe most significant contexts presented in this book is as depicted in Figure 1.4 Althoughthe backbone IP network is shown as a single domain, it may consist of a number ofseparate domains The structure of the local UE includes cases from a simple host to agateway to a network such as a local area network (LAN) If the UE is acting as agateway, it is responsible for providing the IP bearer service management towards theextended network

Quality of end-user experience (QoE)

Excellent Very good Good Fair Poor

RNC/BSC

Figure 1.3 QoE is expressed in ‘feelings’ rather than metrics QoS relates to all mechanisms,functions and procedures in the network and terminal that implement the quality attributes(bearer service) negotiated between the UE and CN

In Figure 1.4 the remote end is shown as a simple host Other more complex cases atthe remote end, such as private LAN with overprovisioning, or possibly LAN prioritymarking, and DiffServ and/or Reservation Protocol (RSVP) capable routing elementsare not depicted The reference point shown at the UE is at the interface to the UE.Within the UE, QoS control could be derived from any of the mechanisms that occuracross that reference point, or it could use a different mechanism internally Although thescenarios currently identified are mainly using DiffServ in the backbone IP network, it isnot mandated that DiffServ must be used for this Other mechanisms, for example, over-provisioning and aggregated RSVP may be used.

The scenario presented in Chapters 3–5 will give examples of concatenating QoSmechanisms in different parts of the network that together can deliver an end-to-endQoS (consistent treatment and interworking between QoS mechanisms implemented indifferent network domains) End to end is by definition intended from a reference point –say, a service access point (SAP) – between two immediately above and below (adjacent)protocol layers, such as, for example, IP and TCP/UDP, through which the layers canexchange data in the UE to the corresponding SAP between the peers (same protocolentity layers) located in the remote host For an example see SAP2–SAP3 in Figure 4.6

1.3 QoE and QoS management

QoE and QoS management can be classified in four interdependent categories: networkplanning, QoS provisioning, QoE and QoS monitoring, and optimisation

Access bearer layer (e.g UMTS bearer)

IP bearer service

Scope of Packet Data Protocol context

End to end QoS delivered to user

End-to-end QoS required by user (QoE)

Figure 1.4 Top-down approach and E2E QoS definition

The calculations thereof are based on the operator’s requirements for coverage, capacityand QoS In detailed network planning, capacity and coverage are analysed for eachrelevant part of the network and interfaces between the entities in communication Thisrequires real traffic estimates and a network topology for each analysed area, the utilisa-tion of accurate models for signal and user data transmission, and the actual networkelement’s characteristics, functionalities and parameters.

QoS provisioning is a process that deploys QoS in networks and mobile terminals Theprocess translates planning results into mechanisms and parameters understandable bynetwork elements and mobile terminals and it further configures them on equipment ordevices

QoS provisioning can be classified in three categories: radio, core and transport QoSprovisioning that configures the QoS mechanisms inside the network; service QoSprovisioning that maps services into QoS profiles (set of bearer service attributes);and terminal QoS provisioning that provides service application specific QoS informa-tion to terminals

With the growth of mobile services, it has become very important for an operator tomeasure the QoS and QoE of its network accurately and improve it further in the mosteffective and cost-efficient way to achieve customer loyalty and maintain competitiveedge A poor QoE will result in unsatisfied customers, leading to a poor market percep-tion and, ultimately, brand dilution

Although QoE is very subjective in nature, it is very important that a strategy is devised

to measure it as realistically as possible The ability to measure QoE will give the operatorsome sense of the contribution of the network’s performance to the overall level ofcustomer satisfaction in terms of reliability, availability, scalability, speed, accuracy andefficiency

Together, these elements define QoE and competitive advantage across today’s based communications networks The experience is expressed in human terminologyrather than metrics An experience can be excellent, very good, good, fair or poor.Two practical approaches to measuring QoE are the following:

packet-1 Service level approach using statistical samples of a population of terminals

2 Network management system (NMS) approach using QoS parameters

The first relies on a statistical sample of overall network users to measure the QoE for allthe users in the network This process involves:

and taking KPI measurements accordingly

Utilising mobile agents in the handsets to make the results more accurate.

service mix

The second is a methodology whereby hard QoS performance metrics from variousparts of the network are mapped onto user-perceptible QoE performance targets TheseQoS measurements are made using an NMS, collecting KPI figures from the networkelements and comparing them with the target levels The process involves:

Cellular network optimisation can be seen as a process to improve the overall networkquality as experienced by the mobile subscribers and to ensure that the network resourcesare efficiently utilised This includes performance measurements, analysis of measure-ment results and updates of the network configuration and parameters The optimisationprocess can be initiated because of several reasons, the most typical are:

use

1.4 Organisation of the book

The purpose of this book is to introduce the principles, practices and researches in mobileservice planning, provisioning, performance monitoring and optimisation in QoE andQoS management This book is intended for both academic and professional audiences(industry)

The first part of the book (Chapters 2–6) lays the foundations for further ing of QoS and QoE management

understand-In Chapter 2 we describe some of the existing and upcoming multimedia services andtheir performance in detail to provide a general understanding of mobile service applica-tions and performances

Chapter 3 presents the latest mobile network QoS standardisation in the 3rd eration Partnership Project (3GPP)

Gen-Chapter 4 describes the packet data transfer across second-generation (2G) and generation (3G) cellular systems, adopter protocols to implement the QoS and radiointerface channels

Chapters 5 and 6 discuss QoS mechanisms in the radio, core and backbone networks,respectively.

In the second part of the book (Chapters 7–10), we discuss the four elements of QoEand QoS management in detail

Chapter 7 ‘Service and QoS aspects in radio network dimensioning and planning’addresses radio dimensioning and detailed planning issues that may arise when deployingmultimedia services in wideband code division multiple access (WCDMA) and enhancedGeneral Packet Radio Service (EGPRS) cellular systems

Chapter 8 ‘QoS provisioning’ examines service and QoS provisioning in detail QoEand QoS measurements including more insights into these methods are discussed inChapter 9 ‘QoE and QoS monitoring’

The objectives, concepts, processes, algorithms and means for QoS and QoE tion across UMTS cellular networks are discussed in Chapter 10 ‘Optimisation’

Mobile Service Applications and Performance in UMTS

Renaud Cuny, Man Li and Martin Kristensson

The purpose of this chapter is to introduce the functional aspects of circuit-switched (CS)and packet-switched (PS) based services and their performance over Universal MobileTelecommunication System (UMTS)

The convergence phenomenon that started some years ago and that is accelerating willgradually remove the traditional boundaries between fixed and mobile communicationsystems In the future, personal communication devices will be multiradio-capable whilebroadband wireless coverage will extend considerably On the other hand, InternetProtocol (IP) based services are expanding all the time and nowoverlap with thoseprovided by CS systems, either fixed or mobile, Voice over IP (VoIP) being one of themost remarkable examples In short, the global trend is that communications will be PSand that more and more devices and networks will support wireless mobility Gettingthere, however, will require effort and time; so, if the trend is clear, we shall not yet ignoreestablished CS systems and services as they will continue to have a key role for manyyears

The functional aspects and performance requirements of mobile services are importantpieces in the overall end-user quality-of-experience management For instance, thenecessary procedures to set up a service will determine how long session establishmentwill take depending on the actual underlying network technology (e.g., cellular or fixedaccess network) Also, once the session has been established, there will typically bespecific throughput and latency requirements to fulfil, which in turn may impose par-ticular services to be used only in certain types of networks As an example, some actiongames may be well-supported in wideband code division multiple access (WCDMA) butnot in the General Packet Radio Service (GPRS) because of too long latencies.Evaluating the overall service performance in a given low- to medium-loaded networkmay be one starting point when considering the launch of a new service If the requiredperformance is not fulfilled, even in the best conditions, it is probably not worth moving

on to the next phase of service deployment At the same time, it is important to note that

QoS and QoE Management in UMTS Cellular Systems Edited by David Soldani,

Man Li and Renaud Cuny © 2006 John Wiley & Sons, Ltd ISBN: 0-470-01639-6

lowservice performance may not always be due to network limitations, but may also, forinstance, be due to less than optimal terminal or server implementations In certain cases,optimising the application or the transport layer or applying, for example, efficientheader or data compression mechanisms may be enough to achieve satisfactoryquality-of-experience levels.

This chapter concentrates mostly on PS services The main reason being that the CSservice’s functional aspects, requirements and performance in UMTS have already beenwidely documented elsewhere (e.g., [1]) Thus, Section 2.1 summarises some key points inthe area and largely refers to other sources The remaining sections – Sections 2.2 and2.3 – focus solely on the PS service’s functional aspects, requirements and performance

in UMTS

2.1 CS service applications

The UMTS network architecture is logically divided between [2] the radio access network(RAN) and the core network (CN) The CN is itself separated into the PS CN domain,the CS CN domain and the IP multimedia CN subsystem (IMS) (see Chapter 3) The CSdomain is an evolution of the Global System for Mobile Communications (GSM)technology that was developed under the European Telecommunication Standard Insti-tute (ETSI) until 2000, and pursued later in the 3rd Generation Partnership Project(3GPP) standardisation body In CS systems, resources are allocated at service sessionsetup and reserved during the entire session duration This approach is well-suited forapplications, such as (multimedia) telephony, that have stringent and stable require-ments in terms of delay and bandwidth and when traffic sources are sending or receivingdata during the majority of the session PS systems, on the other hand, can efficientlysupport any type of service applications, including those that may be very bursty innature, and possibly idle a great part of the session (e.g., web browsing), by dynamicallyallocating network resources on a need basis

AMR speech codec (adopted in 3GPP R99 as a mandatory codec) performance ischaracterised in [4]: unlike previous GSM speech codecs (full-rate, enhanced full-rate andhalf-rate) that operate at a fixed rate and at a constant error protection level, the AMRspeech codec can adapt its error protection level to the radio channel and traffic con-ditions AMR selects the optimal channel (half- or full-rate) and codec mode (speech andchannel bit rates) to deliver the best combination of speech quality and system capacity.This flexibility provides a number of important benefits:

An improved speech quality because of codec mode adaptation, by varying the balancebetween speech and channel coding for the same gross bit rate.

combina-tion of channel and codec mode adaptacombina-tion; this can be controlled by the networkoperator on a cell-by-cell basis

full-rate mode This increased robustness to errors and hence to interference may be used

to increase capacity by operating a tighter frequency reuse pattern in GSM

signal-ling transmitted rapidly in-band

The AMR codec concept is adaptable not only in terms of its ability to respond tochanging radio and traffic conditions but also to be customised to the specific needs ofnetwork operators The AMR codec modes are illustrated in Figure 2.1

Wideband AMR (AMR-WB) was introduced in 3GPP R5 and provides further speechquality enhancements that are essentially due to the larger speech-coding bandwidth(from 50 to 7000 Hz) These improvements make AMR-WB also suitable for applica-tions having high-quality audio requirements

against a mobile Integrated Services Digital Network (ISDN) or Public SwitchedTelephone Network (PSTN) call party

Mobile Service Applications and Performance in UMTS 11

0 5 10 15 20 25

FR 12.2 FR 10.2 FR 7.95

FR 7.4

FR 6.7

FR 5.9 FR 5.15 FR 4.75 HR 7.95

HR 7.4

HR 6.7

HR 5.9 HR 5.15 HR 4.75

Figure 2.1 AMR codec modes

If the setup of the multimedia call fails the call will be set up as a speech call.

vice versa) during the call Service degradation and upgrading

H.324 consists of two mandatory components [6]: H.223 for multiplexing and H.245 forthe control Other optional components are H.263 video codec, G.723.1 speech codecand V.8 bis MPEG-4 video and AMR were later added to the system as optional codecs

CS video quality is more sensitive to the block error rate than voice due to the nature ofvideo compression and, thus, the allowed residual bit error rate is typically very small

2.2 Packet-switched service applications

Before going into the details of PS services, it is worth introducing very briefly the IMSwhich is described in more detail in Chapter 3 The IMS, added in 3GPP R5, contains all

CN elements needed for providing multimedia (IP-based) services [7], [8] The IMSenables operators to offer subscribers multimedia services based on and built uponInternet applications, services and protocols The Session Initiation Protocol (SIP) isthe application layer control protocol used for establishing, modifying and terminatingpeer-to-peer service sessions [9] A peer-to-peer service session could be a simple two-waytelephone call, a collaborative multimedia conference session or, for instance, a networkgame SIP is an Internet Engineering Task Force (IETF) driven signalling protocol based

on the request–response scheme similar to Hypertext Transfer Protocol (HTTP) ling

The browsing service allows a mobile user to browse the Web by using a browser installed

on a mobile phone The user may either type in a URL or click a link in order to access aweb page

The Open Mobile Alliance (OMA) browsing enabler is based on Wireless ApplicationProtocol (WAP) standards from the WAP Forum and is migrating towards Internetprotocols Hence, depending on the software implemented, a mobile phone may use:

a web server [11]; or

in turn contacts a web server [12]

All three protocols are based on the HTTP 1.1 request and response paradigm [10] Asshown in Figure 2.2, a web page is requested by sending a GET request message to a webserver (or a WAP gateway that in turn sends the request to the server) If the operation is

successful, the web server will reply with a GET response message that contains therequested web page A web page may have multiple embedded objects such as images, inwhich case each object is fetched with a separate GET request message A GET responsemessage from a web server contains a status code to indicate the result of the operation.

The MMS is a system application by which a client is able to conduct messagingoperations with a rich set of media contents, such as image, video, etc MMS is anon-real time delivery system, though it is expected that a multimedia message should

be deliverable within a reasonable time frame MMS can interoperate with othermessaging systems – such as the traditional email on the Internet In other words,when one endpoint of the service is an MMS client, the other endpoint for the multimediamessage may be another MMS client, a client on a legacy wireless messaging system or anemail client MMS is specified in OMA in [13]–[16]

An MMS proxy-relay is a network element that interacts with MMS clients on mobilephones to provide MMS services In addition, it provides access to an MMS server thatstores messages Furthermore, it also serves as a gateway when interacting with othermessaging systems (e.g., Internet email) Some implementations may combine MMSproxy-relay and MMS server into one physical element

There are two ways a message may be retrieved by a receiving MMS client depending

on service profiles and/or device settings Immediate retrieval of a newmessage meansthat a receiving MMS client immediately retrieves the message via the MMS proxy-relayupon receiving a newmessage notification In contrast, deferred retrieval means that areceiving MMS client first acknowledges a new message notification and at some laterpoint retrieves the message via the MMS proxy-relay

Figure 2.3 shows the MMS transactions for immediate retrieval In the figure, both theorigination and termination points are MMS clients The MMS protocol data unit(PDU) can be carried by either WSP or HTTP The message notification (M-Notifica-tion.ind) is sent via WAP

Mobile Service Applications and Performance in UMTS 13

GET response (the main page)

GET response (an embedded object) GET request (for an embedded object)

GET response (last embedded object) Page displayed to user

After a user composes a message, he/she clicks the send button on the mobile phone.The MMS client transmits the message to the MMS proxy-relay Upon receiving themessage with no error, the MMS proxy-relay sends back a confirmation to the MMSclient The multimedia message is then forwarded across the mobile network to theterminating MMS proxy-relay and is stored in its associated MMS server The terminat-ing MMS proxy-relay then notifies the originating MMS client.

For immediate retrieval, the MMS client tries to fetch the message with a GEToperation After the message is retrieved, the MMS client sends a Notify response back

to the MMS proxy-relay This response is forwarded to the original MMS proxy-relay,which then sends a delivery indication (M-Delivery.ind) to the originating MMS client toacknowledge the status of the message delivery If the user has requested a deliveryreport, the MMS client will inform the user upon receiving the M-Delivery.ind Other-wise, the user is informed only when the delivery is not successful

For deferred retrieval, a receiving MMS client responds to a message notificationimmediately But the message is not retrieved until a later time – for example, when theuser asks to read the message

Depending on the service settings on the receiving mobile device, sending of a deliveryreport back to the original user may be denied In other words, the original MMS clientcannot assume that a delivery report (M-Delivery.ind) is guaranteed for every messagesent

M-NotifyResp.ind M-Delivery.ind

Notify user

Notify user if report requested

Message stored at MMS server

Interactions across network

Interactions across network

User A UE A Orig MMS proxy-relay Term MMS proxy-relay UE B User B

2.2.3 Content download

OMA is defining a generic content download over-the-air specification [17] As specified,

a download user agent is an agent or software function in the device responsible fordownloading a media object A download descriptor contains information about a mediaobject and instructions to the download agent about how to download it It allows theclient device to decide whether it has the capabilities to install and render/execute themedia object

The OMA specification supports two scenarios:

In both scenarios, the download agent may send a notification to the server in order toconfirm the status of the transaction This notification is likely to be mandatory in a pay-per-transaction model where the confirmation of a successful installation of a mediaobject typically triggers server-end billing actions

Figure 2.4 shows the message flows for a separate delivery of download descriptor andmedia object A user is initially presented with a reference to the download descriptor.The reference may be on a web page, inside an email or an MMS message, or stored inmemory

If the user has the intention of pursuing the download, he/she will click the reference toobtain the descriptor The download descriptor is then transferred to the mobile device.The transfer mechanism or protocol may be HTTP or secure HTTP (HTTPS) but canalso be through MMS, email or some instant messaging protocol The download agent

Mobile Service Applications and Performance in UMTS 15

Verification

Descriptor

Notify userValidate the action Retrieve media

Download media

NotificationConfirmation