UMTS and Mobile Computing

UMTS and Mobile Computing

For a listing of recent titles in the Artech House Mobile Communications Series, turn to the back of this book.

UMTS and Mobile Computing Alexander Joseph Huber Josef Franz Huber

Artech House Boston • London www.artechhouse.com

Library of Congress Cataloging-in-Publication Data Huber, Alexander Joseph. UMTS and mobile computing / Alexander Joseph Huber, Josef Franz Huber. p. cm. — (Artech House mobile communications library) Includes bibliographical references and index. ISBN 1-58053-264-0 (alk. paper) 1. Mobile communication systems. 2. Wireless communication systems. 3. Global system for mobile communications. I. Huber, Josef Franz. II. Title. III. Series. TK6570.M6 H83 2002 004.6—dc21 2002019676 British Library Cataloguing in Publication Data Huber, Alexander Joseph UMTS and mobile computing. — (Artech House mobile communications series) 1. Mobile computing 2. Mobile communication systems I. Title II. Huber, Josef Franz 004.6 ISBN 1-58053-264-0 Cover design by Igor Valdman UMTS is a trade mark of ETSI (European Telecommunications Standards Institute) registered in Europe and for the benefit of ETSI members and any user of ETSI Standards. We have been duly authorized by ETSI to use the word UMTS, and reference to that word throughout this book should be understood as UMTS.

© 2002 ARTECH HOUSE, INC. 685 Canton Street Norwood, MA 02062 All rights reserved. Printed and bound in the United States of America. No part of this book may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without permission in writing from the publisher. All terms mentioned in this book that are known to be trademarks or service marks have been appropriately capitalized. Artech House cannot attest to the accuracy of this information. Use of a term in this book should not be regarded as affecting the validity of any trademark or service mark. International Standard Book Number: 1-58053-264-0 Library of Congress Catalog Card Number: 2002019676 10 9 8 7 6 5 4 3 2 1

Contents Foreword 1

xi

Foreword 2

xiii

Preface

xv

Introduction

1

1.1

Mobile Computing and Ubiquitous Computing

2

1.2

The Driving Factor of Mobility

5

1.3 1.3.1 1.3.2

Innovation Drivers Moore’s Law Compression Standards for Multimedia: JPEG, MP3, MPEG-4, MPEG-7 Wireless Technologies Migrate to Configurable Radio and Smart Antennas The Internet, Intranets, and Mobility Services and Applications

9 9

12 15 16

References

16

2

The Market for UC

17

2.1

Mobile Market Developments

17

1.3.3 1.3.4 1.3.5

v

11

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UMTS and Mobile Computing

2.1.1 2.1.2 2.2 2.2.1 2.2.2 2.2.3 2.2.4 2.2.5 2.2.6 2.3 2.3.1

Emerging Wireless Personal Area and Wireless Local Area Networks Mobile Satellite Network Markets Internet Market Developments Challenge: Transition from Circuit Switching to Packet Switching Internet Access from Mobile Devices The Web Market Electronic Commerce: A Fundamental Component of Future Multimedia Services Intranet Need for Mobile Extensions Intranet Access from Mobile Devices

20 22 22 25 27 28 29 29 30

Fixed and Mobile Convergence Mobile Computer-Based Communications and UMTS Increasing Mobility of Individuals and the Pressure to Turn Dead Time into Productive Time Key Enablers Broadband Wireless Convergence Broadcasting Convergence Convergence on Devices Convergence and the Creation of New Services

32 33 34 35 35 36

References

36

3

Technologies

37

3.1 3.1.1 3.1.2 3.1.3 3.1.4 3.1.5 3.1.6

Mobile Wireless Communication Technologies WPANs WLANs Wireless WANs Extended Area Networks Other Technologies Technology Positioning and Comparison

37 43 56 63 86 96 98

3.2

UMTS

2.3.2 2.3.3 2.3.4 2.3.5 2.3.6 2.3.7

30 31

100

Contents 3.2.1

vii

3.2.2 3.2.3 3.2.4 3.2.5 3.2.6 3.2.7 3.2.8

Value Chain—Developments Towards Information-Based Services Network Architecture UMTS Radio Access Techniques Core Network Internet Service Provider’s Function Mobile Portal’s Function UMTS Terminal Technologies USIM Cards and Smart Cards

103 105 110 120 129 132 141 144

3.3 3.3.1 3.3.2 3.3.3 3.3.4 3.3.5

UC Appliances (Devices) Card Technologies The iButton Tag Technologies Mobile 3G Devices Devices Summary

145 147 160 168 192 230

References

234

4

Standardization

241

4.1 4.1.1 4.1.2 4.1.3

WPAN and WLAN Standardization Bluetooth IEEE 802.X Standards DECT and PHS

243 243 245 249

4.2 4.2.1 4.2.2 4.2.3

3G Standardization 3GPP Develops Specifications for Global Use Internet-Related Standardization Standard Protocol Layers in UMTS

250 250 252 256

4.3

Addressing and Registration Standards

258

4.4 4.4.1 4.4.2 4.4.3

Standards for Information Encoding Voice Encoding Bitmap, Graphic, and Photographic-Image Encoding Video and Audio Compression

263 265 265 266

4.5

Software, Protocols, Computer Languages, and Smart Cards

274

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UMTS and Mobile Computing

4.5.1 4.5.2 4.5.3

SOAP CORBA Java Programming and Java Remote Method Invocation Jini HAVi UPnP OSGI Home Plug and Play Web Programming and Markup Language Standards WAP Smart-Card Standardization

279 280 280 282 282 283 284 289 291

References

296

5

Applications

299

5.1 5.1.1 5.1.2 5.1.3 5.1.4 5.1.5 5.1.6

UMTS Services and Applications Mobile Internet and Intranet Access Customized Infotainment and Edutainment Multimedia Messaging Services Location-Based Services Voice- and Videotelephony and -conferencing UMTS Services Portability

304 304 306 307 310 315 316

5.2

Examples: WAP and i-Mode

318

5.3 5.3.1 5.3.2 5.3.3

Telemetry Vehicle-Related Mobile Computing Health Care Other Applications

322 324 326 329

5.4

Mobile E-Commerce

329

References

333

6

Resource Issues

335

6.1 6.1.1

Addressing Capacity in Networked Environments Address Schemes

335 336

4.5.4 4.5.5 4.5.6 4.5.7 4.5.8 4.5.9 4.5.10 4.5.11

276 276

Contents

ix

6.1.2

Estimations of Address Capacity

339

6.2 6.2.1

Frequency Spectrum How Much Frequency Spectrum Is Needed for 3G Services? 3G Traffic Capacity Calculations Worldwide 3G Spectrum Identification What Is the UMTS-Specific Spectrum Demand per Operator in the Initial Phase? Spectrum Demand for WLANs or Ad Hoc Networks Worldwide WLAN Spectrum Identification

344

6.2.2 6.2.3 6.2.4 6.2.5 6.2.6

346 347 353 359 359 361

References

363

7

Outlook: Telecom + Datacom + Media = Infocom

365

7.1

Taking Moore’s Law into the Future

369

7.2

Future Network Architectures

371

7.3

Devices

375

7.4

The Smart-Card Issue

377

7.5

New Services and Applications

378

7.6

Mobile Agents

379

7.7

Industry Outlook

380

7.8

Researchers Move to 4G Mobile Radio Systems

381

7.9

Market Development

383

References

384

List of Acronyms

387

About the Authors

415

Index

419

Foreword 1 Any sufficiently advanced technology is indistinguishable from magic. —Arthur C. Clarke, The Lost World of 2001

The dawn of the twenty-first century sees us standing on the threshold of the introduction of the Third Generation Universal Mobile Telecommunications System (UMTS). UMTS is not just an access technology or a technical platform, it is much more: a communication system leading the mobile user of the twenty-first century into a new mobile multimedia world linked with the Internet world. In 2001 NTT DoCoMo in Japan became the first company to offer mobile users Internet access including video calls at comfortable speeds via mobile devices, as well as voice and messaging services. Consumers are now able to enjoy the whole beauty of telecommunications in speed and capacity anywhere and anytime. Alexander and Josef Huber are offering readers very interesting insight into the converging world of mobile broadband multimedia and mobile computing to understand, on one hand, the underlying technology and, on the other hand, the driving forces of service, applications, portals, and more. I very much welcome the publication of this book as a tailored guidance into the complicated issue of modern converging communications. Dr. Bernd Eylert Chairman UMTS Forum March 2002 xi

Foreword 2 Readers of this book will note from its table of contents that it offers a comprehensive review and analysis of the confluence of mobility and computing. As the authors suggest, the ubiquitous computing concept (pioneered by the late Mark Weiser of Xerox PARC) has a natural implication that billions of smart, programmable devices will also be portable and a good many of them will be useful for and used in mobile operation. It is worth distinguishing between portability and mobility. Portable, networked devices may be moved from place to place and used—in place. Mobile, networked devices are intended to be used while in transit. Plainly, a mobile device may serve as a portable device, but a portable device may not be equipped to be used in motion. The requirements that must be satisfied may not be terribly dissimilar. For example, a portable, Internet-enabled device will need an IP address while it is in use, but it might be assigned such an address each time it is pressed into service, and this address need not necessarily be fixed or the same each time the device is used. Techniques like dynamic host configuration are designed to serve this requirement. However, if the device must be found by others, as opposed to always initiating contact, then additional methods must be sought. The concept of mobile IP has been explored in considerable detail by the Internet Engineering Task Force and generally involves the use of a home proxy that retains a permanent IP address and is responsible for keeping track of the current actual IP address associated with the mobile device. Other ideas have been put forward, such as dynamic domain name services in which the IP address associated with a domain name is dynamically changed. xiii

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UMTS and Mobile Computing

In the world of IPv6, which is beginning to emerge from its experimental condition into native mode operation, ideas, such as a 64-bit unique device identifier and a separate 64-bit routing identifier, are combined into a 128bit IPv6 address. The Instant Messaging service of AOL among other peer-to-peer applications has created a widespread appreciation for the concept of presence. In this case, interested parties look to on-line databases to discover the whereabouts (i.e., IP address) of a party associated with a particular identifier. These applications allow users to select their own identifiers and the client side of the application updates the database as the client discovers its most recently assigned IP address. Looking up an identifier in such a database allows a form of rendezvous, permitting one party to signal the other, either through a rendezvous server (as with AOL’s Instant Messaging) or directly, in the event that the actual IP address is revealed to the party wishing to rendezvous. There are myriad technical and policy issues arising from the consideration of mobility, not the least of which concerns the privacy of the mobile party whose whereabouts may be revealed as a consequence of the operation of presence and rendezvous mechanisms. Moreover, the stage is being set for the interaction of billions upon billions of programmable devices. One cannot help but wonder what emergent properties will be revealed as this amount of software, together with all its various bugs, is made to interwork over the Internet and other networks. Particularly striking about this book is its wide-ranging scope and the innovative perspective the authors bring to the subject. There is little doubt in my mind that the mobile environment will not merely enable us to blaze new trails in networking, but will force us to do so, thanks to the many challenges these capabilities will place before us. One suspects that the policy challenges may well be much more difficult to surmount than the technical ones, which will be interesting enough in their own right. Vinton G. Cerf Camelot March 2002

Preface Over the last 10 years, dramatic advances in computing power and software have enabled significant developments in computing, networking, and mobility. Personal computers, CD-ROM and DVD technology, digital television, mobile and satellite telecommunication networks, fiber-optic transmission, and the Internet and intranets have had considerable impact on the development of our society. Developing countries, in particular, have benefited from mobile communications technologies, which have made possible a very fast growth in their telecommunications infrastructures. By the end of 2001, the mobile networks market, for example, has reached approximately 950 million users, and the Internet has more than 400 million. The enormous progress in information and telecommunication technologies over the past decade has led to the creation of an information society—a term that describes a society characterized by knowledge-based workers, new flexible work practices in education, industry, and private life, intelligent equipment, and mobility and networking in multimedia. In this information society, information is an important production factor in an increasingly global competitive market. Business processes are based more and more on efficient information and communication technologies. The world economy and society is changing. Large and small businesses alike are being organized differently; they are becoming more and more global rather than regional or local. Information plays an increasingly important role. Many organizations are looking to identify and capitalize on the promise of new market opportunities in multimedia created by these technological developments. Greater pressure on time and the need for xv

xvi

UMTS and Mobile Computing

mobility and personalization lead to a growing demand for mobile access to services—anytime, anywhere. Multimedia is a catchword that is used in various ways, either as an indication of the dawning of a great time when we reach the promised land of milk and honey, or on the contrary, where it seems to be the ultimate stage of communications. If not already here, the time is near when terminals will enable virtual work teams, even when on the move, to focus on common tasks. People on the street will be able to access information instantly on local films fitting their taste—and download video clips of potential shows if requested. Tourists will download directly to their handhelds the map and historical information of a desired sight. Commuters will be able to play a round of bridge with friends while traveling to work. Alternatively, the commuter could enjoy a personalized newspaper. There will be machine-to-machine communications (e.g., in vehicles and households). Visionaries like Mark Weiser, who worked for the Computer Science Laboratory at XEROX Parc USA, had by 1988 already started to talk about a new paradigm in computing, where computers would be everywhere, and become more and more integrated into natural environments. He imagined computers so embedded, so naturally integrated, that we would use them without even thinking about it. He called this vision ubiquitous computing. Driven by the success of the World Wide Web in the 1990s, enthusiasm for the New Economy was reinforced by the emerging discussion of the Universal Mobile Telecommunication System (UMTS) on a global scope, which represented the principal of third-generation (3G) mobile network technology. In 2001, however, critical voices and press views introduced doubt to the promise of these new technologies. These doubts remind us of similar critics in history—critics of revolutionary inventions, such as book printing, the steam engine, railways, and automobiles—who caused vigorous debates about their value for and future impact on society. The big question always is, how will paradigm changes be handled, and how fast will changes take place? Paradigm changes are always difficult; society’s acceptance threshold is sometimes like a wall that hinders the breakthrough of new ideas and concepts. Knowledge and visibility can lower this threshold. This book contributes to the debate by describing the status of ubiquitous computing from a wireless networking perspective and focusing on 3G mobile technology. Third-generation mobile technology takes us from pure talking and listening to seeing, from voice to video—just like we went from radio sound to television pictures in the past. Already, both the technologies and the market demand exist. From a technological point of view, we see two

Preface

xvii

waves of innovation coming together in a timely, synchronous manner, thus encouraging new developments on both sides because of their synergies. On the computing side we see the simultaneous miniaturization and growth of computing power: the wave of mobile computing. On the networking side, we see mobile networks and the Internet coming together: the wave of mobile multimedia communication. This is the beginning of something new. We also see that a new understanding of advanced communications is taking place, which drifts away from the stupid network paradigm. The network is no longer just bit transport and switching; it now collects, aggregates, and prepares information on the applications level related to end users and devices. In the next stage of development, the actual situation of a person or device will be taken into account and the age of situation-dependent computing and communications will begin. This is what we understand to be the coming ubiquitous computing era. We thank our supporters, who helped us prepare this book. Our special thanks go to Michaela and Heidi for their editorial assistance and to Erika and Oliver for their appreciation.

1 Introduction It is a fact: The economy is going global. No wonder that global networking plays an increasing role and that information is an increasingly important factor in daily business. In 2001, the Internet enabled more than 400 million users worldwide to access several billion Web pages, and in the emerging area of e-commerce, huge amounts of money were spent on goods and services. Another fact is that the cost of information technology is falling much faster than for any previous technology. Over the past few decades, the real price for computer processing power has dropped by 99%, an average decline of 35% per year. The size and weight of computers have become considerably smaller, and mobile computers have reached the performance previously only seen with desktops. It is obvious that the stupid network paradigm will not continue; instead, network intelligence will be the keyword of the future. Network intelligence means functionality—which is flexible regarding fixed and mobile access, which has the knowledge of where the user is, which is able to aggregate content related to personal profiles, and which manages mobility. Of course, the available Internet protocols (IPs) will play a distinctive role and will challenge the telecommunication companies and the computer industry in many areas. What about the markets? The growing wireless and Internet and intranet markets will challenge the computer industry in many fields. While the wireless markets require small and lightweight portable devices with intelligence tailored to users’ needs, the Internet and intranet markets require 1

2

UMTS and Mobile Computing

higher transmission bit rates, more processing power, and increased memory capacity. As computing becomes increasingly mobile, communication systems are becoming increasingly interdependent. As this trend continues, the computing community will be forced not only to develop revolutionary systems, but also to redefine computing, including its hierarchical system architectures and operating systems (OSs), its traditional computer languages, and its networking structures. The focus on development efforts towards miniaturization, networking, personalization, portability, and mobility emphasizes this trend. Moore’s Law may continue to provide duplication of processing power every 18 months, and new computer-controlled stationary and portable devices with higher performance and low power consumption will enrich the computer world. These devices will pave the way to mobile computing.

1.1 Mobile Computing and Ubiquitous Computing Discussion about ubiquitous computing (UC, or ubicomp) has been going on for many years. UC describes the evolution of computing towards the socalled third era of computing. Mobile computing will be a main contributor to this development. The main aim of UC is to embed many small and highly specialized devices within the everyday environment in such a way that they operate seamlessly and become transparent to the person using them. They will operate either off-line or on-line. UC products aim to be everywhere (e.g., by being portable), to be small, and to be aware (of their environments, users, the contexts). Products and devices embodying these characteristics will provide a physical entity with complete freedom of movement as well as freedom of interaction. In his famous 1991 article, “The Computer for the 21st Century” [1], Mark Weiser introduced his vision of UC. The cornerstones of this vision are that computers as they are known today will be replaced by a multitude of networked computing devices embedded in our environments and that these devices will be invisible in the sense of not being perceived as computers. UC has two main features: • Ubiquity: Interactions are channeled through multiple interfaces

rather than a single workstation.

• Transparency: The technology becomes so embedded in everyday life

that it essentially becomes invisible to users.

Introduction

3

Mark Weiser called UC the “third wave in computing, just now beginning: First were mainframes, each shared by lots of people. Now we are in the client-server personal computing era, with the person as the client being dependent on a machine, the server. Next comes personal mobile computing, still client-server-based. Finally, UC is seen as the age of calm technology, when technology recedes into the background of our lives” [2]. The defining words will not be intelligent or agent, but rather invisible, calm, and connection. Many computers will serve each person everywhere in the world. The UC era’s crossover point with desktop computing is thought to be around 2005 to 2010. The UC era will be defined by many computers shared by each of us. We may access some of these computers in the course of a few minutes of Internet browsing. Others will be embedded in walls, chairs, clothing, light switches, cars—in everything. UC is fundamentally characterized by the connection of things in the world with computation. This will take place at many levels, including the microscopic. Mark Weiser envisioned the future as one where embedded computers would bring other worlds to us in new ways—sometimes in ways so unobtrusive that we will not even notice our increased ability for informed action. As an example of how this might work, Weiser describes the kind of music your wake-up device will play: “The kind of tune [it] plays to wake me up will tell me something about my first few appointments of the day. A quick urgent tune: 8 a.m. important meeting. Quiet, reflective music: Nothing until noon.” In this way, the computer “can be suggestive without being intermediating. Computers will act like books, windows, walks around the block, phone calls to relatives. They won’t replace these, but augment them, make them easier, more fun. Dwelling with computers, they become part of the informing environment, like weather, like street sounds” [1, 2]. Thus, mobile com- puting could help to free our minds from unnecessary work so that we can focus on the things and issues that are really important, interesting, and challenging. There is much talk today about thin clients, meaning lightweight Internet access devices costing only a few hundred dollars. UC will see the creation of thin servers, which will cost only tens of dollars or less and will put a full Internet server into every household appliance and piece of office equipment. The social impact of embedded computers may be analogous to two other technologies that have become ubiquitous: writing, which is found everywhere from clothes labels to billboards, and electricity, which surges invisibly through the walls of every home, office, and car. Writing and electricity have become so commonplace, so unremarkable, that we forget their huge impact on everyday life. So it will be with UC.

4

UMTS and Mobile Computing

Two predecessors of the coming UC era are found in fields of embedded microprocessors and the Internet. It is easy to find 40 microprocessors in an average home in the United States today: in alarm clocks, in microwave ovens, in TV remote controls, in stereos and TV sets, and in children’s toys. These microprocessors do not yet qualify as UC for two reasons: they are mostly used one at a time, and they are still masquerading as old-style devices like toasters and clocks. But if they were networked together, they would become an enabling technology for UC. If they were tied to the Internet, they would be connected with millions of information sources: clocks that find out the correct time after a power failure, microwave ovens that download new recipes, children’s toys that are ever refreshed with new software and vocabularies, paint that cleans off dust and notifies you of intruders, and walls that selectively dampen sounds are just a few possibilities [3]. These examples belong to mobile computing, an enabler for UC. Let us consider such development in three phases. The first phase is one where there are millions of computing devices, many of which are working off-line. They range in size from smaller than that of a memo pad to larger than that of desktops and computer towers. In this phase there are also the mobile terminals of first- and second-generation (1G and 2G) wireless networks, which provide voice and simple data. Their interconnection capabilities are still limited with regards to bit rate and reachability. The second phase adds multimedia mobility. Many computing devices in this phase will have more enhanced mobile data communications capability (e.g., multiservice networking). Universal use and portability of devices and services will play an important role. It will be possible to present a virtual home environment (VHE) to the user. Third-generation (3G) mobile networks will provide both multimedia communication with medium to high bit rates and the necessary networking support for client-server-based computing required for the mobile Internet. The term multimedia communication means the interaction of a human being with either one or a group of other human beings or a machine or computer, anywhere on the globe, exchanging or retrieving information by means of a dialog. In a multimedia communication, more complete information can be transferred by combining visual, audio, and manual elements, such as still or moving pictures, graphics, movies, sound, music, data, or any combination of these. Personalization is the key concept in the third phase. In this phase, mobile computing will not only be related to persons; the pet, the car, the office, and the home that are related to a person will have a communication relation with the person. Personalization in the multimedia sector already has its beginnings in phase one and two, when roaming takes place and the

Introduction

5

roaming person or device is identified with a personal address. In phase three, however, the position of an individual, say a person or a device, and the user’s need will additionally determine the selection of locationand person-related parameters and situation-dependent content. Learning and adaptive networked environments will address user needs, and personalization will become part of nearly all devices in the future. The immediate ad hoc environment will play an important role in this wireless and mobile world. This will lead to personal area or ad hoc networks being embedded into 3G wide area mobile networks. Peer-to-peer communication will come into play and provide autonomous many-to-many communications. Examples are cars interacting with other cars as a first step, and persons with interaction support as an additional step. The third phase will be the era of situation-dependent computing. These development phases will only happen if sufficient radio coverage in wide area and personal areas is available to provide acceptable bit rates and sufficient traffic capacity. Mobile computing and small appliances are already found in many environments operating off-line. Currently, there are product developments and prototypes that support Mark Weiser’s theory and that might prove him right: lightweight Internet access devices are available from different manufacturers like Palm, Handspring, Compaq, and Apple, to name a few. In addition, many mobile handhelds are made Internet capable. Internetenabled household appliances and office equipment are also already available, like the interconnected smart refrigerator [4] or the Internet-enabled washing machine [5]. Thin servers and embedded computing devices are available, like Texas Instruments’ TINI [6], the Matchbox Server from Professor Vaughan Pratt of Stanford University [7], and Cell Computing’s Card PC [8]. The new Internet Protocol version 6 (IPv6), which is coming into use, allows a unique address for any computing device. In order to realize full and complete UC scenarios, however, additional work and research is necessary in many different areas of computing, including ad hoc wireless communication networks, converged radio network solutions, network organization, service and object discovery, portable multimedia user devices, positioning, and adaptive ergonomic user interfaces.

1.2 The Driving Factor of Mobility In order to understand the forthcoming developments towards the third wave in computing, it is important to analyze market trends in a broader

6

UMTS and Mobile Computing

context. The old vision of the Internet was built around desktop PCs. The new vision adds a myriad of smaller portable devices like notepads, laptop PCs, personal digital assistants (PDAs), mobile handhelds, and hometelevision set-top boxes. None of these will replace the PC. Rather, they will broaden the total marketplace for delivery and processing of information. The Internet will change from a wireline-based medium for e-mail, advertising, marketing, and customer support to a common platform for transactions and business applications. At the same time, mobile IP-based networks and wireless technologies are emerging that will change the behavior of consumers. Mobility is a new and increasingly widespread feature of our daily life. It brings new features into the Internet and opens the door for a variety of new services and applications. Figure 1.1 shows the growth of these markets in contrast to the fixed telecommunications services. In addition, the expected growth of mobile Internet users is shown as a share of the total mobile market. Mobile data communication has been for a long time the province of companies using dedicated technologies for specific purposes. A number of developments in recent years, however, mean that the picture is changing: • Cellular networks. The scale on which Global System for Mobile

Communications (GSM) is being globally adopted, combined with the technologies of wideband code division multiple access (WCDMA) and IP transport, leads to a fundamental change in the mobile environment: Increased functionality provides a platform for Mobile networks (total)

Subscriptions worldwide (millions)

2,000 1,800 1,600

Fixed networks (total) Mobile Internet (share of mobile networks)

1,400 1,200 1,000

Fixed Internet (total)

800 600 400 200 0

1995

2000

2005

2010

Figure 1.1 Global market forecast for the Internet, fixed telecommunications, and mobile networks. (Source: Siemens AG.)

Introduction

7

the development of widespread services and applications, particularly as enhancements to basic systems start to provide higher speed data services. • Internet. Today the Internet is widely known and used for work and

leisure alike. Its growth has been phenomenal and its importance lies as much in changing attitudes about the use of communications technology as in any single piece of functionality it provides. Its power lies in its flexibility, which allows the same basic infrastructure to power a range of applications, from basic messaging to multimedia conferencing.

• Intranet. The corporate world has been quick to see the potential

benefits of the Internet and to adopt Internet technologies as a way of enabling access to corporate information and the construction of virtual communities within organizations.

• Terminals. Laptops, notebooks, smart phones, and PDAs are cur-

rently the most important mobile computing terminals, but this is changing as smaller product forms begin to meet the functionality requirements of mobile users, in terms of interface, weight, size, and battery power. For an increasingly mobile workforce, smart phones and handheld devices will play a large role in facilitating work. Peripherals, such as Personal Computer Memory Card International Association (PCMCIA) cards provide a standard interface for mobile devices, and commonality in software is increasingly the norm.

• Changing work patterns. Increasingly, sections of the workforce are

working flexibly from home or on the move. Much of the demand for mobile connectivity comes from professional and managerial groups who need to remain connected to their core information and contacts while away from base. Mobile Internet and intranet will form a core component of this connectivity.

Wireless Internet and Mobile Internet—Is There a Difference?

The likely impact of wireless developments on the marketplace has been underestimated. The breakthrough occurred with the introduction of digital mobile cellular systems (2G) in the early 1990s—just like the Internet after the introduction of the World Wide Web (WWW, or the Web). Initially built on the basis of the traditional telecommunications network standards, these systems are bringing mobility and person-related services to the end

8

UMTS and Mobile Computing

user. With the evolution from 2G to 3G mobile networks, wideband radio access and Internet-based protocols will dominate and prepare the way from a mobile handset today to a mobile multimedia device in the future. Providing wireless access to the wireline Internet brings, of course, more flexibility and facilitates penetration. It is not, however, generating new services. New services come with new enabling functions—like mobility, personalization, and localization capabilities—which are the characteristics of 3G mobile systems. This is the motivation for the industry to evolve the wireline Internet to a mobile Internet with new capabilities and applications. Key enabling functions for the mobile Internet are as follows: • IP-transparency. All elements involved in the end-to-end communi-

cations path have to support IP, both in the fixed and in the mobile parts of the network.

• Mobility management. It has to function in a globally networked

environment for roaming.

• Addressing. It must allow every user a unique address capability,

which is independent from the user’s location.

• Personalization of information and positioning. There must be means

to provide such functionality.

• Positioning. The individual must be positioned to enable location-

dependent services.

• Security. It has to be provided end-to-end for fixed and mobile users.

Such preconditions will make the mobile Internet different from a wireless Internet that is understood as the Internet with the provisioning of wireless access in addition to wireline access. Mobile Internet brings more value and integrates mobile and fixed users; this is understood as convergence. The combination of Internet technology with mobile connectivity holds out the prospect of the marriage of two of the biggest and fastest growing markets in telecommunications. The mobile Internet will be a generator of new services, which will emerge from new features of a universal network that will reach the user anywhere in the world and that will support users by knowing their location and current environment. It will enhance e-commerce by enabling a mobile device to do such things as mobile shopping and mobile identification. Developing packages of services, terminals, and applications for users will be one of the key challenges to the mobile supply community over the coming decade. Another challenge will be the new

Introduction

9

business value chain, which provides many new business opportunities for market players.

1.3 Innovation Drivers 1.3.1

Moore’s Law

The phenomenon known as Moore’s Law1— the processor doubles its performance every 18 months to 2 years, while cost and power consumption fall almost as dramatically—does not appear to be approaching its limits (see Figure 1.2). Limits may be set, however, by the ability of the industry to generate the exponential capital investments needed to create fabrication facilities for each technology step. Such limitations will have profound implications for the extent to which chip technologies will influence radio technologies in the future. Within the next few years, the implementation of software radio will determine the cost and flexibility of mobile terminals. The steady down-scaling of complimentary metalloxide silicon (CMOS)–technology dimensions has been the main stimulus to the growth 10

10 9

10 Components per chip

8

10

7

10

6

10

5

10

4

4 Gbit 1 Gbit 256 Mbit 64 Mbit 16 Mbit 4 Mbit 1 Mbit Alpha 256 Kbit Pentium Intel 486 Intel 386

DRAM Processors

Gate arrays Pentium 4 Micro 2000

Intel 80286

10

3

10

1980

1990 2000 Market launch year

2010

Figure 1.2 Chip technologies.

1. Gordon Moore, cofounder of INTEL, said in 1965, “The pace of microchip technology change is such that the amount of data storage doubles every year or at least every 18 months.”

10

UMTS and Mobile Computing

of microelectronics and computers over the past two decades. The more an integrated circuit is packed, the higher its circuit speed and the lower its power dissipation. Advances in lithography will enable CMOS-technology to be built for many more years. There are views that Moore’s Law will continue to hold over the next 10 to 15 years (the Intel Study Micro 2011 predicts one billion transistors per chip in 2011). If this is true, then by about 2015, designers will have to work on the molecular level. This molecular nanotechnology will fundamentally alter the way of manufacturing. A good example of such development is Intel’s Pentium processor. At the start of the Pentium series, processor power was measured by a clock rate of 150 MHz and the number of transistors was 140 million. By 2000, both the clock frequency and the number of transistors had increased by a factor of six; these improvements were reflected in increased functionality and performance. By 2001, the AMD Athlon processor reached a clock rate in excess of 1.3 GHz and was composed of more than 1 billion transistors. By mid-2001, the 2-GHz Intel Pentium 4 arrived on the marketplace, providing even better performance than the Athlon, especially for video applications. These numbers demonstrate that we have approached a technological level that will revolutionize the organization and architecture in machines and systems. This may lead to dynamic optimization and adaptation. The high levels of processing, memory, and communications power predicted for handheld and wearable computers (mobile multimedia terminals and mobile TV sets) in the next 10 years, particularly combined with digital video broadcasting (DVB) and the Internet explosion, will create a step-change in the way in which individuals communicate with each other and access and use information. The functionality, performance, and costs of these devices will be determined by key technologies. Significant component technologies that will simplify the use and reduce the cost of mobile devices include (1) display technologies, such as plasma display panels (PDP) and cholesteric liquid-crystal (CLC) screens, and (2) voice- and man-machine interface technologies, such as handwriting and voice recognition. It is clear, however, that more research needs to be devoted to the user interface if a mass market for mobile multimedia is to be achieved. In the longer term, holographic displays and natural language processing will make devices much more user friendly, though it is difficult to predict when these will become commercially viable. Taking into account the high processing power demand and the relatively flat projections for improvements in battery technology, it is possible that these more exotic user interface forms may be restricted to mains-powered environments.

Introduction 1.3.2

11

Compression Standards for Multimedia: JPEG, MP3, MPEG-4, MPEG-7

Compression technologies began their success with the achievement of digitized voice: Effective encoding algorithms were developed in order to transmit analog signals over digital channels. After the successful implementation of a number of encoding standards—such as the full-rate, half-rate, and the adaptive multirate codecs for voice, the still picture JPEG, the moving MPEG-2, and the audio compression standard MP3—new enhanced coding algorithms, particularly for low to medium bit rates on radio transmission channels with variable delay characteristics, are being developed. What are driving these developments are the limited amount of frequency spectrum available and the consequent requirement to minimize the amount of transmitted data. Dynamically changing traffic characteristics must also be taken into account. In addition to a number of companies developing their proprietary encoding solutions, both the International Telecommunication Union (ITU) and the International Organization for Standardization (ISO) are developing standards for video and audio coding for medium to low bit rate transmission. MPEG-4, developed by ISO for mobile and wireless multimedia communications, will be usable on cellular mobile and satellite systems. MPEG-4 was born out of the need for very low bit rates by high and efficient compression algorithms, particularly for mobile and wireless multimedia communications. It was originally targeted primarily at very low bit rates, but over time its focus broadened beyond just high compression. High priority was placed on the following key functions provided by MPEG-4 (which were not supported by existing standards): • Content-based interactivity: • • • •

Content-based multimedia data access tools; Content-based manipulation and bit stream editing; Hybrid natural and synthetic data coding; Improved temporal random access.

• Compression: • •

Improved coding efficiency; Coding of multiple concurrent data streams.

• Universal access: • •

Robustness in error-prone situations; Content-based scalability.

12

UMTS and Mobile Computing

The MPEG-4 algorithm supports efficient coding of multimedia video and audio data as individual objects. The improved power of MPEG-4 over its predecessors (MPEG-1 and MPEG-2) comes from its content-based functionality, which allows highly flexible access and manipulation of audio-visual (AV) objects in a very efficiently compressed domain. The video coding scheme of MPEG-4 is mainly based on the H.263 video-coding algorithm from the ITU. The basic configuration of H.263 is an extended version of ITU-T H.261. It is a hybrid of interpicture prediction to utilize temporal redundancy and transform coding of the remaining signal to reduce spatial redundancy. 1.3.3

Wireless Technologies Migrate to Configurable Radio and Smart Antennas

Configurable radio, or software-defined radio (SDR) [9], allows for the dynamic configuration of the radio parameters of mobile terminals and base stations (software radio). This technology enables a mobile user device to accommodate two or more air interfaces without additional hardware, and as such will be a key enabler for the third wave in computing. Configurable radio is a way of realizing multimode terminals, which can operate by software control in different frequency ranges and with different air interfaces; this may be a cost-effective means of developing global markets for terminal and infrastructure equipment, enabling manufacturers to gain from significant economies of scale. Downloadable applications and software intermediation by mobile agents promise to relieve the complexity barriers that make it difficult for users of today’s computing equipment to understand their systems and to keep them up to date with new software. Potentially, these technologies may reduce the inherent complexity and cost of the terminal. In the longer term, artificial intelligence technologies promise self-learning and self-adaptive systems. The subsequent reduction in complexity of services and interfaces will break down the barriers that would otherwise prevent exploitation of the benefits of mobile multimedia services. Software technologies, such as artificial intelligence, fuzzy logic, and intelligent agents, are likely to be combined to provide powerful yet easy-to-use information and entertainment applications. The significant near-term impact of software radio will be in the field of service and applications innovation, which will use downloadable software applications as a tool to allow rapid and flexible service customization and

Introduction

13

new degrees of operator differentiation. As technology advances, it will become feasible to download software for increasingly lower layers of the protocol stack—initial commercial implementations of software radio are already beginning to happen. Technology enablers are shown in Figure 1.3; they include the following: • Analog-digital conversion and digital signal processing: low-power

high-MIPS2 products;

• Silicon capability: reducing geometries and operating voltages; • Real-time software download; • PersonalJava and the JavaCard: rapidly evolving portable software

technology.

Smart antennas are adaptive, which promises improved spectrum efficiency of mobile cellular systems. The aim of a smart antenna is to maximize the antenna gain in the direction of the user signal and to minimize the antenna gain along the direction of interfering mobile users. Smart antennas react intelligently to the received radio signal, continually modifying their

Digital DigitalRadio radio Technology technology

A/D performance Digital signal processing Increased processing power Increased memory capacity Low-power baseband controller Field programmable gate arrays

Software Software Technology technology

Realtime SW download Realtime kernel Virtual machine Frequency management Driver

Dynamic radio equipment reconfiguration by downloadable software at any protocol layer

Figure 1.3 Software-defined radio.

2. Million instructions per second.

14

UMTS and Mobile Computing

parameters to optimize the transmitted and received signal. This allows them to do the following: • Increase coverage and capacity by reducing interference between

adjacent mobiles;

• Offer space division multiple access (SDMA), where frequencies are

assigned on a per-mobile rather than a per-cell basis, allowing vastly increased capacity;

• Enable user location in space, allowing the introduction of advanced

location-based services.

Smart antennas may be used in two different ways: 1. As a spatial filter to reduce cochannel interference so as to increase the system efficiency by reducing the cluster size; 2. To reuse the traffic channels by beamforming more time inside the same cell. Figure 1.4 shows typical smart antenna characteristics with multiple beams; these will change dynamically. Mobile user Cluster 1

30

60

90

Figure 1.4 Smart antenna characteristics.

Mobile user 0

Cluster 2

−30

−60

−90

Introduction 1.3.4

15

The Internet, Intranets, and Mobility

Since 1992, both the Internet and mobile networks have had a dramatic impact on nearly all facets of modern life. They will certainly continue to restructure the business value chain for many of the traditional services and processes that we currently use. Thus, it can be safely said that the Internet and mobile development will have a great impact on the future. The Internet, which today is a heterogeneous network that deals mainly with e-mail and information content, is perhaps the most significant technology driving a general understanding of and familiarity with IT interfaces, such as the PC, as well as societal acceptance of information technology. Future generations of the IP, including IPv6, will combine wireless access and content-based services even further. Many articles have been written on the Internet’s so-called last mile problem, which appears to be the bottleneck with regard to bandwidth and accessibility by residential and business users. To meet this challenge, wireless access technologies were developed that provide two-way communications with increasing bandwidths. In recent years, the first release of the Universal Mobile Telecommunication System (UMTS) [10] was developed to enable mobile multimedia. Its impact on multimedia services and interface design will be considerable and will be realized in terms of increased applicability of mobile computing, personalization, ease of use, wide availability of and access to global services, as well as improvement in the general level of IT literacy through greater exposure to the Internet and intranets. The convergence of UMTS with the Internet will encourage Internet applications development with a strong focus on mobile services and will probably change the Internet dramatically. The worldwide perception initiated through the ITU vision of IMT-2000 is that wireless cellular systems and the Internet will take personal communications to the Information Society by delivering voice, graphics, video, and other broadband information direct to the user. These systems will move mobile communications forward from 2G systems—which have created a mass market for mainly voice-based digital wireless services between 1990 and 2000—to encompass fully multimedia services. Mobile multimedia communication services will provide both terminal and service mobility on mobile networks, taking advantage of the convergence of existing and future fixed and mobile networks and the potential synergies that can be derived from such convergence. If new systems and devices are able to learn and adapt to suit the environment and user needs (as a result of developments in artificial intelligence), the subsequent reduction in complexity and

16

UMTS and Mobile Computing

reduced costs of devices and services could open telecommunications markets up to almost limitless possibilities for service variety. 1.3.5

Services and Applications

Making the Internet mobile is not just about adding a wireless access technique to the existing infrastructure. Mobile Internet goes far beyond this and will include the addition of a number of service enablers—mobility, user identity and security, location information, and personalization—which will also improve the existing Internet. Such attributes will make a mobile Internet possible, with inherent new service capabilities and new business opportunities. Anywhere and anytime describe a situation-, location-, and person-driven multimedia infrastructure with devices that will lead us to the achievement of mobile computing.

References [1] Weiser, M., “The Computer for the 21st Century,” Scientific American, UC paper, September 1991, http://www.ubiq.com/hypertext/weiser/SciAmDraft3.html. [2] Weiser, M., http://www.ubiq.com/hypertext/weiser/UbiHome.html. [3] Weiser, M., and J. Seely Brown, Xerox PARC, “The Coming Age of Calm Technology,” October 1996, http://www.ubiq.com/hypertext/weiser/acmfuture2endnote.htm. [4] Southport Retravision, http://www.southport-retravision.com.au. [5] Margherita2000, http://www.margherita2000.com/sito_uk/it/home.htm. [6] Texas Instruments, “TINI,” http://www.iButton.com/TINI. [7] Pratt, V., “Matchbox Server,” http://wearables.stanford.edu. [8] Cell Computing, http://www.cellcomputing.com. [9] Buracchini, E., “The Software Radio Concept,” IEEE Communications Magazine, Vol. 38, No. 9, September 2000, pp. 138–43. [10] UMTS Forum, UMTS Forum Report No. 1, A Regulatory Framework for UMTS, UMTS Forum, 10–12 Russel Square, London WC1B5EE, United Kingdom, October 1999.

2 The Market for UC 2.1 Mobile Market Developments Wireless mobile networks have a clear lead over the Internet in terms of penetration [1]. Although today the network infrastructure is still mainly voice-related, every mobile device represents a special-purpose computer that provides a variety of functions, including data services like short message service (SMS). Technology innovations will change these devices over time, making them ever more like mobile computing devices that access the Internet. Even the mobile networks themselves will be IP-based in future. It is expected that by approximately 2010 more than 50% of the mobile devices used in cellular networks will provide Internet-based services. The wireless market not only comes from analog and digital conventional telecommunications network markets, it is also a new market. The traditional telecommunications market was dominated by one product: voice communications. The mobile networks emerged later and took advantage of the existing market in the sense that the first mobile phones were able to communicate with hundreds of million of phones on the fixed networks globally. Later, the mobile market evolved with the provision of international roaming, a unique feature making the mobile user communication independent from its location, providing reachability anywhere and anytime. Still later, the mobile networks changed from an environment dominated by voice to one where text messaging and enhanced data services are equally important. The new Internet market seems to have developed in a similar way as the fixed telephone network market in the past: Wireless mobile access to the Internet for e-mail and Web applications—both dominating in the current 17

18

UMTS and Mobile Computing

Internet—will be key to launching the mobile Internet. After having reached a critical mass market size for new mobile Internet services, the market could emerge on its own and become an even greater factor than the original Internet market. The forecast in Chapter 1 indicates such developments. Of course, the transition to the mobile Internet also requires new service concepts and an in-depth understanding of the new user. Customer segmentation focusing on customer value and availability of services at the right price will be key factors to success. Additionally, content needs to scale to the various display sizes of different terminals and also requires end-to-end interoperability in order to ensure wide end-user acceptance. Figure 2.1 shows the development steps of wireless terrestrial cellular technologies, also called generations. First were analog technologies, which allowed voice services only. Second-generation technologies next began to offer text-based data services—the SMS is a successful example. Internetenabling network technologies were developed on top of the 2G systems: Wireless application protocol (WAP) [2, 3], i-mode [4], general packet radio service (GPRS), enhanced data rates for GSM evolution (EDGE), and upgraded IS-95 technologies are typical examples. The question that is often asked is what is the motivation for a 3G system, such as UMTS? Current market analyses suggest that in addition to evolved 2G mobile services, such as GSM, there is a need for a new generation wireless wideband system with characteristics, such as video, multimedia, flexible service provision, bit rates of up to approximately 384 Kbps for wide area, universal coverage and vehicular speed, and up to 2 Mbps for local area coverage. UMTS [5] will meet these demands according to its specifications, which are laid down in the ITU-R framework standards. UMTS at the outset was seen as the convergence of wireless local loop, cellular mobile, paging, private mobile radio, and other 2G applications. It has evolved, however, into a system that will take the personal communications user into the new information society by providing higher bit rate data exchange—that is, broadband multimedia capabilities and convergence with the Internet. As the wireless market moves towards multimedia, operators will need to ensure that the subscribers using such services are effectively supported wherever they happen to be located (roaming). Mobile data applications are commercially viable today, but future mobile network enhancements will enable operators to offer a broader, more profitable range of (multimedia) applications and services. Current offerings from cellular network operators include information on stock prices, weather forecasts, sports, traffic, and other Internet content

1G systems

Trunked mobile radio

Microwave point-tomultipoint

2G systems

Analog cellular

Trunked mobile radio

3G systems

Digital cordless

Digital cellular

Local area

TETRA (Europe)

CT2 DECT (Europe)

D-AMPS CDMA (USA)

Bluetooth DECT+

AMPS (USA)

TETRA POL (Europe)

PACS (USA)

GSM (Europe)

WLAN HIPERLAN2 BRAIN

iDEN APCO25 (USA)

PHS (Japan)

PDC (Japan)

Proprietary systems

IMT-2000 UMTS CDMA 2000 UWCC

The Market for UC

NMT TACS (Europe)

Wide area cellular

Proprietary systems

19

Figure 2.1 Wireless terrestrial cellular technologies.

20

UMTS and Mobile Computing

for mass markets, most of which are developed by WAP content providers. The success of the i-mode [4], described in Chapter 5, has been driven by its early entry into the market, as well as by the development of content by more than 3,000 information providers. The rapid growth and current penetration of this service (some 30 million subscribers) has demonstrated the acceptance of data services in future networks. There are a number of reasons why WAP has not yet been as successful as i-mode: the business model, the circuitswitched transport, the markup language WML, and user behavior. The key enabler for the mobile data consumer mass market is the packaging of applications and presentation of content within an easy-to-use terminal device. This captures the imagination of the consumer in the same way that the latest generation of mobile handsets and tariffs combined with voice messaging services has driven the wireless voice markets. These enable previously unconscious and undefined, or wholly new, user needs to be identified and satisfied; this process results in the creation of completely new, previously unknown classes of services. The next generation of mobile terminals is expected to come in steps with increasing bit rates towards multimedia (voice, data, text, image, and slow scan video) and based on a combination of functions seen in the notebook, handheld, and mobile phone. This means that for 3G services and applications, a variety of mobile terminals designed on a new data platform and targeted at various market segments will emerge, with voice as one of the features. It should come as no surprise to learn that the number of Internetcapable mobiles will soon outnumber the quantity of Internet-capable PCs. The growth rates of PCs sold to the marketplace are tending backwards, already indicating a saturation in developed regions. This could have a strong impact on the development of the Internet itself (IPv4 versus IPv6). There is a belief that the introduction of mobile Internet services will accelerate the already rapid growth of both mobile and Internet services: convergence. Figure 2.2 shows the forecasts for mobile subscriptions in 2G and 3G mobile networks. 2.1.1

Emerging Wireless Personal Area and Wireless Local Area Networks

The market developments of digital enhanced cordless telecommunications (DECT) and the Personal Handy Phone System (PHS, Japan) in the last decade indicated increasing demand for systems with limited mobility [e.g., in the home and office environment, and partly also in the public environment (PHS)]. The systems were predominantly seen as for voice applications

The Market for UC

21

World (total) 2“

Mobile users

2“ 1“5

1“5 1“

500‘

730‘ 260‘

1990

650‘ 500‘

285‘ 185‘ 2000

Asia (+RoW) 900‘

350‘ 2005

560‘ 540‘

Europe

N/S America

2010

Figure 2.2 Forecasted wide area mobile network markets. (Source: Siemens.)

related to wireline corporate or public networks [public switched telephone network (PSTN), integrated service digital network (ISDN)]. Roaming with wide area mobile networks has not taken place, although market success was quite high—mainly in Japan with approximately 20 million PHS units, and in Europe with more than 100 million DECT units [6]. The equipment was also upgraded for data applications. Increasingly, new technologies will come onto the market, and these will be more focused on data applications and will offer higher bit rates and IPs in short-range scenarios. In addition to DECT, which was accepted as a 3G ITU standard with its improvement to 2 Mbps, new technologies like Bluetooth and wireless local area networks (WLANs) will increasingly dominate in this market, mainly in the indoor environment. For WLANs, roaming with wide area mobile networks is under discussion. Some manufacturers offer proprietary solutions already. The forecasts for WLANs worldwide indicate between 10 and 20 million units in 2005 [7]. In contrast to the licensed public networks, the regulatory conditions for this market with general allowances for, say, equipment use, give far more flexibility to the industry to operate networks successfully and to compete with products in various environments. The frequency spectrum is usually allocated for license-exempt use in order to allow self-provided networks. There is a relatively large spectrum available in the 2.4- and 5-GHz range. The DECT/PHS- and UMTS-bands account for approximately 50 MHz of bandwidth; the industrial-scientific-medical (ISM)

22

UMTS and Mobile Computing

band is 83-MHz wide, and the 5-GHz bands for WLANs provide 200 to 400 MHz of bandwidth. Self-provided mobile networks and wireless radio access systems are usually personal or local area or corporate or regional networks typically for low mobility or semistationary use. They are in service in a number of countries around the globe. There is no clear technology winner in this market, because there is no real need for a common standard like in mobile cellular networks, which require worldwide roaming. The relevance of some technologies in connection with wide area mobile networks, however, should not be underestimated. For example, the value of Bluetooth as a complementary interface to cellular radio could play a significant role in the future. WLANs and high-performance radio local access network (HIPERLAN) are primarily considered as radio local area networks (RLAN) or as wireless local loop systems. There are also private mobile radio (PMR) systems with larger radio coverage (city) for emergency services (police, rescue) and for closed user groups (such as taxi drivers). These networks undergo technology changes that provide voice and data services. Integrated digital enhanced network (iDEN), the American Police Communication Organization (APCO) 25 in the United States, and trans European trunked radio (TETRA) and TETRAPOL in Europe are examples of 2G trunked-radio systems. 2.1.2

Mobile Satellite Network Markets

Satellite communications were once seen as a serious threat to the terrestrial mobile market, but now they are viewed only as a niche technology. There are only a few new projects to be seen in the future, like Globalstar, ICO, and Teledesic. The largest network in terms of subscribers is the Immarsat network with approximately 300,000 users.

2.2 Internet Market Developments All the major players in the IT industry are betting significant amounts of money on the successful transformation of the Internet into a pervasive medium—connecting users to personalized universes of dynamic content, applications, and services, via any smart, connected device. Pervasive computing, however, is about much more then connectivity. It is the final step in the transformation of computing from a single resource to a technology with distributed resources and democratized access. The price of admission to this

The Market for UC

23

market is a secure, reliable infrastructure that can scale to a large number of network-connected devices either stationary or mobile. The Internet was in existence for about three decades before it entered the current phase of mass-market acceptance. The trigger was the introduction of interfaces, such as Mosaic and the Web, which transformed the Internet into a user-friendly environment. Another important development was the introduction of mass-market applications, such as spreadsheets and word processing. Until such time, the PC was merely a cheap alternative to minicomputers. As shown in Figure 2.3, the origin of the Internet, after the first research work from Kleinrock, lies in the ARPANET, which was born in a military laboratory in 1969. The aim was to allow computer scientists and engineers working on military contracts all over America to share expensive computers and other resources. E-mail, as it became known, quickly turned the network into a communications medium. Until 1983 the Internet consisted of fewer than 500 host computers, almost exclusively in American military labs and academic computer-science departments. But the word was getting out to other academics. By 1987 the Internet had grown to include 28,000 host computers at hundreds of different universities and research labs around the world. No other method for networking universities around the world was so universal and so flexible. The Internet as a heterogeneous network was adaptive for all kinds of access and carrier networks, private or public. Users invented ways for many people to participate in open discussions; they created software and document libraries on the network and made them accessible to all. During the late 1980s, while the Internet was growing in the academic world, a networking revolution of another sort was taking place in the business world. Businesses realized that, having traded their mainframes for a multiplicity of PCs, they needed some way to recapture the mainframe’s ability to share data and devices, such as printers. So they strung wires around their offices and connected the PCs together. The IP was used in these networks, and it became a de facto world standard. These local area networks (LANs) did more than save money; they changed the way people worked. E-mail took off within offices and, soon, between them, as companies created wide area networks (WANs) to connect distant workplaces. But there it stopped. Different software and hardware standards used by different companies made creating wider networks a nightmare of incompatibility. Again, the Internet’s applications, predominantly the Simple Mail Transfer

24

JAVA WWW (CERN)

TCP concept USA, England, Hawaii

*

TCP/IP standard

1 billion Web pages

100–200 million servers

43 million servers †

New domain names

ICANN domain names

Internet rollout

Name server

2–3 billion Web pages

150 million users

300 million users

400 million users

1998

2000

2001

ARPANET concept/operation

1968

1969

1974/75 *

1983

1986

1990 1991 1995

ARPANET: Advanced Research Project Association Network/Department of Defense USA ICANN: Internet Corporation for assigned names/numbers

†

Figure 2.3 The Internet.

UMTS and Mobile Computing

NSFNet 10,000 hosts

100,000 hosts

300 million Web pages

The Market for UC

25

Protocol (SMTP), the File Transfer Protocol (FTP), and the Hypertext Transfer Protocol (HTTP), provided the necessary compatibility. In homes, PCs had made computer power affordable, and modems had allowed them to be connected over telephone lines to commercial on-line services and bulletin boards (electronic discussion groups and software libraries usually set up by enthusiasts). Both of these grew steadily, but not explosively. Each had disadvantages. The networks offered by CompuServe, the leading on-line service provider, and others were national, even global. In mid-1993 something new happened: The Internet sprouted multimedia wings. A combination of special software and a way of connecting documents allowed users to travel the network with pictures, sound, and video, simply by pointing and clicking a mouse. Suddenly, the Internet was not just a way to send e-mail and download the occasional file. It was now a place to visit, full of people and ideas: It was cyberspace. It was a new medium, based on broadcasting and publishing, but with another dimension added: interactivity. Internet veterans had known this for years; they could see the potential behind the screens of plain text and baffling computer commands. But thanks to the Web, the friendly, multimedia side of the Net, a much broader audience started to catch on to it. Since 1988 the Internet as a whole has doubled in size every year. In 2001 it reached 100 to 200 million host computers, each having the capacity to connect several individual users. During the same period, the Web grew as fast: In just 10 years, from 1992 to 2002, users created more than 2 billion Web pages containing information, entertainment, and advertising. No one knows how many people have contributed to this growth. No communications medium has ever grown as quickly; nor has any other electronicsrelated market. Figure 2.4 shows the wireline Internet growth forecasts (they will probably be surpassed by mobile Internet by 2008 because of the expected tremendous growth on the wireless side). 2.2.1

Challenge: Transition from Circuit Switching to Packet Switching

The rise of the Internet initiated interesting changes in the global telecommunications infrastructure thinking. Computer interworking was originally based on leased lines or on accessing the public telephone network. Over time, data networking based on IP became its own infrastructure; a heterogeneous network called the Internet came into existence. Internet traffic doubles every 6 months now, and it is still mainly data traffic—voice traffic is only partly transported via the Internet and will remain as such in the future. Merged voice and data will emerge in multimedia.

26

UMTS and Mobile Computing

600‘ Internet users

Internet users/hosts

500‘

Internet hosts ~ 400‘

400‘ 300‘

200‘

200‘ 100‘ 100‘ 50‘ 1990

50‘

10‘

1995

20‘

>200‘

>100‘ 56‘

2000

2005

Figure 2.4 Internet growth.

A typical characteristic of the Internet is that data is split up into packets, which do not need a line exclusively for themselves. Packets from hundreds of sources are mixed up by the computer and shoved into a pipe (either the transmission line or the air interface). The router at the other end of the line receives each one, reads its address, and sends it in the right direction. All packet-switched networks follow this principle of data transmission and routing, most of them using the IP protocol. Finally, the server receives the packets from many sources, usually with a far higher bit rate than if transmitted from a single source, and reassembles them appropriately. A main advantage of the packet-switched mode is that the end-to-end user connection is established as a virtual connection, which allows the user to be in an always-on mode. Many new services need such a function, because it saves network resources (e.g., frequency spectrum, transmission capacity) by providing the simultaneous use of a physical line or a frequency channel by transferring packets corresponding to virtual calls. The connectionless IP provides the flexibility for multiservice transport and switching that is important for multimedia. In multimedia communications, several virtual connections have to be managed at the same time. In the circuit-switched mode, which is used mainly for voice connections, the entire bandwidth of the individual channel is dedicated to one

The Market for UC

27

connection for the duration of a call: This is a physical connection. After clearing the call, the channel remains free until another connection is set up. The transmission bit rate remains constant throughout the connection. The exclusive use of a channel guarantees quality of service like throughput and short and constant delay time, but this can tax the total capacity utilization of the system. It consumes resources used to prevent blocking, especially in cases of bursty traffic and long session durations. It is therefore inefficient for always-on applications. The circuit-switched telephone system was designed specifically to satisfy the human ear. The same goal was valid for the mobile networks in their beginnings. Nowadays, with data communications, the advent of packet switching, and the multiplicity of different traffic bit rates, there is more than one set of criteria to satisfy. The data rate needed for voice communication is intolerable for transferring high-resolution images or audio and video with satisfying quality. Conversely, the degree of network latency may not be adequate for real-time voice or video and audio streaming. Quality of service (QoS), therefore, becomes an important topic for packet-switched infrastructures. The most important quality of service requirements are the availability of the network, the throughput defined in bits per second, the latency (which is for voice less than 150 ms), the jitter, and the packet-loss. The sensitivities of services and applications vary depending on traffic type. To cope with the varying requirements, the new approach of multiprotocol label switching is increasingly applied to the infrastructures. 2.2.2

Internet Access from Mobile Devices

As the penetration of Internet, mobile phone, and portable computer usage increases at rapid and parallel rates, it is easy to conclude that their futures will become integrated. Today 75% of wireless phone users in the United States also access the Internet via their PCs. They probably wish to have access to the Internet via their mobile phone as well. Internet access includes e-mail and file transfer services, chat, voice over IP (VoIP), Web browsing, and retrieval of specified information that may be provided on an ongoing basis via a Web-based information service. Table 2.1 shows the percentage of services used in the Internet in 2000. For mobile users, this could include information that is relevant to traveling, such as timetables, traffic updates, hotel and restaurant listings, or urgent data, such as meeting schedules and stock prices. With wireless access to the Internet, the roaming user comes into play. The personalization of information will become a new business factor. It will

28

UMTS and Mobile Computing Table 2.1 Internet Services Usage in 2000 Service

Application Protocol

Usage (%)

Traffic (%)

E-mail

SMTP

97

4

WWW

HTTP

95

65

File transfer

FTP

78

15

Blackboard

NNTP

41

1

Chat

CAT

33

15

Telephony

SIP

24

15

increase both the value of information to the consumer and the level of business for the operator. The greater the value, the more willing the user will be to pay for the service. Information services that respond to users’ needs and give them choices will be compelling. For example, when driving in an unfamiliar area, motorists may value information location for the cheapest gas station within 2 miles—information that can lead to a mobile commerce transaction if the gas is purchased via the debit card on the mobile phone. This type of service includes two important ingredients for success: • Personalization: providing user-specific content; • Localization: transmitting information to users according to their

geographic location.

2.2.3

The Web Market

The Web was invented in 1991 by CERN.1 By the end of 1994 about 4 million Internet users had the right connections to use the Web. The Web is unquestionably the fastest growing part of the Internet. Today, Web browsing is the leading Internet application, together with e-mail, followed by entertainment and work. It is the Web—with its multimedia gloss, interactivity, and emerging secure areas—that most companies would choose as their Internet marketplace. More than 2 billion Web pages already exist currently in the worlds Internet market. 1. CERN created the idea of Web sites. The first premiered at Stanford University on December 12,1991.

The Market for UC

29

The biggest market for the Internet is information, advertising, and marketing, and business is already thriving in these areas. Most of the corporate home pages on the Web amount to little more than the usual marketing gloss, polished to an extra shine by electronic means. E-commerce-enabled Web sites facilitate the buying and selling of goods and services, the processing and authorizing of purchase transactions, and, where possible, the digital distribution of the product. E-commerce will be the cornerstone for mobile commerce. 2.2.4

Electronic Commerce: A Fundamental Component of Future Multimedia Services

Growth in electronic commerce over the next 10 years will continue to drive automation in the retail and finance sector, the growing penetration of PCs at home and in the office, the explosive growth of Internet and intranet hosts and users, and with increased familiarity with credit and debit cards, handheld shopping could be one of a number of revolutionary business changes. Financial institutions and retailers are experimenting with virtual malls, and although user acceptance of the Internet in promoting this trend is still uncertain, it is clear that a key driver of future multimedia services will be the demand for alternative, cheaper means of marketing and distributing goods and services. The success of multimedia services based on financial transactions is predicated on the ability of the industry to allay current user concerns about the security of Web-based transactions. The many facets of commerce include business-to-business (B2B), business-to-employee (B2E), and business-to-customer (B2C), where consumer behavior plays a critical part in its acceptance. The network operator, however, will first have to be content with a small transaction margin of new m-commerce businesses. Clearly, profitability in this case will be strongly dependent on volume (i.e., on the rapid creation of a mass market). 2.2.5

Intranet Need for Mobile Extensions

What the Internet has done for consumers, intranets are about to do for business. Intranets offer large organizations two distinct advantages that the Internet does not: 1. Security. Because intranets are inside inherently secure organizational networks, intranets can offer valuable information many companies simply would not want to make available to outsiders.

30

UMTS and Mobile Computing

2. Bandwidth. Intranets running on Ethernet, or even faster ATMbased networks are able to offer full-motion video, something most Internet users will not experience for a while. 2.2.6

Intranet Access from Mobile Devices

From a security point of view, it is more critical for a business user to connect to their corporate LAN or intranet than to a public Web site. Corporations are rapidly deploying intranets and enabling remote access to them from outside the firewall so that users can gain access to corporate information and databases like price lists, stock availability, order entry, customer records, the corporate directory, or collaborative work-group applications. For mobile executives with electronic organizers, the ability to manage remotely an address book and diary is important. Synchronization of the organizer contents with the main personal information manager on the user’s desktop PC will be critical.

2.3 Fixed and Mobile Convergence As the Internet grows, so does the market for wireless communication devices. Such devices will increase the options for making connections to the global Internet. Mobile customers can already find a wide variety of such wireless devices available. There are numerous radio attachments and infrared devices, and, of course, communications by way of the cellular network is always an option for those willing to pay the fees. The provision of multimedia services in a mobile environment merges several formerly independent markets: computing, (mobile) communications, photography, video and audio processing and presentation, music production, and distribution. Mobile communications is increasingly becoming a multimedia environment that will be no longer limited to two-way voice and low-medium rate data services. The multimedia environment will extend the provision of several high-rate audio, video, and data services that are now only available through wireline networks. The concept of the mobile voice call will be radically changed as multimedia components are added. Data, speech, audio, and images can simultaneously be shared with users who are connected with a speech or video connection—leading to more effective visual communications. In addition, the convergence of voice and data is taking place in the mobile environment with some significant advances in technology. The price for mobile data transmission is going to decline in the next few years while the speed of transmission goes up. People

The Market for UC

31

will be fully mobile and able to access and use information in data-based applications around the world. These trends are generating a great deal of interest in making sure that mobile wireless computers can attach to the Internet and remain attached even as they move from place to place, establishing new links and moving away from previously established links. The combination of Internet technology with mobile connectivity holds out the prospect of the marriage of two of the biggest and fastest growing markets in telecommunications. Key challenges to the mobile supply community over the next decade will be to overcome the problems that this combination poses and to develop packages of services, terminals, and applications that will delight users. This process of convergence has widened to include the field of broadcasting, where much content is produced and distributed via transmitter stations on satellites or the ground or via cable, but also via bi-directional channels like the Internet and mobile Internet (e.g., video on demand). Such convergence can be seen in upcoming distribution networks for DVB and digital audio broadcast (DAB), as well as in the Multichannel Multipoint Distribution System in the United States. The underlying concepts for these networks have evolved to include elements of interactivity. This results in an asymmetrical traffic distribution with high capacity for information download and low capacity for the return channel upload, thus providing a certain degree of interactivity. Business opportunities lie in education and learning, location-based services, infotainment, and elsewhere. Figure 2.5 shows UMTS as the provider of such service convergence in the fields of telecommunication, Internet and computing, and information media. Because the wireless Internet is an unprecedented phenomenon and the required business models and strategies are yet untested, market estimates vary widely, and entry into this market is often associated with risks. There are, however, indicators that provide evidence of its great potential. 2.3.1

Mobile Computer-Based Communications and UMTS

It is conceivable that by 2003 the number of Internet and intranet users will be 500 million worldwide, making it potentially possible for a user with an Internet-capable mobile device to communicate with a mass market base of 500 million fixed Internet users. On the mobile network side, already more than a billion users are estimated to be in the world’s marketplaces. The mobiles will be data-enabled to a large extent. This means that nearly any

32

UMTS and Mobile Computing Internet/Intranet E-Mail WWW IP Protocols E-Commerce

Broadcast media Audio-video on demand Infotainment/education TV and radio distribution Multipoint distribution

UMTS

Telecommunication Realtime connectivity wireless Mobility/roaming/person location Voice, SMS, fax, data

New technology Broadband radio access Smart antenna Circuit-packet-switched transport Multimedia HW, SW Compression techniques

Figure 2.5 UMTS provides convergence.

kind of terminal will be capable of using the Internet in a more or less limited way. By the end of the decade, the PC will be only one amongst several different terminals for home access to the Internet, along with televisions, network computers, mobile terminals, and handheld games units. As a result of these developments, most fixed networked multimedia services, including information and entertainment services, will likely be packet switched with IP and will have asymmetric handling. This will have significant implications for delivery systems for mobile multimedia services, such as UMTS and IMT-2000 [5], because it implies that many mobile multimedia services will be IP-based. This underpins the expectations for the mobile multimedia marketplace and is supported by evidence of three key trends: (1) the increasing mobility of individuals, whether as employees or as individuals; (2) the increasing requirements for responsiveness in business; and (3) the growing demand for communications and access to information while on the move. 2.3.2

Increasing Mobility of Individuals and the Pressure to Turn Dead Time into Productive Time

The world’s urbanization is still rapidly increasing, and large cities are getting bigger and bigger, especially in underdeveloped countries, but also in

The Market for UC

33

developed countries. Consequently, many individuals are spending more time traveling, whether for commuting or for pleasure, thus creating significant growth in dead, or unproductive, time in the workday. Meanwhile, increasing competitive pressures are forcing businesses to increase the productivity of their employees, thus placing greater demands on their time and creating a need to make dead time more productive. The increasing popularity of portable computing devices provides evidence that more workers, particularly those in knowledge-based industries, are becoming more mobile, working remotely from their normal base, and making better use of otherwise dead time.

2.3.3

Key Enablers

Industry players (operators, equipment suppliers, and regulators) will play a significant role in contributing to the development of the market. Positive actions on their part will encourage market take-up through the development and delivery of services that users find affordable, easy to use, and well matched to their needs. The most significant issue that will enable strong market development will be the nature of the regulatory environment governing access to the underlying network infrastructure and the delivery of services over that infrastructure. This framework will be fundamental in determining whether new service providers and their backers find this market easy to enter. This in turn will determine the intensity of competition within the market. It will be crucial for the success of mobile multimedia that service providers obtain costeffective access to mobile networks on fair and reasonable terms. A second fundamental issue enabling market development will be the worldwide acceptance of a harmonized 3G mobile radio standard. Success in achieving this, as opposed to many regional standards, will enable the rapid development of the market through the creation of large terminal and infrastructure equipment markets, which will lead to a reduction in the cost of terminals and network infrastructure. Additionally, roaming agreements will give confidence to the consumer that their purchasing decision is a sound one, and that the terminal purchased will not be superseded by another incompatible system in a short period of time. The development of open standards for service and application development, perhaps using a de facto approach along the lines of the Internet standards model, will also facilitate market development by enabling rapid innovation, simplifying service creation, and ensuring service portability.

34

2.3.4

UMTS and Mobile Computing

Broadband Wireless Convergence

The unique advantages for the 3G mobile services are identified as high bit rates (for information services), always-on access, mobility, and global roaming. With these unique advantages it was forecast that wireless WANs could become the preferred method of access to the information society in the home, office, and public spaces. Since then, however, there have been major developments elsewhere which have enriched this unique opportunity: the WLAN and wireless personal area network (WPAN) systems. Their main disadvantage, however, is that roaming is very limited. There are currently two major technological trends, with a third likely to emerge. The first of these is based on WLAN technology [8–10]: the Institute of Electrical and Electronics Engineers (IEEE)2 802.11 WLAN and the HIPERLAN, both of which have a better mobility capability and bandwidth. HIPERLAN has been merged with the previous European Telecommunication Standards Institute (ETSI) Broadband Radio Access Network (BRAN) project. These broadband wireless access systems are seen now as enhancements in the scope of digital mobile systems, particularly the technologies from 2 Mbps up to bit rates of 11 and 22 Mbps with restricted user mobility and for picocell environments. The second trend is that of Bluetooth, which is a very low-cost wireless link that will become ubiquitously integrated into mobile devices like phones, portable computers and organizers, as well as vehicles, accessories, and peripherals. The Bluetooth industry has realized that this complementary technology can be adapted to provide relatively fast access. It is expected in the future that the Bluetooth and the WLAN technologies will provide a much higher capability than either does today. The third trend is the wireless home network, a relatively new proposal from the DVB community. This group is looking aggressively to take over the home space by combining cable, satellite, and terrestrial broadband delivery with wireless distribution about the home in order to provide for entertainment, telecommunications, and information. All these technologies are considered as elements for convergence with fixed and mobile wide area communication networks. While they do 2. The IEEE is a nonprofit, internationally recognized, independent association with more than 330,000 individual members in 150 countries. It promotes the engineering process of creating, developing, integrating, sharing, and applying knowledge about electro- and information technologies and sciences. The IEEE produces 30% of the world’s published literature in electrical engineering, computers, and control technology, holds annually more than 300 major conferences, and has more than 800 active standards with another 700 under development.

The Market for UC

35

not provide the full dynamic mobility of cellular, they do provide for nomadicity, enabling a user to automatically connect to his home network from different access points. For information services, full mobility may not be as essential as it is for a mobile phone where 100% coverage is essential. For intranet and extranet access, WLAN technology can provide services for nomadic users in offices, airport lounges, and conference centers. While for infotainment, Bluetooth could provide access for such things as music download, cinema booking (with added video clips), and other m-commerce from booths in shopping areas, airports, petrol stations, and supermarkets. The revolution of convergence with mobile WANs has already commenced. The cost of a WLAN card is several hundred U.S. dollars, and it operates in a radio frequency band that does not require an operator license. The costs of Bluetooth will eventually add only a few dollars to the cost of its host product. 2.3.5

Broadcasting Convergence

Some investigations have already begun to identify the synergies in this field. It is clear that broadcasters now own tremendous amounts of useful content that will become so important to customized infotainment services. It is also well known that many people access broadcast content via the Internet and potentially could do so via mobile broadband systems. Broadcasters also own very broadband frequencies, which are not always fully utilized. There has been some use of these broadband channels as Internet return channels already. Currently, there are discussions on using the global system for mobile communications (GSM) or UMTS and combining them with digital broadcast systems like DAB and DVB. The GSM/UMTS channel would allow the user to order information via a DAB or DVB radio broadcast network and manipulate the information received. This does not necessarily have to be an integrated terminal solution; a handheld combined with a TV set using different infrastructures but a common AV management could be quite feasible and economical. 2.3.6

Convergence on Devices

Convergent services, of course, will impact the device side as well. Ongoing developments signal the trend towards both multifunctional and specifically tailored solutions. Multimode terminals useable in a number of different systems standards will handle the complexity of multisystem standards. The emergence of new terminal categories will be further enhanced by dramatic

36

UMTS and Mobile Computing

improvements in connectivity between various devices. The cellular phone will act as a gateway to the world for other personal devices (e.g., PCs, PDAs, and digital cameras). Naturally, some of these functionalities will be integrated with the mobile phone, as in today’s communicators, to complement a modular approach. A key to this enhanced connectivity will be Bluetooth technology and the 3G wireless technology UMTS. 2.3.7

Convergence and the Creation of New Services

The convergence of technology, as well as globalization, e-trade, and e-commerce are drivers for the creation of new services, which will come from the synergies in the formerly separated fields of services, applications, and technologies. Examples are the upcoming services that combine location information of a user or device with useful information from the location area: location-based services. Other examples are in the field of automobilerelated communication, Telematics and Telemedicine, and virtual team support. In addition, personalized access is another attribute that will impact new services in the future.

References [1] UMTS Forum, UMTS Forum Report No. 10, Shaping the Mobile Multimedia Future, UMTS Forum, 10–12 Russel Square, London WC1B5EE, United Kingdom, October 2000. [2] WAP Forum, Frequently Asked Questions, http://www.wapforum.org/faqs. [3] Phone.Com, http://www.phone.com. [4] Kei-ichi, E., “i-mode—Now & Future Toward Mobile Multimedia in 3G,” ITU Telecom Asia 2000 Proceedings, Hong Kong, December 4–9, 2000. [5] UMTS Forum, UMTS Forum Report No. 1, A Regulatory Framework for UMTS, UMTS Forum, 10–12 Russel Square, London WC1B5EE, United Kingdom, October 1998. [6] DECT Forum, http://www.dect.ch; and Ericsson, “DECT Overview,” http:// www.ericsson.com/BN/dect.html. [7] Frost and Sullivan, 1999; http://www.frost.com. [8] HomeRF Working Group, http:// www.homerf.org. [9] HomeRF Working Group, SWAP white paper, “The Shared Wireless Access Protocol (SWAP),” http://www.homerf.org/press/hrfwgmkt.pdf. [10] IEEE, “IEEE 802.16 Broadband Wireless Access (BWA) Standard,” http://grouper.IEEEglobal.org/groups/802/16.

3 Technologies This chapter will give an overview of UC-enabling networking technologies and devices. It will describe technologies for wireless and mobile communication, and for the networking of mobile devices in wireless communication networks. Wireless networks in the local, regional, and wide area are considered in Section 3.1. Section 3.2 focuses on UMTS as the convergent system for mobile communications and mobile computing. Section 3.3 is dedicated to small information appliances, also called devices, that work in UC environments. These can be off-line, wireless, or wireless combined with wireline networked devices. Some example applications and scenarios of those devices are presented in order to describe their major uses. The technologies and devices that the authors think have more business value and are more impact to the UC era will be described in greater detail.

3.1 Mobile Wireless Communication Technologies This section describes the various mobile wireless communication technologies and networks. Such networks enable mobile devices and mobile computers to communicate wirelessly with one another and to access wireline networks like the Internet or various intranets. The term wireless refers to a communications, monitoring, or control system in which electromagnetic or acoustic waves carry a signal through atmospheric space rather than along a wire. In most wireless systems, radio-

37

38

UMTS and Mobile Computing

frequency (RF) or infrared (IR) waves are used. Some are used as monitoring devices, such as intrusion alarms; others employ acoustic waves at frequencies above the range of human hearing. Their typical bit rate is around 115 Kbps. Wireless communication technologies are understood as two-way communication technologies; they can be classified as follows: • Short-range radio systems: WLANs, wireless personal area networks

(WPANs), and home area networks (HANs);

• Medium-range radio systems: regional and wide area networks like

trunked radio systems, public cellular networks, point-to-point and point-to-multipoint systems;

• Long-range radio systems: extended area networks like high-altitude

platform stations and mobile satellite systems.

Figure 3.1 gives an overview and positions the various radio technologies in relation to range and bit rates. As Figure 3.1 shows, bit rates are generally high in short-range radio systems and go down in long-range radio systems. In contrast, mobility is low (50 km/hr) for short-range systems and goes up for long-range systems.

Mobility and cell range Global Long-range vehicular

100 km

Satellite

Medium-range vehicular 300m

2G TDMA CDMA

Short-range r = 1 km Pedestrian 100m indoor Personal area

3G CDMA UMTS BRAIN IEEE 802.11b HIPERLAN 2

DECT Bluetooth 0.1

0.5

2

IEEE 802.11a Hiperaccess 20

155 Mbps data rate per cell

Figure 3.1 Short-, medium-, and long-range radio technologies for bidirectional communications. (Source: Siemens.)

Technologies

39

Short-Range Radio Systems

There are a variety of technologies on the market, from infrared to WLANs. (These are not classified here into 1G, 2G, and 3G, although Bluetooth and WLANs are considered as complementary technologies to 3G.) The following technologies should be noted: • Infrared for very-short-range applications in one room (e.g., remote •

• • • • •

control, PC to mobile, one voice-data channel); Bluetooth for short-range applications (e.g., wireless PC, optimal headset, communications between PC and electronic organizer, home automation); DECT for short- and middle-range application; Home radio frequency systems for short-range applications; IEEE 802.11, 802.15 for short- and medium-range applications; HIPERLAN/2 for short- and medium-range applications; UMTS/time division duplex (TDD) for ranges of 300m or more.

Table 3.1 compares advantages and limitations of these technologies; they can be either complementary or competing. All these technologies cause interference. In a multicell environment, this can dramatically reduce the effectively transmitted bit rate and the cell radius. Some advantages of these different technologies are therefore reduced. Medium-Range Radio Systems

The Advanced Mobile Phone Service (AMPS) in the United States, Nordic Mobile Telephone (NMT) and total access communications system (TACS) in Europe and elsewhere, and JTACS in Japan are analog cellular systems that are still in use today. They permit two-way voice communications and circuit-switched data transmission, and AMPS, through an upgrade, permits cellular digital packet data (CDPD) services. CDPD, which is an overlay to AMPS, offers speeds up to 19.2 Kbps. Circuit-switched transmission sets up and keeps a circuit open between two or more users such that the users have exclusive use of the circuit (channel) until the connection is released. The development of digital technology resulted in the evolution to 2G technology. Time division multiple access (TDMA) standards are dominant here: IS-136 is the relevant U.S. standard; GSM is the European and worldwide accepted de facto TDMA standard. In Japan, another standard called

40

UMTS and Mobile Computing Table 3.1 Short- and Long-Range Radio Technologies

Technology Cellular

Effective Cell Radius Indoor/ Expected Level Outdoor of Penetration Advantages Resid.

Corp.

Limitations

Infrared

No

3m

High

Low

Price, no regulation worldwide

One room, line of sight

Bluetooth

No

10m

Low

High

Nearly all applications

1 Mbps, 8 active devices

Home RF/ SWAP

Yes

50m

High

Low

Combines benefits of 802.11 + DECT

Smaller cells due to EMI

802.1x

Yes

300m

Low

High

High rate—up to 54 Mbps

EMI/lack of interoperability

HIPERLAN/2 Yes

200m

Low

High

Max. 25 Mbps QoS support

Price range

DECT

Yes

50/300m

High

High

Proven technique IMT-2000 member

Frequency band not in every country

Licenseexempt 3G (UMTS)

Yes

200m/2 km

High

High

IMT-2000 — standard global roaming

personal digital cellular (PDC) was developed. Code division multiple access (CDMA) emerged as an alternative in the United States and Korea and led to the development of 3G systems called IMT-2000. Medium-range radio technologies provide low, medium, and high bit rate wireless access of up to 2 Mbps and more (see Table 3.2). The costs are dependent on the expected radio coverage across the country. Generally high mobility is the typical feature of cellular mobile systems like GSM, IS-I36, IS-95, PDC, IMT-2000/UMTS, and other specific systems for data applications. In addition, trunked radio technologies, such as TETRA and TETRAPOL, belong to these systems. High mobility means that the user

Technologies

41

Table 3.2 Medium-Range Radio Systems Effective Cell Radius Advantages

Limitations

AMPS, NMT, TACS, FDMA JTACS

50 km

International coverage

Analog voice

GSM + EDGE

TDMA

50 km

Global coverage, global roaming

Digital voice, up to 384 Kbps data

IS-136 + EDGE, PDC TDMA

50 km

International coverage

Digital voice, up to 384 Kbps data

IS-95

CDMA

50 km

International coverage

Digital voice, 56 Kbps

IMT-2000/ CDMA 2000

MCDMA

10 km

Global systems

up to 2 Mbps

IMT-2000/UMTS

WCDMA

10 km

Global systems

up to 2 Mbps

Technology

Cellular

can be on-line with his or her terminal and remain independent from the moving speeds of up to 200 to 300 km/hr. Automatic hand-off will transfer the user connection from one cell to the other. Second-generation networks are digital mobile telephone networks that offer mainly voice services, such as voice mail and caller ID, as well as the SMS. They are more secure than analog networks and offer greater network capacity. 2G networks permit packet-switched and circuit-switched data transmission at rates of between 9.6 and 14.4 Kbps and permit GPRS bit rates of up to approximately 115 Kbps. GPRS is the beginning of packet-switching transport in 2G networks, and therefore, it will have always-on features. GPRS implementation involves overlaying a packet-based air interface on the existing circuitswitched GSM network; the mobility management remains the same. This operation requires a new backbone network as well as a radio network upgrade. GPRS will also have sufficiently high bit rates in order to provide for Internet surfing. Packet-switching means that a GPRS radio resource is used only when users are actually sending or receiving data, as opposed to dedicating a radio channel to each user for a fixed period of time. This means that large numbers of GPRS users can potentially share the same channel bandwidth and be served from a single cell. The downside, however, is that all users in the cell compete for the same bandwidth.

42

UMTS and Mobile Computing

One of the problems with using various 2G technologies is their lack of interoperability. A GSM phone cannot be used on a CDMA network and vice-versa. Only a few dual-standard terminals exist on the market. In an effort to promote global service capabilities, the ITU promoted an initiative called International Mobile Telecommunications-2000 (IMT-2000), or 3G systems. Although UMTS is the most prominent standard in the framework of IMT-2000, one common standard did not emerge, and now there are five standards (see Section 3.1.3.2) on the radio and two on the core network side. The main criterion for compliance with 3G standards is data access with speeds up to 2 Mbps for quasistationary use (low mobility), 384 Kbps for medium mobility up to 120 km/hr, and 144 Kbps at traveling speeds of 500 km/hr (high mobility). Long-Range Radio Systems

High-altitude platform stations and satellite technologies are seen today mainly as a complement to terrestrial mobile radio networks for extending to areas with low population density. As GSM approaches worldwide radio coverage, it is now more efficient and cheaper to use a triband handheld that can roam from country to country than it is to use terrestrial networks. A similar situation will appear in the future with the establishment of IMT-2000/UMTS. There are four main types of long-range radio systems. They can either be satellite-based or high-altitude platform stations (HAPS). Table 3.3 shows how these systems compare with their terrestrial counterparts.

Table 3.3 Long-Range Radio Technologies GEO

MEO

LEO

HAPS

Altitude

36,000 km

10,000–15,000 km

700–1,500 km

20 km

Number of satellites

3–4

6–20

40

—

Number of cells

800

~ 800

3,000

1/area

Signal delay

300 ms

~ 150 ms

50 ms

30 ms

Costs/coverage

Low

Medium

High

National

Subscriber capacity versus bandwidth

Low

Medium

Medium

Medium

Technologies 3.1.1

43

WPANs

WPANs provide communications in the closest environments (e.g., for indoor distances up to about 10m; for WLANs the distances are up to 100m). Thus, these networks preferably are used to connect a headset with a mobile device or to allow communication between a PDA and a desktop PC. A future step could be personalization, where devices in close proximity to a person would take notice of the person and start to interact in a personalized manner rather than in a general way. For example, a car would know individual personal adjustments (seat, temperature, music) depending on the key code of the driver; a TV set would know the user’s regular programs and viewing habits. 3.1.1.1 Bluetooth

Bluetooth [1] is a global computing and telecommunications industry specification for wireless short-range connectivity for mobile phones, computers, handheld computing devices, PDAs, headsets, other wearable devices, computer peripherals including printers, and human interface devices, such as datapads and mice. Using this technology, users of cellular phones, pagers, and PDAs will be able to buy a three-in-one phone that can double as a portable phone at home or in the office, quickly get synchronized with information in a desktop or notebook computer, initiate the sending or receiving of a fax, initiate a print-out, and, in general, have all mobile and fixed computer devices be coordinated. The technology requires that a low-cost transceiver chip be included in each device. Thirteen profiles currently exist for Bluetooth applications (as shown in Figure 3.2), and an additional 12 are under discussion. The 13 profiles are the generic access profile (GAP), service discovery profile, intercom, cordless telephony, serial port, headset, dial-up networking, fax, LAN access, generic object exchange, object push, file transfer, and synchronization. Additional profiles include PAN, local positioning, still image, AV, and video streaming. Each device is equipped with a microchip transceiver that transmits and receives data in the ISM frequency band of 2.4 to 2.4835 GHz that is available globally (with some variation of bandwidth in different countries). In addition to data, up to three voice channels are available. Each device will have a unique 48-bit address from the IEEE 802 standard. Connections are 1:1. The maximum range is 10m. The aggregate bit rate is 1 Mbps (later, up to 2 Mbps). The net bit rates depend on traffic characteristics, which are shown in Table 3.4. A frequency hop scheme (slotted TDMA) allows devices

44

Mobile sets

Video camera

Advanced hands-free

Stationary sets

Internet/ Intranet

GPS

Cellular network Pocket PC

Printer

PDA

Contactless electronic key Electronic payment

Figure 3.2 Bluetooth connectivity.

Desktop LAN equipment

Desktop

UMTS and Mobile Computing

Car

Technologies

45

to communicate even in areas with a great deal of electromagnetic interference. Built-in encryption and verification is provided to make sure that the right information arrives securely at the right partners. Bluetooth’s masterslave network configuration allows point-to-point communication, piconets (a cluster of eight devices), and scatternets (interconnected piconets, 10 clusters maximum). There is a lot of hype around Bluetooth, and many companies have introduced their first products. These companies are also working on implementations of the specification. Although the specification is good, it still takes some time until the mass market is reached. There are five primary criteria for the deployment of Bluetooth: 1. 2. 3. 4. 5.

Small implementation; Open specification; Low power; Low cost; Ad hoc connectivity.

There are some doubts as to whether the technology will be able to deliver its promises: Uncertainties exist with the propagation of 2,400–2,500-MHz signals within confined areas and with the interference caused to the operating device in scenarios where WLANs coexist. Although the 2,400-MHz ISM frequency band is currently unlicensed, operators still need to apply for permission to operate services in some countries. It is unclear how long the band will remain unlicensed if the current rate of exploitation of this resource continues. From a networking point of view, there is great interest to integrate Bluetooth with WANs like UMTS and the Internet. There are still open questions on how to manage such a connection (e.g., as a simple point-topoint local call or as a subnetwork with always-on connectivity). (See the Bluetooth home page for more details [1].) The market expectations for Bluetooth are high. By 2005, a billion units should be brought to the market place. The basic problem of Bluetooth is interoperability. The Bluetooth Special Interest Group (BSIG) has resolved some of these problems, although there is still some work to do. For example, Bluetooth products need to be tested at a qualified test facility to ensure compliance with specifications. Testing of Bluetooth products is currently done against designated protocol test products called Blue Units. These can test a number of key functions, but their use is limited to partial testing of the baseband and link management functions. Coexistence with

46

UMTS and Mobile Computing

other radio interfaces integrated into the same device (e.g., GSM, GPRS, UMTS, IS-95) is of great importance. Bluetooth Basic Functions and Parameters

The main components of Bluetooth are as follows: • The radio transceiver with frequency hopping; • The baseband link control; • The link management software; • The antenna subsystem.

The transceiver is responsible for transmitting and receiving signals with the frequency hopping oscillator (1,600 hops per second) on a frequency modulated carrier. Spread spectrum schemes are used for point-to-point and -multipoint connections. For North America and most parts of Europe, it hops among 79 channels spaced 1 MHz apart, between 2.400 GHz and 2.4835 GHz (ISM band). In France and Spain, there is less spectrum available, and the system has only 24 channels. Bluetooth supports three transmit power classes: • Class 1 allows +20 dBm maximum output power with a maximum

distance of up to 100m (depending on the environment).

• Class 2 allows +4 dBm maximum output power with a maximum

distance of up to 10m.

• Class 3 allows 0 dBm maximum output power with a maximum dis-

tance of 1 to 2m.

Class 1 requires additional power amplifiers; the other classes are covered in the chip sets. The current specifications allow up to eight devices, which can automatically configure themselves into a piconet of one master and seven slaves. A slave can communicate with more than one master; this allows communication between several piconets. Synchronous traffic can be handled with 432.6 Kbps in either direction, and asynchronous traffic with 721 Kbps in one direction and 57.6 Kbps in the return direction. The key parameters of Bluetooth are shown in Table 3.4.

Technologies

47

Table 3.4 Bluetooth Specifications: Key Parameters Characteristic

Specification

Remarks

Carrier frequency (MHz)

2,400– 2,483.5 (ISM band) 79 carriers

France: 2,446.5–2,483.5 MHz Japan: 2,471–2,497 MHz Spain: 2,445–2,475 MHz

Modulation

Gaussian-filtered binary frequency-shift keying at a line rate of 1 Mbps

Modulation index is 0.32, nominal; may range from 0.28 to 0.35 Peak deviation allowed is 175 kHz

Frequency hopping

1,600 hops per second in normal operation; four special hopping sequences for connection setup

—

Transmit power

Class 1: 1–100 mW Class 2: 0.25–2.5 mW Class 3: 1 mW

Power control is required by power class 1; optional for other classes

Operating range (m)

0.1–10m

Up to 100m with power class 1

Maximum throughput

Asymmetric link with up to 721 Data throughput is lower than the Kbps in one direction and 57.6 1-Mbps line rate because of Kbps in the other protocol overhead Symmetric link with 432.6 Kbps in both directions

Bluetooth Products

A number of manufacturers are increasingly implementing the Bluetooth specification into such devices as notebooks, PCs, handhelds, PDAs, and mobile phones. The first Bluetooth headset was introduced by GN Netcom (GN9000) in 2001. It communicates with any standard phone as well as other Bluetooth-enabled devices. This includes Ericsson’s R250 mobile phone, one of the first mobile devices with Bluetooth connectivity. Bluetooth 2 in Development

Some companies (including Toshiba and others) are already working on Bluetooth version 2, which will have greater range (approximately 100m), more bandwidth, and more participants. Some companies of the BSIG want to increase the capabilities of Bluetooth so that it becomes more like a WLAN and maybe even someday replaces the WLAN in various scenarios.

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UMTS and Mobile Computing

BlueSky

BlueSky is a system for low-cost, low-power, indoor wireless networking for non-PC devices developed by IBM in 1998. At that time Bluetooth did not exist. When the BSIG was established, it was found that both systems shared the same goals. The development of the initial BlueSky project was then stopped because of the following inherent disadvantages in contrast to Bluetooth: • No peer-to-peer communication (needs an access point); • Module too big; • No IP network connectivity.

The next version of the BlueSky system will be built on top of Bluetooth. 3.1.1.2 HANs

The term home area network describes the one communication network at home that would interconnect all kinds of electronically controlled devices. Home Phoneline Network Alliances (HomePNA) are looking at ways to establish a network that covers the home as a whole. Likewise, a home radio frequency (HomeRF) system or a WLAN can accomplish the same. A variety of radio technologies are considered for home area applications; they are listed in Table 3.5. Possible HAN techniques are Ethernet, wireless Ethernet, WLAN, IEEE 1394, home audio-video interoperability (HAVi), and DECT. DECT is dominantly used in Europe, Asia, and South America for telephone and fax communications. One manufacturer in Germany is providing DECT modems for PC connections [3]. WPANs, Bluetooth, and infrared are appropriate for even smaller environments, basically for communication links between different personal user devices. A HAN, however, would tether those LANs. HANs connect computers, devices, and possibly a residential gateway. Figure 3.3 shows a HAN. Networking technologies are starting to invade the ordinary home—to carry, for example, telephone conversations; television, compact disc, digital versatile disk, MP3 music programs, and DVDs; signals from surveillance cameras; commands for controlling appliances; and multimedia flows from the Internet. With home networking, it is also possible for electric utilities to remotely control the flow of electricity into individual homes and to read their meters automatically.

Table 3.5 Wireless Home Radio Network Technologies

Application

Characteristics

Frequency Band (GHz)

Modulation

Bit Rate (Mbps)

Standardization Organization

802.11b FHSS

Wireless data networking

Encryption available

2.4

FH

0.5–3

IEEE

802.11b DSSS

Wireless data networking

—

2.4

Direct sequence

0.5–11

IEEE

Highspeed 802.11a

High-speed WLANs

Broadband multimedia 5 2.4

Discrete multitone/orthogonal FDM Spread spectrum

6–54 11

IEEE

HIPERLAN/2 Broadband radio access for IP networks (BRAIN)

High-speed multimedia LANs

Voice, data, video, can 5.4–5.7 coexist with 2.4-GHz systems, IP-based

Gaussian phase-shift keying

25

HIPERLAN Forum

Digital enhanced Voice and data for home Integrated voice and cordless data and offices telecommunications (DECT)

1.85–1.920 (country specific)

Gaussian frequency-shift keying

2

ITU/ETSI

UTRA-TDD

1.9/2

TD/CDMA

2

3GPP

Wireless communication High bit rate TDD for multimedia

Technologies

Radio System

Source: [2].

49

50

UMTS and Mobile Computing

DECT 1.9 GHz PDA ISM band 900 MHz 2.4 GHz 5 Hz Embedded Web server

HAN

Home area network

Coax Phone Power RF

Ethernet /HAVi Phone line Power line (control and data) Wireless (home RF) Home-office WLAN

PAN

HPnP

Entertainment LAN IEEE 1394, HAVi

Figure 3.3 HANs. (Source: [4].)

At present, these networks fall into four major application areas: 1. Computer interconnection for accessing the Internet and connecting multiple PCs with peripherals for communications and entertainment; 2. Telephone and fax interconnections for internal and external communications; 3. TV and radio distribution lines; 4. Controlling items like lights, appliances, climate-control systems, and surveillance cameras. If the HAN is connected to the Internet, the user can do remote control via the Internet. This is known as the mini-Internet with embedded Web servers. The embedded Web server provides a user interface for accessing the control and supervisory functions for a home or a facility (for corporate applications).

Technologies

51

The physical basis of these networks is frequently voice-grade telephone wiring and coaxial cable, but electric power lines are also being used, as are wireless schemes, mainly in the ISM band. For HANs to succeed, home networks will have to be based on standard products operable with any of the media. These products include transceivers, network gateways, small servers, sensors, and controller-accepted OSs. For mass-market acceptance, networks will have to be inexpensive and easy to install, configure, and operate. Wireless home area technology is quickly developing for data and voice communications (see Table 3.5). In many situations it can provide a convenient and inexpensive networking solution in a home or small office. Since most homes with two or more personal computers were built before the recent explosion in telecommunications, they are not wired for a telephone in every room. Installing twisted wire-pairs all over the premises would be difficult. Power lines or telephone wires in the homes can also be used for all kinds of home networking: desktop PCs, printers, camcorders, cameras, and scanners all can be interconnected via ordinary copper telephone or power lines. Technologies support up to 25 nodes for distances across 20m and 1-Mbps bit rates over telephone wires are possible. A HomeRF system can either work as an ad hoc network of devices, which support only data communications, or as a managed network under control of a connection point. The HomeRF standard [5] is an open specification supported by more than 100 member companies to deliver a broad spectrum of affordable, interoperable consumer devices capable of both tollquality voice and high-speed data networking. Current supported applications include cordless voice telephony, in-home distribution and sharing of broadband data services, and file and print sharing. In 1999 seven leading companies—Cayman Systems, Compaq, IBM, Intel, MobileStar Network, Motorola, and Proxim—had HomeRF products. Planned HomeRF technology enhancements will support higher data rates, isochronous voice, audio, and streaming video communications, as well as broadband wireless Internet access outside the home. These enhancements will enable a whole new class of applications, including cordless telephony, streaming music and video, and broadband wireless Internet connectivity in public hot spots. HomeRFs operate in unlicensed frequency bands. They use the Shared Wireless Access Protocol (SWAP) to allow RF digital communications between PCs and consumer electronic (CE) devices for wireless voice and data communications anywhere in and around the home. This is actually an intermediate system between a WLAN and a WPAN like Bluetooth. SWAP

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UMTS and Mobile Computing

provides data communications and data sharing for up to 127 PCs, peripherals, cordless telephones, and other devices with a network stack. It also permits up to eight voice connections. It has up to 100 mW of power, which permits operation over a distance of up to 45m. SWAP uses the ISM band, which is available worldwide. It combines elements of the existing DECT and IEEE 802.11 standards. The protocol architecture closely resembles the IEEE 802.11 WLAN standards in the physical layer and extends the medium access control (MAC) layer with the addition of a subset of DECT standards to provide isochronous services, such as voice. As a result, the SWAP MAC layer can support both data-oriented services, such as Transmission Control Protocol/Internet Protocol (TCP/IP), and the DECT/GAP protocols for voice [6]. HomeRF products have already been released, including Intel’s AnyPoint products, PC cards, and PCI cards. Since Bluetooth is being introduced into such appliances, it is worth comparing SWAP HomeRF technology with Bluetooth (Table 3.6). 3.1.1.3 IEEE 802.15 Wireless Personal Area Network

In March 1999 the IEEE P802 LAN/MAN Standards Committee (LMSC) announced the formation of a new group called the P802.15 Working Group to develop standards for WPANs for portable and mobile computing devices. Portable and mobile computing devices are defined as unobtrusive computing devices, networking devices, software, and peripherals that are worn or carried by individuals to enhance their ability to perform productive work as well as to provide entertainment. The P802.15 Working Group works closely with special interest groups, such as Bluetooth and the Industry Consortia. The working group also solicits industry input, in general, on market requirements and technical solutions for a WPAN with 0 to 10m range, data rates of less than 1 Mbps, low power consumption, small size (less than 0.5 in3), and low cost relative to target device. The goal is to create standards that have broad market applicability and deal with the issues of coexistence and interoperability. The P802.15 products are optimized for the following: • Low cost relative to target device; 3

• Small size of approximately 0.5 in (excluding antenna and battery); • Power management—very low current consumption (average 20 mW

or less at 10% transmit/receive load);

• Asynchronous or connectionless data links;

Technologies

53

Table 3.6 Comparison of HomeRF and Bluetooth HomeRF (SWAP 1.2)

Bluetooth

2.4-GHz frequency hopping

2.4-GHz frequency hopping

50 hops per second radio

1,600 hops per second

Optimized for voice and data in homes

Optimized for smart phones and computer devices

~ 1 Mbps

432.6 Kbps or 721/57.6 Kbps

Distance: 50m (house and yard)

Distance: 10m

8 near-line-quality voice links

3 near-line-quality voice links

Unlimited device links per base

7 device links per base

Peer-to-peer networking

Point-to-point and -multipoint connections

“Native“ TCP/IP support

Point-to-point TCP/IP support

Low-power paging mode

Low-power standby mode

Lower transmit power possible

Higher transmit power possible

Based on 802.11 FH, OpenAir, and DECT

Based on TDD, packet transport

• The coexistence of multiple wireless PANs in the same area (20

within 400 ft2);

• Range of 0 to 10m; • Networking support for a minimum of 16 devices; • Bridge or gateway connectivity to other data networks; • Delivered data throughput of 19.2 to 100 Kbps (actual one device to

one device);

• Communicability between all devices within a WPAN; • QoS that supports a variety of traffic types. 3.1.1.4 DECT

The DECT system [7] is a local area wireless access system standardized by the ETSI for cordless communications in residential, corporate, and public environments, and providing for voice and data traffic. DECT is designed especially for a small area with a large number of users, such as in cities and corporate complexes. The system capacity depends on available frequency

54

UMTS and Mobile Computing

bandwidth; it has a technical limit of up to 100,000 users per km² of floor space in an office environment. The key features of DECT are designed to allow high capacity while maintaining high speech and data quality. Especially important is the unique DECT quick, seamless (no interruption), decentralized intercell or intracell handover, which elegantly copes with changing conditions, without need for central control. DECT is the most successful cordless standard worldwide. It is a family member of the ITU IMT-2000 radio standards. There are more than 100 million DECT systems in the marketplaces in Europe, Asia, Africa, and North and South America. Figure 3.4 shows DECT’s technical characteristics and the layer structure. The Concept of the Basic DECT Base Station

The basic DECT base station consists of one single radio transceiver that can change frequency from slot to slot. This comes from the system’s flexibility, where the base station can on each time frame operate on all twelve duplex time slots, each slot operating independently on any of the 10 DECT carriers. While operating on different carriers, each call connected to the same base station always uses a different time slot.

C-Plane

U-plane

Signaling Interworking application process

Application processes

Management entity

DECT technical characteristics RF channels

Data rate

Network layer Data-link control layer

Data-link control layer

Medium-access control layer Physical layer DECT layer structure

Transmit power

MC TDMA/TDD (multiple channel time division multiple access/ time division duplex*); max. 10 carriers, 1.782 MHz carrier spacing/12 duplex TDMA slots per carrier 1152 kbps Frame length 10 ms 24 × 0.417 msec traffic slots (twelve for each direction) Transmission burst 361 ms with 56 ms guard space 250 mW peak/10 mW average

Speech encoding 32 kbps (“half-rate“ 16 kbps), G.721ADPCM Modulation GMSK (BT = 0.5) (Gaussian minimum shift keying) Equalization None (but will use spacial diversity) *This is referred to as TDMA/FDMA/TDD

Figure 3.4 DECT.

Technologies

55

With a complexity comparable to that of a DECT handset, the base station has a capacity corresponding to 12 radios and a combiner in traditional analog land mobile radio systems. It offers a high grade of service with high traffic capacity. Dynamic Channel Selection

DECT utilizes a simple but efficient and robust dynamic channel selection (DCS) procedure. DECT physical channels are allocated decentralized between each portable device and its closest base station. For each call, the portable device chooses a channel that for the time being is best for the wanted local connection. The most basic advantage of this is that different systems, systems operators, and types of services can, in a self-organizing way, utilize the same lump of available channels without prior distribution of channels to specific services or base stations. Mobile radio systems with in-principle fixed channel allocation—like NMT, TACS, AMPS, and GSM—do not provide this important feature. In addition, these systems need to be planned to a worst-case situation, while DCS takes the actual interference situation into account. Furthermore, driven by customer needs, each service or equipment provider can increase its own capacity by increasing its base station density. As a consequence of the DCS procedure, there is no need to plan in detail how many channels are needed per base station. This maintains a high grade of service even with local density variations. Call Setup Using Base Station Beacon Channels

Each base station is always active on at least one channel, and every active channel broadcasts system information and base station identification. This allows any portable (by receiving only) to identify any system or base station within reach. When a handset has recognized a desired system simply by listening, the receiver locks to it by locking on any active channel on the strongest (nearest) base station. In this idle locked state, the handset listens every 160 ms for a possible paging call from the system. When the handset wants to contact the system, either because it wants to originate a call or because it has been requested to do so by a paging call from the network, the DCS procedure looks for a free physical channel and accesses the system by sending an appropriate burst. Setting up calls (or handing them over) to the closest (strongest) base station provides stable DCS, high capacity, and high link quality.

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UMTS and Mobile Computing

Handover

In order to accommodate very small cells, the need arises for quick and seamless handover, requiring neither central control nor complicated procedures. The key to seamless handover is TDMA in combination with decentralized DCS. The old link is maintained on one slot in the portable device, while the new link is set up in parallel on another time slot. When the new link is established, the (new) base station requests the central to make a seamless switch from the old to the new radio link. The handover is device-controlled: while it communicates on the original link, it scans the other channels and records free channels and the identities of base stations that are stronger than the current one, and is thus prepared to perform a quick handover. Handover is made as soon as another base station is stronger than the one of the current connection. Thus, in a well-engineered system it is always performed before the quality decreases. The nature of DCS is that a channel in use can occasionally get stolen, and therefore the quick DECT seamless intercell and intracell handover increases the capacity and cuts call curtailments drastically. DECT does not depend at all on the old channel to quickly set up the new one. In a simple DECT application, the DECT base station is hooked up to the outlet of the public telephone system (the PSTN), as shown in Figure 3.4. The base station operates on 10 carrier frequencies simultaneously, and each carrier frequency provides for 12 duplex channels. Thus, a single base station can support theoretically up to 120 mobile units at the same time. The average transmission power of 10 mW (peak power of 250 mW) provides for indoor mobility typically up to 50m and 300m outside of buildings. Despite this low power, DECT offers ISDN speech quality, which clearly outperforms analog systems and even other cellular phone systems, such as GSM. From an addressing point of view, DECT follows the ITU E.164 subnetwork addressing scheme and can be fully integrated into private branch networks. Personal Handyphone System

PHS is similar to DECT, but exists only in Japan and in a few other countries. It has 20 million devices in Japan that provide for both voice and data. 3.1.2

WLANs

A LAN is a network of interconnected workstations sharing the resources of a single processor or server within a relatively small geographic area. Typically,

Technologies

57

this might be within the area of a small office building or campus. Usually, the server has applications and data storage that are shared in common by multiple workstation users. With a WLAN, a mobile user can connect to a server through a radio connection. Wireless technologies for LAN connections include frequency hopping, spread spectrum, microwave, and infrared light. Several companies developed the first WLAN products about a decade ago. Early WLAN systems were expensive, and their data rates were too low. They were prone to signal interference and consumed power of far in excess of 100 mW for bit rates from 200 Kbps up to 1 Mbps. The interoperability problem between systems of different manufacturers was another reason why this standard did not reach market success until recently. The systems work like the more advanced standardization products in the unlicensed frequency band in the 2.4-GHz range. In mid-1990 IEEE formed the P802.11 Working Group with the aim to develop a common standard. This standard was completed by 1997 and comprised three physical layer solutions: two radio-based solutions (frequency hopping and direct sequence) and one infrared. The MAC layer is common regardless of the physical layer used. 3.1.2.1 IEEE 802.11 Wireless Local Area Network Standard (802.11a and 802.11b)

The client-server network uses an access point that controls the allocation of transmit time for all stations and allows mobile stations limited roaming from cell to cell within the same WLAN environment. Roaming between different WLANs may cause interoperability problems and is dependent on the backbone network. The access point is used to handle traffic from the mobile radio access system to the wired or wireless backbone of the client-server network. This arrangement allows for point coordination of all the stations in the basic service area and ensures proper handling of the data traffic. The access point routes data between the stations and other wireless stations or to and from the network server. Typically, WLANs are controlled by a central access point called an access controller or gateway, which includes functions for IP access control. WLANs are used mainly in the corporate sector, but also in small office environments and in homes. WLAN cards with a size of 176 × 54 × 5/10 mm (PC card extended type II) give laptop and desktop users wireless data access up to theoretically 11 Mbps. The cards also are compatible with a wide range of pocket computers and handheld devices (PDAs) equipped with a type II or type III PC card slot. They support peer-to-peer or ad hoc networking to wired Ethernet networks via access points. The WLAN access

58

UMTS and Mobile Computing

controller, sometimes referred to as a wireless bridge, provides the radio coverage with theoretical cell radii from 20 to 100m indoors and, depending on the product, up to 300m outdoors. Point-to-point connections with directional antennas allow larger distances of up to 2 to 3 km. Practical cell radii vary depending on the product. Benchmark tests [8] have shown that IEEE 802.11 frequency hopping spread spectrum (FHSS) techniques reach their limits at 3 Mbps, while the direct sequence spread spectrum (DSSS) techniques may achieve higher bit rates up to 11 Mbps depending on transmit power, cell size, number of simultaneous users, application, and cellular environment. Twelve products from different manufacturers were benchmarked with file transfer of 64-MB date files and TCP/IP traffic with 4-KB block size. The throughput results varied depending on the terminal distance (d ) to the access point (Table 3.7). Typically, user environments are offices, business parks, and various campus areas, corporate buildings, railway stations, airport lounges, and hotels. Some manufacturers also provide solutions that can be integrated into a public WAN [e.g., by using the subscriber identity module (SIM) card for GSM access, the WLAN terminal will get the SIM inserted and have access software to communicate with GSM]. The WLAN is connected to the GSM network by a server, which takes over authentication and mobility management. For 3G networks like UMTS, such functionality is presently under research in the Broadband Radio Access for IP-Based Networks (BRAIN) program (see Section 3.1.2.2). Table 3.7 Ranges and Bit Rates of IEEE 802.11b WLANs—Measurements and Specific Targets Maximum Bit Rates Indoor Office

Semiopen Office

Measured Values*

On-sight Office

Specified Target Values

Distance from access point

d = 2.5m

21m

45m

60m

100m

300m

Max. bit rate for FTP (Mbps)

2.6–6

1.3–4.8

0.5–5

11

2

1

Max. bit rate for TCP/IP (Mbps)

2.7–6.1

2.5–5

0.5–5

11

2

1

*(e.g., 2.6–6 depending on the product)

Technologies

59

IEEE 802.11a

This standard specifies a different physical layer 1 than 802.11 (and 802.11b) by using orthogonal frequency division multiple access (OFDMA). The target is to achieve 54-Mbps bit rates. The IEEE 802.11a specification amendment from 1999 defines the physical and the MAC layer. 802.11a products are foreseen to operate in the United States from 5.8 to 5.9 GHz and, according to the ITU WRC 2000 resolution 736, also in the 5.47–5.725-GHz and 5.15–5.35-GHz range. IEEE 802.11b

Products based on this specification also work in the ISM band. Their physical layer uses DSSS, whereby interference is reduced, thus higher spectral efficiency and low power consumption is achieved in contrast to IEEE 802.11. In contrast to FHSS, which has a smaller carrier bandwidth (1 MHz) compared to DSSS (11 MHz), it provides higher transmission bit rates and distance. DSSS, however, offers fewer potential channels and less scalability. IEEE 802.11b products are available in all parts of the world and have the following technical properties: • Up to 14 channels; • Frequency range ISM band; • 5-MHz carrier channel spacing in European Conference of Postal • • • • • • • • • • •

and Telecommunications Administrations (CEPT) countries; Direct sequence spread spectrum modulation technique (11 chips code); PCMCIA type II interface; Media Access Protocol CSMA/CD with ACK; Card dimensions: 118–180 × 54 × 5–12 mm; Frame error rate < 8%; Peer-to-peer or point-to-multipoint communication; Power consumption; Transmission approximately 300 mA; Output power up to approximately 30 or 40 mW; Ranges (theoretical values) up to 200m; Bit rates up to 11 Mbps.

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UMTS and Mobile Computing

WLANs are completely protocol transparent like Ethernet or Token Ring LANs. Interoperability problems usually come from the higher bit error rates and propagation delay times of the WLAN. The WLAN MAC works similar to that of the Ethernet IEEE 802.3. Two methods for access exist: 1. The centralized approach, called point coordination function (PCF); 2. The decentralized approach, called distribution coordination function (DCF). The Ethernet basic access method is used in the DCF mode: it is called carrier sense multiple access/collision avoidance (CSMA/CA). Collision detection (CD) is not used because it cannot be distinguished from other radio-related distortions. Instead, the WLAN uses collision avoidance (CA). IEEE 802.11b WLAN can be interfaced with IEEE 802.3 or 802.5 wired LANs, depending on the manufacturer’s product compliance with the standard. HIPERLANs

In 1996 the European Radio Committee (ERC) decided with ERC/DEC/(96)03 to dispute the frequency band 5.15 to 5.25 GHz for HIPERLANs conforming to ETSI standards. Furthermore, it was agreed that the band 5.25 to 5.35 GHz was to be designated for use on a regional and national basis. Regarding the frequency bands in the ITU Region 1 CEPT [Europe and the Commonwealth of Independant States (CIS; the former Soviet Union)], the following was decided: • To use 5.15 to 5.35 GHz for HIPERLANs (HIPERLAN/2) in-

doors, with a maximum output power of 200 mW;

• To use 5.47 to 5.725 GHz for HIPERLANs indoors and outdoors,

with a maximum output power of 1W.

HIPERLANs were specified within the framework program called BRAN. HIPERLAN/1 provides bit rates up to 23.5 Mbps and is compatible with Ethernet and Token Ring LAN standards according to ISO 8802.3 and 8802.5. User mobility is restricted within the local service area only. The technical specification was released by ETSI in 1997.

Technologies

61

HIPERLAN/2 provides up to 25 Mbps and is foreseen to be linked with IP networks. The typical operating environment is indoors. Restricted user mobility lies within the local service area. Linking with WANs is on a proprietary basis. The modulation scheme is different from HIPERLAN/1. HIPERACCESS (also known as HIPERLAN/3) and HIPERLINK were studied for the purpose of multimedia use with high bit rates up to 155 Mbps in higher frequency ranges (e.g., 17 GHz). 3.1.2.2 HIPERLAN/2 and BRAIN

HIPERLAN/2 is a WLAN based on ETSI standards. BRAIN [9] is a research project under the Information Society Technology (IST) program of the European Union working to define an open architecture for integrated mobile radio access networks with IP-based core networks (e.g., UMTS and Internet). Roaming is a key issue including a handover algorithm between different types of radio networks. WLAN systems complement wide area cellular networks in specific environments, and indoors, they provide higher bit rates with high-capacity hot-spot coverage. They are complementary also regarding the frequency bands. The regulatory issues regarding roaming between license-exempt networks and licensed public operator networks (coexistence of radio networks with different owners) are not yet clarified on a global basis. The main issues in the development of BRAIN specifications are as follows: • To define quality of service types for transport over the radio link; • To specify an efficient IP transport over the radio link; • To define mobility and handover mechanisms between WLAN and

UMTS;

• To define service-oriented IP layer for convergence.

The BRAIN radio interface is HIPERLAN/2, which defines the physical and data link control layer with error control, the MAC layer (see Table 3.8). The convergence layer enables interconnection with different link layers, such as Ethernet and FireWire. Also, the Internet IPv4 and IPv6 specifications have to be supported. ETSI and the HIPERLAN/2 Global Forum (H2GF) signed a cooperation agreement in 2001 to ensure future standardization in this sector (ETSI project EPBRAN).

62

UMTS and Mobile Computing Table 3.8 BRAIN Layer Based on HIPERLAN/2 BRAIN Layers

HIPERLAN/2 Specifications

Layer 3

Service-specific convergence layer (IP) Common convergence layer Radio link control Error control

Layer 2

MAC

Layer 1

Physical layer

3.1.2.3 WLAN Deployment and Products

WLAN deployments are beginning to appear with the simplest configuration of a point-to-point interconnection between two computers. Two computer WLAN cards allow spontaneous connectivity without accessing the Internet or an intranet. Of course, drivers need to be installed, the configuration of the client and server-software needs to be set up, and the communication needs to be initialized and executed. Each host has its own radio cell as long as the peer-to-peer communication can take place. In case of a multihost configuration, a hub has to be put in place (the star configuration according to IEEE 802.3). Such a configuration has the status of an ad hoc network, again without connection to the Internet or an intranet. If needed, however, a configuration with the setup of an access point allows the interconnection with an existing wireline Internet or intranet. The logical function of the access point is called a bridge to a LAN or Internet environment. The communication between clients and server remains completely transparent. The access point also allows an extension of the WLAN via twisted pairs to extend the distance between WLANs. WLAN products include the following: • Aironet’s [10] IEEE 802.11 compliant in-building WLAN product

lines include several types of products like access points and WLAN adapters. They are available with 900-MHz or 2.4-GHz DS radios or 2.4-GHz FH radios.

• Lucent Technologies’ Orinoco [11] is conforming to the IEEE

802.11b standard. It provides Ethernet quality performance to

Technologies

•

• •

• • • •

63

mobile workers within an enterprise and is backward compatible with the earlier 10Base2 coax network systems. Proxim [12] offers RangeLAN2 as a multistandard WLAN. Their MobileStar system provides T1 connectivity to the Internet using RangeLAN2. RangeLAN2 is based on the OpenAir standard and is interoperable with over 40 different devices. The Symphony Cordless Networking Suite is a cordless 1.6-Mbps Ethernet LAN with a 150-ft range through walls and floors using 2.4-GHz spread spectrum technology. RangeLAN802 is Proxim’s IEEE 802.11 product line. It has the interoperability certification from the Wireless LAN Interoperability Forum (WLIF). Intermec [13] also offers WLAN products that are compliant to OpenAir and IEEE 802.11. Nokia Networks [14] offers WLAN products, P022 access controllers, and C110/111 WLAN cards that are based on IEEE 802.11b with connectivity to GSM and partial roaming capabilities (SIM card–based). Siemens IGate is compliant with IEEE 802.11b. It is designed similar to an access router solution with a wireless interface. Symbol WLAN’s [15] WLAN technology is based on IEEE 802.11. WebGear [16] designs wireless local area networking for business and home applications. Z-Com Wireless Networking Company [17] offers IEEE 802.11 WLAN compliant products.

Other manufacturers include BreezeCOM, Diamond Home Free, NDC Instant Wave, Nortel Bay Stack, and RadioLAN. 3.1.3

Wireless WANs

WANs are generally understood as being nationwide or regional networks using medium- and long-range radio technologies. Cellular arrangements are required in order to achieve the expected radio coverage with acceptable amount of spectrum. Radio access techniques may vary—they are often understood as technologies in the scope of 1G, 2G, and 3G systems (see Figure 3.5). First-generation systems use analog radio access techniques based on frequency division multiple access (FDMA). For mainly the same applications, 2G systems use digital radio techniques, such as TDMA and CDMA.

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UMTS and Mobile Computing

Migration

Migration

1G

2G

3G

Future evolution

Analog speech

Digital speech + low-rate data up to < 50 kbps

Very high bit-rate software radio

NMT, AMPS, TACS

GSM, PDC, IS-95 IS-136 (D-AMPS)

Multimedia services (≤ 2 Mbps) 2+G services IMT-2000, UMTS, CDMA 2000, UWC136

1980

1990

2000

2010

Figure 3.5 Wireless WANs. (Source: Siemens.)

Third-generation systems involve multimedia applications which require wideband systems; thus, CDMA, which uses wideband frequency carriers, is the dominating technique, partly combined with TDMA. 3.1.3.1 Radio Access Techniques

Cellular mobile communication systems, cellular telephone systems, and wireless communication systems all use radio-wave analog or digital transmission in which a subscriber has a wireless connection from a mobile device or telephone to a relatively nearby transmitter. The transmitter’s span of coverage is called a cell. Generally, cellular mobile communication service is available in urban areas and along major highways. As the user moves from one cell or area of coverage to another, the device is effectively passed on to the closest available cell transmitter. Second-generation cellular mobile communication systems today offer data speeds typically up to 20 to 50 Kbps, and service is paid depending on the duration of the call or data packets. A cordless telephone is simply a phone with a very short wireless connection to a local wireline network—DECT is one example. A personal communications service (PCS) may comprise both. Wireless communications systems use several different access techniques, usually referred to as air interfaces. The principal common access techniques include the following: • FDMA; • TDMA;

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• CDMA; • Combinations of TDMA and CDMA or TDMA and CDMA with

smart-antenna techniques (TD/SCDMA).

FDMA—often referred to AMPS, NMT, or TACS—uses narrowband channels of spectrum, each carrying one telephone circuit, in a system where any mobile can access any one of the frequency channels. Existing analog cellular systems use FDMA. (See Figure 3.6.) TDMA divides each carrier frequency into a number of time slots, each of which constitutes an independent telephone or data circuit. Each call is assigned a time slot. The Telecommunications Industry Association (TIA), which is today named the Cellular Telecommunications Industry Association (CTIA), endorsed TDMA in 1990, and some North American digital cellular and PCS systems use TDMA. Additional TDMA standards are the PDC System developed in Japan and the GSM. Endorsed by ETSI in 1990,

e Tim

Signal power

Channel allocation via frequency carriers: FDMA

Carrier

f1

f2

f3

f4

fx

Channel allocation via time slots: TDMA Frequency

e

CDMA

Tim

Signal power

Channel allocation via spreading code

Carrier bandwidth f = (f1 + f2 + f3 + … + fx + …) Figure 3.6 TDMA, FDMA, and CDMA.

Frequency

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GSM uses TDMA with frequency hopping in that it divides each carrier frequency into a number of time slots; in addition, other frequency carriers are used for frequency hopping. GSM is the primary standard for wireless communications systems, and there are nearly 500 GSM networks worldwide [18]. CDMA is a form of spread spectrum packet-based wireless transmission technique. Instead of using frequencies or time slots, it uses mathematical codes and spread spectrum technology to transmit and distinguish between multiple wireless conversations. Its bandwidth is much wider than that required for simple point-to-point communications because it spreads the information contained in a signal of interest over a much greater bandwidth. Where FDMA techniques transmit one connection per carrier and TDMA techniques are limited to a definite number, CDMA techniques have no hard limit to transmitting a high number of channels. All these access techniques have their advantages and disadvantages, which are taken into account when selecting between air interface proposals. Theoretical investigations, computer simulations, and available technologies also contribute to this process. Theoretically, all the access techniques are comparable. The theory is laid down in the Shannon formula, which defines the channel capacity as a function of the used bandwidth and the signal-tonoise ratio related to Gaussian noise conditions: C = B log2 (1 + S/N ) where C = the channel capacity in bits per second, B = frequency bandwidth in hertz, and S/N = signal-to-noise ratio. The Shannon formula says that a given capacity can be obtained as follows: • By assigning the channel to a narrow band and pursuing at the

same time a high value of S/N—this is typically the case in FDMA/TDMA systems;

• By using a much wider band (factor 10 to 30), admitting for lower

values of S/N. This case arises in CDMA where all users are transmitting and receiving on the same frequency band and each connection perceives a signal like noise. The discrimination between different user information is performed by assigning different codes to the users.

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The same code is used for subsequent information during a connection, for encoding on the transmit side and for decoding on the receive side. All the schemes can be used also in combination (e.g., TDMA/ CDMA). The most promising solution for 3G systems that allow wide frequency band transmitters is to use direct sequence CDMA for the so-called frequency division duplex (FDD) mode: one wideband frequency carrier is used in either direction. For duplex traffic it makes use of paired frequency bands (uplink/downlink). In addition, in case of allocation of unpaired frequency bands, the so-called TDD mode is used: time division duplex combined with CDMA. Forward and backward direction of traffic flow is handled via time slot assignments within the same band; the signals are encoded and spread over the entire frequency band. An additional function is introduced in CDMA technologies: the reuse of the same frequency carrier in the neighbor cells; connection hand-off is handled by codes. This mechanism guarantees the connection continuity (while the mobile terminal is crossing cell borders) by doubling the active channels between the mobile terminal and an equivalent bridging point in the network. This double path is maintained along the connection, so that the continuity is ensured through an asynchronous acquisition-release process, which relaxes the stringent time constraints characterizing the hand-over execution in the present systems. The acquisition and release process that takes place along a connection is driven by the signal level received by the mobile terminal in its actual position. This is called macrodiversity, which provides great advantages in terms of quality of service, but it induces a significant complexity on the access network and in the terminal. In fact, the network must identify the combining and multicasting point that recovers, in the upper direction, a single path from the multiplicity of equivalent paths in progress in the radio interface (combining) and create, in the downward direction, the necessary equivalent paths to be directed towards the mobile terminal. This point changes dynamically with terminal movement and may be allocated at different hierarchical levels, depending on the network topology. 3.1.3.2 From 1G to 2G and 3G Systems

There are some 1G systems still in the marketplace. All systems use FDMA radio access techniques. The most prominent system is the Analog Mobile Phone System (AMPS), which was developed in the United States in the 800-MHz bands. In the 1990s, it reached worldwide distribution, as a de facto standard. Worldwide roaming was not really possible due to some restrictions on internetwork signaling and authentication. There are other

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1G systems like NMT, TACS, and C-Net developed in Europe. They also gained market acceptance beyond the European region. Of these, AMPS (also known as the IS-54 EIA/TIA standard) was the only system that was upgraded with second-generation radio access techniques (digital AMPS, DAMPS). It continued on the core network (IS-41 standard) side with some past restrictions—for example, limitations for international roaming and numbering, end-user security items, and international charging conventions. AMPS and DAMPS are still the most widely deployed cellular systems in the United States and Canada, as well as in Latin America. In the United States, these systems provide 98% coverage. DAMPS represents the evolution of AMPS to digital radio access. DAMPS is also known as the IS-136 radio standard. Second-generation systems introduced digital technology into the radio transmission. They use different radio access techniques. The most prominent systems are described as follows. Cellular Digital Packet Data

The Cellular Digital Packet Data (CDPD) system is an overlay on existing AMPS and DAMPS cellular voice systems that supports packet data transmission over the same frequencies. Modular and flexible, the CDPD system can be integrated with existing AMPS/DAMPS systems from other suppliers. It can also coexist with 2G TDMA and CDMA technologies. The system complies with the specifications set forth by the CDPD Forum, a consortium of leading companies in the wireless communications and computer industries. Subscribers to CDPD services benefit from such advantages as computer-aided dispatch, immediate status information on field technicians, higher productivity per worker, better response time to customers, immediate access to current and accurate computer-based information, and rapid responses to emergencies. Data transmission takes place during idle times on voice channels without adversely affecting voice quality. For AMPS networks, this is accomplished by detecting idle voice channels (sniffing) and switching to them to transmit and receive data. CDPD operates at 19.2 Kbps with an actual throughput between 8 and 11 Kbps. On TDMA and CDMA, it uses dedicated frequencies. Packet signals from multiple users are combined over the same channel, which provides far more revenue per channel than circuitswitched data solutions. Conformance to industry-standard protocols, such as OSI/CLNP, makes CDPD compatible with major public and private packet-switching

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networks. The use of an open systems architecture provides flexibility and expansion beyond that of existing controller or router-based systems. CDPD radios use existing Series II equipment for data transmission, eliminating the need for separate T1/E1 links, antennas, and amplifiers. You can mix voice, data, and digital technologies on the Series II wideband amplifier. The result is lower equipment costs with uncompromised voice service and superior data communications performance, without reengineering cell sites. TDMA

TDMA is a technology used in digital cellular mobile communications. Each frequency channel is divided into time slots in order to increase the amount of data that can be carried over one carrier. TDMA is used by D-AMPS, GSM, and PDC. Each of these systems, however, implements TDMA in a somewhat different and incompatible way. An alternative multiplexing scheme to FDMA with TDMA is CDMA, which takes the entire allocated frequency range for a given service and multiplexes information for all users across the spectrum range at the same time. The TDMA scheme was first specified in the GSM standard in 1987, then in the Electronics Industry Association/Telecommunication Industry Association (EIA/TIA) Interim Standard 54 (IS-54). IS-136 is the evolved IS-54 standard and is used today in the United States together with GSM, the 2G TDMA standard. It is operating in the 800–900-MHz band and, like GSM, also in the PCS 1.9-GHz band. AT&T is the largest IS-136 operator with 15 million users in 2001. It simultaneously offers a GSM1900 service. Other operators follow, with a combined subscription of approximately 12 million users in 2001. The Universal Wireless Communication Consortium (UWCC), a group of leading IS-136 operators and manufacturers (launched in 1995), promoted TDMA/IS-136-based technology innovations and standards. In 2002, key players in the United States created a new trade organization to promote the evolution from IS-136 to EDGE and UMTS. The digital cellular service IS-136/D-AMPS has added to FDMA an additional subdivision of each channel using TDMA to get three channels for each AMPS channel, tripling the number of calls that can be handled on a channel. The beginning of the EIA/TIA standard goes back to 1988. The CTIA published a set of user performance requirements on the existing AMPS standard, with the inclusion that a new digital system would be compatible to the analog technology. The frequency band was the same as for AMPS: from 824 to 849 MHz for mobile station transmit and 869 to 894 MHz for base

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station transmit with the same channel spacing parameters. The first issue of air interface specifications was approved as IS-54 (dual mode) standard by 1991. In 1994 an enhanced specification was released, designated IS-136; its main feature was the addition of a digital control channel. New services like SMS, data, and fax were introduced later in these networks. The way of the standard goes clearly in the same direction as GSM, with EDGE/GPRS and UMTS. The TDMA developments in Japan took place in the early 1990s and specified the Personal Digital Cellular (PDC) System, which operates in the 800-MHz (843–940 MHz) and 1.5-GHz (1429–1453 and 1477–1501 MHz) band. The standard is quite similar to GSM and later also included a packet service with 9.6 Kbps, which was used to introduce the mobile Internet i-mode offerings. The PDC evolution continues with IMT-2000/ UMTS, where Japanese industries are contributing actively. CDMA

CDMA is based on spread spectrum transmission, which allows multiple users to share the same radio frequency spectrum simultaneously by assigning each active user a unique code. Code can be conceptualized as a scrambling algorithm that randomizes the transmission so it appears as a noise to all receivers except the intended receiver. As a part of call setup (when the sending begins), the recipient is told the specific code used for that call and then unscrambles the desired signal (while all other signals appear as noise). This technique allows numerous voice or data calls to be simultaneously transmitted on one radio frequency carrier. To operate successfully, all accessing signals must be received at a similar level. Thus, power control is essential to the successful operation of individual terminals while roaming. The different codes for the mobiles also allow them to reuse the same frequency carrier in adjacent cells to be switched over via soft hand-off, since a terminal may be served by several base stations at any one moment. This technique allows an increase in network capacity. The first CDMA mobile cellular systems were built in the United States and in South Korea. The standard was called IS-95. Later innovations were released after 2000: cdma2000, a trademark of TIA, provides data services in a number of steps. The data rates shown in Table 3.9 are theoretical values; the practical values are lower (e.g., 1 RTT in Korea has 70 to 90 Kbps). Verizon Wireless in the United States is probably the largest IS-95/cdma2000 operator worldwide with 20 million IS-95 voice users and approximately 1 million data users in 2001. The second largest is SK

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Table 3.9 CDMA Development Year

Standard

Bit Rate

Carrier Rate

Developed by

1996

IS-95A

9.6/14.4 Kbps

1.25 MHz

USA

1999

IS-95B

64 Kbps

1.25 MHz

Korea/Japan

2001

1 RTT (IS-95C)

144 Kbps

1.25 MHz

Korea

2002

1 EV-DO

2 Mbps (theoretical)

1.25 MHz (data only)

USA

2003+

1 EV-DV

2 Mbps (theoretical)

1.25 MHz (data and voice)

USA

3 × RTT

2 Mbps (theoretical)

5 MHz

USA

Telekom in South Korea with 11 million users in 2001. These operators have taken up data services on the basis of 1 × RTT. IS-95 innovations are also known as narrowband CDMA because its carrier bandwidth is 1.25 MHz in contrast to the 5-MHz bandwidth of the so-called wideband CDMA (WCDMA), which is part of the UMTS radio standard. Narrowband CDMA performance depends on multipath channels. CDMA typically provides better capacity in long delay spread channels. Downlink fast power control improves CDMA capacity performance in short delay channels but reduces capacity in long delay spread channels. A growing number of industry observers, however, point out that WCDMA brings higher data speeds; thus, fewer 3G service licensees will take the CDMA 2000 route. The WCDMA development took place in Japan and in Europe. In Japan, Nippon Telephone and Telegraph (NTT) DoCoMo started research work in the early 1990s, and in Europe development began in 1995 under the research program of the European Commission (EC) called advanced communications technologies and services (ACTS) and future radio multiple access schemes (FRAMES). The future radio multiple access scheme (FRAMES) project was the terrestrial radio interface research project dealing with wide area broadband transmission up to 2 Mbps and higher. This project also undertook studies on combined TDMA-CDMA principles and investigated the basic architecture for the wideband CDMA standard. Both

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were accepted by ETSI in 1998 as a proposal for a global 3G standard to the ITU [18]. This standard was also supported by the Japanese standardization organization, the Association of Radio Industry and Business (ARIB), and by Telecommunications Technology Committee (TTC) Korea. It comprises two operational modes: FDD, which is WCDMA, and TDD, which is TD-SDCMA/low chip rate (LCR) or TD-CDMA/high chip rate (HCR). GSM

GSM is not just a radio standard, it specifies a complete digital cellular network from the mobile terminal to the radio and switching part. Approximately 500 GSM networks are operating in 170 countries worldwide. It provides almost complete coverage in Western Europe, and growing coverage in the Americas, Asia-Pacific, and Africa [18]. In 1987 the European Union issued a directive to all member states to clear until 1991 the same frequency bands from 890 to 915 MHz for mobile transmission and from 935 to 950 MHz for base station transmission. Several air interface candidates were put forward with the final decision in March 1987 to adopt the TDMA narrowband proposal. This proposal is based on a 200-kHz carrier bandwidth, each with eight time slots. Power control technique and frequency hopping are used to increase system capacity by reducing average interference levels. Benefits of GSM Because GSM is the most commonly used 2G protocol, serving more than 600 million subscribers by the end of 2001, and because WCDMA/EDGE is emerging as the accepted 3G technology, this evolutionary pathway offers clear advantages in the depth and quality of its terminal, infrastructure, and application portfolios. The economies of scale associated with this global standard ensure good selections and competitive prices for these products. Standardization ETSI has established comprehensive standards for GSM technology, ensuring the interoperability of terminals and infrastructure. Similarly, the Third Generation Partnership Project (3GPP) has served in this same role during standardization activities aimed at UMTS, working to ensure that global roaming and interoperability can be provided through a highly standardized 3G framework. These standards allow operators to select base stations and other equipment offered by a number of competing vendors. An open, standardized technology also ensures more reliable roaming performance and the smooth compatibility of elements across networks and geographic regions.

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GSM is the incubating technology for many of today’s most popular value-added wireless services. In fact, features like SMS, the circuit and packet data services, and the location-based services are deployed by taking advantage of a wide user reachability. Notable features available via GSM include the following: • SMS chat, picture messaging, ring tones, logos and icons, •

• •

• • • • •

datagram-switched via control channels; Circuit-switched data at 9.6 to 14.4 Kbps to high-speed circuitswitched data (HSCSD) at n × 14.4 Kbps (e.g., 2 time slots = 28 Kbps; 3 time slots = 43 Kbps); WAP, circuit-switched and packet-switched via GPRS; Packet data: GPRS with bit rates of 20 to 40 Kbps; enhanced GPRS with bit rates of 50 to 120 Kbps depending on the number of assigned timeslots; Location-based services (Cell ID, EOTD, TDOA, and GPS); Accessories (handspring visor GSM module, telematics, and more); SIM card (security, m-commerce, SIM Toolkit, class 2 SMS handset configuration control, prepaid card, and future micropayment); GSM Supplementary Services (voice mail, SMS, e-mail conversion, unified messaging); Integration with enhanced message service and instant messaging on the Internet.

The unique global roaming features of GSM allow cellular subscribers to use their services in any GSM service area in the world in which the home operator has a roaming agreement. That means the phone you use in France could work in Germany, Australia, Finland, New Zealand, North and South America, Africa, and even in China, depending on your provider’s roaming agreements. GSM-enabled phones have a smart card inside called the SIM. The SIM card is personalized. It identifies the personal account to the network and provides authentication, which allows appropriate billing and personalized services. GSM is the most widely used of the three digital wireless telephone technologies (IS-136, GSM, and CDMA) and uses TDMA in different modes: circuit-switched time slots (single slot for voice and data up to 14.4 Kbps, multiple slots up to 8 × 9.6 Kbps) and packet switched (up to more than 100 Kbps, also with higher modulation schemes). GSM digitizes

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and compresses data, then sends it down a channel with other streams of user data, each in its own time slot or in combined time slots. It operates at either the 900-MHz or the 1,800–1,900-MHz frequency band. It includes HSCSD, GPRS, and EDGE (with an improved modulation scheme). GSM is the de facto leading cellular standard in the world. According to the GSM Association, GSM has reached nearly 500 networks worldwide in 2001. Since many GSM network operators have roaming agreements with foreign operators, users can continue to use their mobile phones when they travel to other countries. A number of U.S. operators are using GSM; for example, AT&T has built a GSM overlay network to IS-136, Voicestream, Cingular has a nationwide GSM 1,900-MHz network also. The GSM system architecture is shown in Figure 3.7 [19].

GSM Core Network Components

main functional entities:

The circuit-switching system contains five

1. The mobile services switching center (MSC) performs the telephony-switching functions for the network. It controls calls to and from other telephone and data communications systems, such as the PSTN, ISDN, public land mobile network (PLMN), and public data networks and various private networks as well.

CSE

EIR HLR/AC

CAP A GSM BSS

MAP MSC

Gb

SGSN

ISUP

GTP

CSE = CAMEL server CAP = CAMEL application part MAP = Mobile application part ISUP = ISDN user part GTP = GPRS tunneling protocol A, Gb = Radio base station interfaces

G-MSC

GGSN

ISUP

IP

N-ISDN

IP networks

X.25 X.25

Figure 3.7 GSM system architecture.

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2. The visitor location register (VLR) database contains all temporary subscriber information needed by the MSC to serve visiting subscribers. 3. The home location register (HLR) database stores and manages subscriptions. It contains all permanent subscriber information, including the subscriber’s service profile, location information, and activity status. 4. The authentication center (AC) provides authentication and encryption parameters that verify the user’s identity and ensure the confidentiality of each call. This functionality protects network operators from common types of fraud found in the cellular industry today. 5. The equipment identity register (EIR) database contains terminal identity information that prevents calls from stolen or defective mobile phones. Base Station System

entities:

The base station system (BSS) contains two functional

1. The base station controller (BSC) is a high-capacity switch that is responsible for radio-related functions, such as handoffs, management of radio network resources, and cell configuration data. It also controls the radio frequency power levels in base transceiver stations and mobile phones. 2. The base transceiver station (BTS) is the radio equipment needed for serving each cell in the network. GPRS [19, 20] brings IP-based services to the mobile marketplace via tunneling and supports the convergence of data networking and mobile telecommunications. As nonvoice services begin to predominate the wireless environment, the GPRS core represents a secure carrier investment, a basis for 3G services, and an optimized transition step to 3G. A fully featured GPRS solution complies with ETSI and ANSI standards and provides full roaming support and vendor interoperability. GPRS functions as an ideal bearer platform for WAP services. Well-integrated GPRS billing solutions provide optimized control of revenues generated by the introduction of WAP services. These systems support access- and content-based billing, prepaid billing, and provide for the smooth migration GPRS Packet Network Components

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to transaction-based micropayment models. Carriers should consider any GPRS solution’s ability to integrate into their current service and billing architecture. GPRS is implemented in the radio part as well as in the switching part. It is designed around a number of guiding principles: • Always-on. End-to-end packet-switching that allows the sending or

receiving of information at any time;

• High bit rates. There is a theoretical raw data rate up to 171.2

Kbps—the effective data rates are lower (about 60 to 115 Kbps) depending on environments and mobility parameters;

• Improved usage of the radio resources. The same radio channel can be

shared between several users (GPRS);

• Simultaneous voice call and data transfer. Data can be sent or received

even during a circuit call for voice;

• Billing based on time and volume. Subscribers are billed on the dura-

tion of the call and on the number of bytes received or sent, whatever the duration (packet switched).

GPRS keeps the same radio modulation as the GSM standard, as well as the same frequency bands, the same frequency hopping techniques, and the same TDMA frame structure. In addition, it manages packet segmentation, radio channel access, automatic retransmission, and power control. The major new element introduced by GPRS is an overlay core network that will process all the data traffic. It comprises two network elements: 1. Serving GPRS support node (SGSN) keeps track of the location of individual mobile stations and performs security functions, access control, and packet transport. 2. Gateway GPRS support node (GGSN) encapsulates packets received from external packet networks (IP) and routes them towards the SGSN. Enhanced Data Rate for Global Evolution EDGE will improve GPRS. By introducing a new radio modulation, and therefore a new generation of transceivers, it will be possible to triple the bit rates from standard GPRS. A

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world-class EDGE system can be implemented through rapid and affordable software upgrades and the addition of EDGE-capable transceivers to existing base stations. EDGE also uses the existing GPRS core infrastructure and does not require the deployment of new core network elements. Because EDGE/WCDMA are based on a common GPRS core network, operators can plan a smooth and cost-efficient evolution from GSM/GPRS to 3G capabilities. In most implementations, the spectrum required to deploy an EDGE transceiver is the same as adding an ordinary GSM transceiver. Leading EDGE solutions offer broad backward compatibility with existing network hardware and software systems. GPRS or EDGE solutions do not require the addition of a proprietary network core. The GPRS core is built on interfaces that are open and fully standardized. Practically seen, EDGE offers data rates of approximately 20 Kbps per time slot, compared to approximately 10 Kbps for GPRS even in poor C/I conditions. In more favorable conditions, and when supported by intelligent radio enhancements, EDGE can deliver data rates of approximately 50 to 60 Kbps per time slot, or up to three times the expected Kbps rate per time slot of GPRS. When deployed with eight full-speed Kbps time slots, EDGE can theoretically achieve maximum data user rates of 473 Kbps. PCS

PCS is defined as a wireless personal cellular radio using various digital technologies. PCS networks exist mainly in the United States and Canada and use different standards (TDMA, IS-136, CDMA, IS-95, and GSM). The personal in PCS distinguishes this service from cellular by emphasizing that PCS is designed for greater user mobility, unlike cellular, which was designed for car phone use with transmitters that provided coverage of highways and roads. Technically, cellular systems in the United States operate in the 824–849-MHz frequency bands; PCS operates in the 1,850–1,990-MHz bands. PCS today is a collection of heterogeneous cellular systems with different standards. The only common basis is the spectrum plan (PCS plan), which is subdivided into a number of nationwide or regional frequency bands of different sizes. Approximately 15 countries in the Americas accepted this spectrum plan fully or partly, which allows in principle any radio access technique and network standard. This freedom led to a number of partly incompatible networks, which exist in parallel across the country. Multimode terminals need to allow cross-network mobile communications. In addition, heterogeneity increases with the allowance for system evolution to 3G.

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Meanwhile, a number of Latin American countries decided for a shared spectrum plan, which allows the deployment of standard ITU conformist networks (2G and 3G), as well as PCS networks. PMR

First-generation PMR was developed after WWII. It was typically used for communication within one organization and in a limited geographical area. The equipment evolved from heavyweight, bulky radios operating at VHF frequencies to small-sized handhelds operating in the UHF band. Several enhancements have been introduced over the years, like selective calling, status reporting, digital signaling, and data communication facilities. Usually, not enough traffic is generated to justify the assignment of exclusive frequencies, so communication channels have to be used on a shared basis. Trunked PMR and Public Access Mobile Radio

The first-generation trunked PMR made more efficient use of the spectrum by dynamically allocating radio channels in the system. As this process was controlled by a centralized unit, only reasonably sized organizations or service providers could employ the technology. The dynamic channel allocation (DCA) principle could alleviate the demand for spectrum in the existing land mobile frequency bands, but no mass user migration into trunked radio operation was reported. Major standards were Radiocom 2000, Mobitex, and MPT 1327. Digital Short-Range Radio

Digital short-range radio (DSRR) was aimed to fulfill the needs of small business PMR users. It operates on the principle of self-trunking or DCA without a centralized control unit. TETRA

TETRA, a standard for 2G trunked PMR equipment, has been completed by ETSI. This recently published standard covers voice and data applications. The European operators Dolphin Telecom and Telefónica Móviles are among a new brand of service provider expanding the profile of TETRA users beyond its historical base of public security and safety services. There is also a demand amongst fleet managers and workforces in the field, who require a mobile solution that facilitates push-to-talk, group communications, and emergency calls.

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The TETRA frequency bands of 380 to 385 and 390 to 395 MHz have been designated for emergency services, such as police and fire brigades. For civil use the bands 410 to 430, 870 to 876, and 915 to 921 MHz have been designated as preferred bands. If these are not available, the bands 385 to 390, 395 to 399.9, and 450 to 470 MHz should be used. Public-access mobile radio (PAMR) is a development that provides radio space and similar facilities for public closed user groups, such as taxi drivers, police, and health services. TETRA and TETRAPOL are in commercial use in Europe providing digital voice and data capabilities, with encryption where appropriate, with the following characteristics: • It can operate from 100 MHz to 1 GHz, but is typically deployed • • • • • • •

around 400 MHz; 25-kHz radio channels providing four time slots, each supporting 7.2 Kbps voice or data; Bandwidth on demand facility up to 28.8 Kbps, by cojoining up to four time slots; Rapid access (call setup: 0.25s), high reliability, and security; Full duplex or simplex speech; Call prioritization; It allows group-wide communications and real-time conferencing; In its direct mode, radio terminals communicate directly by using single frequencies.

The United States, Australia, and South Africa are also considering TETRA for PAMR. A half-rate speech facility is under investigation to double useful voice capacity. IEEE 802.16 Broadband Wireless Access

In April 1999, the IEEE P802 LAN/MAN Standards Committee announced another formation: the P802.16 Working Group to develop standards for broadband wireless access (BWA) [21]. The group concentrates on the standardization of fixed BWA systems, focusing on those operating in the licensed spectrum near 30 GHz, but the standards are intended to be broadly applicable from 10 to 66 GHz. Developed by a study group involving 97 people from over 70 companies, the P802.16 Working Group objectives include both a coexistence specification and an air interface enabling the

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transport of data, voice, and video services. The result is expected to bring numerous manufacturing advantages, providing an industry with the potential to compete successfully by providing alternatives to wired access links that utilize fiber, cable, or telephone lines. The expected standards will concern broadband wireless access systems, and, although wireless, will not deal with mobile systems. It is rather intended as an alternative to wired last-mile access links and will use fixed base stations to provide broadband data to businesses or homes. The term broadband refers to telecommunication that provides multiple channels of data over a single communications medium, typically using some form of frequency or wave division multiplexing. The base stations may be either terrestrial, in orbit, or mounted on airplanes or dirigibles in the stratosphere. The customer terminals can carry two-way communications for Internet access, digital video, telephony, and other services. As large blocks (on the order of 1 GHz) of microwave and millimeter wave spectrum are becoming available, BWA networks are being deployed and developed in many countries throughout the world. Most of the frequency allocations are near 24, 28, 31, or 40 GHz. Many companies believe that the cost and performance of such systems will be competitive with wired broadband access networks. In the United States, BWA systems operating near 24 and 38 GHz began commercial service in 1998. The charter for the BWA Study Group was to develop new projects leading to BWA standards that do the following: • Use wireless links with microwave or millimeter wave radios; • Use licensed spectrum; • Are metropolitan in scale; • Provide public network service to fee-paying customers; • Use point-to-multipoint architecture with stationary rooftop or

tower-mounted antennas; • Provide efficient transport of heterogeneous traffic supporting QoS; • Are capable of broadband transmissions greater than 2 Mbps. Local Multipoint Distribution System and Multichannel Multipoint Distribution System

These wireless access technologies provide two-way high bandwidth connections for stationary use. Various countries are adopting the Local Multipoint Distribution System (LMDS). The frequency range of LDMS lies between

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24 and 31.3 GHz in the United States. A key advantage of these systems is that they can be used for symmetric and asymmetric traffic applications. For example, LMDS permits data rates of up to 1.54 Gbps downstream and up to 200 Mbps upstream. These bit rates indicate that LMDS is generally a system for larger computer applications. The Multichannel Multipoint Distribution System (MMDS) was originally used for pay-TV applications. The bit rates are 300 Kbps to 3 Mbps upstream and downstream. It operates in the 2.15 to 2.68 GHz range. The IEEE 802.16 standard specifies the physical layer and MAC layer [22]. IMT-2000/UMTS—A Global Achievement

Second-generation wireless mobile systems are still constrained in terms of the data rate they can offer and their flexibility to manipulate a multiplicity of multimedia services. There is a growing need for a system capable of managing and delivering a much wider range of information services to the mass market. Worldwide understanding of this objective led to the major new 3G mobile system being developed within the framework that has been defined by the ITU, known as IMT-2000. A fundamental goal of IMT-2000 is to provide universal coverage and to enable seamless roaming between multiple networks. In this regard, IMT-2000 is far more than just an improved version of today’s 2G systems. The two landmark decisions that were taken by ITU member states in 2000 to formally approve IMT-2000 standards and identify additional spectrum for 3G systems have given the entire mobile industry clear signals to realize the dream of global wireless systems. The licensing process based on the initial IMT-2000 bands gained momentum in many countries across Asia, Europe, and Latin America. Commercial operations in Asia and Europe commence between 2001 and 2002. ITU’s vision that people should be able to communicate anytime and anywhere globally is about to become a reality. In Japan, Korea, and in Europe, research and standardization activities began in the early 1990s and were aimed to release the first set of standards before 2000 in order to meet the introduction deadline in 2002 [23]. The standardization framework of IMT-2000 has been defined by the ITU as an open international standard for a high-capacity, high data rate mobile telecommunications system incorporating both terrestrial radio and satellite components. The main focus of IMT-2000 is the air interface. UMTS is being standardized in an IMT-2000 framework, whereby the specifications are developed by 3GPP, a global standardization initiative created in December 1998. The project is based on a concept facilitating coordination

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between regional standardization organizations, forums, and other industry groups. Ownership of the specifications is shared between partners. In cooperation with regional and national standardization bodies around the world, 3GPP aims to produce detailed standards to satisfy growing market needs for global roaming and service availability. The focus of the 3GPP’s standardization work is the entire network, comprising radio and core network elements as well as end-user equipment standards, smart cards, and the integration with the Internet. The partner standards development organizations are ETSI, ARIB, TTC, the T1 Committee, the Telecommunications Technology Association (TTA), and the China Wireless Telecommunications Standards (CWTS) Institute. The origin of UMTS can be traced back to the mid-1980s. As thinking on the post-2G environment began to be stimulated, the European Commission (EC) published a green paper and follow-up report that assumed a regional focus for developments in telecommunications. In 1985 the EC instigated a pan-European research program known as Research and Development in Advanced Communications for Europe (RACE), to consolidate requirements and propose solutions for the communications environment at the end of the millennium [18]. Figure 3.8 shows the collaboration between ITU and external organizations in the development of IMT-2000 radio interface framework standards, which were approved in Istanbul as ITU-R Recommendation M.1457 [24]. It should be mentioned that another 3GPP called the 3GPP2 was established by the U.S. TIA in collaboration with CWTS, ARIB, Japan’s TTC, Korea’s TTA, and the U.S.’s Standards Committee T1, in order to achieve international cooperation in the development of technical specifications based on cdma2000. 3GPP and 3GPP2 maintain a relationship for interoperability between their standards. UMTS is an important part of wider initiatives to satisfy the needs of corporate users and the mass market. Complementary work is underway throughout the UMTS Forum and other industry organizations on every aspect of the emerging information society: multimedia, information, and content. UMTS seeks to build on and extend the capability of IMT-2000 mobile, cordless, and satellite technologies by providing increased capacity, data capability, and a far greater range of services using an innovative radio access scheme and an enhanced, evolving core network. In early 1998, the EC published the “EC Proposal for a European Parliament and Council Decision on the Coordinated Introduction of UMTS”

Technologies

ETSI

Consortial Europe partnership 173 companies*

ARIB

Japan 37 companies

TTC

18 companies

TTA

Korea 25 companies

T1

IMT-F

3GPP

UWCC

USA

TIA

22 companies

CWTS

China 9 companies

83

C IMT-DS IMT-TC

ITU

IMT-SC

-MC IMT

3GPP2 IMT-2000 radio interfaces Standards development organizations

*Individual members Figure 3.8 Industry collaboration on IMT-2000 radio interfaces. (Source: ITU, 2000.)

to ensure that EU member states undertook the appropriate steps to implement the ERC’s decision on spectrum allocation. This, in combination with the existing licensing directive, will ensure UMTS services can commence in 2002. In the United States, any licensee is free in principle to implement any technology it chooses. Potential candidate bands for 3G technologies are the PCS bands, the remaining IMT-2000 bands, and parts of the UHF TV bands. Key Technologies

This section describes some of the key technologies essential for the successful introduction of UMTS. Figure 3.9 gives an overview on the ITU terrestrial radio interfaces and core networks belonging to the IMT-2000 system family. It indicates that two of the radio interface standards and two of the core network standards belong to UMTS. Ten candidate terrestrial specifications were submitted to the ITU-R TG 8/1 [18, 23]. Following harmonization initiatives between the original candidates, five were actually approved for use in the spectrum identified for IMT-2000:

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IMT-DS W-CDMA (UTRA) FDD direct spread

IMT-TC UTRA TDD TD-SCDMA time code

IMT-MC CDMA 2000 multicarrier

IMT-SC UWC-136 single carrier

IMT-FT DECT frequency time

Paired spectrum Unpaired spectrum

Flexible connection between radio modules and core networks based on operator needs UMTS

Evolved Core networks GSM (MAP)

IP-based networks

Internetwork roaming

Network-to-network interfaces

Evolved ANSI-41

Figure 3.9 ITU-IMT-2000 terrestrial framework standards.

1. IMT-DS: The FDD standard for UMTS (UTRA-FDD) based on CDMA. Several of the original ITU proposals were merged into this proposal. The standard is developed within 3GPP. 2. IMT-TC: The TDD standard for UMTS (UTRA-TDD) based on CDMA including the Chinese proposal for TD-SCDMA with a channel spacing of 1.6 MHz. The standard is developed within 3GPP. 3. IMT-SC: UWC-136 (also called EDGE) was developed for the evolution of GSM/GPRS into IMT-2000 in the U.S. 1,900-MHz bands. It contains 200-kHz and 2.4-MHz channel spacings. In Europe, EDGE is planned for the evolution of GSM in the 900- and 1,800-MHz bands. 4. IMT-MC: cdma2000 coming from the evolution IS-95—this is the standard using CDMA multicarrier technology, version 1x with channel spacings of 1.25 MHz and version 3x with channel spacings of 3.75 MHz. The standard is under development within 3GPP2.

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5. IMT-FT: DECT, as standardized by ETSI, is operated in Europe at 1,880 to 1,900 MHz, the lower portion of the IMT-2000 bands. Wider additional implementation is not foreseen at this point in time. UWC-136 is more or less identical with GSM-EDGE. UWC-136 and cdma2000 are currently under development for operation in the PCS frequency bands (1,850–1,990 MHz). UTRA is under development for the globally harmonized 3G frequency bands identified in the ITU radio regulations in S5.388 (1,900–1,980, 2,010–2,025, and 2,110–2,170 MHz) within 3GPP. Implementing the CDMA and EDGE technologies in a single terminal will add to the complexity of terminals, which is further exacerbated by the difference in spectrum implementation between Europe and the United States and other countries adopting the PCS frequency plan. On the UTRA-side, compatibility with GSM will be provided from the beginning: dual-mode and multiband terminals will ease interoperability of different standards and frequency bands, respectively. For interoperability with cdma2000, however, the complexity of these terminals quickly increases with growing divergence and the cost factor should be kept in mind even though economies of scale will ameliorate the situation. It is still important to strive for worldwide harmonized frequency bands in order to keep the complexity and costs to a minimum. The IMT-2000/UMTS community has chosen aggressive time scales for the introduction of IMT-2000/UMTS in order to meet the demands of customers in the early twenty-first century. The target date for its introduction has been set to 2001. NTT DoCoMo fulfilled this requirement with the first public service take-up in the fourth quarter of 2001. To meet this deadline, UMTS followed a phased approach that allows its capabilities to be improved over time following its introduction. It is designed as an open system that can evolve to incorporate new technologies as they become available. This will allow UMTS to increase its capability much in the same way that GSM evolved from the original data capability of 9.6 Kbps to GPRS (up to 50 Kbps and eventually to 115 Kbps) and then to EDGE technology (up to 240-Kbps effective bit rates). Satellite Component

At its initial service launch in 2000, the satellite component of IMT-2000/ UMTS will be able to provide a global coverage capability to a range of user terminals. These satellite systems are planned to be implemented using the

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S-band mobile satellite service (MSS) frequency allocations identified for satellite IMT-2000 and will provide services compatible with the terrestrial systems. They are still under investigation.

3.1.4

Extended Area Networks

3.1.4.1 Mobile Satellite Systems

UC can only be complete if the low-density areas on the globe are also covered. The value of UC in these areas lies in the fields of environmental supervision, oceanic observation, and in communications for the shipping and transport industry. Satellite systems are the only means for maritime and global coverage. The goal of mobile communications from the beginning has been to enable the user to communicate while traveling on land, at sea, or in the air. Terrestrial cellular mobile systems cannot completely fulfill such requirements, thus, satellite systems are needed. MSSs are two-way voice and data communications with a handheld terminal, where the final link to the MSS subscriber is via a satellite. Satellite allows 100% outdoor/wireless radio coverage. Figure 3.10 shows an example of how an MSS system delivers a call. The call is transmitted from the user in Africa via a satellite to the nearest

Internet PSTN Internet PSTN

Mobile Internet on the sea

Figure 3.10 MSS call delivery.

Mobile Internet in the cabin

Mobile Internet on the ground

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87

earth station and gateway. The call is then routed over the PSTN to the United States, terminating at the called party’s premises. Satellite-based radio communication systems in the last decade have been aiming to serve the needs of maritime and aeronautical users with voice and data communications using FDMA and TDMA technologies. Their evolution continues at least for Inmarsat (I, II, III, P) and a few other systems. Wideband transmission links can be offered, however, usually up to no more than 144 Kbps for mobile application. Mobile satellite communications are also distinguished by the positioning of the satellites in the orbit. Three different types of orbit constellations can be considered (see Figure 3.11): • Geostationary Earth orbit (GEO) systems—for example, Inmarsat; • Medium-Earth orbit (MEO) systems—for example, Globalstar; • Low-Earth orbit (LEO) systems—for example, Iridium and

Teledesic.

The number of satellites necessary to cover the Earth fully differs depending on their altitude. Also, the choice of the orbital constellation has

GEO

MEO

LEO

Figure 3.11 Alternative system solutions satellite technology.

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to take into account not only the quality of service offered to the user, but also the feasibility and technical risk and costs of the satellites themselves and the problem of procuring and managing the number of satellites. GEO systems become very complex in view of the high number of beams needed and the long delay time for voice calls. MEO and LEO systems are complex in that they have to incorporate handoff between cells and dynamically manage the satellite-user coverage as the satellites move relative to the Earth and at a high speed. It appears from market and business investigations that satellite systems seem to be more in a niche market than in the mass market. The market forecasts from the UMTS Forum show no more than 18 to 20 million users worldwide in 2010 [25]. This will presumably lead to developing future mobile satellite systems as complements to terrestrial mobile cellular networks. The integration of the satellite component to a terrestrial network takes place via the transport and switching network. Examples are Iridium and Globalstar. Both projects use the backbone network GSM technology in order to integrate the satellite component in a seamless way. Ways to Integrate Satellite Systems into Terrestrial Mobile Cellular Networks

The definition of the interworking functionality between a satellite system and the terrestrial infrastructure determines the complexity of the solution. The number of interfaces should therefore be minimized, as well as the scope of service features. Two solutions can be seen: 1. A satellite system as a global network in the orbit (as shown in Figure 3.12). The satellite system appears from every terrestrial network as an international network with its own country code. The subscriber’s number in the satellite system is not bound to any country code on the ground. The calling subscriber A must always add the international prefix and country code to reach subscriber B. Automatic roaming with GSM networks is handled in the same way as between international GSM networks. 2. SAT-PCN appears as an extension of existing PLMNs (as shown in Figure 3.13). This is valid for all derivatives of GSM: GSM 900, DCS 1800, and PCS 1900. The SAT-PCN uses the country codes of the terrestrial cellular networks and gets an additional national network code for SAT-PCN. The subscribers will get a country code depending on their home base. For such solutions, a dual-mode terminal is essential. The functionality of the dual-

Technologies

89

Global SAT coverage with global access code

A Country 1

Coverage only via satellite

No competition

C

B Country 2

Full terrestrial coverage

Country 3

Partial terrestrial coverage

Competition field

Figure 3.12 Global satellite networks compete with terrestrial networks.

SAT coverage with country access code 3

SAT coverage only with country access code 1

A

B

C

Country 1

Country 2

Country 3

No terrestrial coverage

Full terrestrial coverage

Partial terrestrial coverage

Figure 3.13 SAT-PCN appears as extension to national networks.

mode terminal depends on how roaming will be offered: as basic nonautomatic roaming or as roaming with handover between SAT-PCN and GSM.

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Combinations of these two solutions will be possible if the SAT-PCN is used as logical extension of the terrestrial PLMN and if the operator organization allows combined business in a country. Such a combination would allow an efficient and economical radio coverage in countries with both low population density areas and cities and hot spots. Examples are Australia, former CIS states, Russia, Asia, Africa, and North and South America. In this third alternative, the SAT-PCN would be addressed by using its national prefix. It remains unclear, however, whether such a solution would be acceptable from a regulatory point of view. This configuration is shown in Figure 3.13 [26]. The ITU Telecommunications Sector (ITU-T) decided to provide the SAT-PCN’s E164 country code, +881. For each of the SAT-PCNs, an additional digit will be the specific address information (e.g., ICO = +8810; Odyssey = +8812; Iridium = +8816; Global Star = +8818). The ITU-T also decided the E212 (IMSI) code to be the mobile country code (MCC) 901 for all SAT-PCN operators. Terminals

All the present satellite PCN programs use the dual-mode terminal. GSM, the most successful digital mobile standard, is considered to be the basis for such development. This means that 900-MHz handhelds (2W) should be combined with 1,600/2,400-MHz high-frequency parts and different digital processing functions. The same development could be done for PCN systems in the United States and PDC systems in Japan. In addition, multimode solutions could be considered if the customer base justified this development. Radio Frequencies for Satellite Systems

According to the decision in the radio conference WARC 2000, the assigned frequencies in the 1.6- and 2.1-GHz range allow satellite PCNs a maximum bandwidth of 16.5-MHz for both the uplink and downlink, as well as 2 × 30 MHz for the satellite component of UMTS. Teledesic, an upcoming project that belongs to the broadband radio networks, lies in the 20/30-GHz range. It is a real alternative to the satellite PCNs presently under development. It aims to be operational by 2005 and uses the switching and transport principles of radio ATDMA. It is important to note that some of these systems are complementary to their terrestrial counterparts. For example, Orbcomm is considering teaming up with mobile data operators in the United States (such as Ardis and RAM) to offer a nationwide mobile data service. The narrowband MSS systems are

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91

all going to offer dual-mode phones, which function with both cellular and their own systems. The broadband systems are able to offer high bandwidth service because of the availability of spectrum at high frequencies. However, since the frequency is very high, the wavelength is very short, resulting in propagation problems. Teledesic is mainly targeting areas where broadband communications will not be delivered via fiber networks or via cellular networks in the medium term. The data-only systems offer packet-switched data services between 2.4 and 4.8 Kbps, as well as fax, paging, and position location services. Their main applications are for monitoring, tracking, and controlling. These systems offer store-and-forward type services. The time delay between a message being sent and it being delivered is dependent on the location of satellites. Narrowband MSS systems will offer a range of cellular-like services, including voice, data services up to 9.6 Kbps, and a range of value-added services. For 3G networks, proposed candidates for the satellite radio component are shown in Table 3.10. Such MSS systems will deliver medium- to high-bandwidth services, mainly for fixed applications. The most important applications will be access to the Internet via high-speed data communications, as well as digital multimedia applications, such as desktop videoconferencing. Systems like Teledesic will offer data transmission speeds of up to 1.5 Mbps for stationary use; it is not yet considered for the radio part of 3G networks. The Main MSS Operators

More than 40 companies have filed with the ITU for spectrum in which to deploy MSS systems. There are a number of global narrowband MSS systems: Iridium, Globalstar, ICO, Constellation Communications (CCI), Ellipso, and Immarsat. Immarsat is currently the most successful system with approximately 300,000 users in 2001. It is continuously improved to transport data in addition to voice. Immarsat has developed a new integrated satellite communications platform that enables businesses to extend their fixed LAN into a mobile global area network (GAN). This GAN gives access to the high quality and speed of a full mobile ISDN service and, through the GAN mobile packet data service, the cost-effective flexibility of a mobile IP service. Iridium [27] was initially a consortium of manufacturers and service providers led by Motorola, operating the LEO-based MSS system. The system began offering services in November 1998 using a constellation of 66 satellites. The FCC awarded Iridium a license to offer MSS in the United States in January 1995. Iridium’s first satellites were launched in May 1997.

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UMTS and Mobile Computing Table 3.10 Proposed Solutions for the Satellite Component of IMT-2000/UMTS

Project Initiator

Satellite Constellation

Air Interface

User Bit Rate

ICO

10 MEOs 10,390 km

MF-TDMA

Up to 144 Kbps

Inmarsat-4

2 GEOs at 40,000 km (1.5 bis 1.6 GHz)

MF-TDMA

144–432 Kbps (portable/terminal)

Boeing

16 MEOs 20,180 km

CDMA + TDMA

(> 1 Mbps)

Celsat (Echostar)

3 GEOs

CDMA

—

GS-2 (Globalstar)

64 LEOs at 1.420 km + 4 GEOs

CDMA

Up to 144 Kbps

ESA SW-CDMA

Global LEO/MEO

CDMA Chiprates: 3.84 Mcps 1.92 Mcps

32-Kbps handheld 144-Kbps portable terminal

ESA SW-CTDMA

For regional GEO/MEO systems CDMA/TDMA Chiprates: 3.84 Mcps 1.92 Mcps

Up to 183 Kbps

It was the world’s first handheld global satellite telephone, data, and paging network. Iridium was taken over by the U.S. government in early 2001 and continues its service for civilian and military use. Globalstar [28] is a consortium of European, Korean, and U.S. telecommunications companies headed by Loral Space and Communications and Qualcomm. The system provides voice, SMS, roaming, positioning, and facsimile and data transmission. It consists of a constellation of 48 LEO satellites and transmits calls from wireless phones or fixed phone stations to a terrestrial gateway, where they are passed on to existing fixed and cellular telephone networks. As a wholesaler, Globalstar sells access to its system to regional and local telecommunications service providers around the world. The system was operational by 2000; however, it did not continue owing to financial problems. ICO has its roots in the Inmarsat consortium. Most of Inmarsat’s signatories are also direct investors in ICO. Hughes, the largest manufacturer of commercial communication satellites, is the system’s prime contractor and holds a stake in the company. ICO is an MEO-based MSS system. ICO’s

Technologies

93

constellation consists of 12 satellites, including two in-orbit spares, which will be operational by 2003. The services bit rates are up to 144 Kbps. Constellation Communications (CCI) is a consortium comprising Orbital Sciences, Bell Atlantic Global Wireless, Raytheon E-Systems, and SpaceVest. It planned to launch a 12-satellite LEO equatorial system, including one in-orbit spare by 2001. CCI will focus on both cellular and fixed markets. CCI plans to offer a global service, using an additional 42 satellites (including seven in-orbit spares), in 2003. Ellipso is a privately owned company whose main shareholders include Ellipso Private Holding, Venture First II, Israel Aircraft Industries, and The Boeing Company. Ellipso is an MEO-based MSS system based on a constellation of 16 satellites. It planned to start service in equatorial regions by the end of 2001, followed by global service in 2002. Ellipso’s main focus is the fixed market. There will also be a number of GEO systems, particularly in the Asia Pacific region. The main systems are ACeS, APMT, and ASC. EAST and Thuraya will deploy MSS covering Europe, Africa, and the Middle East. The Asia Cellular Satellite (ACeS) consortium is the most advanced regional GEO player. The ACeS system was conceived and initiated by Pasifik Satelit Nusantara (PSN), an Indonesian satellite telecommunications company. The two other shareholders include the Philippine Long Distance Telephone Company and Jasmine International Overseas Company. ACeS is based on the use of one geostationary satellite. Its commercial service started in 2000. Asia-Pacific Mobile Telecommunications Satellite (APMT) was founded by a consortium of Chinese and Singaporean investors. The venture is made up of founding partners APMT Singapore (Singapore Technologies Telemedia) and China APMT, which comprises six organizations from the People’s Republic of China. Full commercial service was expected for the third quarter of 1998. The launch of the service has now been rescheduled. The Afro-Asian Satellite Communications (ASC) is an Indian-based venture between Indian Telecom operator Essar Telecom, the Essel Group, and Videsh Sanchar Nigam Limited (VSNL), India’s international telecommunications service provider and a wholly government-owned company. ASC aims to launch one GEO satellite to cover mainly Eastern Europe, Africa, and Asia Pacific. Issues related to financing the ASC venture, however, have put a question mark over the whole project. The Thuraya Satellite Telecommunications Company was established in January 1997 in Abu Dhabi, UAE, as an autonomous body. A number of regional telecommunications service providers and Gulf-based investment

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companies have bought into the project with the partner list now numbering 15, including Etisalat, its founder and the United Arab Emirates’ national telephone company. Thuraya intends to use a single operating satellite, although a second operating satellite is planned if extra capacity is required. Euro-African Satellite Telecommunications System (East) is a joint venture between Matra Marconi Space and Digimed, a fully owned subsidiary of the Cyprus Telecommunications Authority. The project uses two colocated satellites using L-band for mobile services and Ku-band for fixed village booth phone type applications. Fixed services are expected to be up and running by the last quarter of 2002. This should be followed by the introduction of East mobile services by the end of 2003. Most of these systems will use spectrum at 1.6 GHz. These systems represent 2G GEO-based MSS systems. Compared with 1G systems, such as Optus and AMSC, they will use powerful satellites with multiple beam antennae, enabling user terminals to be handheld. Other systems include AMSC, OmniTRACS, and Planet 1. American Mobile Satellite Corporation’s (AMSC) SkyCell satellite services [29] deliver dispatch, voice, and data communications to businesses with remote or mobile situations. It provides a nationwide two-way radio network for dispatch communications, circuit-switched data transmission, telephone connectivity, and Group 3 fax across the continental United States, Alaska, Hawaii, and the Caribbean, and their coastal waters. Qualcomm’s OmniTRACS [30] is a satellite communications and tracking system. It is promoted as an interactive information management system that includes two-way mobile communications, satellite tracking, and fleet management software, and enables real-time messaging, performance monitoring, and systems integration. Both AMSC and OmniTRACS are targeted mostly at the long-haul trucking industry. Their cost is high and data rates are severely limited. Comsat [31] provides worldwide satellite telecommunications by using the global INTELSAT and Inmarsat satellite systems. Comsat’s personal mobile communications service Planet 1 uses portable, notebook-sized satellite telephones to provide seamless voice (4.8 Kbps), fax (Group 3), e-mail, and data communications (Hayes compatible data with 2.4 Kbps) on a global basis. Global Positioning System

The global positioning system (GPS) is a satellite-based navigation system, which is not to be used for two-way wireless communication. It is mentioned because it enables worldwide automatic localization for everybody and

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95

anything, and, as such, is an important element for UC devices and location-based services. A new project called Galileo, which is similar to GPS, has been initiated by the European Union. It should be ready for service in 2006 and 2007. The GPS Receiver The GPS receiver communicates with notebooks, handheld PCs, or PDAs. Connection is usually established by the RS-232 interface or via infrared [32]. The Handheld Navigator The Handheld Navigator is a GPS receiver for

positioning that includes additional technology for car navigation, mapping, and agricultural applications. It provides a navigation screen and can take up map memory cards with detailed street maps. Zooming and other features are offered by this product [33]. 3.1.4.2 High-Altitude Platform Stations

The World Radiocommunication Conference 2000 (WARC 2000) decided in Resolution COM 5/13 upon the use of high-altitude platform stations (HAPS) to provide IMT-2000 in the 1,885–1,980-, 2,010–2,025-, and 2,110–2,170-MHz frequency bands in region 1 (Europe, Africa) and region 3 (Asia-Pacific), and the 1,885–1,980- and 2,110–2,160-MHz frequency bands in region 2 (North and South America). HAPS are physical platforms or flying objects (e.g., a zeppelin) in a quasigeostationary position approximately 21 km in altitude (in the stratosphere) (see Figure 3.14). Built-in radio base stations shall be capable of supplying an area of 150 km up to 1,000-km diameter with radio coverage. Directional antennas shall provide the deployment of spot beam radio cells of a high quantity. HAPS can be seen as an option or extension of terrestrial mobile cellular systems. Sky station systems seem to be the first products in this market, built by an industry group including Lockheed, Alenia Spazio, Dornier, Thomson CSF, United Solar Group, and Airship Technologies Systems, United Kingdom. Two-Way Paging Services

Two-way paging services (including American Mobile and Bell South), such as Pagenet, Mobitex and Skytel in the USA, offer limited bandwidth with excellent coverage, but as with the truly national networks, cost is high and they are designed primarily for small e-mail messages and low-intensity applications, such as daily status checking. Motorola’s Reflex pager network will allow bit rates up to 144 Kbps.

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Stratosphere

Base station

21 km

UAC (75-km diameter)

SAC (150-km diameter) RAC (600 km diameter)

UAC = Urban area coverage SAC = Suburban area coverage RAC = Regional area coverage

Figure 3.14 HAPS.

3.1.5

Other Technologies

For the sake of completeness, we will now describe briefly some other popular technologies like infrared, a wireless but not truly mobile communication technology, and IEEE 1394/FireWire, a wireline serial bus technology for consumer electronics. 3.1.5.1 Infrared Data Association

Infrared connectivity provides wireless interoperability between mobile communication devices. The Infrared Data Association (IrDA) [34] is an international organization that creates and promotes interoperable, low-cost infrared data interconnection standards that support a walk-up, point-topoint user model. The standards support a broad range of appliances and computing and communications devices. After overcoming initial problems with drivers, lack of support from Microsoft, and neglect of notebook manufacturers, IrDA could establish itself because of its capability to connect handhelds and infrared-enabled mobile phones to notebooks and PCs. This technology basically enables two-way cordless infrared light transmission, and, as such, offers only limited advantages for UC scenarios: • The receivers and transmitters must be in direct line of sight of each

other. This reduces the amount of flexibility you have for movement

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within the room without interrupting the signal. Unlike RF, you cannot cover the receiver or put it anywhere where the direct line of sight will be blocked. • It is capable of indoor or evening use only. • High-intensity or fluorescent lights cause interference. • Large areas require multiple emitter panels, which will increase the

cost of the system.

• Quality varies with the company.

3.1.5.2 IEEE 1394 and FireWire

UC connectivity also encompasses wireline technology, which is useful for comparison with wireless technologies (e.g., regarding bit rates and applications). The technologies IEEE 1394 and FireWire are very similar. IEEE 1394 is a wireline high-frequency transmission standard for plug’n’play and high-speed serial bus connections between PCs, storage and peripheral devices, and digital consumer electronics. IEEE 1394 will be used in PCs, PC peripherals, digital TVs, camcorders, and other consumer digital electronics equipment. The IEEE 1394 bus protocol supports both isochronous and asynchronous transfers over the same set of four signal wires, offering the ideal solution in connectivity for all multimedia applications and home networking needs. FireWire is Apple Computer’s version of the IEEE 1394 highperformance serial bus standard for connecting devices to the personal computer. FireWire provides a single plug-and-socket connection on which up to 63 devices can be attached with data transfer speeds up to 400 Mbps. The standard describes a serial bus or pathway between one or more peripheral devices and computers. FireWire and other IEEE 1394 implementations provide the following: • A simple common plug-in serial connector with a thin serial

cable, hot-plug, and plug-and-play capability without disrupting the computer;

• A very high bit rate that will accommodate multimedia applications

with 100 and 200 Mbps.

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In time, IEEE 1394 implementations are expected to replace and consolidate today’s serial and parallel interfaces, including Centronic parallel, RS232-C, and SCSI. The first products to be introduced with FireWire include digital cameras, digital video discs (DVD), digital video tapes, digital camcorders, and music systems. Because IEEE 1394 is a peer-to-peer interface, one camcorder can dub to another without being plugged into a computer. 3.1.6

Technology Positioning and Comparison

In this section we try to position and compare the described network technologies. First of all, we may state that there are a number of technologies with different standards for more or less the same services. It will be left to the market to decide which technology will best meet user’s demands. In the HAN, WPAN, and WLAN market, we see a number of technologies sharing the same unlicensed frequency bands. Given that frequencies will be unlicensed, and that owners of individual premises rather than government authorities will grant installation permissions, business models may differ radically from those of public telecommunications networks. Some carriers may see this as a threat and actively oppose it, while others may see it as a powerful complement to their current technologies. This market may go up to the order of several hundred million units over the next few years. Unfortunately, the superseding technology could probably occupy spectrum in the same environment as other technologies, thus degrading their performance. Interference between coexisting systems in the same band because of different radio schemes is an additional burden. In order to avoid this, it is hoped that in the long run, WLANs will migrate to 5 GHz, which may eliminate most coexistence problems. The question of interoperability in this sector can only partly be answered in a positive way. In the field of wide area technologies, the overall system aspects have an important role. They also come into play for pure radio-related interoperability matters, especially if users roam internationally. In contrast to the HAN, WPAN, WLAN sector, here there are only two competing system standards, both encompassing different radio (and core network) and, consequently, also terminal solutions. Both are operating in separated licensed frequency bands per operator, allowing exclusive use of radio technology in each band. This helps to avoid interference and coexistence problems. In some countries, however, where frequency bands are not bound to a certain standard, considerable guard band loss between adjacent bands has to be accepted. This leads to less efficient spectrum utilization. This happens in various American countries, where the frequency license allows mixed

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deployment of 2G and 3G systems, even with different radio standards. The impact on the market is fragmentation because of subdivided standards use. A first conclusion is related to the 3G market: it is the existing footprint of 2G system technology. GSM, for example, has reached (with some exceptions) worldwide coverage. The backward-compatible UMTS allows seamless transition from GSM to 3G with global roaming and interoperability. It will be difficult for the competing cdma2000 technology, which is incompatible to GSM and UMTS as well as to IS-136, to play an equivalent role on the marketplace. It can be foreseen that IS-136 will migrate to UMTS and not to cdma2000 as there are different migration paths from IS-95 to cdma2000, compared to GSM and IS-136 to UMTS. In the sector of extended area networks with satellites and HAPS, there still exists a situation of many singular projects trying to catch a market share. The total market, whether regional or global, has too many obstacles on the regulatory side—for example, both the cross-border circulation of terminals and the low user potential may not justify network investment. However, sufficient spectrum is globally available and, according to ITU regulations, practically no license fees exist to drive up the costs for frequencies. It has to be said that a consolidation of the various radio interfaces would be most beneficial for all projects. Then, a business plan for a satellite IMT-2000 project could be positive. A second conclusion is the issue of spectrum for new technologies. The allocation of new frequency bands for 3G is important. Many states in the world follow the ITU recommendation this way. Presently, it is only possible outside North America. For WLANs, HIPERLAN, and WPANs, new spectrum in the 5-GHz range is under investigation. The dominance of GSM and WLANs in the market today promises UMTS and IEEE WLANs a far larger market compared to other technologies. Bluetooth can be seen as complementary to GSM and UMTS or cdma2000. In Europe, Africa, and Asia Pacific, there will be harmonized bands for UMTS-based 3G network technology. In other parts of the world, there may also be cdma2000. The third conclusion relates to bit rates and capacity. They are determined by radio network technology, radio dimensioning, and frequency bandwidth. Each of the radio techniques has its own bit rate limits, although it is certain that upgraded 2G systems are closer to their limits compared to 3G technologies, which are in the beginning of their life cycles. Bit rate and capacity are essential factors for radio systems. The potential of wideband CDMA with a frequency bandwidth of three times more than IS-95 or 25 times more than GSM is a clear indicator for more capacity. WLANs, HIPERLANs, and WPANs are also using wide frequency bandwidth from

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1–11-MHz radio channels, but they allow higher bit rates than 3G. They will be used, therefore, mainly in the business sector. The market requirement is a main point in a scenario, where a trade-off between bit rate and traffic capacity has to be made. The overall limitation is the available frequency spectrum that the operator has. Thus, it has to be decided to start with market-acceptable bit rates that provide sufficient traffic capacity for a good business development. It may be assumed that WAN applications will probably provide 64 to 384 Kbps for the majority of applications. A final remark should be made regarding WPANs, which are mainly for stationary and quasistationary use. HomeRF and Firefly are intended for networking mobile devices to PCs anywhere in the home. The HomeRF Working Group and the BSIG are doing joint work to define interoperability specifications. Bluetooth will become integrated over time into smart phones, PDAs, and laptops, and will be combined with wide area wireless technologies. Some countries still need to adopt this integration allowance into their regulatory environment.

3.2 UMTS Support for UMTS comes from the UMTS Forum, a global industry association with over 250 members [35], and more generally from worldwide industry discussions worldwide that favor UMTS as a concept that goes beyond IMT-2000. This technology integrates essential elements from the Internet with the IMT-2000 radio access and core network. In the mediumto long-term, it will use Internet-based protocols according to IPv4/v6 throughout the network. This convergence with the Internet model allows new services—UMTS will therefore be able to provide more services than just mobile radio networks in the past or wireless access to the Internet. UMTS is a wideband, circuit- and packet-based transmission system of text, digitized voice, video, and multimedia with data rates up to (and possibly greater than) 2 Mbps. It aims to offer a consistent set of services to mobile computer and mobile phone users no matter where they are located in the world. Based on GSM communication standards and endorsed by major standards bodies and manufacturers worldwide, UMTS has become the dominating 3G standard for mobile users—even before its introduction in 2001 and 2002. Once UMTS is fully implemented, computer and phone users can be constantly attached to the Internet as they travel and, as they roam, have the same set of capabilities no matter where they are traveling. In later development stages, users will have access through a combination of

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terrestrial and satellite wireless interfaces. Until UMTS is fully implemented, users can have multimode devices that switch to the currently available technologies, such as GSM 900, GSM 1800, GSM 1900, or others. The frequency spectrum for UMTS has been identified as terrestrial frequency bands 1,885 to 2,025 and 2,110 to 2,170 MHz for like IMT-2000 systems, and 1,980 to 2,010 and 2,170 to 2,200 MHz for the satellite part of UMTS systems. The new air interface using WCDMA will offer superior performance in relation to GSM in terms of higher data rates and capacity. The second major distinguishing feature in contrast to GSM is its IP-based network architecture, which supports both voice and data services via packet transport and switching. GPRS, the first stage of service and network evolution from today’s GSM systems to commercial UMTS networks, already meets UMTS goals, such as global roaming and personalized voice and data services. The WAP-service from GSM and i-mode from PDC are examples of its entry into the Internet world. UMTS, however, allows transparent wireless Internet access. It will bring Internet developments in a new direction characterized by mobility, personality, location dependency, and high bit rate access. The reasons are as follows: • Mobility allows HTML and XML content delivery and m- com-

merce.

• Person-related communication allows the development of cus-

tomer profiles and the distribution of value-added information to customers.

• Location information opens up a new service segment to deliver

context-specific services combined with location and personal profiles.

The question arises as to which services will result from UMTS. It is clear that a single killer application will not emerge; however, the mobile Web could be a powerful service creator. UMTS enables many services, some of which originate with 2G and will become more affordable using 3G [e.g., the enhanced message service, (EMS)]. Services that already exist on the Internet will be greatly improved with location, interactivity, mobile multimedia, and customer segmentation based on lifestyle management. The demand for increased personal productivity will also be of importance. The blurring of boundaries between business and consumer markets, and between work and home, will continue.

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Table 3.11 indicates the way potential UMTS services relate to Internet and intranet applications and protocols and to their functional elements ISP, portal, and the application-specific servers. The market value of a potential service can be estimated by considering aspects of service use: the number of sessions, the traffic volume, the QoS (real-time interactive or delaytolerant), and, of course, the willingness to pay for the service. Such estimations will have a considerable impact on the planning and dimensioning of the UMTS network elements that deal with the services specifically. The ISP function seems to be required for nearly all future services. Its positioning depends on how long circuit-switched transport will be used. There is also high value in the portal function: the Japanese experience with i-mode indicates that more than 50% of the service sessions are via their portal function. Another value can be seen for e-mail, SMS, and instant messaging services: E-mail is about to dominate in the wireline Internet, SMS dominates in the mobile networks, and instant messaging is emerging on the Internet. It is not visible yet that they will merge, but they will certainly be linked together. The role of database download or streaming of audio (MP3) and video (MPEG-4), and how they will be transported, needs to be discussed further.

Table 3.11 UMTS Services and Their Relation to the Internet and Intranets Service Category

Session Type

Protocols

Internet Elements

Location-based infotainment edutainment

WWW

HTTP, WML cHTML, xHTML

ISP, portal, servers

Intranet access (mobile VPN), All types—transparent mobile office, mobile tunnel commerce

IP, higher layers ISP, firewall server, transparent corporate portal

Internet access

All types—transparent tunnel

IP, higher layers ISP, portal transparent

Multimedia messaging

SMS, e-mail, downloading

SMTP, SMS, IP

ISP, e-mail, SMS-server

Audio, video doc. download

File transfer, streaming

MP3, MPEG-4, FTP, IP-based

ISP, portal, database server

Voice, real-time audio, video

Interactive/dialog streaming/one-way

SIP

Media gateway

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It is for certain that UMTS will embrace functions from the Internet model in addition to functions from the traditional model in telecommunications, which was developed for point-to-point and station-to-station twoway communications. In order to accomplish this convergence, additional network elements are needed as an integral part of the UMTS concept. The new elements are identified in the context of information-based services: the ISP function, portal operation with transaction-switching functions, the content-based billing functions, and possibly also the application service provider (ASP) functions. They are shown in Figure 3.15. The convergence point for supplying information and entertainment to the end user will be the mobile multimedia portal, which will be the end user’s preferred point of entry into and interaction with IP-based services and content. The portal will also aggregate the content and search for user-specific information. The mobile multimedia portal will perform applications-oriented switching in the future. 3.2.1

Value Chain—Developments Towards Information-Based Services

The traditional telecommunications network value chain is characterized by the establishment of a physical (circuit-switched) or virtual (packet-switched) connection between two endpoints: station-to-station or person-to-person. Connection-oriented services are the basis for the charging principles of time and distance used, and end-to-end security and QoS is provided on that basis (see Figure 3.15, upper part). The new UMTS services segments require the extension of this model. Here, in addition to the user-to-user connection model, the user-to-computer or client-server model comes into play (see Figure 3.15, lower part). This can be achieved by providing access connections via a circuit- or packet-switched network from a user terminal and then, in a second step, building up a session to get the content. With the Internet, the terminal user has an account with an ISP or with a corporate IP network server (intranet server). Transparent access to the ISP is considered as a tunnel: It is the typical ISP access via the fixed telecommunications networks (PSTN or ISDN). In the UMTS architecture, it is foreseen that IP protocols will be stepwise implemented via software releases in the access and core network. The result will be a UMTS-ISP function that will provide general IP access tunnels to the Internet or intranets for all mobile users. As is shown in Figure 3.16, the migration to the integrated ISP function is already underway, being directed by the global standardization project 3GPP, which defines three steps:

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UMTS and Mobile Computing End-to-end connection security, QoS, billing

Terminal A

Radio access network

Access + transport network (e.g., PSTN)

Transport network (e.g., GSM, IS41)

Terminal B

Traditional services model (voice, fax, data, SMS)

Terminal

Radio access network

Transport network

ISP

Portal

Content

Content-related services model (WWW, e-mail)

Figure 3.15 UMTS combines the traditional and new value chain.

1. UMTS will provide a GPRS-based core network overlay for IPtransport in addition to the existing upgraded GSM circuitswitched core network. The function of GPRS is to provide IP access via pipes (tunnels) from the mobile terminal to an ISP in the Internet or to a corporate network ISP. The ISPs may be attached to either the visited or home GPRS network. The GPRS core network will use the same radio interface as is used for circuitswitched services. This allows mobile terminals with GPRS to be compatible with mobile terminals without GPRS using circuitswitched tunnels. UMTS Release 99, sometimes called Specification Release 3, introduces the new UMTS radio network, the universal terrestrial radio access network (UTRAN), with both FDD and TDD modes. The basic structure of the core networks will not change much from that of GSM with its GPRS overlay. Mobility management remains more or less the same. The core network will allow IPtransport up to 384 Kbps and circuit-switched transport common for real time non-IP and IP services with 64 Kbps. The circuitswitched channels can be used to carry IP traffic with a guaranteed bit rate for the user. MMS is also defined. 2. UMTS Release 4 adds some functionality (e.g., MMS additions) but will not involve substantial changes. For unpaired frequency use in the TDD mode, the low chip rate technique TD-SCDMA is part of this release.

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3. Beginning with Release 5 (formerly known as Release 2000—All IP network), UMTS will merge both the radio and the core network to a single IP network and add multimedia services based on IP. This network will include the ISP function and will therefore enable the UMTS operator to be an ISP. The details of this migration have not yet been decided upon. A migration step that is independent from the all-IP approach involves the introduction of a transaction-switching and portal function into the UMTS network. It does not require further standardization because these functions belong to the existing IETF standards. This is a necessary step for providing the mobile user still on the HTTP protocol and applications level with the new personalized access and control features for receiving information (e.g., depending on location and personal number) with the increased quality and security the user expects. For roaming between operators (e.g., internationally), a basic set of rules and standards will be necessary for portal functionality. The portal functions lie in the application layer according to the ISO model. In case of m-commerce, the portal will migrate to an applications-oriented switching platform. Figure 3.16 shows the development of the standard. Circuit-switched access, for instance to an ISP, provides a physical channel with a guaranteed bit rate during the user session. Time- and distance-dependent charging is the cost factor that hinders a market success for content-based services. In contrast, packet-switched access tunnels allow always-on with volume-dependent charging. The bit rate is dependent on the actual traffic load and therefore is not guaranteed since many users will share a common channel. Sharing a common channel is a very important concept. In UMTS Release 3 and 4, it is deployed as an aggregation of tunnels from a SGSN to a GGSN and to one or more ISPs, providing a transparent pipe through which terminals may access ISPs. This tunnel is established during the Packet Data Protocol context activation by the GPRS tunneling protocol (GTP). During this process, the terminal uses the access point name (APN) to identify the ISP with which the terminal is to register. This process will change with Release 5, where the ISP will be in the UMTS network; thus, user registration will take place there. 3.2.2

Network Architecture

As already mentioned, the initial UMTS network architecture is built upon the GSM model (see Sections 3.1 and 3.2). It is comprised of UTRAN and

106

UMTS and Mobile Computing UMTS standard release

UMTS release 99

UMTS release 4

UMTS release 5 and beyond IP Multimedia (IM)

Packet

Packet-switched access tunnels to ISP

Circuit

Circuit-switched voice, data

Core network

Packet

IP SGSN/GGSN

Circuit

Circuit-switched VMSC/GMSC

Radio network

Packet

≤ 384 kbps

Circuit

64 kbps

Services

Mobile Internet ISP VoIP

All IP

All IP

Figure 3.16 UMTS standard releases and services.

the core network, along with the circuit and packet domain as well as additional service and management components. In 2000, the UMTS Forum developed the so-called extended vision—mobile Internet model for information-based services. It is shown in Figure 3.17 [36]. This evolutionary step is from the GSM model to a converged model that integrates components from the Internet. Figure 3.17 shows the elements of the total value chain and indicates the degree of standardized and commercial areas of the elements involved. It is clear that a UMTS terminal will be a commercial product to a large extent. The standardized part of it will be dominated by the air interface standard, the universal subscriber identity module (USIM) standard, and the IP protocol part with encoding and decoding. The ITU framework standards, the 3GPP-specified detailed standards, and the IETF/ISO/IEC standards will also play a role. The radio and core network, as well as the network applications related to the core network (e.g., prepaid service and other intelligent network services) belong to the ITU IMT-2000 and the 3GPP standards. The ISP functions belong to the IETF/ISO standards, as do the portals. The content provision, however, is highly dominated by commercial products and de facto standards. Figure 3.18 shows the radio access network for the GSM air interface and for UTRAN. 3GPP Release 99 is comprised of both the UMTS and GSM standard for coexistence and compatibility, including roaming

Technologies Commercial

IMT-2000

107

Internet

Commercial

UMTS UMTS

Terminal

Radio network

Core network

Network applications

Portals

ISP

Content provision

Business chain Figure 3.17 Extended vision—mobile Internet. (Source: UMTS Forum.)

Circuit domain

GSM radio BSC

BTS SIM

Abis

A

MSC

Gb

Node B FDD

RNC

Node B TDD

RNC lub

lucs

lups

Other PLMN

HLR, AC

UMTS radio

USIM

PSTN ISDN

GMSC

Intranet

SGSN

GGSN

ISP

Portal

Content

Packet domain Internet

Figure 3.18 UMTS architecture including GSM components (Release 99).

between 2G and 3G networks. This combination is seen as a practical case, since UTRAN radio coverage will not be available throughout the whole country over a certain period of time after network start-up. On the other hand, since dual-mode UMTS/GSM terminals will provide compatibility

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and roaming between both radio networks (see Section 3.2.7), it seems to be an economical approach. On the network side, which can be seen in the figure where the cross-connections are linked with the radio parts, lies the circuit domain and the packet domain, as well as the mobility and call control of both. GSM and UMTS services can be handled by common network elements. This enables those operators that have both a GSM and UMTS license to decide whether to configure two separate core networks (one for GSM, one for UMTS) or to combine them. Of course, not all services can be offered by both radio networks. There will be limitations on the GSM side, both technologically and service-wise. Hereto, the core network comprises the circuit domain for all circuit-switched services (mainly voice). For data, so-called bearer services are offered, which are (on the GSM side) generally up to 14.4 Kbps and for HSCSD up to n × 9.6 Kbps. The practical bit rates go up to approximately 30 to 50 Kbps. On the UMTS side, the circuit domain offers 64-Kbps bearers. They are quasitransparent bit-transport pipes for IP or non-IP service access. The packet domain provides packet-based connection-oriented transport with bit rates up to 384 Kbps (Release 99) and even higher bit rates with subsequent UMTS releases. Virtual connections are provided that allow the end user to be always on. The next element after the GGSN is the ISP [37]. The ISP function accomplishes the user registration for entering the IP-based infrastructures (domain-based addressing). This is the junction with the Internet and intranets. This function may be enriched with additional features that deal with the operators’ service offerings—for example, access to improved WAP servers and similar services, which require protocol support beyond pure IP transport. Finally, the portal function is shown as another important element for UMTS. It is a key element for mobile Web services and it will be the key element for personalized user access to information and transaction-based billing (which goes beyond volume charging taking place in the transport layer). Such functions will be provided in the future. The telecommunications management network is responsible for the total management of both the packet and circuit domains, including the radio part and—depending on ownership—also the ISP and portal functions. The Signaling and Control Plane

For packet- and circuit-switched transport services, UMTS uses the longterm IP-transport infrastructure comprised of high-speed routers with highcapacity transmission links. In the short term, as already described, a separate circuit-switched transport exists for voice and data services. Along with the

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upcoming Internet transport infrastructure, the network needs (for both the transport and switching infrastructures) an overlay network to deal with the overall multiservice and transport infrastructure signaling and control (see Figure 3.19). This signaling and control plane will evolve from UMTS Release 99, with separated physical entities for circuit- and packet-switched services, up to Release 5, with its harmonized all-IP transport and switching platform. Domain-specific routing will be needed in the beginning and will be common later; mobility management, however, will remain more or less independent from this evolution. The separation of transport and signaling control is inherent to the packet domain of UMTS, since only IP-based services should not be impacted by UMTS-specific control functions at all. Hence, the total access network including the GSM radio part and the UMTS-switching and transport domains may be regarded as an access network to the Internet. This includes global roaming with physical roaming features and user authentication as well. In addition to the signaling and control plane, a service plane deals with the network feature support, which goes beyond the described basic access and switching functions. Such features deal, for example, with the customized access for mobile enhanced logic (CAMEL) protocols to provide a

Intelligent Intelligent Network network Services services

ValueValue Added added Services services

Applications Applications

Service plane

Open service API

Signalling Signaling

Mobility Mobility

Security Signalling Security Signaling Authentication conversion Conversion authentication

Radio Radio Access access

Core Core

MGWY

Signaling and control plane

Standard network API

Figure 3.19 Layered service architecture.

Bearer plane

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UMTS and Mobile Computing

virtual home environment for roaming users in their visited networks. The application program interface (API)—a common programming interface— should allow flexible multivendor solutions. 3.2.3

UMTS Radio Access Techniques

The ETSI decision in January 1998 [18] on the radio access technique for UMTS combined two technologies: WCDMA for paired spectrum use and TD-CDMA for unpaired spectrum use—both should form one common standard. This dual-mode approach ensures an optimum solution for all the different operating environments and service needs. The specifications for both modes were finally worked out by 3GPP and approved in December 19991 [18, 23]. WCDMA is a direct-sequence CDMA scheme using a single carrier with a bandwidth of 5 MHz. With this radio scheme, users’ information bits are spread over an artificially broadened bandwidth. This is done by multiplying the information bits with a pseudorandom bit stream, which is several times as fast. The bits in the pseudorandom bit stream are referred to as chips; the stream is known as the spreading code. It increases the bit rate of the signal by a ratio known as the spreading factor (typical values are 4 to 16). On the receiving side are the correlation receivers. They store exact copies of all the spreading codes. The received data stream is multiplied by these codes, and the information is selected with the same codes as used for transmission. The decoded user signal is increased by the spreading factor; this is called processing gain. Low user bit rates get a lot of processing gain with high spreading ratios, while high user bit rates get less processing gain because of their lower spreading ratios. The spreading and despreading allows all the radio base stations in a network to use the same frequency carrier (reuse 1). Terminals are responsible for strict power control so that signals from all terminals arrive at the base station with the same strength. The WCDMA spreading codes have a variable length of 4 to 512 chips in the downlink and 4 to 256 chips in the uplink. All the spreading occurs on 10-ms radio frames at a constant chip rate of 3.84 Mcps. WCDMA has two modes that are distinguished by the separation of the two communication directions. FDD employs separate uplink and 1. This radio interface specification developed by 3GPP is contained and referenced in two parts (IMT-2000 CDMA Direct Spread and IMT-2000 CDMA TDD) of the new ITU-R Recommendation M.1457 [24] which was approved by the ITU-R Radiocommunication Assembly (RA-2000) in May 2000.

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downlink frequency bands with constant frequency offset between them. TDD has the uplink and downlink direction in the same band and timeshares the directions with a guard period in between. Both modes will be used in parallel and will provide the user with the benefit of both radio access principles in overlapping application scenarios. The access scheme for both modes is shown in Figure 3.20. The combination of both modes enables the operator to provide radio coverage in all environments: at home, in the office, and in the public area. The two UMTS modes enable all kinds of spectrum to be obtained (paired for FDD and unpaired for TDD) at enhanced efficiency, and they are both accepted by regulators, globally acting operators, and vendors. FDD Mode

The FDD mode is intended for high-speed vehicular and low-speed pedestrian use in public macro- and microcell environments with typical data transfer rates of up to 384 Kbps. FDD is especially suitable for wide area coverage due to its potentially high reach. Furthermore, through the use of spreading capabilities, FDD efficiently adapts to the varying user data rates required for diverse applications and also to asymmetric traffic as long as it is balanced in total for uplink and downlink spectrum utilization. Higher bit rates beyond 384 Kbps are also possible and will be offered in microcell

Time

Power density

Power density

Time

Channel bandwidth

Channel bandwidth

WCDMA

TD/CDMA (HCR) TD/SCDMA (LCR)

FDD mode

TDD mode

Figure 3.20 UTRA adaptive modes: (a) FDD mode, and (b) TDD mode.

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UMTS and Mobile Computing

environments. Their spectral efficiency depends on low mobility applications (e.g., pedestrian use up to 10 km/hr). FDD is especially suitable for the following: • Public macro- and microcell environments; • Licensed applications; • Symmetrical access using identical frequency bandwidths for uplink

and downlink;

• Up to 144 Kbps with high mobility (e.g., fast trains up to 500 km/hr); • Up to 384 Kbps for mobility up to 120 km/hr; • Higher bit rates in cells dedicated for low mobility use. TDD Mode

The TDD mode is applicable basically in all environments. It provides distinct advantages in micro- and picocell environments (e.g., for licensed and unlicensed use, for cordless applications, and for wireless local loops). TDD is especially suitable for environments like city centers, business areas, airports, shopping malls, and fairs, where applications tend to create highly asymmetric traffic (e.g., Internet Web access). The reason is that it facilitates the particularly efficient use of the available unpaired spectrum and supports data rates of up to 2 Mbps for low mobility use (pedestrian). TDD is also ideal for corporate networks since it provides the same services on the corporate site as it does outside in combination with FDD for wide area coverage with separate, simplified network planning (practically no cell breathing effect) on the campus. TDD is especially suitable for the following: • Public micro- and picocell environments; • Licensed applications for outdoor and indoor use; • Unlicensed private or corporate applications; • Asymmetrical access within one single frequency band; • Up to 2 Mbps with low mobility (pedestrian) and stationary

applications;

• Up to 384 Kbps with mobility up to 120 km/hr.

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3.2.3.1 Deployment Aspects of the Two Operation Modes

The FDD mode uses two identical amounts of paired spectrum for uplink and downlink, separated by a center gap called the duplex distance (see Figure 3.21). The best frequency utilization is achieved when there is identical traffic in both directions. The basic bandwidth is 5 MHz. The minimum spectrum assignment for uplink and downlink is 2 × 5 MHz. Asymmetrical spectrum allocations for FDD may be considered—for example, as a combination of one uplink channel with two or more downlink channels; however, only a very limited flexibility in coarse steps can be achieved. The usage of such arrangements places additional burdens on terminal implementation (e.g., resulting from the necessary capability to deal with variable duplex spacing). The TDD mode uses only one (unpaired) piece of spectrum for uplink and downlink (see Figure 3.21). Both transmission directions are dealt with sequentially; they are separated in time. The flexible and adjustable allocation of time slots, which is required for each direction, allows coping with traffic asymmetries in a flexible way. The TDD specification with 15 time slots (high chip rate) allows for capacity variations [downlink to uplink (DL:UL)] between 14:1 and 2:13. The low chip rate TDD mode allows variations from 11:1 to 1:11. For large traffic asymmetries (for example, with significantly higher traffic in the downlink than in the uplink) the FDD spectrum is not used Energy

FDD

Uplink channel

Downlink channel Frequency split

Frequency

Energy

TDD

Uplink channel

Downlink channel Time split

Figure 3.21 FDD and TDD. (Source: Siemens.)

Time

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UMTS and Mobile Computing

effectively (uplink band being partly empty). For high traffic asymmetries (e.g., 10:1) and in a given amount of spectrum the TDD mode can theoretically (asymptotically) carry up to nearly twice the traffic capacity compared to FDD. This feature applies to the link, cell, cell cluster, and network levels. The TDD mode can thus create higher revenues for operators for a given spectrum width and the related spectrum costs. The spectrum requirements with asymmetric traffic conditions are lowest for network implementations based on the TDD mode alone or with a mixed FDD/TDD approach; they are significantly higher when only the FDD mode should be used. 3.2.3.2 Bit Rates and Traffic Capacity

The performance of a radio transmission technology cannot easily be calculated. When using mathematical formulas, too many parameters play a role in the radio field and the complexity of functions increases. To achieve spectral efficiency figures, many software tools have been developed by radio technology research programs. It is difficult to achieve comparable evaluation results because requirements of radio technology as well as the techniques used for radio transmission have changed over the years. Often, for a specific system, quite different numerical values of spectrum efficiency are reported because of the different scenarios adopted by the group of experts doing the investigations. It is evident that the performance of a radio transmission technology can only be compared on the basis of the same path loss model, the same traffic and environment scenario, and the same mobility model. Both uplink and downlink have to be considered, at both the link level and the system level—both are relevant for a good simulation result. The radio technology performance for UMTS services has to be considered for many types of service: There are several service categories (see Chapter 4), which have different bit-rate, QoS, and capacity requirements. There are also different aspects from a user’s and from an operator’s perspective: • The user’s perspective. There is a multichannel requirement—a con-

trol channel, a real-time channel for voice and video telephony (probably circuit-switched with a guaranteed bit rate and very short delay time), and a data channel with a higher bit rate demand, delay tolerant and varying QoS. In the all-IP radio network, these channels are all virtual channels.

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• The operator’s perspective. The total traffic capacity of the radio cell

in relation to the frequency band and a high number of users are the main required factors. Thus, the spectral efficiency factor and the number of real-time channels with guaranteed bit rate, as well as non-real-time channels, play the deciding role. In case of small cells, the impact of trunking loss lowers the capacity according to the Erlang formulas.

For circuit-switched systems that are dimensioned with the Erlang formula [38], the channel efficiency measured in channels per cell is taken into account. Each channel has a predetermined bit rate for a certain service (e.g., for voice, it is 64 Kbps in ISDNs and 13/6.5 Kbps in GSM networks [39]). Voice encoding, voice activity detection, and forward error correction are included. The spectral efficiency of the radio channel is the maximum achievable bit rate per hertz; it determines the performance of the channel. The numerical values for such systems were investigated quite often. An example can be found in [39]. The channel efficiency of GSM is calculated, also the spectral efficiency factor, which for GSM is 54 Kbps/MHz/cell. 3.2.3.3 Performance Factor Bit Rate

Discrete user channel bit rates and the number of channels were usually the basis for channel capacity estimations in 2G systems. In 3G, with its packet transport mechanisms, the total bit rate and channel capacity of a radio cell is the primary target. This capacity can be shared by a number of users who have initiated sessions and who are sending or receiving datagrams with bit rates, depending on their terminals [40]. In CDMA radio systems, the maximum achievable bit rate per user may vary in the radio cell depending on the distance of the mobile user from the base station. In the cell border, the signal-to-noise level is low, so only medium bit rates can be achieved, using appropriate modulation schemes. In the center area of the cell, a higher signal-to-noise level is available, so high bit rates can be achieved using higher modulation schemes. Such link adaptation techniques can be advantageous if packet-switched transport is used. The bit rates for a given radio channel and technology can be achieved by computer simulations. Simplified calculations based on the chip rate, frequency band width, frame structure, time slots, and modulation schemes are described briefly for the UTRA operation modes FDD and TDD.

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FDD Mode

The carrier bandwidth of WCDMA is 5 MHz, the frequency reuse factor is 1, and the chip rate is 3.84 Mcps. A radio frame has a duration of 10 ms and comprises 15 time slots. The number of chips per time slot is therefore (3.84 ∗ 106 × 10−2 s)/15 = 2,560 chips/time slot With a spreading factor of 4 and each time slot carrying 640 bits in a 10-ms radio frame, the uplink bit rate per second is (640 × 15)/0.01s = 960 Kbps With burst type 1 [23, pp. 28–29; 40, p. 170] each slot can carry 488 bits instead of 640 bits, which yields the following bit rates, dependent on the different modulation schemes for the uplink and downlink: • Uplink (data modulation BPSK): 488 × 15/0.01s = 732 Kbps • Downlink (data modulation QPSK): 488 × 15 × 2/0.01s =

1,464 Kbps

With multicoding, higher bit rates can be calculated. TDD Mode

The carrier bandwidth of the TDD mode (for high chip rate) is 5 MHz, the frequency reuse factor is 1, and the chip rate is 3.84 Mcps. The radio frame has a duration of 10 ms. There is also the LCR version (TD-SCDMA), where the frequency reuse factor may be either 1 or 3, the carrier bandwidth is 1.6 MHz, and the chip rate is 3.84/3 = 1.28 Mcps. In the following example, the bit rate is calculated for the LCR TDD scheme. The 10-ms radio frame is divided into two subframes of 5-ms duration. There are seven time slots per subframe (one time slot is used for control). Two radio frames allow in total 12 time slots for user uplink or downlink traffic (e.g., 2 time slots up and 10 time slots down relate to a traffic asymmetry of 1:5). It should be noted that in asymmetric operation at least one time slot must be allocated for each direction. The 5-ms radio subframe has for each time slot 864 chips. Among the seven time slots, the first one is always allocated for signaling purposes. The time slots for the downlink and for the uplink are separated by a

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guard-period (16 chips). In each subframe there is one switching point (called midamble = 144 chips). The guard-period and the switching point both represent an overhead of 18.5%. For user traffic, 2 × 352 chips are available in total. Each data symbol is spread by CDMA code. If a spreading factor of Q = 16 is applied, the calculated number of data symbols is N = (2 × 352 chips)/16 = 44 data symbols per time slot Each of the data symbols is QPSK modulated, according to the specified radio system. It originates two encoded data bits. This leads to a user bit rate per time slot of R = (2 × N ) / frame duration = (2 × 44)/(5 × 10−3s) = 17.6 Kbps. Traffic asymmetry 5:1 means 10 time slots assigned for downlink and 2 time slots assigned for uplink traffic. If a loading factor of 0.6 is applied, the spreading figure will be 10 instead of 16. The calculation finally results in the following user bit rates: • Downlink: RD = 10 × 17.6 Kbps × 10 = 1,760 Kbps • Uplink: RU = 2 × 17.6 Kbps × 10 = 352 Kbps

In case of symmetrical traffic, the calculation would result in 1,050 Kbps for both the uplink and the downlink. 3.2.3.4 Performance Factor Traffic Capacity

One of the consequences of the WCDMA system is that maximum user bit rates cannot directly be used to calculate the total traffic capacity per cell. If link adaptation is used for IP-based traffic, bit rates may differ depending on the distance to the base transceiver station. The traffic capacity of a given radio cell for a particular technology can therefore only be a result of computer simulations. Spectral efficiency figures have been produced for UMTS/UTRA in a series of investigations with predefined and comparable analytical models. Basically three different transport classes have been investigated:

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1. For voice services of 8 Kbps; 2. For long constrained delay (LCD) data services bit rates from 64 Kbps up to 2,048 Mbps for indoor 3 km/hr, up to 384 Kbps for outdoor 3 km/hr, and up to 144 Kbps for vehicular up to 120 km/hr; 3. For unconstrained delay data (UDD) services with automatic repeat request (ARQ) and no loss of data over the radio link, the same bit rates were simulated as for the LCD services. The simulations took place on a link level and on a system level. Detailed information can be found in [23]. On a system level, three relevant UMTS environments were simulated: 1. Indoor office; 2. Outdoor-to-indoor pedestrian; 3. Vehicular environment as a macro-environment with cell site distances of 6 km. On the transport side, circuit-switched and packet-switched transport was simulated. The simulation results were approved by ETSI for submission to the ITU-R for the IMT-2000 candidate selection. The following system-level spectral efficiency factors were achieved for FDD (uplink/downlink): • Voice (50% activity): 86–132/70–125 Kbps/MHz/cell; • LCD: 140–330/210–461 Kbps/MHz/cell; • UDD: 168–449/290–453 Kbps/MHz/cell.

Most traffic capacity calculations use spectral efficiency factors, which are lowered in order to keep some reserve for unknown impacts in the field. For example, in [41], a factor of 80 Kbps/MHz/cell and 200 Kbps/MHz/cell is used for voice and data services, respectively. For TDD, the system level simulation results [23, Chapter 2.3] were based on the same scenarios as for the FDD mode. This means that macrocells with cell site distances of 6 km were also simulated here. The TDD mode allows the introduction of DCA, which brings a capacity gain of about 25%. In addition, smart antenna techniques improve spectral efficiency considerably. In the standard case, it was found that the downlink is more critical than the uplink. (For example, on the uplink antenna diversity can be

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applied to improve the efficiency.) Thus, only the downlink was simulated. The following simulation results were achieved for TDD/HCR downlink: • Voice (50% activity): 70–48 Kbps/MHz/cell; • LCD: 62–330 Kbps/MHz/cell; • UDD (with ARQ): 320–642 Kbps/MHz/cell.

Note that the UDD service is seen as a packet-switched service where no loss of data is expected over the radio link due to ARQ. It works in such a way that the first data transmission is nearly uncoded. If it fails, the second transmission works with improved coding. If the second transmission also fails, only the burst with the worst bit error rate is retransmitted. After 10 to 20 retransmissions the session will be dropped. 3.2.3.5 High-Speed Downlink Packet Access

The UTRA air interface standard evolution, which is under discussion in the global standardization project 3GPP, considers packet data downlink transmission rates of up to 10 Mbps within the same carrier of 5-MHz bandwidth. For the uplink, the maximum bit rates are according to the regular standard specifications (≤ 2 Mbps). 3.2.3.6 Transport Connections in the Radio Access Network UTRAN

The WCDMA-based radio interface is capable of multiplexing different bit rates and different services over a 5-MHz wideband single frequency carrier system. The frequency reuse factor of 1 makes it necessary for the separation of user information to be done via demultiplexing of encoded data. Thus, it is effective to transport the received information on the base station via statistical multiplexing channels [i.e., those utilizing asynchronous transfer mode, (ATM)] to the radio network controller (RNC). Applying ATM to very low bit rate mobile voice streams in a mobile communications network necessitates a so-called layered cell structure, also known as ATM Adaption Layer 2 (AAL2), which multiplexes several minicells into one ATM cell to prevent degradation of the QoS due to the delay in filling out the payload of a regular ATM cell. A major impact in CDMA systems is related to soft handover in the access network, when the handset communicates with more than one base station. In order to work seamlessly, connection setup has to be performed within 100 ms or less during soft handover. Because of strict radio-level synchronization needs between soft handover legs, these AAL2 connections are required to meet strict delay and delay jitter requirements

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regardless of the type of user payload (i.e., regardless of whether voice or data is transmitted). Furthermore, AAL2 also allows a reduction of the number of transmission lines and correlated costs needed to support multiple connections to handle soft handover in WCDMA-based UMTS. In all, the ATM/ AAL2-based UMTS access network provides core-network-technologyindependent access for mobile terminals to all core networks and network services. 3.2.3.7 The Satellite Radio Component of UMTS

Besides the ITU framework satellite standards, some standardization activities exist for the satellite component of UMTS. These are based upon the terrestrial air interface WCDMA with the FDD and TDD mode. Modifications were made in the following areas