The Wireless Data Handbook, Fourth Edition. James F. DeRose Copyright © 1999 John Wiley & Sons, Inc. ISBNs: 0-471-31651-2 (Hardback); 0-471-22458-8 (Electronic)

THE WIRELESS DATA HANDBOOK

THE WIRELESS DATA HANDBOOK FOURTH

EDITION

James F. DeRose JFD Associates

A WILEY-INTERSCIENCE

PUBLICATION

JOHN WILEY

INC.

& SONS,

New York / Chichester

/ Weinheim / Brisbane I Singapore / Toronto

This book is printed on acid-free paper. @ Copyright 0 1999 by John Wiley & Sons, Inc. All rights reserved. Published simultaneously in Canada, No part of this publication may be reproduced, stored in a retrieval systemor transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except as permitted under Sections 107 or 108 of the 1976 United, States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 750-4744. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 605 Third Avenue, New York, NY 10158-0012, (212) 850-6011, fax (212) 850-6008, E-Mail: [email protected]. For ordering and customer service, call l-800~CALL-WILEY. ISBN O-471-22458-8 Libraty

of Congress

Cataloging

in Publication

Data:

DeRose, JamesF The wireless data handbook I James F. DeRose. - 4th ed. p+ corn. “A Wiley-Interscience publication.” ISBN O-47 l-3 165 l-2 (alk. paper) 1. Wireless communication systems. 1. Title. TK5103.2D47 1999 62 1.3645’6-dc2 1 99-30369 Printed in the United States of America, 10987654321

The Wireless Data Handbook, Fourth Edition. James F. DeRose Copyright © 1999 John Wiley & Sons, Inc. ISBNs: 0-471-31651-2 (Hardback); 0-471-22458-8 (Electronic)

CONTENTS

PREFACE I GETTING

STARTED

1 A Short History

of Data Radio

3

1.1 In the Beginning

/ 3

1.2 Private Networks

Lead the Way / 4

1.3 Rise of Public Packet Switched Networks

I 5

1.4 Circuit Switched Skims the Early Cream / 6 1.5 Packet Switched Gates Creak Open / 7 1.6 New Wireless Data Alternatives

/ 8

1.7 Summary / 8 References I 9

2 Data Network

Types

11

2.1

A Rough Sort of Two-Way

Systems / 11

2.2

Private Systems / 11 2.2.1 Overview / 11 2.2.2 Estimating Private Users / 15

2.3 Public Systems / 16 2.3.1 Satellite Systems / 16 2.3.1.1 One-Way Paging / 17 2.3.2 Terrestrial Systems / 17 2.3.2.1 Packet Confusion / 18 2.4 Summary I 18 References / 19 V

vi

CONTENTS

3

Key Public

Network

Characteristics

20

3.1 Coverage / 20 3.2 Penetration I 21 3.3 MessageLength / 21 3.4 MessageRates I 22 3.5 Device Speed I 23 3.6 Connectivity I 23 3.7 Summary 1 24

4

Public Terrestrial

Packet Switched

Networks

4.1 Messaging/DispatchOrientation / 25 4.2 Alphanuneric Paging Orientation I 26 4.3 RepresentativeNationwide Networks I 27 4.3.1 Advanced Radio Data Information System / 27 4.3.2 BellSouth Wireless Data / 30 4.3.3 SkyTe12 I 31 4.4 RepresentativeRegional Networks / 32 4.4.1 Cellular Digital Packet Data / 32 4.4.1.1 Ameritech / 34 4.4.1.2 AT&T Wireless / 34 4.4.1.3 Bell Atlantic Mobile / 35 4.4.1.4 GTE MobileCorn / 36 4.4.1.5 CDPD Summary / 36 4.4.2 Cellular Control Channel I 38 4.4.2.1 Cellemetry / 38 4.4.2.2 Aeris Communications / 40 4.5 RepresentativeMetropolitan Networks / 42 4.5.1 Introduction I 42 4.5.2 Metricom Ricochet I 42 4.5.3 Teletrac I 44 4.6 Notable Closings / 46 4.6.1 AirTouch CDPD / 46 4.6.2 Cellular Data Incorporated / 46 4.6.3 Cincinnati Microwave I 47 4.6.4 CoveragePLUS / 47 4.6.5 Electrocom Automation / 47

25

CONTENTS

4.6.6 4.6.7 4.6.8 4.6.9 4.6.10 4.6.11 4.6.12 4.6.13 4.6.14 4.6.15

vii

Geotek I 48 Global Vehicle Tracking System / 49 Kustom Electronics / 49 Magnavox (Nav-Corn) Automatic Vehicle Location / 50 Mobile Data International / 50 Motorola Tracknet/Diversified Computer Systems(DCP) / 50 Navtech / 50 Pacific Communication Sciences / 5 1 Pinpoint Communications I 5 1 RAMTrack I 52

4.6.16 RadioMail I 52 4.6.17 Skywire I 52 References I 52

5

Public Terrestrial

Circuit Switched

Networks

57

5.1 RepresentativeNationwide Networks / 57 5.1.1 HighwayMaster: A Stubborn Fighter / 57 5.1.2 Nextel: Good Field, No Hit / 60 5.1.3 PeopleNet: A New Kid on the Block / 61 5.2 RepresentativeRegional Networks / 62 5.2.1 Data over Analog Cellular Voice Channels / 62 5.2.1.1 Modern Pools / 63 5.2.2 Broadband PCS: GSM I 65 5.2.2.1 Introduction / 65 5.2.2.2 RepresentativeGSM Carriers / 65 5.2.2.3 The GSMAlliance / 67 5.3 Notable Closings I 68 5.3.1 AirTouch Cellular and CTA / 68 5.3.2 Rockwell/GTE Mobile I 68 References I 68

6 Public

Satellite

Networks

6.1 Introduction / 70 6.2 Geostationary Satellite Systems / 7 1 6.2.1 GEOS Overview / 71 6.2.2 OmniTRACS / 71

70

. .. VIII

CONTENTS

6.2.3 6.2.4

AMSC Skycell I 72 GEOS Summary / 74

6.3 Low Earth-Orbiting Satellites / 74 6.3.1 LEOS Overview / 74 6.3.2 Orbcomm I 74 6.3.3 GlobalStar / 75 6.3.4 LEOS Summary / 76 6.4 Notable Closings / 77 6.4.1 Geostar / 77 6.4.2 MARCOR Humminbird / 77 6.4.3 Meteorburst Approaches I 77 6.4.3.1 6.4.3.2 6.4.3.3 6.4.3.4

Introduction / 77 Broadcomm / 78 Pegasus Messaging / 78 Transtrack / 78

References I 78 7

Hybrid

Networks

80

7.1 Terrestrial Packet/Satellite / 80 7.1.1 AMSUARDIS Multimode System / 80 7.1.2 BSWD/Norcom / 81 7.2 Terrestrial Packet/Circuit Switched Cellular / 82 7.2.1 CS-CDPD / 82 7.2.2 BSWD Strategic Network / 82 References I 83

II BUSINESS 8

Fitting

101: PRICE AND QUANTITY Applications

to Public

FIXATIONS

Offerings

8.1 Network Price Positioning / 87 8.2 Representative Public Packet Switched Networks / 87 8.2.1 ARDIS Examples / 88 8.2.1.1 8.2.1.2 8.2. I.3 8.2.1.4

Short-Message Service / 88 Basic Message Unit Pricing / 89 DataPak Pricing / 90 Two- Way Messaging Services / 90

87

CONTENTS

ix

8.2.1.5 “All-You-Can-Eat” Pricing / 91 8.2.2 BSWD Examples / 92 8.2.2.1 WirelessLotus Notes / 92 8.2.2.2 WyndMail Pricing / 92 8.2.2.3 Two-Way Paging / 93 8.2.3 CDPD Examples / 93 8.2.3.1 Low-Volume Usage / 93 8.2.3.2 High-Volume Usage / 95 8.2.3.3 “All You Can Eat” Plans / 95 8.3 Comparative Pricing: Nationwide Carriers I 97 8.3.1 Mobile Office I 97 8.3.2 Electronic Mail / 97 8.3.3 Nationwide Two-Way Paging I 99 8.4 Establishinga RepresentativePacket Switched Price Curve / 101 8.4.1 ARDIS / 101 8.4.1.1 Internal TrafJic: RadioMail / 101 8.4.1.2 External From/To/Date Trafsic: RadioMail / 102 8.4.1.3 ARDIS Test Results / 103 8.4.2 BAM CDPD I 104 8.4.2.1 Test Conditions / 104 8.4.2.2 BAM Test Results / 104 8.4.3 Creating a RepresentativePacket Curve I 105 8.5 Establishinga RepresentativeCircuit Switched Cellular Curve / 106 8.5.1 Data Using Voice Tariffs / 106 8.5.1.1 Selecting a RepresentativeCellular Tariff / 106 8.5.1.2 Establishing the Connect Time / 106 8.5.1.3 Estimating the CustomerData/MessageRate / 107 8.5.1.4 Application Variables / 108 8.6 Summary / 110 References / 111

9 Subscriber

Growth:

History

and Barriers

9.1 Approach I 112 9.2 Public Packet Switched Networks / 113 9.2.1 Cross-Network Applications: E-mail / 113 9.2.1.1 RadioMail / 113 9.2.1.2 WyndMail / 114

112

X

CONTENTS

9.2.2 9.2.3 9.2.4 9.2.5 9.2.6 9.2.7 9.2.8 9.2.9 9.2.10

9.2.1.3 Zup-it / 114 ARDIS I 114 BSWD / 117 CDPD / 118 Geotek I 120 Metricom Ricochet / 121 SkyTe12 / 122 Teletrac / 124 Analog SMRS I 124 Public Packet Switched Summary / 125

9.3 Public Circuit Switched Subscribers / 127 9.3.1 Data over Cellular / 127 9.3.1.1 Practical Counting Problems / 128 9.3.1.2 Search for the Right Ballpark / 129 9.3.1.3 Sanity Checks / 129 9.3.1.4 Realistic Expectations / 134 9.3.2 BroadbandPCS: GSM I 134 9.3.2.1 Voice Subscriber Growth / 134 9.3.2.2 Data Estimates / 135 9.3.3 ESMR: Nextel Digital Subscribers I 135 9.4 Public Satellite Networks I 136 9.4.1 AMSC / 136 9.4.2 OmniTRACS / 137 9.5 summary I 139 References / 140 10

Market

Opportunity

10.1 Second Era of Low Hanging Fruit / 144 10.2 Some Unpleasant History / 148 10.2.1 Job-Based Market Opportunity Approach / 148 10.2.2 1996 Projections: 1987 Work / 149 10.2.3 Analyzing the Data / 153 10.3 A New(er) Look at Jobs / 153 10.4 summary / 159 References / 160

144

CONTENTS

11

Airtime

Price Projections

11.1 Great Expectations

Xi

161 / 161

11.2 Subscriber Capacity Potential / 161 11.3 List Price History: CDPD

/ 162

11.4 Voice/Data Channel Resource Competition: CDPD / 163 11.4.1 Choosing a Representative Carrier / 163 11.4.2 Establishing a Representative Voice Profile / 164 11.4.3 Estimating Voice Capacity per Cell / 164 11.4.4 Estimating Voice Revenue per Sector / 165 11.45 Calculating the Required Data Revenue / 166 11.5 Estimating Future Data Price Levels / 167 References / 168

III BUSINESS 102: OTHER THINGS IMPORTANT TOO 12 Coverage

ARE

Versus Capacity

12.1 Introduction

/ 171

12.2 Key Coverage Philosophies / 172 12.2.1 ARDIS / 172 12.2.2 BSWD / 173 12.2.3 ARDIS Versus BSWD: Representative 90% Coverage Contours / 174 12.2.4 Improving Building Penetration with More Base Stations / 175 12.2.5 CDPD / 176 12.2.6 Other Coverage Considerations / 177 12.2.6.1 Transmit Power Levels / 177 12.2.6.2 External Antennas / I79 12.2.6.3 Repeaters / 179 12.3 Estimating Coverage Without Field Tests I 179 12.3.1 License Examinations / 179 12.3.2 CoverageMaps / 182 12.3.2.1 Obfuscation, Not Illumination / 182 12.3.2.2 Useful But with Careless Errors / 183 12.3.2.3 Misleading / 185

171

xii

CONTENTS

12.3.3

ZIP Code Predictors

I 187

12.4 Field Tests / 190 12.4.1 Simplified Approaches / 190 12.4.2 External Approaches / 191 12.4.3 Summary Field Test Results / 192 12.4.3.1 Street-Level Tests / 192 12.4.3.2 12.5

In-Building

Tests / 195

Capacity Cost of Better In-Building Penetration / 196 12.5.1 Agreeing on a Baseline / 196 12.5.2 Single-Base-Station Cities / 197 12.5.3 12.5.4

Putting Multiple Base Stations to Work / 197 Future Outlook: Coverage Versus Capacity / 199

12.6 Summary / 199 References

I 200

IV SOME PRIMITIVE 13

Understanding

TECHNICAL Airtime

CONSIDERATIONS

Protocols

203

13.1 The Packet Revisited / 203 13.1.1 Message Segmentation: The Flag / 203 13.1.2 Address Field I 204 13.1.3 Control Field / 204 13.1.4 Information Field / 206 13.1.5 Frame Check Sequence Field / 207 13.2 Error-Handling Approaches I 207 13.2.1 Philosophy / 207 13.2.2 Error Detection Versus Correction Basics / 208 13.2.3 Error Detection Versus Correction: Vendor Examples / 208 13.2.4 ARQ Alternatives / 212 13.2.4.1 ARQ Variations / 212 13.2.4.2 Practical Results / 213 13.2.5 Data Flow Example / 214 13.3 Fade Rate Versus Fade Duration / 214 13.3.1 Characteristics of a Fading Channel / 214 13.3.2 13.3.3

Fade Rate / 215 Fade Duration / 217

CONTENTS

13.3.4

Optimum Target Velocity

13.4 Synchronization

XIII-”

/ 218

Errors I 22 1

13.5 Inbound Access: Contention Mode I 222 13.5.1 13.52 13.5.3

ALOHA / 222 Slotted ALOHA / 223 SlottedCSMA I 223

13.6 Retransmission

Rates / 225

References I 228

14 Estimating 14.1

Airlink

Introduction

Capacity: / 230

14.2 Illustrative Single-Base-Station 14.2.1 ARDIS / 231 14.2.2 CDPD / 233 14.3 Multicell 14.3.1 14.3.2 14.3.3 14.3.4 14.3.5

230

Packet Systems Comparison

/ 230

Capacity / 238 Base Station Quantity Mismatch / 238 CDPD Sector Impact / 239 CDPD Channel Hopping / 241 Busy-Cell-Factor Impact / 241 Message Rate Activity

I 243

14.4 Dealing with TCP/IP Impact / 244 References I 246

15

Enabling

“Soft”

247

Technologies

15.1 Alphabet Soup / 247 15.2 Modulation I 247 15.2.1 Circuit Switched I 247 15.2.2 Packet Switched I 250 15.2.2.1 Narrow-Band Low-Speed Devices / 250 15.2.2.2 Narrow-Band Medium-Speed Devices / 251 15.2.2.3

Wide-Band High-Speed Devices / 251

15.3 Error Detection: V.421V.42 Fast and MNP4llO 15.4 Data Compression:

I 252

V.42BISand MNP5/7 I 253

15.5 On-Going Enhancements to Alphabet Soup Modems / 254 References I 255

xiv

CONTENTS

V PUTTING 16

IT TOGETHER

Device Alternatives

259

16.1 Introduction: Combinationsand Permutations I 259 16.2 Modem Complexity / 261 16.3 Cellular SpearheadsModem Development / 262 16.4 Voice/Data Push-Pull / 263 16.4.1 Positioning Tussles / 263 16.4.2 Voice Devices Swallow Modems / 263 16.4.2.1 Voice Devices Try to Do It All / 263 16.4.2.2 A Compromise:SmartPhones/ 264 16.4.2.3 Annoying ResidualProblems / 265 16.4.3 Data Devices Swallow the Radio / 267 16.4.3.1 External Radio Modems / 268 16.4.3.2 PC Card Radio Modems / 269 16.4.3.3 Under-the-Cover Solutions / 271 References I 277

17

Connectivity

279

17.1 Introduction / 279 17.2 Defining the Problem / 279 17.2.1 Origins / 279 17.2.2 Connectivity Goals / 280 17.3 Supporting Software I 282 17.3.1 Radio Modems / 282 17.3.1.1 Single-Network Implementations / 282 17.3.1.2 Multiple-Network Implementations / 283 17.3.2 Exploiting Gateways / 285 17.4 Nongateway Host Connectivity Options / 288 17.4.1 All Wireless / 288 17.4.2 Dial-Up / 289 17.4.3 Public Data Networks / 290 17.4.4 Leased-LineConnections / 291 References / 291

CONTENTS

18 Systems

and Subsystems

Xv

292

18.1 Control Approaches / 292 18.2 Decentralized: Metricom Ricochet / 293 18.3 Partially Decentralized: BSWD / 294 18.4 Partially Centralized: CDPD / 296 18.5 Centralized: ARDIS / 298 185.1 System Approach / 298 18.5.2 System Details / 299 18.5.3 Network Availability / 300 References / 301 19 User Applications 19.1 Vertical Versus Horizontal 19.2 Vertical 19.2.1 19.2.2 19.2.3 19.2.4

302 / 302

Application Examples: Field Service / 304 IBM’s DCS / 304 Pitney Bowes’ AIM I 309 Sears / 310 A Generic Approach I 310

19.3 Horizontal Application Examples: E-mail / 3 16 19.3.1 The Search for the “Killer App” / 316 19.3.2 Limiting the Search / 317 19.3.2.1 Overview / 317 19.3.2.2 Standardization Muddles / 318 19.3.3 Gateway Example: RadioMail / 320 19.3.3.1 Structure / 320 19.3.3.2 Key Functions / 320 19.3.4 Wireless E-mail Service Example: BSWD I 321 19.4 Horizontal Application Example: Two-Way Paging / 321 19.4.1 Introduction / 321 19.4.2 BSWD Makes Its Move / 322 19.4.3 ARDIS Counterattacks / 324 19.4.4 Meanwhile, At SkyTel . . . I 325 19.5 Summary I 325 References I 325

xvi

CONTENTS

20

Network

Mythologies

328

20.1

Introduction

20.2

CDPD is an Open Standard; ARDIS and BSWD are Proprietary / 328

20.3

ARDIS has Limited Capacity / 329

20.4

ARDIS is Old Technology

20.5

BSWD has Inferior In-Building

20.6

Packet Provides Faster Access than Circuit Because it is Always Connected / 330

20.7

CDPD has High User Bit Rates / 33 1 20.7.1 20.7.2 20.7.3

/ 328

/ 330 Coverage / 330

Big Claims and Shrinking Claims / 33 1 Combinatorial Pinging: A CDPD Static Bit Rate Test / 331 Realistic CDPD Bit Rates in a Busy Channel / 332

20.8

CDPD will Move to Higher Bit Rates When They are Available / 333

20.9

ARDIS, BSWD, CDPD (Pick a Name) Will be Out of Business Soon I 334

20.10

When Wireless Data Succeeds, It Will be a Great Business! 20.10.1 ARDIS / 334 20.10.2 BSWD / 336 20.10.3 CDPD / 337

References

/ 334

I 338

VI APPENDIXES Appendix

A

Acronyms

343

Appendix

B

IBM Auto-alert

351

Appendix

C TCP/lP

Appendix

D Number

of ARDIS Subscribers

354

Appendix

E

Number

of BSWD Subscribers

362

Appendix

F Number

of CDPD Subscribers

367

Count:

BAM Inbound

Message

352

CONTENTS

Appendix

G Number

of HighwayMaster

Appendix

H

of OmniTRACS

Appendix

I Connecticut

Appendix

J

ARDIS Cost-Benefit

Appendix

K

CDPD Log Sample

Index

Number

Base Station

Subscribers

Subscribers

Sites

Example

(January

xvii

370

371

375

378

30,1995)

380

383

PREFACE

This fourth edition of the Wireless Data Handbook will begin to reach readers in 1999, the centennial year of Marconi’s first sale of data radio to the British Navy. For the army of fresh, young people now turning their impressive energy and intellect to this growing field, it is fitting to have enough historical perspective to understand the work of their predecessors. As the title states, this book is devoted to data with only passing reference to voice-and then only as voice and data impact each other. It is also focused on wide area, mostly mobile, applications; it does not cover in-building, wireless LANs. By far the greatest emphasis is on public wide area networks, with a conscious effort to make fair business comparisons among the many competing alternatives. While key technology, which includes airtime protocols, must be discussed, this book is mostly application and business oriented. The necessary technical discussions tend to deal with practical matters, such as the impact of long message lengths on user transmission success. The mathematics require no more than high school algebra. This is not an engineering manual. If you need to calculate path losses, understand turbo coding, or approximate chi-square probability distributions, this is not your book. The core of this book is a nuts and bolts examination of realistic wireless applications and the networks that can serve them in the short term. Considerable emphasis is placed on deflating unrealistic vendor claims. The time horizon is short, with the most extended market opportunity projection ending in 2005. This book is not visionary. You will find no refrigerators scanning milk carton expiration dates in order to wirelessly place a replenishment order at your local supermarket. For carriers, the market opportunity estimates tend to be bearish. In my view the estimates are realistic and no apology is made for failing to project a hockey stick upsurge in short term network revenues. After 42 years of struggling in a market that was always on the brink of exploding. I concluded about ten years ago that the model was wrong. One of the original assumptions was that available spectrum was rare and precious, with limited subscriber capacity. It would be controlled by a very few network operators, who could command premium prices for a limited number of highly profitable applications. But there has been no practical spectrum shortage. In 1985 CTIA and Telocator successfully lobbied for an additional 12 MHz of spectrum for cellular since the xix

xx

PREFACE

combined five year forecast for the top 30 markets was projected to be 1.5 million subscribers. The “. . . population will suffer an unacceptable decline in their grade of service or be denied cellular service unless the additional allocation is granted.” Now we have perhaps 40 times that many cellular subscribers, with a plethora of noncellular voice alternatives. There is a local analogy. When I moved to Stamford, CT in 1982 there was a single, presumably profitable, restaurant which featured tablecloths. Today Stamford has 15 yellow pages of restaurant listings, with every ethnic variation. Individual restaurant owners make a living, but most are privately for sale in this fiercely competitive environment. So it is with wireless networks. There are no realistic capacity restrictions in the near term. A dozen network alternatives are routinely available for prospective customers. Only one or two network offerings are profitable, and casualties are legion. Most networks are (privately) for sale-or at least open to a deal. Prices are dropping with hard fought competitive bidding to gain market share. Inappropriate solutions are being touted by some carriers who ignore actual limitations such as realistic data transmission rates. Wide area, wireless data is growing very nicely but is not dominated by any one service provider. The long held dream of a new, uniquely profitable, business opportunity is in ashes. End users are the real beneficiaries of this struggle, and I’m now happy to be one of the latter. James F. DeRose Stamford, CT 06902 December 1998 jderoseQ2way.net

ABOUT THE AUTHOR

James F. DeRose has been a data radio consultant since 1987. He is the author of numerous reports in the field; this is the fourth edition of the Wireless Data Handbook. For thirty-two years Mr. DeRose was a designer, manager, and executive for IBM in its first golden age, specializing in telecommunications product development. He began his career on SAGE in 1955; his enthusiasm for his first data radio application (AWACS) was fueled by the devastating collapse into the sea of the “Texas Tower” wireline predecessor. Mr. DeRose worked on the Gemini/Apollo project, managed the development of the 1966 NYSE Floor Trading System, and was Systems Manager for IBM’s initial SNA product line, the 3600 Banking System. For three years he endured the hardship of acting as Planning & Advanced Technology Manager for all communications products developed at IBM’s lab on the French Riviera. From 1983 to 1985 he was the Director of IBM’s Data Radio Project, a precursor to the present-day ARDIS. Mr. DeRose was a member of the Computer Science graduate faculty and Director of the Telecommunications program at Iona College. He is a Sloan Fellow and Stanford graduate (MMS). He lives on Long Island Sound where he and his wife Judy spend summers luring their seven grandchildren onto the sailboat with the excuse that it’s good experience for them. He can be contacted at jderoseQ2way.net.

xxi

The Wireless Data Handbook, Fourth Edition. James F. DeRose Copyright © 1999 John Wiley & Sons, Inc. ISBNs: 0-471-31651-2 (Hardback); 0-471-22458-8 (Electronic)

I GETTING STARTED

The Wireless Data Handbook, Fourth Edition. James F. DeRose Copyright © 1999 John Wiley & Sons, Inc. ISBNs: 0-471-31651-2 (Hardback); 0-471-22458-8 (Electronic)

1 A SHORT HISTORY OF DATA RADIO

1.1 IN THE BEGINNING In 1899, four years after Marconi’s first wireless telegraph, the British Navy converted to data radio.1 The Czar’s Navy quickly followed. By 1905 the Japanese had mastered the key techniques and began to intercept messages from the Russian Vladivostok fleet cruising secretly south of Tokyo Bay. Japan’s victorious Battle of Tsushima followed. Driven by continued military demands, wireless data technology leaped forward. In 1914 the hapless Russians lost the Battle of Tannenburg because of German intercepts of their land-based data radio communications and in 1917 the British successfully employed radio telegraph in tanks at the Battle of Cambrai2; by 1918 these same units were adapted for aircraft. In World War II both the United States and Germany communicated with and controlled their widely scattered submarine fleets via data radio. During this period H. C. A. Van Duuren3 devised the technique still known as ARQ (Automatic Repeat reQuest), one of those disarmingly simple ideas that seems so trivial in retrospect. The idea was to ensure that a block of characters had been successfully transmitted through the use of error detection. A detected error was followed by a signal from the receiver asking the transmitter to repeat the block. In the late 1950s wireless teletype units such as the CY2977LG were in use in high-profile applications like the media pool aboard Air Force One. The Semi-Automatic Ground Environment (SAGE) air defense system began testing digitized radar information sent by data radio from airborne early warning aircraft. The more complex messages were separated from the continuously repeating X and Y coordinates. A header identifying the radar address was added to the data. These manageable segments were clear forerunners of what would later be called “packets.” 3

4

A SHORT HISTORY OF DATA RADIO

These packets traveled from aircraft to ground station over dedicated radio circuits, as in today’s data-over-cellular. In 1957 data radio modems reached speeds of 2000 bits per second (bps), competitive with landlines of the time; by 1967 the General Dynamics ANDEFT/SC-320 modem achieved 4800 bps.4 In the early 1960s, building on the seminal work of Shannon5 and Hamming,6 commercially practical error correction techniques were available. The stage was set for commercial exploitation of this knowledge base. 1.2 PRIVATE NETWORKS LEAD THE WAY In 1969 IBM began to develop a mobile data radio system for police departments. Fueled by block grants from the Law Enforcement Assistance Administration (LEAA), other vendors, including Kustom, Motorola, Sylvania/LTV, and Xerox, offered alternatives. IBM’s 2976 Mobile Terminal System was announced on May 12, 1972 (see Appendix B). A polled system, it nonetheless achieved good throughput for its time with a combination of high (∼5400 bps) airlink transmission speeds, forward error correction (which consumed half the bits), and ARQ. The IBM system was a failure and was withdrawn in 1974. Competition fared little better. The failure causes were many: 1. The termination of LEAA funding in 1973 2. The physical inadequacy of the devices: big, heavy, hot, noisy, and unreliable 3. A crushing lack of software support: for example, no dispatch applications 4. Unreadiness of the customers: no data bases or applications in place, inability to cost justify the necessary development activity But the dreamers persisted. In 1970 the successful University of Hawaii’s ALOHA system had established fundamental inbound contention techniques.7 In 1975 Kleinrock and Tobagi8 codified carrier sense multiple-access (CSMA) methods, permitting greatly improved inbound performance. Mobile Data International (MDI), founded in 1978 to provide a data radio system for the Vancouver (B.C.) police, began to work with Federal Express in 1979. The following year the first 12 commercial terminals employing CSMA were delivered to the pioneering package delivery service. Very quickly the Federal Express device count grew to 25,000 units, which attracted Motorola’s eye. MDI was purchased, then extinguished. Meanwhile, IBM’s Service Research organization had been privately piloting briefcase-sized “portable” radio terminals, developing a business case for the applications that would yield economic payoff. In November 1981 a contract was signed with Motorola for the Digital Communication System (DCS). Nationwide rollout began in April 1984 and was essentially complete two years later with the installation of more than 1000 base stations.

1.3

RISE OF PUBLIC PACKET SWITCHED NETWORKS

5

DCS was a packet switched, pedestrian (low-target-velocity) oriented system that broke much new technical ground. It used a single frequency on adjacent base stations, with deliberately overlapping coverage patterns, to achieve better in-building penetration. The end-user device was hand held, incorporating integrated radio modems and internal dual diversity antennas for improved reception at walk speeds.

1.3 RISE OF PUBLIC PACKET SWITCHED NETWORKS Of equal business importance, with the signing of the DCS contract, IBM and Motorola agreed to work together on a shared network approach. The initial opportunity estimates were enormous: 5 million subscribers were thought possible by 1987. Within IBM this period later came to be known as the first era of low hanging fruit. But during the period 1983–1985 there were serious business disagreements between the two equally proud companies. IBM better understood the application development barriers that would hinder rapid roll-out of this technology, having struggled to place experimental customers on DCS via the then-extant IBM Information Network. Motorola had a sounder grasp of the infrastructure changes necessary to provide a high-availability system and had begun development of its own, independent network. The proposal to build a public network resting on the shoulders of DCS was rejected by the decision-making elements of both IBM and Motorola for complex (and often emotional) internal business reasons. After the collapse of the joint venture negotiations, Motorola unveiled its own public packet switched network, the Digital Radio Network (DRN). This system used DCS-class base stations but with area controllers sharply modified for both performance and high availability. DRN began in Chicago in 1986 (Ericsson began Mobitex in Sweden the same year). As IBM expected, making a market was an extraordinarily difficult task. It was four years before DRN-Chicago had ∼135 external users9; Los Angeles, rolling out second, took 20 months to achieve about the same number; New York, 18 months behind Los Angeles, reached the 135 milestone after one year. Clearly a positive learning curve existed, but the absolute pace was exceedingly slow.10 Five years after the negotiations failed, the plan was refurbished, principally by the incorporation of Motorola’s high-availability DRN switching centers. The venture was agreed to by IBM, surprising since the airtime protocol remained proprietary to Motorola. The Advanced Radio Data Information System (ARDIS) was announced in January 1990. The system has been in continuous evolution ever since: new devices, a new higher bit rate protocol, additional frequencies, roaming capability, and extraordinary redundancy added to achieve high availability. The customer base has grown slowly to ∼40,000 at the end of 1994, reaching ∼80,000 at the close of the third quarter of 1998.11 Building a market remains a continuous struggle. On July 6, 1994, protracted disagreements between the two ARDIS partners were resolved when Motorola bought out IBM. There were multiple reasons for this transaction. Paramount was Motorola’s desire, and willingness, to make the required

6

A SHORT HISTORY OF DATA RADIO

infrastructure investments necessary to drive horizontal markets12 with their Envoy/Marco devices. Envoy/Marco subsequently failed. At the close of 1997 Motorola, deciding that network management was not its forté and discouraged with the general failure of horizontal market thrusts throughout the industry, sold ARDIS to American Mobile Satellite Corporation (AMSC). AMSC was likely influenced by the fact that ARDIS had won the United Parcel Service (UPS) contract, with devices to be supplied by Motorola. Further, ARDIS had successfully partnered with AMSC on combined terrestrial/satellite devices for trucks. The two companies were not strangers. In October 1990 RAM announced its public data service based upon Ericsson’s newest Mobitex design. Initially plagued by a lack of nearly everything—adequate base stations/coverage, hand-held modems—and a conviction that horizontal applications were the path to success, RAM’s failure to achieve an adequate subscriber base was extraordinarily painful. BellSouth Mobility became an essentially equal RAM partner in 1992 with the investment of $300 million in urgently needed cash. Infrastructure deployment rates jumped. Nationwide coverage was achieved in June 1993, albeit with a less extensive coverage footprint than ARDIS. By year-end 1994 RAM claimed to have ∼27,000 paying subscribers13 (most in vertical markets) and several intriguing business relationships. As at ARDIS, subscriber growth comes slowly: RAM claimed ∼36,000 users at the close of the third quarter of 199514 and probably reached ∼70,000 at year-end 1997. BellSouth assumed 100% operational control of RAM on March 18, 1998,15 renaming the company BellSouth Wireless Data (BSWD).

1.4 CIRCUIT SWITCHED SKIMS THE EARLY CREAM In 1983 the first data users improvised low-speed connections to their host computers using ordinary modems over voice cellular “circuits.” Users treated these dial connections much as they used ordinary landlines. They are now greatly helped by far better modem capability, most cellular ready, and the formation of carrier modem pools in most major metropolitan areas. Facsimile transmission alone, usually from a portable computer to a wireline fax, has created thousands of casual public data radio users. In early 1992 UPS made a direct connection of its own leased facilities to cellular mobile telephone switching offices (MTSOs), bypassing the public switched network landlines. This resulted in very advantageous pricing, though there were time connection limits. By February 1993 UPS had approximately 50,00016 operational units with this reduced tariff arrangement, significantly more subscribers than DRN/ARDIS had achieved after seven years of effort. But the struggle to deal with scores of cellular carriers—even though a consortium was created to smooth the path—led UPS to begin the conversion to a nationwide packet switched solution. ARDIS, beginning in late 1998.

1.5

PACKET SWITCHED GATES CREAK OPEN

7

Some carriers formed dedicated circuit switched data organizations similar to Sprint’s national cellular data team formed during the Spring of 1993.17 By mid-1994 most carriers had cellular modem pools in operation in at least some cities. The ostensible reason for pool deployment is to avoid forcing users to convert the modem facilities at their host sites. Another important reason is that dialing to a pool gives the carriers the ability to distinguish between voice and data calls. Custom tariffs can follow. An interesting example is that of Cellular One in Buffalo, NY, which charges $0.15 per minute for data calls made during peak hours.18 The advent of low-cost (