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`CELLULAR DIGITAL
`
`PACKET DATA
`
`MUTHUTHAMBY SREETHARAN
`
`RAJIV KUMAR
`
`ID ~ti:tecli Hfouse P.cd51isners e a s T o N
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`Page 1 of 56
`
`GOOGLE EXHIBIT 1016
`
`

`

`
`
`Page 2 of 56
`
`Page 2 of 56
`
`

`

`CELLULAR DIGITAL PACKET DATA
`
`Page 3 of 56
`
`

`

`•
`
`The Artech House Mobile Communications Series
`
`John Walker, Series Editor
`
`Advanced Technology for Road Transport: IVHS and A TT, Ian Carling, editor
`An Introduction to GSM, Siegmund M. Red!, Matthias K. Weber,
`Malcolm W. Oliphant
`CDMA for Wireless Personal Communications, Ramjee Prasad
`Cellular Digital Packet Data, Muthuthamby Sreetharan and Rajiv Kumar
`Cellular Radio: Analog and Digital Systems, Asha Mehrotra
`Cellular Radio Systems, D. M. Balston, R. C. V. Macario, editors
`Cellular Radio Performance Engineering, Asha Mehrotra
`Mobile Communications in the U.S. and Europe: Regulation, Technology, and
`Markets, Michael Paetsch
`Land-Mobile Radio System Engineering, Garry C. Hess
`Mobile Antenna Systems Handbook, K. Fujimoto, J. R. James
`Mobile Data Communications Systems, Peter Wong, David Britland
`Mobile Information Systems, John Walker, editor
`Pe.rsonal Communications Networks, Alan David Hadden
`RF and Microwave Circuit Design for Wireless Communications,
`Lawrence E. Larson, editor
`Smart Highways, Smart Cars, Richard Whelan
`Understanding CPS: Principles and Applications, Elliott D. Kaplan, editor
`Wireless Communications in Developing Countries: Celular and Satellite Systems,
`Rachel E. Schwarz
`Wireless Communications for Intelligent Transportation Systems, Scott D. Elliott,
`Daniel J. Dailey
`Wireless Data Networking, Nathan J. Muller
`Wireless: The Revolution in Personal Telecommunications, Ira Brodsky
`
`For a complete listing of The Artech House Telecommunications Library,
`turn to the back of this book.
`
`Page 4 of 56
`
`

`

`CELLULAR DIGITAL PACKET DATA
`
`Muthuthamby ~reetharan
`Rajiv Kumar
`
`Artech House
`Boston • London
`
`Page 5 of 56
`
`

`

`Library of Congress Cataloging-in-Publication Data
`Sreetharan, Muthuthamby
`Cellular digital packet data/ Muthuthamby Sreetharan and Rajiv Kumar.
`p.
`cm.
`Includes bibliographical references and index.
`ISBN 0-89006-709-0 (alk. paper)
`1. Wireless communication systems.
`2. Cellular radio.
`II. Title.
`transm1ss1on.
`I. Kumar, Rajiv.
`TK5103.2.S79
`1996
`004.6'6-dc20
`
`3. Radio-Packet
`
`96-13238
`CIP
`
`-
`~l ll~
`17<
`.,·
`
`-
`)
`
`I
`
`C~,
`.
`\ \._ \
`,,
`, _ __.
`/
`c::::,-~ /'/
`British Library Cataloguing in Publication o';t1 · ·
`Sreetharan, Muthuthamby
`Cellular digital packet data
`1. Mobile communications systems 2. Cellular Radio 3. Wireless
`communication systems
`I. Title II. Kumar, Rajiv
`621.3'8456
`
`I
`
`·172,. :J V
`-
`. c..rr!
`I ,:r -~
`
`,.
`
`;""lr'_)
`
`/'
`
`-•
`
`I
`
`••
`
`ISBN 0-89006-709-0
`
`Cover design by Kara Munroe-Brown
`
`© 1996 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, includ(cid:173)
`ing 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 informa(cid:173)
`tion. Use of a term in this book should not be regarded as affecting the validity of any trade(cid:173)
`mark or service mark.
`
`International Standard Book Number: 0-89006-709-0
`Library of Congress Catalog Card Number: 96-13238
`
`10987654321
`
`Page 6 of 56
`
`

`

`To my mother, who perished during the 1987 Sri Lankan army's onslaught on
`Jaffna; to my father, who taught me, by example, the important values in life;
`and to young Tamil men and women who gave their lives defending the
`freedom and dignity of the people of Thamil Eelam.
`
`- M. Sreetharan
`
`To my wife, Amy, and daughter, Sonali, without whose support I would not
`have known about CDPD.
`
`- Rajiv Kumar
`
`Page 7 of 56
`
`

`

`,.,.,.
`
`CONTENTS
`
`Preface
`
`Acknowledgments
`
`Chapter 1
`
`Introduction
`1.1
`Background
`1.2
`Cellular Digital Packet Data (CDPD)
`1.2.1 A Brief History
`1.2.2 Overlay on Analog Cellular
`1.2.3 Dedicated and Shared RF Channels
`1.2.4 Network Connectivity
`1.2.5 CDPD System Performance
`CDPD Applications
`1.3.1 Embedded Systems With Bursty Data Transfer
`Requirements
`1.3.2 Handheld Interactive Computing
`
`1.3
`
`Chapter 2 Wireless Technologies With Data Capability
`2.1
`Cellular Systems Overview
`2.1.1 The AMPS System
`2.1.2 Digital Cellular Systems
`Circuit-Switched Cellular
`
`2.2
`
`VII
`
`xv
`
`XVII
`
`1
`2
`4
`5
`6
`7
`9
`9
`11
`
`11
`12
`
`15
`16
`16
`21
`28
`
`Page 8 of 56
`
`

`

`viii CELLULAR DIGITAL PACKET DATA
`
`2.5
`2.6
`
`2.3 Wireless Data in GSM-Based Systems
`Private Packet Systems
`2.4
`2.4.1 RAM Data
`2.4.2 ARDIS
`2.4.3
`Summary of Private Packet Networks
`Specialized Mobile Radio
`Personal Communication Services
`2.6.1
`Evolution of Cordless Phones-The CT Series
`2.6.2 DECT
`2.6.3 DCS-1800
`2.6.4 N-CDMA and DS-SS
`2.6.5
`PCS Technology and Standards
`2.6.6 Microwave Relocation for PCS Deployment
`2.7 Mobile Satellite Services
`2.7.1 Geosynchronous Systems
`2.7.2 Low-Earth-Orbit Systems
`2.8 Wireless LANs
`2.9
`Summary
`
`Chapter 3 Architecture
`Service Provider's Perspective of the CDPD
`3.1
`Network Architecture
`Intermediate Systems
`3.2
`3.3 Mobile Data Intermediate System
`3.4 Mobile Data Base Station
`3.4.1 Channel Stream
`3.5 Mobile-End System
`3.5.1 Network Entity Identifier
`3.5.2 M-ES Internal Structure
`Fixed-End System
`3.6
`3.7 Network Servers
`3.7.1 Authentication Server
`3.7.2 Accounting Server
`3.7.3 Network Management Server
`3.7.4 Message Transfer Server
`3.7.5 Location Server
`3.8 Network Interfaces
`3.8.1
`The A Interface
`3.8.2 The E Interface
`3.8.3 The I Interface
`Communications Architecture
`3.9.1 Reference Architecture
`3.9.2 CDPD Network Subprofiles
`
`3.9
`
`30
`32
`33
`33
`34
`34
`35
`36
`36
`38
`39
`40
`42
`42
`44
`44
`46
`48
`
`51
`
`51
`55
`55
`56
`56
`56
`57
`57
`58
`59
`60
`60
`60
`62
`62
`62
`63
`63
`63
`63
`63
`64
`
`Page 9 of 56
`
`

`

`Chapter 4 Airlink Interface
`4.1
`Introduction
`4.2
`Overview of Data Flow
`4.3 Main Functions of the Layers
`The Physical Layer Functions
`4.4
`4.4.1 RF Channel Management
`4.4.2 Data Transfer
`4.4.3
`Transmit Power Requirements
`4.4.4 Modulation/Demodulation
`4.5 Modulation Technique
`Spectral Efficiency Considerations
`4.5.1
`4.5.2 Constant Envelope Modulation Schemes
`4.5.3 QPSK and OQPSK
`4.5.4 Minimum Shift Keying
`4.5.5 Gaussian Minimum Shift Keying
`4.6 MAC Layer Functions
`4.6.1 Main MAC Layer Functions
`4.6.2
`Forward Channel
`4.6.3 Reverse Channel
`4.6.4 Channel Timing_ Requirements
`Summary
`
`4.7
`
`Chapter 5 Link Layer Protocol
`Introduction
`5.1
`Overview of the Link Layer
`5.2
`Services Offered by This Layer
`5.2.1
`Interfaces With Other Protocol Layers
`5.2.2
`5.3 Model of Operation
`5.3.1 Unacknowledged Operation
`5.3.2 Acknowledged Operation
`5.3.3
`TEI
`5.3.4 Data Link States
`Formats of Fields
`5.4.1 Control Field Parameters
`5.4.2
`Frame Ty"pes
`5.5
`Link Establishment Procedure
`5.6
`Sleep Mode
`5.7
`Broadcast Data Transfer
`5.8 Multicast Data Transfer
`5.9
`Typical Flow Scenarios
`5.9.1 Multiple Frame Operation Establishment
`5.9.2 Acknowledged Data Transfer
`
`5.4
`
`Contents
`
`ix
`
`69
`69
`69
`72
`73
`73
`74
`74
`75
`76
`76
`77
`78
`79
`81
`83
`83
`90
`94
`98
`101
`
`103
`103
`104
`105
`106
`109
`109
`110
`110
`113
`113
`113
`115
`118
`119
`120
`121
`121
`121
`122
`
`Page 10 of 56
`
`

`

`x CELLULAR DIGITAL PACKET DATA
`
`5.9.3
`5.9.4
`
`Unacknowledged Data Transfer
`Intra-Area Cell Transfer
`
`Chapter 6
`
`Chapter 7
`
`6.2
`
`6.3
`
`6.5
`
`Subnetwork-Dependent Convergence Protocol Layer
`6.1
`Need for the Subnetwork Protocol Layer
`6.1.1 Multiple Network Protocols That Use the
`Link Layer
`Overview of SNDCP
`6.2.1 Model of Operation
`6.2.2
`SN-DATA Protocol Data Unit
`Header Compression
`6.3.1 TCP/IP Protocol Header Compression
`6.3.2 CLNP Protocol Header Compression
`6.4 Data Compression
`6.4.1 Model of Operation
`Segmentation and Reassembly
`6.5.1
`Segmenting and Reassembly Over the
`Acknowledged Class of Service
`Segmenting and Reassembly Over the
`Unacknowledged Class of Service
`Encryption and Decryption
`
`6.5.2
`
`6.6
`
`Radio Resource Management
`7.1
`Cell-Based Network Architecture
`7.1.1 Omni/Sectored Cells
`7.1.2 Adjacent Cells
`7.1.3
`Frequency Reuse and Cell Clusters
`7.1.4 Adjacent Areas
`7.1.5 CDPD Frequency Pools and AMPS System
`7.1.6 Color Codes
`Radio Resource Management: Main Goals
`Radio Resource Management Protocol
`7.3.1 Message General Format
`7.3.2
`Information in RRME Messages
`Key Functions of Radio Resource Management
`7.4.1 RRMEs
`7.4.2 MDBS RRME Functions
`7.4.3 M-ES RRME Functions
`Radio Frequency Coverage
`7.5.1 Cell Boundaries in AMPS and CDPD
`7.5.2 Comparison of Receiver Sensitivities
`7.5.3
`Power Balance
`
`7.2
`7.3
`
`7.4
`
`7.5
`
`122
`123
`
`127
`127
`
`128
`128
`128
`131
`132
`133
`135
`136
`137
`138
`
`138
`
`139
`140
`
`141
`141
`142
`142
`144
`145
`147
`148
`150
`151
`152
`153
`159
`159
`159
`163
`174
`175
`176
`179
`
`Page 11 of 56
`
`

`

`8.5
`
`chapter 8 Mobility of M-ESs
`Introduction
`8.1
`8.2 Mobility Levels and Routing of NPDUs
`8.2.1 CDPD Entities
`ISO/IP Routing Framework
`8.2.2
`8.3 Mobility Management Elements in M-ESs
`8.4 Mobility Management Elements in MD-ISs
`8.4.1 Mobile Home Function (MHF)
`8.4.2 Mobile Serving Function (MSF)
`Cell Transfer
`Intra-Area Cell Transfer
`8.5.1
`Interarea Cell Transfer
`8.5.2
`8.5.3 Routing of Data Packets
`8.6 Mobility of Multicast M-ESs
`8.6.1 Registration and Location Update
`8.6.2 Redirection and Forwarding
`8.7 Mobile Network Location Protocol (MNLP)
`8.7.1 MNLP Overview
`8.7.2 Addressing Scheme for MNLP Protocol
`8.7.3 Encapsulation Formats
`Information Base Within the MDIS
`8.7.4
`8.7.5 MNLP Message Formats
`8.7.6 MNLP Protocol Functions
`8.8 Mobile Network Registration Protocol
`8.8.1 MNRP Overview
`8.8.2 MNRP Message Formats
`8.8.3 MNLP Protocol Functions
`8.9 Mobile-IP Protocol
`
`Chapter 9 Network Management
`9.1
`Introduction
`9.2 Overview of CDPD Network Management
`9.3
`CDPD Management Functions and Capabilities
`9.3.1 Configuration Management
`9.3.2
`Fault Management
`9.3.3
`Performance Management
`9.3.4 Resource Management Functions on
`CDPD Network Elements
`Security Management
`9.4.1
`Security of Management
`9.4.2 Management of Security
`9.4.3 Airlink Security
`
`9.4
`
`Contents xi
`
`181
`181
`182
`182
`184
`188
`188
`188
`188
`189
`189
`191
`191
`193
`193
`193
`194
`195
`195
`195
`198
`199
`205
`207
`207
`208
`211
`212
`
`215
`215
`215
`216
`216
`217
`219
`
`220
`222
`222
`222
`224
`
`Page 12 of 56
`
`

`

`xii CELLULAR DIGITAL PACKET DATA
`
`9.5
`
`Accounting Management
`9.5.1 Overview of CDPD Accounting
`9.5.2 Accounting Model
`9.5.3 Accounting Meter
`9.5.4 Accounting Server
`9.5.5 Accounting Meter Management Attributes
`
`Chapter 10 A Day in the Life of an M-ES
`10.1
`Introduction
`10.2 M-ES Configuration
`10.3
`Interfaces for Mobile-End Systems
`10.3.1 Serial-Interface With AT Command Set
`10.3.2 SLIP/PPP Interface
`10.4 Registration Sequence
`10.4.1 Phase-1: Initial Channel Acquisition
`10.4.2 Phase-2: TEI Assignment
`10.4.3 Phase-3: Link Establishment
`10.4.4 Phase-4: Encryption Message Exchange
`10.4.5 Phase-5: CDPD Network Registration
`10.5 Data Transfer
`10.5.1 Burst-Mode Applications
`10.5.2 Continuous-Mode Applications
`10.6 Application Issues
`10.6.1 Reasons for TEI Assignment Failures and
`TEI Removals
`10.6.2 Reason for Registration Failures
`10.6.3 Reason for Loss of Registration
`10. 7 Summary
`
`Chapter 11 CDPD Deployment and Operational "Issues
`11.1
`Introduction
`11.2 CDPD Overlay Architectures
`11.2.1 OMNICells
`11.2.2 Multisectored Cells
`11.2.3 Simulcast
`11.2.4 Sparse Deployment
`11.3 Frequency Allocation and Management
`11.3.1 Co-Channel Interference
`11.3.2 Adjacent Channel Interference
`11.3.3 Coordination of AMPS and CDPD
`Frequency Pools
`11.3.4 Efficient Algorithm Match
`
`227
`227
`228
`228
`229
`235
`
`237
`237
`237
`239
`239
`240
`240
`241
`242
`243
`244
`244
`245
`245
`246
`249
`
`249
`250
`251
`252
`
`253
`25 3
`253
`254
`254
`254
`254
`255
`255
`256
`
`257
`257
`
`Page 13 of 56
`
`

`

`-
`
`11.4 Cell Capacity and Load Management
`11.4.1 Multiple MES Operation
`11.4.2 Load Balancing
`11.5 GMSK and FM Radio Operation in the
`CDPD Modems/MDBS
`11.6 Half-Duplex MESs
`11. 7 Antenna Issues
`11. 7.1 Cell-Site Antennas
`11. 7.2 Mobile Antennas
`11. 7.3 Typical Problems With Cell-Site Antennas
`11.8 System Tuning
`11.8.1 MAC Layer Parameters
`11.8.2 MDLP Layer Parameters
`11.8.3 Radio Resource Management Parameters
`11.9 Current State of CDPD Deployment
`
`Chapter 12 Evolving CDPD Issues of the Future
`12.1 Adaptation to Evolving Cellular
`Telephony Technology
`Impact of CDPD on PCS
`12.2
`12.3 Circuit-Switched CDPD
`12.3.1 CS CDPD Network Architecture
`12.4 Equal Access Provision
`Interoperability Within Wireless Networks
`12.5
`12.6 Pricing Structures
`12.7 Security Issues in CDPD Networks
`12.7.1 Security Issues Related to the CDPD
`Authentication Protocol
`12. 7.2 General Infrastructure-Related Security
`
`Contents x111
`
`258
`258
`258
`
`260
`262
`263
`263
`263
`265
`265
`266
`267
`268
`269
`
`271
`
`271
`273
`273
`274
`276
`277
`280
`280
`
`281
`283
`
`Appendix A Directory of Companies and Organizations Relevant to CDPD
`
`285
`
`Appendix B State of CDPD Deployment
`
`About the Authors
`
`Index
`
`295
`
`301
`
`303
`
`Page 14 of 56
`
`

`

`CHAPTER 1
`,,,,,,
`
`INTRODUCTION
`
`Cellular digital packet data (CDPD) is a wireless technology that provides packet(cid:173)
`switched data transfer service using the radio equipment and spectrum available in
`the existing analog mobile phone system (AMPS)-based analog cellular networks.
`AMPS technology is used mainly in the United States and therefore initial deploy(cid:173)
`ment and use of CDPD will predominantly be in the U.S. markets. Demand for wire(cid:173)
`less data transmission capabilities is rising sharply, and currently available wireless
`data technologies have not been popular with the wireless users because of their cov(cid:173)
`erage, cost, and throughput (speed) limitations. Overlaid on the widely deployed
`AMPS radio infrastructure in the United States, CDPD has the potential to provide
`users with nationwide coverage that cannot be met by other competing wireless tech(cid:173)
`nologies. Further, CDPD promises a low cost service to its subscribers because:
`
`• CDPD shares the use of the AMPS radio equipment on the cell sites;
`• CDPD uses excess capacity in the allocated spectrum for the analog v01ce
`systems;
`• CDPD network usage cost is based on the volume of data transferred and not
`on the connection time.
`
`The protocol architecture of CDPD is chosen so that the available infrastruc(cid:173)
`ture of the terrestrial data network can be integrated as an extension to the CDPD
`ne.twork, as shown in figure 1.1. In effect, the CDPD network provides a connection(cid:173)
`less routing framework-an Internet protocol (IP) or connectionless network proto-
`
`1
`
`Page 15 of 56
`
`

`

`2 CELLULAR DIGITAL PACKET DATA
`
`~ / A-Interface
`
`'
`
`/
`
`/
`
`/
`
`~ /
`
`M-ES
`F-ES
`MOBS
`MD..fS
`IS
`
`Mobile End System
`Fixed End Svetem
`Mobile Data Bue Station
`Mobile Data lntarmediata System
`lntennediata Systam
`
`FIGURE 1. 1 Overall CDPD network architecture. (Source: (1).)
`
`col (CLNP) network layer packet transfer facility-to allow a mobile end system
`to connect to another end system via the IP-based Internet or CLNP-based OSI
`networks.
`This chapter provides a brief historical background to the cellular networks
`thac serve as the basic framework for the deployment and the operation of the CDPD
`networks. The architecture and operation of the CDPD networks are also introduced
`so that the core differences between competing or complementing wireless data tech(cid:173)
`nologies can be identified for engineering or managerial decision making.
`
`1.1 BACKGROUND
`
`Within the last 20 years the wireless field has experienced unprecedented growth into
`a new industry. Fueled by advances in radiofrequency, satellite, and microelectronic
`
`Page 16 of 56
`
`

`

`Introduction 3
`
`1;i 10 gies, and aided by the convenience of instant and tetherless access to tele(cid:173)
`C~" .' n; and messaging portable devices, wireless technology will spawn mass markets
`f> 100 •celess communication devices and applications.
`.
`for w~able 1.1 lists the chronology of landmark events in RF spectrum allocation
`and in the growth of the cellular technology reveals that most of the advances are
`relatively recent.
`
`TABLE1.1
`Landmark Events in the Cellular/Wireless Field
`
`Event
`
`2 MHz was believed to be the highest usable frequency and the National Association of
`Broadcasters warn of impending frequency shortage.
`
`FCC was set up as an independent regulatory body to allocate spectrum, to define rules
`for services, to provide licenses to users, to certify wireless products, and to police the
`r~dio spectrum.
`
`Bell System proposal to the FCC for a 75-MHz spectrum in the 800-MHz band for use in
`cellular.
`
`FCC tentatively allocates 75 MHz for a wireline common carrier.
`
`Cellular system design with cells, frequency reuse schemes submitted by AT&T Bell
`Laboratories.
`
`FCC allocates 40-MHz spectrum with 666 channel pairs with one cellular system per
`market.
`
`First cellular trials conducted in Chicago.
`
`FCC implements the two-carrier per geographic area licensing.
`
`First meeting of the Groupe Special Mobile (GSM) group.
`
`Personal communication services concept emerges as a future technology.
`
`FCC allocates additional 5 MHz for each band, allowing 83 additional channels per band
`(A and B).
`
`CDPD patent was filed by three IBM staff members.
`
`Initial specification of CDPD by the consortium of carriers and IBM.
`
`Number of wireless users in U.S. reaches 20 million.
`
`Narrowband and broadband PCS spectrum auctioned by the FCC with the promise for
`near universal access to messaging, mobile telephony, and data exchange. Beginning of
`extensive deployment of CDPD infrastructure, third-party CDPD modem development,
`and third-party application software development.
`
`Year
`
`1925
`
`1934
`
`1958
`
`1970
`
`1971
`
`1974
`
`1978
`
`1981
`
`1982
`
`1985
`
`1986
`
`1991
`
`1993
`
`1994
`
`1995
`
`Although the United States serves as the main market for the AMPS technology
`(over 85% of the worldwide AMPS subscribers are in the U.S.), other countries such
`
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`4 CELLULAR DIGITAL PACKET DATA
`
`as Australia, New Zealand, several Asian countries (such as Indonesia, the Philip(cid:173)
`pines, Hong Kong, and Singapore), and several South American countries (such as
`Chile and El Salvador) also use AMPS as their primary wireless cellular technology
`[2]. CDPD, within its current stage of development, can be easily deployed in these
`foreign markets once the technical success and the cost advantage to the CDPD cus(cid:173)
`tomer are demonstrated in the U.S. markets.
`In 1993, anticipating the growth in the demand for wireless access to exchange
`data, a consortium consisting of the following carriers was formed to generate a
`specification for the CDPD technology:
`
`• Ameritech Mobile Communications, Inc.;
`• Bell Atlantic Mobile Systems Conte! Cellular, Inc.;
`• GTE Mobile Communications, Inc.;
`• McCaw Cellular Communications, Inc. ;
`• NYNEX Mobile Communications, Inc.;
`• PacTel Cellular;
`• Southwestern Bell Mobile Systems;
`• US West Cellular.
`
`The CDPD specifications embody the following major design goals:
`
`• Compatibility with existing data networks;
`• Ability to support present and future data network services and facilities
`through standardized access to CDPD network;
`• Allowance of maximum use of the existing commercial data network infra(cid:173)
`structure and provision of support to multiple data network protocols.
`
`In addition, more generic goals associated with mobile systems, which include
`seamless roaming, security/privacy, protection of the network from fraudulent users,
`and support of a wide range of mobile stations (such as portable, low-power hand(cid:173)
`held) are also part of the design goals of the CDPD network.
`
`1.2 CELLULAR DIGITAL PACKET DATA (CDPD)
`
`The original idea for using the spare bandwidth in AMPS system to transmit data is
`credited to Robert Miller, Victor Moore, and Thomas Pate (IBM, Florida) and de(cid:173)
`scribed in a U.S. patent filed in 1991. The abstract of the patent, which contains
`Figure 1.2, is given below:
`
`A method for performing Cellular Data Networking (CDN) in an Ad(cid:173)
`vanced Mobile Telephone System (AMPS), wherein said AMPS includes
`a set of cellular telephone voice transceivers, each tuned to one of a pre-
`
`Page 18 of 56
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`

`

`Voice
`
`Voice Tranceivers
`
`Duplexors etc
`
`To Antenna
`
`Introdu ctio11 5
`
`----·-------------- · - -- - --· --
`
`Data
`
`CON Companion
`Transcalve111
`
`Analyzer
`
`FIGURE 1 .2 Organization of transceivers. (S ource: [3] .)
`
`selected set of communication channels, and means for coupling each
`transceiver in said set of transceivers to an antenna to facilitate the per(cid:173)
`formance of duplex radio communications over said set of channels, in(cid:173)
`cluding at least one data transceiver, and a set of sensors coupled to each
`transceiver in said set of transceivers, comprising the steps of:
`
`a) determining when there is unused air time to switch said data trans(cid:173)
`ceiver onto the channel to which a particular one of the transceivers in
`said set of transceivers is tuned;
`
`b) determining when to turn said given data transceiver off based on
`sensing a demand for the channel to which the given data transceiver
`is tuned by said particular transceiver;
`
`c) identifying time slots that are unused by said AMPS on each of said
`channels; and
`
`d) assigning selected unused time slots identified in step (c) for data
`transmission purposes.
`
`It has to be noted that the AMPS system has been in operation since 1978, and
`no one suggested the overlay possibility until this patent was filed. Therefore, what
`af)pears to be a straightforward evolution of the AMPS system may not have hap(cid:173)
`flened if not for the above "invention."
`
`il!.i.1 A Brief History
`
`ttlle early p.art of 1990, under a project called CelluPlan I, researchers at IBM (Boca
`
`ton, Flor.i.d,a) started looking into employing cellular phones as a means to transfer
`
`Page 19 of 56
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`

`

`6 CELLULAR DIGITAL PACKET DATA
`
`data (circuit-switched cellular) using a data modem built by Communicate and a cel(cid:173)
`lular phone from Novatel. They soon discovered that modem attributes, terrain, and
`the noisy airlink affected the reliability of the data transfer. While analyzing the air
`channel in AMPS cell sites to characterize its behavior, they found that even in the
`busiest cell sites a significant portion of the time individual RF channels were not
`used, giving rise to the idea that it may be possible to use the idle time on an RF-chan(cid:173)
`nel to transfer data with the ability to hop to different "free" RF channels when voice
`system began using the channel. IBM and Nova tel built a simple prototype to demon(cid:173)
`strate the feasibility of the idea and CelluPlan-II was born. Attracting the consent of
`McCaw to commit to wireless data as an important technology, IBM in partnership
`with McCaw and subcontracting to PCSI, started specifying the Celluplan-II technol(cid:173)
`ogy. The task of convincing the carriers to adopt to the IBM-McCaw plan was left to
`Machaley of McCaw and Moore of IBM, and this effort culminated in the consor(cid:173)
`tium being formed with all major carriers with the exception of Bell South, which had
`a vested interest in RAM Data. Concerns about possible RF interference of the new
`technology with the operational AMPS system were dismissed after some internal
`tests were conducted by McCaw. During 1992, IBM's involvement in the project di(cid:173)
`minished. A field trial of the initial technology derived from CelluPlan-II was held in
`the San Francisco Bay Area in the second half of 1992 and early part of 1993. Mean(cid:173)
`while, an improved version of the CDPD technology, which was more tailored to the
`Internet world, was developed by a team led by Mark Taylor (McCaw) for the CDPD
`forum. The consortium, later including Bell South, announced the availability of the
`CDPD specifications in San Jose (1993) in the presence of some major companies
`such as Sears, which expressed commitment to CDPD as a user. By patenting the
`technology, IBM ensured that the technology transfer was accomplished at no cost to
`the carriers and was able to serve as a neutral third party to bring the carriers to(cid:173)
`gether to build the infrastructure necessary to support CDPD. The technology speci(cid:173)
`fication that defined the airlink as Gaussian minimum shift keying (GMSK) and a
`data rate of 19.2 Kbps was based on the premise that an inexpensive CDPD modem
`is key to the success of CDPD. These requirements allow off-the-shelf components
`available in the cellular industry to be used, minimizing the modem cost.
`
`1.2.2 Overlay on Analog Cellular
`
`Utilizing the unused bandwidth in the AMPS system and the ability to share cell-site
`hardware are the two factors that gave birth to the CDPD technology as a low-cost
`alternative to existing private packet data technologies.
`In sharing the same set of frequenc:ies allocated to the AMPS, no additional
`functionality is imposed on the AMPS. The implication is that the AMPS system will
`continue to allocate and use frequencies assuming that there are no other potential
`users of its frequencies. It is the responsibility of the CDPD system to continuously
`monitor ("sniff") the AMPS frequencies and employ the unused frequencies. How(cid:173)
`ever, when the AMPS radio is independently assigned the frequency the CDPD sys-
`
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`

`Introduction 7
`
`,
`15
`te!TI .
`
`·sfog the sniffing subsystem in the CDPD has the responsibility to switch the
`t~H ~ithin 40 ms, thereby not causing imerference with AMPS operation. The
`
`ca.;;;~ system then has to find another unused frequency. The mobile-end systems
`~-BSs) that were tuned to th~ old~r fre~uen~; wil) recognize the disappearance of
`~he C-DPD carrier and h_a~e to _identify ~ new available CDPD frequen.cy and co?-
`.
`: the session with minimal interruption to the data flow. The CDPD network will
`f · f
`.
`nnue ·
`·
`'d ·
`·
`I
`d
`CDPD f
`to
`requency
`• ~ tlie M-ESs in prov1 mg a vanety o m ormat1on re ate
`~s'.~s and so forth so chat M-ESs can acquire CDPD channels efficiently.
`1'00
`1Jihe extent to which CDPD is overlaid on the AMPS system ends with the air
`meat. Jn the area of sharing the cell-site hardware, one of the most expensive com(cid:173)
`s:ents in a cell site is the real estate for the cell site and the associated antenna
`:ubsyscem. The CDPD_ ca? fully share t~e ~MPS antenna ~ubs~stem by suitabl~ com(cid:173)
`bin.ing the RF transmit. signals an~ splitting t.he RF receive. s1~~ls. The sharm~ ?f
`po er. amplifiers (PAs) 1s also possible dependmg on the availability and compat1bil(cid:173)
`icy g,f the AMPS PAs. In the mobile telephone switching office (MTSO), the AMPS
`voice, ca·lls carried by the Tl links from the cell sites are multiplexed and connected to
`the publ'ic switched telephone network (PSTN). The CDPD network traffic from the
`cell site is also carried by the same shared Tl links, and in the MTSO this multiplexed
`c!lara ttaffic uses a configured router as the gateway to the terrestrial IP/OSI data net(cid:173)
`w0rks. Figure 1.3 shows the relationship of the CDPD overlay with the AMPS infra(cid:173)
`structure.
`
`1.2.3 Dedicated and Shared RF Channels
`
`The frequency allocation scheme in a carrier's AMPS network and the carrier's pref(cid:173)
`eFence in phasing in of the CDPD network will largely determine the configuration of
`fre~uenoies for use by the CDPD network. In an AMPS system, each cell will have
`multiple radios and a set of frequencies assigned to the cell. Similarly, the CDPD
`system will have a frequency pool configured for each of the cell. In a typical
`AMPS/CDPD setup, the cell configuration (sectored, omni, etc. ), and the RF foot
`print for the AMPS and CDPD will be as closely matched as possible.
`The CDPD use of the frequencies allocated for AMPS fall into two different
`groups: dedicated frequencies and shared frequencies.
`
`II5Jedicated Frequencies
`
`l hese are frequencies assigned by the carrier for sole use by the CDPD network. The
`CDPD hardware/software do not implement special procedures to monitor the use of
`11\ese "dedicated" frequencies by other network(s).
`In, this case, the cooperating AMPS system RF-engineeri ng personnel must
`manually enforce that the AMPS frequency pool does not include any dedicated fre(cid:173)
`quencies marked for use by the CDPD system. Failure to continually establish this
`mutually exclusive frequency allocation condition every time a new frequency plan
`
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`

`

`8 CELLULAR DIGITAL PACKET DATA
`
`AMPS
`quipman
`
`Mobile
`Swi1cning
`CMtar
`(MSC)
`
`AMPS
`Equipmool
`
`Base Station
`
`COPO
`Equipmoot
`Mobile Data
`Bate Station
`(MOSS)
`
`To>icallv, the
`COPO i 1--slots
`are add~ to
`spare slots In Iha
`'1xiating AMPS THinkl
`
`COPO
`Equipment
`
`Mobile Oeta
`lntennediata
`~•tam
`(MDIS)
`
`lntenne6ote
`System (IS)
`
`(Router)
`
`Call Site
`
`MTSO
`(Mobile Teklphone Switching Office)
`
`FIGURE 1.3 CDPD overlay with AMPS.
`
`for AMPS is established and implemented will result in the CDPD system interfering
`with voice,
`
`Shared Frequencies
`
`The frequencies that the AMPS and the CDPD can share are called shared frequen·
`cies. The AMPS system is not expected to be aware of any other potential users of its
`frequencies. It is the responsibility of the CDPD system to use the shared frequencies
`when the AMPS system is not using it (a call is not active on chat frequency) and ro
`relinquish the frequency when the AMPS starts using it before causing any undue
`
`Page 22 of 56
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`

`

`Introduction 9
`
`ference with the voice system. Special hardware that sniffs voice frequencies and
`. .
`iuter ers a carrier switchoff within 40 ms from the time of detection needs to be em(cid:173)
`
`trt:;ed in the CDPJ? necwor~ f~r harmonious_ sha:ing of freq~encies. 1:'his stringent
`
`P •tc:;boff time requirement eliminates any audible mterference m the vmce system by
`sW~ving the CDPD carrjer from the air during the initial setup time of the voice call,
`re fore the beginning of any voice activity.
`be CDPD design allows the switched off carrier (on detection of voice activity) to
`be replaced with another "available" frequency by the base station, and has proce(cid:173)
`dur,es implemented in the M-ESs to search and tune to a new frequency, making the
`lraosition transparent to the application. In CDPD i~plementations we can_ find both
`~»figurations. In markets where there are frequencies available for exclusive use by
`rhe CbPD, the carriers tend to prefer a dedicated channel CDPD setup. This simpli(cid:173)
`fies,the CDPD hardware, and hence the cost, as sniffing subsystem hardware is not
`t:e'1)uired. In addition, this simplifies the operational software in the CDPD system
`and minimizes the chance for interference with the more important (revenue-wise)
`1;1<'>ke system. The inefficiency in the data transfer mechanism arising from interrup(cid:173)
`cien due to channel "hopping" that occurs in a shared frequency CDPD configura(cid:173)
`ti@n..i also avoided.
`
`1.2.4 Network Connectivity
`
`6)ne of the main objectives in the CDPD network specification and design is to use
`the functionally proven and extensively deployed existing data network infrastruc(cid:173)
`rure as an integral part of the CDPD network.
`The open system interconnection (OSI) protocol suite is based on the OSI refer(cid:173)
`ence model defined by the International Organization for Standardization and lnter(cid:173)
`ngt(0nal Electrotechnical Committee (ISO/IEC). Although OSI is predicted to become
`mie primary networking solution of choice in the next several years existing OSI im(cid:173)
`pJementations are few and skeletal. In contrast, TCP/IP-based networks have pro