AUERBACH
`
`BEST PRACTICES SERIES
`
`. Broadband
`Networking
`
`Editor
`JAMES TRULOVE
`
`Telit Wireless Solutions Inc. and Telit Communications PLC Exh. 1015 p. 1
`
`

`
`library of Congress Cataloging-in-Publication Data
`
`Broadband networking / James Trulove, editor.
`p. cm.- - (Best practices)
`Includes bibliographical references and index.
`ISBN 0-8493-9821-5 (alk, paper)
`1. Local area networks (Computer networks). 2. Broadband communication systems. 3.
`Multimedia systems. 1. Trulove, James. 11. Series. 111. Best practices series (Boca Raton, Fla.)
`TK5103.4.B76525 1999
`004.6'8-dc21
`
`99-044955
`CIP
`
`This book contains information obtained from authentic and highly regarded sources. Reprinted
`material is quoted with permission, and sources are indicated. A wide variety of references are
`listed. Reasonable efforts have been made to publish reliable data and information, but the author
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`quences of their use.
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`
`© 2000 by CRC Press LLC
`Auerbach is an imprint of CRC Press LLC
`No claim to original U.S. Government works
`International Standard Book Number 0-8493-9821-5
`Library of Congress Card Number 99-044955
`Printed in the United States of America 1 2 3 4 5 6 7 8 9 0
`Printed on acid-free paper
`
`Telit Wireless Solutions Inc. and Telit Communications PLC Exh. 1015 p. 2
`
`

`
`Contents
`
`2
`
`3
`
`4
`
`5
`
`6
`
`7
`
`INTRODUCTION: THE CONVERGENCE OF MEDIA IN THE NElWORK ... xi
`PART I
`ISSUES IN MULTIMEDIA CONVERGENCE .......................... 1
`1
`Business Impact and Implications of Multimedia ...................... . 3
`Phil Evans
`Business Aspects of Multimedia Networking ................... ....... .. 11
`T M. Rajkumar and Amitava Haldar
`Broadband Applications and Technology Requirements .. ...... 23
`James W Conard
`Placing Images and Multimedia on the
`Corporate Network ........ ................. ....... ...................... ................. 35
`Gilbert Held
`Infrastructure Requirements for Reliable Converged
`Networking ........ ........................... ................ ... .................... .......... 47
`James Trulove
`Global Multimedia Networking: A Web of Controversy ........... 61
`Keith G. Knightson
`Integrating Voice and LAN Infrastructures and
`Applications ................ ................................. .............. ......... .... ...... 77
`David Curley
`TECHNOLOGIES FOR
`MULTIMEDIA CONVERGENCE ........................................... 95
`Multimedia Networking Technologies ..... ... ........... .............. ...... 99
`T M. Rajkumar and Amitava Haldar
`Integrated Services: The Multimedia Internet ...... .. ................ 113
`John Galgay
`Voice and Video on the LAN ..... .. ...... ...... .............. ..................... 139
`Martin Taylor
`Internet Voice Applications ........... ........... ....... .. ........................ 149
`Frank J Bourne
`Voice over Frame Relay .......................................... .................... 161
`Daniel Bahr and Wendy Roberts
`
`PART II
`
`8
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`9
`
`10
`
`11
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`12
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`vii
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`Telit Wireless Solutions Inc. and Telit Communications PLC Exh. 1015 p. 3
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`

`
`ix
`
`INDEX ............................................................................................................................ 527
`
`ABOUT THE EDITOR ............................................................................................... 525
`
`CONCLUSION: CONVERGING THE FUTURE ................................................... 517
`
`Dale Smith
`Access Architectures and Multimedia ..................................... 501
`G. Thomas des Jardins
`Multimedia Networks ................................................................. 487
`A Simulation Method for the Design of
`Luc T Nguyen
`Issues in Managing Multimedia Networks ............................... 479
`Erik Fretheim
`Managing the Multimedia Network .......................................... 457
`MULTIMEDIA SERVICES ............................................ : ...... 455
`MANAGEMENT AND DESIGN OF
`
`38
`
`37
`
`36
`
`35
`
`PART V
`
`Gerald L. Bahr
`Extending the Reach of Data ..................................................... 441
`Cellular Digital Packet Data (CDPD):
`Nathan J Muller
`Broadband Network Access ...................................................... 425
`Customer Premises Equipment (CPE) for
`James Trulove
`Wiring Media Support for Multimedia LANs ........................... 413
`Amin Lieman and Martin Miller
`Security of Wireless Local Area Networks ............................... 403
`
`34
`
`33
`
`32
`
`31
`
`Andres Llana, Jr.
`Wireless Communications for Voice and Data ........................ 391
`Gilbert Held
`Preparing for Cable Modems ..................................................... 383
`John R. Vacca
`Satellite Delivery of Data, Voice and Video Services .............. 371
`Gilbert Held
`Choosing Asymmetrical Digital Subscriber Lines (ADSL) ..... 363
`Andres Llana, Jr.
`The Emerging Advantage of xDSL Technology ........................ 353
`CONVERGENCE SERVICES ............................................... 351
`DELIVERY OF MULTIMEDIA
`
`John R. Vacca
`Backbone ...................................................................................... 335
`Convergence of IP, ATM, and SONET /SDM at the
`G. Thomas des Jardins and Gopala Krishna Tumuluri
`ATM LAN Emulation .................................................................... 317
`David H Axner
`ATM Cell Relay Transport for Broadband Services ................ 299
`G. Thomas des Jardins
`ATM Circuit Emulation Services ................................................ 291
`Tim Kelly
`Transport over Frame Relay: Issues and Considerations ...... 279
`Roohollah Hajbandeh
`T1, T3, and SONET Networks .................................................... 259
`MULTIMEDIA CONVERGENCE ......................................... 257
`TRANSPORT SERVICES FOR
`
`Frederick W Scholl and Gilbert Held
`Networking Approaches for Multimedia LANS ....................... 243
`Jeffrey Weiss
`Bandwidth Utilization ................................................................. 229
`Video Compression Techniques and
`Gilbert Held
`Working with Images in Client/Server Environments ............. 221
`Johnny S. KWong, Prerana Vaidya, and Armin R. Mikler
`Dynamic Bandwidth Allocation in Broadband ISDN ............... 211
`Christine Perey and Matthew Feldman
`Videoconferencing over IP Networks ....................................... 193
`John Fiske
`Building an IP PBX Telephony Network ................................... 185
`Daniel A. Kosek
`Voice Compression and Silence Suppression .......................... 175
`
`viii
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`30
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`29
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`28
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`27
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`26
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`PART IV
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`25
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`24
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`23
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`22
`
`21
`
`20
`
`PART III
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`19
`
`18
`
`17
`
`16
`
`15
`
`14
`
`13
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`441
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`0-8493-9821-5/00/$0.00+$.50
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`. © 2000 by CRC Press LLC
`
`the same channel in an adjacent cell.
`(as shown in Exhibit 34.1) so that channels can be reused without having
`One method of channel reuse is to divide the channels into seven groups
`
`market giving 416 channels per licensee.
`sion (FCC) licenses 832 channels to a cellular market, with two licenses per
`transmit and receive) capability. The Federal Communications Commis(cid:173)
`mission and one for reception, providing full-duplex (Le., simultaneous
`frequency (RF) channels. Each channel has two frequencies, one for trans(cid:173)
`serviced is divided into individual cells. Each cell has its own set of radio
`The cellular telephone system gets its name from the fact that an area to be
`CELLULAR TELEPHONY
`
`is implemented.
`phone system technology -and then describes CDPD technology and how it
`telephone companies and the Internet. This chapter reviews cellular
`as well as other hardwire networks that are already in place, such as the
`CDPD takes advantage of the existing cellular telephone infrastructure
`
`dream.
`technologies that ultimately will help achieve what is now an elusive
`anywhere in the world. Cellular digital packet data (CDPD) is one of the
`ness in the field is for a universal digital dial tone that they can use from
`The dream of business travelers and employees who need to conduct busi(cid:173)
`
`Gerald L. Bahr
`
`I
`
`• I
`
`come with the efficient and timely flow of mission-critical information.
`applications. In doing so, they can realize competitive advantages that
`rier-provided broadband services to support bandwidth-intensive
`ment and standardized interfaces, users can access new and emerging car(cid:173)
`to reap the advantages of broadband services. With the appropriate equip(cid:173)
`
`DELIVERY OF MULTIMEDIA CONVERGENCE SERVICES
`
`Telit Wireless Solutions Inc. and Telit Communications PLC Exh. 1015 p. 5
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`

`
`443
`
`tion (OSI) architecture. The design of many CDPD systems uses another
`
`The CLNS protocol is a centerpiece of the Open Systems Interconnec(cid:173)
`
`vidually according to its destination.
`tionless network services (CLNS) protocol, which routes each packet indi(cid:173)
`open networking architectures. Specifically, CDPD supports the connec(cid:173)
`connectionless networking protocols and supports several of the leading
`Protocol Support. CDPD can be used in conjunction with most existing
`
`or better can be expected.
`modulation. It is connectionless oriented. A bit-error rate of nearly 3 x 108
`algorithm. It is designed to be a robust, reliable protocol and uses digital
`Reliability. CDPD employs the Reed-Solomon forward error-correcting
`
`paragraphs.
`benefits provided by CDPD are discussed briefly in the following
`protocol support, quick setup time, coverage, and competitive pricing. The
`CDPD is often chosen for remote wireless service because of its reliability,
`
`The Benefits of CDPD
`
`Ameritech, Comcast, and Sprint Cellular.
`Mobilenet, Bell-Atlantic-NYNEX Mobile, AT&T Wireless, Vanguard Cellular,
`CDPD network services are currently being implemented by GTE
`
`It Monitoring vending machines.
`• Product, inventory levels, and pricing information.
`• Internet access.
`CD Information service, such as for taxi and truck dispatching.
`It Field service for checking of sales calls by sales representatives.
`4& Silent alarms that show the location, cause, and time of event.
`It Road traffic reports.
`
`III Filing health care insurance claims from on-site and the retrieval of
`It Home or remote-site monitoring through the use of telemetry.
`• Credit card authorization machines (e.g., for use by taxi drivers).
`
`patient data by medical personnel.
`
`• Remote data base access and mobile office functions (e.g., facsimile
`
`and e-mail).
`
`Some typical applications for CDPD use are:
`
`channels just for data traffic.
`fic has priority over CDPD traffic, the service provider may reserve some
`knows that data was being transmitted on the channel. Although voice traf(cid:173)
`traffic and switches to another channel so quickly that a voice user never
`carried on the channel. Using the snooping algorithm, CDPD detects voice
`without excessive loading or interference to the voice traffic that is being
`
`442
`
`channel hopping, CDPD technology fills this idle time with digital data,
`very heavy traffic loads. By using a very fast "snooping algorithm" and
`Statistically, a voice channel is idle 30% or more of the time, even during
`
`col (TCP /IP) can be achieved.
`of up to 19.2K bps over the Transmission Control Protocol/Internet proto(cid:173)
`voice channels during idle channel times. Using this technique, a baud rate
`CDPD breaks the data into packets and transmits them over the cellular
`
`information on the same channels used by cellular telephones.
`specification provides the ability for mobile data users to transmit digital
`specification (release 1.0) in July 1993 and began deployment in 1994. The
`Pacific Telesis Group, and Southwestern Bell Corp. -published its CDPD
`operating companies -Ameritech Corp., Bell Atlantic Corp., Nynex Corp.,
`A consortium comprising McCaw Cellular, GTE Corp., and five regional Bell
`
`HOW CDPD WORKS
`
`number of users can be accommodated.
`erage. By reusing the frequencies in adjacent cells, a virtually unlimited
`the size of the cell shrinks in diameter, and cells are added to provide cov(cid:173)
`mize range without adjacent channel interference. As the use increases,
`transmitted power as well as the mobile radio's transmit power to maxi(cid:173)
`the hand off. The MTSO monitors the RF signal strength and adjusts its own
`signal from one cell to another, generally without the user being aware of
`The power of the cell structure is realized by the MTSO handing off the
`
`local access transport area and long-distance service providers.
`mobile telephone switching office (MTSO). The MTSO then connects to the
`according to location. Each transmitter and receiver is connected to the
`in diameter. Each cell has its own set of frequencies, which alternate
`Depending on the number of users, a cell's size ranges from 1 to 20 miles
`
`Exhibit 34.1 Cellular Telephony: Channel Reuse
`
`Cellular Digital Packet Data (CDPD): Extending the Reach of Data
`
`DELIVERY OF MULTIMEDIA CONVERGENCE SERVICES
`
`Telit Wireless Solutions Inc. and Telit Communications PLC Exh. 1015 p. 6
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`

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`445
`
`411 Traffic count in bytes and packets.
`• The number of active, registered, and rejected users.
`
`In addition, the MD-IS is a source of useful statistics regarding:
`
`encryption for the wireless data link.
`ing usage information to an accounting application, and providing
`
`• Move serving functions for maintaining a registration directory, feed(cid:173)
`
`transfers to another cell.
`scribers' M-ESs and providing forwarding instructions when an M-ES
`@ Mobile home functions for maintaining a directory of registered sub(cid:173)
`
`landlines. It also provides directory functions, such as:
`formance, and managing traffic connection between mobile users and
`ment modules for authenticating and locating subscribers, monitoring per(cid:173)
`frame-relay network. It acts as an interface to administration and manage(cid:173)
`either from the same MDBS or another one or to a fixed end system via a
`CDPD system. It routes traffic between the MDBSs and other M-ES users
`The Mobile Data intermediate System (MD-iS). The MD-IS is the heart of a
`
`ing, and predictive hopping.
`planned hops) through the use of adaptive hopping, channel snoop(cid:173)
`• Voice channel monitoring of channel hopping (Le., both forced and
`
`checking, and Reed-Solomon decoding.
`
`-Reverse channel (to the MDBS) through data packetization, error
`
`frame recognition, frame delimiting, and Reed-Solomon encoding.
`
`-Forward channel (to the M-ES) through error detection and correction,
`s Media access control through the data link relay, including control of the:
`
`synchronization.
`mation, best hopping list, current cell information, and
`-Forward-channel (Le., M-ES) messaging, such as adjacent cell infor-
`-Radio channel selection and configuration.
`. management of:
`• Managing the radio resource through the airlink interface, including
`
`that transmits and receives data from the M-ES. MDBS functions are:
`
`The Mobile Data Base Station (MDBS). The MDBS is the part of the system
`
`part of, or mounted in, a computer, a car, or a handheld unit.
`that sends and receives data from the mobile data base station. It can be
`The Mobile End Station (M-FS). The M-ES is actually a wireless modem
`
`The four basic network elements are shown in Exhibit 34.2 and
`
`described in the following paragraphs
`
`link technologies.
`include new OSI network layer standards, such as IPv6 and alternative air(cid:173)
`
`444
`
`port new technologies at various levels of interconnection. Examples
`CDPD is an open architecture that is designed to accommodate and sup(cid:173)
`The CDPD Architecture
`
`the actual amount of data transferred rather than for connection time.
`
`Charges. Unlike the charges for cellular service, CDPD charges are for
`
`Data Rate. CDPD supports data rates at 19,200 bps, with a realized
`
`throughput of approximately 9,600 bps.
`
`ers keeps pricing and service offerings competitive.
`choice of providers for the service. The wider number of available provid(cid:173)
`ensures a
`which is provided by more than one provider in a given area -
`
`Competitive Pricing. CDPD's use of existing cellular phone technology -
`
`erage that the cellular voice network does today.
`hybrid service have been fully deployed, they offer the same universal cov(cid:173)
`
`Coverage. Once CDPD and the recently adopted CDPD/circuit-switched
`
`seconds versus 20 to 30 seconds for a typical analog setup.
`
`Setup Time. A CDPD connection is typically established in less than 3
`
`cell, compared to nearly $1,000,000 if implemented separately.
`lar technology, the cost to install the service is approximately $50,000 per
`
`Leveraging the Existing infrastructure. Because CDPD uses existing cellu(cid:173)
`
`User Support. Because CDPD uses existing cellular technology, the num(cid:173)
`
`ber of users it can support is virtually unlimited.
`
`EUI-48) are allowed to decode the received data.
`the manufacturer). Only M-ESs that have a valid equipment identifier (Le.,
`and a 24-bit unique CDPD mobile end station (M-ES) number (assigned by
`The EUI48 consists of the 24-bit company_id (assigned by the IEEE/RAC)
`
`Engineers (IEEE), as defined in the CDPD system specification.
`identifier (EUI-48) assigned by the Institute of Electrical and Electronics
`thus preventing the use of stolen modems. Each card uses an equipment
`mobile data intermediate system (MD-IS) also verifies user authentication,
`ping. Encryption and decryption use the RC4 encryption algorithm. The
`
`Security. The user's identity is protected, as is user data from eavesdrop(cid:173)
`
`the file transfer protocol.
`cols, such as the World Wide Web, the simple mail transfer protocol, and
`(IP), which in turn supports many Internet-related applications and proto(cid:173)
`and billing applications. In addition, CDPD supports the Internet protocol
`OSI protocol, the X.400 messaging standard, to pass data to the accounting
`
`Cellular Digital Packet Data (CDPD): Extending the Reach of Data
`
`DELIVERY OF MULTIMEDIA CONVERGENCE SERVICES
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`Telit Wireless Solutions Inc. and Telit Communications PLC Exh. 1015 p. 7
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`

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`447
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`correction code and detection information. This scheme allows for the
`bols that carry user data. The remaining 16 6-bit symbols carry the error(cid:173)
`symbols of 6 bits in length. The 63 symbols are divided into 47 6-bit sym(cid:173)
`Exhibit 34.3. This scheme provides for the data to be transmitted as 63
`COPO uses the Reed-Solomon (63,47) coding scheme as shown in
`
`without the need for retransmission.
`execute a decoding algorithm that provides recovery of the original data,
`error-correction bits. Even if some data bits are corrupted, the receiver can
`The forward error-correction algorithm pre-encodes the message with
`
`than consuming bandwidth for retransmissions.
`throughput is realized because it frees up bandwidth for new data rather
`missions than would a more typieal error-correction scheme. Greater
`the receiver, when they are detected. This prevents more potential retrans(cid:173)
`many satellite telemetry transmissions. It is used to correct problems at
`COPO uses the same type of forward error correction that is used with
`
`REED·SOLOMON FORWARD-CORRECTION ENCODING
`
`OSI protocols.
`frames arrive in the correct order, CDPD calls for higher-level Internet or
`wireline network or passed on to another mobile user. To ensure that the
`network management system (Le., MD-IS), where they are either sent to a
`a channel is free. The frames are picked up by the MOBS and passed to the
`the frame immediately; otherwise, it waits a random amount of time until
`of the idle/busy flag. If the flag indicates that the channel is idle, it transmits
`The M-ES transmitting device monitors the forward channel for the state
`
`collision-detection (CSMA/CD) protocol used with Ethernet devices.
`tion (DSMA/CD), which is similar to the carrier-sense-multiple-access-with(cid:173)
`using a protocol called digital-sense multiple access with collision detec(cid:173)
`frames are sent over one of the 30 KHz channels in the cellular network
`encrypted, and formatted into frames by the CDPD M-ES device. These
`Data from the transmitting device (e.g., laptop computer) is segmented,
`CDPD sends packet data on unused voice channels on the cellular network.
`
`The Technology
`
`network services administered and provided by the CDPD network operator.
`Internet and typically MCI, Sprint, and AT&T). Internal F-ESs are value-added
`works that are outside the control of the CDPD network operator (e.g., the
`which the CDPD provider wishes to connect. External F-ESs are those net(cid:173)
`
`The Fixed End System (F-ES). The F-ES is any normal wireline network to
`
`• Performance of data transfers between the MOBS and the M-ES.
`@ The number of retransmissions caused by errors.
`
`Cellular Digital Packet Data (CDPD): Extending the Reach of Data
`
`446
`
`DELIVERY OF MULTIMEDIA CONVERGENCE SERVICES
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`Telit Wireless Solutions Inc. and Telit Communications PLC Exh. 1015 p. 8
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`

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`449
`
`zeros to indicate that it is the last block in the transmission.
`indicator is interspersed into each code block. The last block contains all
`transmitted in a single burst to the mobile base station. A 7-bit continuity
`word that is used on the forward channel. Up to 64 encoded blocks may be
`The reverse-channel data is encoded by the same Reed-Solomon code
`
`The Reverse Channel
`
`that the mobile stations use, as provided by DSMA/CD.
`on the number of micros lots delay. This provides for the random access
`delay before trying to access the reverse channel again. The delay is based
`If the flag is set to the busy state, the mobile station initiates a random
`flag from the forward channel. If the flag is set to idle, it begins to transmit.
`A mobile end station wishing to transmit data, first checks the idle/busy
`
`next block of data.
`mobile base that the data was received correctly and that it can send the
`cessfully, the decode status flag is set on the reverse channel, notifying the
`
`When the mobile end station decodes the Reed-Solomon code word suc(cid:173)
`
`reverse channel is in use.
`is set to busy on the forward channel, notifying all other M-ESs that the
`detected from a mobile station (on the reverse channel), the idle/busy flag
`flags, and the Reed-Solomon blocks for error correction. When data is
`chronization word), a reverse-channel idle/busy status flag, decode failure
`the mobile station synchronization (using the 22-bit reverse channel syn(cid:173)
`
`The forward channel is received by all mobile stations. This provides to
`
`rection control block boundaries, and acquire reverse-channel flags.
`synchronize the DSMA/CD micros lot clock, determine forward error-cor(cid:173)
`The forward channel is used to transmit flags, which are in turn used to
`
`Exhibit 34.4 The Frame/Packet Format
`
`--------420 Bits in 21.875 ms ... 19.2K bps
`
`The Frame/Packet Format
`
`I IIIIII III1IIII
`)P I ~~o~::!t~"....
`
`and Detection
`
`•
`
`448
`
`tinuous except for the interruption of the radio frequency channel hopping.
`The forward channel (Le., base-ta-mobile channel) is considered to be con(cid:173)
`The Forward Channel
`
`algorithm.
`
`Encryption and decryption are provided using the built-in RC4 encryption
`
`zation signals that are discussed later in this chapter.
`bit block of data. Each block is then combined with the flags and synchroni(cid:173)
`code word over a 64-ary alphabet, using 6-bit symbols. This results in a 378-
`The resultant 282-bit block is then encoded by the Reed-Solomon (63,47)
`
`site. (The frame packet format is illustrated in Exhibit 34.4)
`274-bit data stream to detect cochannel interference from another MDBS cell
`Solomon encoding. An 8-bit color code is added to each block prior to each
`exclusive-ORed with a pseudorandom sequence generator after Reed(cid:173)
`enhance synchronization, the information and parity bits in each block are
`Synchronization is extremely important in decoding the packets. To
`
`ter than 2.75 x 108•
`Solomon (63,47) coding provides for an undetected error probability of bet-
`a raw data rate of 19.2K bps to approximately 9.6K bps. Use of the Reed(cid:173)
`the overhead for the forward error correction reduces that throughput from
`However, the reliability that Reed-Solomon provides does come with a price:
`rather than individual Os and Is, allowing the handling of bursts of errors.
`The Reed-Solomon coding system is based on groups of bits (Le., bytes)
`
`in each 378 bits transmitted.
`possibility to correct up to 8, 6-bit symbol errors, or up to 48 corrupted bits
`
`Exhibit 34.3 The Reed-Solomon Forward Error-Correction Code Block
`
`(i.e., Busy or Idle)
`Decode Status
`Flag Block
`
`47 6-Bit Data Symbols
`
`Reed-Solomon (63,47) Block
`
`(378 Bits)
`
`/\
`I B
`
`I
`
`I
`
`(User Data)
`
`Cellular Digital Packet Data (CDPD): Extending the Reach of Data
`
`DELIVERY OF MULTIMEDIA CONVERGENCE SERVICES
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`Telit Wireless Solutions Inc. and Telit Communications PLC Exh. 1015 p. 9
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`

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`451
`
`The physical layer provides the following functions:
`
`M-ES is transmitting at the correct radio frequency power output.
`level is measured at both the M-ES and the MOBS to determine whether the
`minimum-shift-keying modulation at the transmitters. The received signal
`width-time product of BwT 0.5. Data transmission uses Gaussian-filtered
`channel interference, a Gaussian pulse-shaping filter is used with a band(cid:173)
`
`Layer 1: Physical. To maintain channel bandwidth and avoid adjacent
`
`represented in Exhibit 34.6, is discussed in the folloWing paragraphs.
`to operate without change. The CDPD implementation of the OSI model,
`protocols. This design approach allows existing applications to continue
`CDPD design ensures that no impact is exerted on thetransport and higher
`
`The CDPD Implementation of the OSI Model
`
`• Layer 7' Application. This layer presents services to the end user.
`
`other formats for number representation or file formats.
`layer 7). Included are character formats, such as EBCDIC or ASCII and
`used when passing information to and from the application layer (Le.,
`• Layer 6: Presentation. The sixth layer negotiates the syntax that will be
`sessions, or logical links, between two logical names on the network.
`• Layer 5: Session. This layer supports logical naming and establishes
`
`for resending unacknowledged packets.
`such features as acknowledgments, sequence numbers, and time-outs
`transfer of end-to-end information between stations. It implements
`@ Layer 4: Transport. The fourth layer is responsible for the reliable
`
`Exhibit 34.5 The OSI Seven-Layer Model
`
`WorkstationJHost
`
`Gate.vay. Router, or Bridge
`
`Intermediate
`
`The OSI Seven-Layer Model
`
`Workstation/Host
`
`450
`
`and route information (Le., packets) to the appropriate networks.
`of data throughout the network. It must recognize network addresses
`Ii Layer 3: Network. This layer is responsible for the routing and switching
`
`the media access control and the logical link control layers.
`network using the services of layer 1. Layer 2 is also subdivided into
`The packet format, which layer 2 describes, is transmitted over the
`and rules for establishing a link with another device on the network.
`• Layer 2: Data Link. The second layer defines a basic packet structure
`
`the electrical encoding scheme are part of this layer.
`sent to, and received from the network. The raw transmission rate and
`• Layer 1: Physical. The first layer consists of the bit stream of data as
`
`model breaks down as follows:
`communications are explored in the next section.) The full seven-layer
`Exhibit 34.5. (The ways in which CDPD uses these first three layers for
`CDPD uses layers 1 through 3 of the seven-layer OSI model, as shown in
`
`The OSI Model
`
`model.
`nications protocols are at least compared to, if not developed around, this
`developed before OSI and even a few since, today virtually all data commu(cid:173)
`Systems Interconnection (OSI) model. Although many standards were
`the International Standards Organization developed the seven-layer Open
`In an effort to help make data communications more open and universal,
`
`munications protocols.
`X.2S, along with all of their physical and electrical properties, are also com(cid:173)
`they are not the only protocols used in networking. RS-232, RS-488 , and
`true that IP and the internetwork packet exchange (IPX) are protocols, but
`layer or transport layer as referenced by the OSI model are protocols. It is
`Unfortunately, many have come to the conclusion that only the network
`
`defined layer to another.
`rent) to the various software layers used to hand off information from one
`the physical connector and electrical properties (Le., both voltage and cur(cid:173)
`interface. For communications devices, a protocol covers everything from
`A protocol is a standard or method by which two entities communicate or
`
`What Is a Protocol?
`
`next packet.
`and implements an exponential back-off before trying to retransmit the
`decode status flag. If an error is indicated it immediately stops transmission
`to transmit until it detects an error in its received data, as signaled by the
`When the mobile station gains access to the reverse channel, it continues
`
`'\
`
`Cellular Digital Packet Data (CDPD): Extending the Reach of Data
`
`DELIVERY OF MULTIMEDIA CONVERGENCE SERVICES
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`Telit Wireless Solutions Inc. and Telit Communications PLC Exh. 1015 p. 10
`
`

`
`453
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`• Multiplexing of NPOUs from different layer-3 protocol entities onto a
`
`single data link connection.
`
`• Encryption and decryption of layer-3 NPOUs and exchange of encryp(cid:173)
`
`tion keys.
`
`ED CompreSSion and recovery of redundant protocol control information
`
`from NPOUs using the TCP /IP protocol.
`
`• Segmentation and reassembly of network protocol data units
`• Mapping of data primitives.
`
`(NPOUs).
`
`lowing functions to OSI layer 3 (Le., the network layer):
`SNOCP provides for connectionless-mode services and provides the fol(cid:173)
`
`Layer 3: The Subnetwork-Dependent Convergence Protocol (SNDCp).
`
`o A channel idle/busy flag. This flag notifies the system that the reverse
`
`channel is idle or busy.
`
`mobile base station.
`ous forward error-correction block was successfully decoded by the
`• A block decode status flag. This flag notifies the system that the previ(cid:173)
`
`flags used on the forward channel to control the reverse channel are:
`mobile) channel are used to signal the reverse channel. The two types of
`channel directly, periodic channel status flags on the forward (Le., base-to(cid:173)
`
`Because the mobile receiver cannot sense the status of the reverse
`
`Ethernet standard.
`technique is similar to the CSMA/CO protocol that is used in the IEEE 802.3
`the slotted reverse (Le., mobile-to-base) channel. As previously stated, this
`MAC-Layer Management. The OSMA/CO access method is used to control
`
`received blocks.
`encoding is used at the link layer to provide error correction in the
`coding is used to detect and correct transmission errors. Reed-Solomon
`transparency and frame boundary delimitation. Forward error-correction
`MAC layer. Flag sequence and zero-bit stuffing techniques maintain data
`of the information, the logical link