TM
`
`Telecom Dictionary
`
`Ray Horak
`
`Wiley Publishing, Inc.
`
`

`

`Webster’s New World® Telecom Dictionary
`
`Published by
`Wiley Publishing, Inc.
`10475 Crosspoint Boulevard
`Indianapolis, IN 46256
`ŒŒŒCŒ~zŽCx„‚
`
`Copyright © 2008 by Wiley Publishing, Inc., Indianapolis, Indiana
`
`Published simultaneously in Canada
`
`ISBN: 978-0-471-77457-0
`
`Manufactured in the United States of America
`
`10 9 8 7 6 5 4 3 2 1
`
`Library of Congress Cataloging-in-Publication Data
`
`Horak, Ray.
`Webster’s New World telecom dictionary / Ray Horak.
`p. cm.
`ISBN 978-0-471-77457-0 (pbk.)
`1. Telecommunication—Dictionaries. I.Title.
`TK5102.H65 2007
`621.38203—dc22
`
`2007024232
`
`No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means,
`electronic, mechanical, photocopying, recording, scanning or otherwise, except 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) 646-8600. Requests to the Publisher for permission should be addressed to the Legal Department,
`Wiley Publishing, Inc., 10475 Crosspoint Blvd., Indianapolis, IN 46256, (317) 572-3447, fax (317) 572-4355, or online at
`http:/
`/ www.wiley.com/ go/ permissions.
`
`Limit of Liability/ Disclaimer of Warranty:The publisher and the author make no representations or warranties with respect
`to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without
`limitation warranties of fitness for a particular purpose. No warranty may be created or extended by sales or promo-
`tional materials.The advice and strategies contained herein may not be suitable for every situation.This work is sold
`with the understanding that the publisher is not engaged in rendering legal, accounting, or other professional services. If
`professional assistance is required, the services of a competent professional person should be sought. Neither the publisher
`nor the author shall be liable for damages arising herefrom.The fact that an organization or Website is referred to in this
`work as a citation and/ or a potential source of further information does not mean that the author or the publisher endorses
`the information the organization or Website may provide or recommendations it may make. Further, readers should be
`aware that Internet Websites listed in this work may have changed or disappeared between when this work was written
`and when it is read.
`
`For general information on our other products and services please contact our Customer Care Department within the
`United States at (800) 762-2974, outside the United States at (317) 572-3993 or fax (317) 572-4002.
`
`Trademarks: Wiley, the Wiley logo,Webster’s New World, the Webster’s New World logo,We Define Your World, and
`related trade dress are trademarks or registered trademarks of John Wiley & Sons, Inc. and/ or its affiliates, in the United
`States and other countries, and may not be used without written permission. All other trademarks are the property of
`their respective owners.Wiley Publishing, Inc., is not associated with any product or vendor mentioned in this book.
`
`Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available
`in electronic books.
`
`

`

`100Base-T4
`
`6
`
`100Base-T4 A 100Base-T extension that specifies Cat 3 or better unshielded twisted pair (UTP),
`operating in either half-duplex (HDX) or full duplex (FDX) over distances up to 100 meters. See also
`100Base-T, Cat 3, FDX, HDX, and UTP.
`
`100Base-TX A 100Base-T extension that specifies Cat 5 or better unshielded twisted pair (UTP),
`operating in either half-duplex (HDX) or full duplex (FDX) over distances up to 100 meters. See also
`100Base-T, Cat 5, FDX, HDX, and UTP.
`
`100VG-AnyLAN (100 Mbps Voice Grade Any LAN) Standardized as IEEE 802.12, 100VG-AnyLAN
`supports Ethernet,Token Ring, and other LAN standards, incorporating a collisionless polling technique.
`The standard is considered obsolete, having been overwhelmed by Ethernet. See also Ethernet, IEEE, and
`Token Ring.
`
`1000Base-LX (1000 Mbps; Baseband; Long range) The IEEE 802.3z media specifications for Giga-
`bit Ethernet (GbE) transmission over multimode fiber (MMF) and single-mode fiber (SMF), using a wave-
`length of 1300 nm and 1310 nm, respectively. The modal bandwidth for the MMF options ranges from
`400 MHz/ km to 500 MHz/ km, and maximum distance is 550 meters.The letter X indicates that 8B/ 10B
`signal encoding technique is used. See 802.3z for comparisons. See also 8B/ 10B, IEEE, MMF, modal band-
`width, and wavelength.
`
`1000Base-SX (1000 Mbps; Baseband; Short range) The IEEE 802.3z media specifications for
`Gigabit Ethernet (GbE) transmission over multimode fiber (MMF) with a core diameter of either 50µ or
`62.5µ, using a wavelength of 850 nm.The modal bandwidth ranges from 160 MHz/ km to 500 MHz/ km,
`and maximum distance ranges from 220 meters to 550 meters.The letter X indicates that 8B/ 10B signal
`encoding technique is used. See 802.3z for comparisons. See also 8B/ 10B, IEEE, MMF, modal bandwidth,
`and wavelength.
`
`1000Base-T (1000 Mbps; Baseband;Twisted pair) An IEEE standard (802.3ab, 1999) similar in con-
`cept to the predecessor 10/ 100Base-T, 1000Base-T translates to 1000 Mbps (theoretical transmission rate)
`Baseband (one transmission at a time over a single, shared channel), over Twisted pair media.The original
`specifications called for Cat 5 cable to support Gigabit Ethernet (GbE) over four pairs and distances up to
`100 meters. Cat 6 cabling specifications include unshielded twisted pair (UTP), shielded twisted pair
`(STP), and screened twisted pair (ScTP) rated at 250 MHz over distances up to 220 meters. See also
`10Base-T, 100Base-T, baseband, Cat 5, Cat 6, channel, Ethernet, GbE, hub, IEEE, repeater, ScTP, standard, STP,
`transmission rate, and UTP.
`
`1010XXX The number format in the United States for accessing an interexchange carrier (IXC) for
`casual callers without a presubscription agreement with an IXC and for dial-around purposes in the event
`that the presubscribed carrier is suffering from network congestion or a failure.The format originally was
`10XXX, but competition encouraged the formation of so many IXCs that the format had to be expanded.
`See also IXC and presubscription.
`
`1394 The IEEE specification for a data transport bus between a host computer and peripherals, such as
`high-density storage devices and high-resolution still and video cameras, and is designed to eliminate the
`bottleneck at the serial port of a LAN-attached PC. 1394 increases the speed of the Small Computer System
`Interface (SCSI) to100, 200, and 400 Mbps to support take full advantage of high speed LANs. A single
`1394 port can support up to 63 peripherals over a six-conductor cable up to 4.5 meters in length, and as
`many as 16 cables can be daisy-chained to extend the total length to as much as 72 meters. IEEE 1394
`is known as FireWire in Apple Computer terminology. See also bus, daisy chain, host, LAN, PC, peripheral,
`and SCSI.
`
`1xEV-DO (one carrier EVolution-Data Optimized) A high data rate (HDR) version of Code
`Division Multiple Access 2000 (CDMA2000) that employs 16-QPSK modulation in support of a peak
`data rate of 2.4 Mbps on the downlink and 153 kbps on the uplink. In a fully loaded cell, 1xEV-DO
`supports average aggregate throughput of 4.1 Mbps on the downlinks and 660 kbps on the uplinks.
`
`

`

`7
`
`23B+D
`
`1xEV-DO can run in any band and can coexist in any type of network. See also 16-QPSK,
`CDMA2000, downlink, modulation, throughput, and uplink.
`
`1xRTT (one times Radio Transmission Technology) The initial version of CDMA2000, with one
`times referring to standard channel width). See CDMA2000.
`
`256-QAM A variation on the quadrature amplitude modulation (QAM) signal modulation scheme.
`256-QAM yields 256 possible signal combinations, with each symbol representing eight bits (28 = 256).
`The yield of this complex modulation scheme is that the transmission rate is eight times the signaling rate.
`In the United States, 256-QAM is used in digital CATV applications. See also amplitude, bit, modulation,
`QAM, signal, signaling rate, symbol, and transmission rate.
`
`2B+D Synonymous with basic rate interface (BRI) and basic rate access (BRA). Referring to the ITU-T
`specification for an ISDN interface supporting two bearer (B) channels and one data (D) channel. See also
`ISDN and BRI.
`
`2B1Q (2 Binary 1 Quaternary) A line coding technique, with echo cancellation, used in North
`America for ISDN basic rate interface (BRI). 2B1Q is a form of pulse amplitude modulation (PAM) that
`uses four (i.e., quaternary) levels of amplitude (i.e., voltage), each of which represents two adjacent bits in
`a bit stream, and is accomplished by varying the voltage at nominal levels of ±1 (actually 0.833) and ±3
`(actually 2.5) volts, as illustrated in the accompanying figure. As 2B1Q impresses two bits on each baud,
`the baud rate is halved, and a baud rate of 80 kilobaud will support a signaling rate of 160 kbps. Because
`statistics force the line voltage to be positive half the time and negative half the time, on average, the sig-
`nal power lies at a frequency of 40 kHz, which is half the baud rate. 2B1Q also is the electrical line cod-
`ing technique used in high-bit-rate digital subscriber line (HDSL). 2B1Q also is known as 4-level pulse
`amplitude modulation (4 PAM). In European and many other countries, the line coding technique
`employed is 4 Binary 3 Ternary (4B3T). See also 4B3T, baud rate, bit rate, BRI, echo cancellation, HDSL,
`ISDN, and PAM.
`
`0
`
`1
`
`0
`
`0
`
`1
`
`1
`
`1
`
`0
`
`Baseband Digital Signal
`
`0
`
`1
`
`0
`
`0
`
`1
`
`1
`
`1
`
`0
`
`+3V
`
`+1V
`
`0V
`
`-1V
`
`-3V
`
`2B1Q Line Coding
`
`2 Binary 1 Quaternary (2B1Q) See 2B1Q.
`
`23B+D Synonymous with primary rate interface (PRI). Referring to the ITU-T specification for an
`ISDN interface supporting 23 bearer (B) channels and 1 data (D) channel. 23B+D is compatible with T1
`and J-1, and is used in North America and Japan. See also ISDN and PRI.
`
`

`

`53
`
`Barker code
`
`signals are equal in voltage to ground but opposite in polarity, which has the effect of reducing radiated
`energy and, therefore, reducing attenuation. See also unbalanced and UTP. 2. Referring to symmetrical rela-
`tionship. For example, the X.25 protocol suite includes Link Access Procedure-Balanced (LAP-B), a bal-
`anced protocol that operates in Asynchronous Balanced Mode (ABM), which refers to the fact that the
`devices have a balanced, rather than a master/ slave, relationship.Therefore, a device at either end of the link
`can initiate a dialogue at any time. See also ABM, LAP-B, master/ slave, and X.25.
`
`balun (balanced/ unbalanced) A passive device, often a transformer, used to couple an electrically bal-
`anced device, medium, or system and an electrically unbalanced device, medium, or system.A balun com-
`monly is used to connect an electrically balanced twisted pair to an electrically unbalanced coaxial cable.
`The term balun is a contraction of balanced to unbalanced transformer. See also balanced, coaxial cable, passive,
`transformer, twisted pair, and unbalanced.
`
`band A continuous group, or range, with an upper limit and a lower limit. In analog terms, the width
`of a band or channel is defined as the upper and lower frequencies in a range of frequencies.The ITU-T
`defines standard optical transmission windows in bands of wavelengths. See also bandwidth and window.
`
`band-pass filter A device that passes all signals in a designated frequency (electrical) or wavelength
`(optical) band, but absorbs, attenuates, blocks, rejects, or removes all other signals. See also absorption, atten-
`uation, band, electrical, frequency, high-pass filter, low-pass filter, optical, signal, and wavelength.
`
`bandwidth The measure of the capacity of a circuit or channel. More specifically, bandwidth refers (1)
`to the total frequency range on the available carrier in Hertz (Hz) for the transmission of data, or (2) the
`capacity of a circuit in bits per second (bps). There is a direct relationship between the bandwidth of an
`analog circuit or channel and both its frequency and the difference between the minimum and maximum
`frequencies supported. Although the information signal (bandwidth usable for data transmission) does not
`occupy the total capacity of a circuit, it generally and ideally occupies most of it.The balance of the capac-
`ity of the circuit may be used for various signaling and control (overhead) purposes. In other words, the
`total signaling rate of the circuit typically is greater than the effective transmission rate. In an analog trans-
`mission system, bandwidth is measured in Hertz (Hz). In a digital system, bandwidth is measured in
`bits per second (bps). See also bps, carrier, Hz, overhead, signaling and control, signaling rate, throughput, and trans-
`mission rate.
`
`bandwidth-on-demand Referring to capacity available through a network as required by an applica-
`tion, perhaps during the course of a call. Asynchronous transfer mode (ATM) offers guaranteed band-
`width-on-demand, at least theoretically, adjusting the amount of bandwidth required to support a call once
`the call is established and guaranteeing that it will be available when required. As an example, real-time
`compressed voice over ATM may require no bandwidth during periods of prolonged silence, but requires
`guaranteed bandwidth at precise intervals during periods of speech activity. Frame relay offers bandwidth-
`on-demand within the limits of the committed information rate (CIR), on average, and within the limits
`of the port speed, as resources are available. ISDN and some other network services also offer bandwidth-
`on-demand, defined in various ways. See also ATM, bandwidth, call, CIR, compression, frame relay, ISDN, port,
`and real-time.
`
`barge-in A feature of a key telephone system (KTS) or PBX, barge-in allows an authorized user from
`an authorized station to join, without invitation, an active call on a call in progress through the use of an
`authorization code the user enters via the telephone keypad. See also KTS, PBX, and station.
`
`Barker code A coding scheme used in direct sequence spread spectrum (DSSS) radio systems. Barker
`code is a sequence of N values of +1 and –1, with N equaling 2, 3, 4, 5, 7, 11, or 13 bits. IEEE 802.11b
`wireless LANs (WLANs) operating at 1 Mbps and 2 Mbps use an 11-bit Barker code, 10110111000.The
`code has certain mathematical properties that make it ideal for modulating radio waves. The basic data
`stream is subjected to a swap algorithm with the Barker code to generate a series of data objects called
`chips. Each bit is encoded by the 11-bit Barker code, with each group of 11 chips encoding one bit of
`
`

`

`Barker code
`
`54
`
`data.At 5.5 Mbps and 11 Mbps, 802.11b specifies the use of the more efficient complementary code key-
`ing (CCK). See also 802.11b, algorithm, bit, CCK, chip, DSSS, and WLAN.
`
`baseband 1. Refering to a signal in its original form, without being altered in any way, whether by
`modulation or conversion. 2. A single-channel transmission system, i.e., a transmission system that supports
`a single transmission at any given time. All contemporary wired local area networks (LANs) are baseband.
`See also broadband, channel, and LAN.
`
`base station (BS)
`
`See BS.
`
`basic input/ output system (BIOS) See BIOS.
`
`basic rate access (BRA) See BRA.
`
`basic rate interface (BRI) See BRI.
`
`basic service Pure and simple transmission capability over a communication path subject only to the
`technical parameters of fidelity and distortion criteria, or other conditioning. Basic service does not alter
`the form, content, or nature of the information. See also enhanced service and POTS.
`
`battery A connected group of (one or more) electrochemical cells that store electric charges and generate
`direct current (DC) through the conversion of chemical energy into electrical energy. See also common
`battery, DC, electricity, energy, and local battery.
`
`baud A signal event, signal change, or signal transition, such as a change from positive voltage to zero
`voltage, from zero voltage to negative voltage, or from positive voltage to negative voltage. The baud is
`named for Emile Baudot, inventor of the teletype. See also Baudot code and baud rate.
`
`Baudot, Emile (1845–1903) Best known as the inventor of the teletypewriter, or teletype, an auto-
`matic printing telegraph machine that used a typewriter-style keyboard rather than a telegraph key.As the
`dot-and-dash Morse code system was not highly compatible with this automated approach, he invented
`and patented (1874) a five-bit coding scheme that became known as Baudot code. See also Baudot code,
`Morse code, teletype, and typewriter.
`
`Baudot code A five-bit data coding scheme invented by Emile Baudot in the 1870s for use in the
`Baudot Distributor, a sort of automatic telegraph that supported higher speed transmission over a circuit
`between two synchronized electromechanical devices.The Baudot Distributor soon gave way to the tele-
`type (TTY), which also employed the Baudot coding scheme, subsequently known as International Telegraph
`Alphabet #2 (ITA #2). Updated in 1930, Baudot is limited to 32 (25) characters. Considering that each bit
`has two possible states (1 or 0), 5 bits in sequence yield 25 (32) possible combinations. Because 32 values
`is not sufficient to represent all 26 characters in the English alphabet, plus the 10 decimal digits, necessary
`punctuation marks and the space character, the shift key operates to shift between letters and other char-
`acters. Baudot employs asynchronous transmission, with start and stop bits separating characters.Telephone
`Devices for the Deaf (TDDs) and telex machines still use ITA #2. See also asynchronous transmission, code
`set, TDD, telegraph, telex, and TTY.
`
`baud rate The number of signal events, signal changes, or signal transitions occurring per second over
`an analog circuit, such as changes from positive voltage to zero voltage, from zero voltage to negative volt-
`age, or from positive voltage to negative voltage. The baud rate can never be higher than the raw band-
`width of the channel, as measured in Hz. Baud rate and bit rate, often and incorrectly, are used
`interchangeably.The relationship between baud rate and bit rate depends on the sophistication of the mod-
`ulation scheme used to manipulate the carrier. The bit rate and baud rate can be the same, if each bit is
`represented by a signal transition in a unibit modulation scheme.The bit rate can be higher that the baud
`rate, as a single signal transition can, and generally does, represent multiple bits. See also bit rate, carrier, and
`modulation.
`
`

`

`cdmaOne (code division multiple access One)
`
`90
`
`cdmaOne (code division multiple access One) A U.S. term for cellular radio systems based on
`EIA/ TIA IS-95a, and also known as CDMA Digital Cellular and Personal Communications System (PCS). See
`also cellular radio and PCS.
`
`CDMA2000 (Code Division Multiple Access 2000) A 3G cellular radio system based on earlier
`CDMA versions TIA/ EIA IS-95a and IS-95b, CDMA2000 has been standardized by the EIA/ TIA as IS-856
`and approved by the ITU-R as part of the IMT-2000 family. The initial version, known as CDMA2000
`1xRTT offers 2.5G capabilities within a single standard 1.25 MHz channel, effectively doubling the voice
`capacity of the predecessor 2G cdmaOne systems and offering theoretical data speeds up to 153 kbps
`through the use of quadrature phase shift keying (QPSK) modulation.An enhanced 3G version known as
`1xEV-DO is a high data rate (HDR) version that employs 16-QPSK modulation in support of a peak data
`rate of 2.4 Mbps on the downlink and 153 kbps on the uplink. 3x, also known as IS-2000-A, is an
`enhancement that uses three cdmaOne carriers for total bandwidth of 3.75 MHz. See also 16-QPSK,
`1XEV-DO, 1xRTT, 2G, 2.5G, 3G, 3x, bandwidth, carrier, CDMA, cdmaOne, cellular radio, downlink, IMT-
`2000, ITU-R, modulation, QPSK, and uplink.
`
`CDPD (Cellular Digital Packet Data) A method for data transmission over analog Advanced Mobile
`Phone System (AMPS) cellular radio networks. CDPD takes advantage of the natural idleness between dis-
`connections and connections during the break and make process to transmit packetized data at rates up to
`19.2 kbps, using either the Internet Protocol (IP) or the ISO Connectionless Network Protocol (CLNP).
`The frequency-agile CDPD modems search for available channels over which to send encrypted packets
`during the periods of channel idleness. Ultimately, CDPD proved too complex, too bandwidth-limited,
`and too expensive, especially as data-ready 2.5G and 3G networks made their appearances and analog cel-
`lular networks were phased out.The last of the CDPD networks were decommissioned around the end of
`2005. See also AMPS, analog, break and make, cellular radio, CLNP, encryption, IP, ISO, and modem.
`
`CDR (Call Detail Record). Synonymous with station message detail record (SMDR). See SMDR.
`
`CDSU (Channel Data Service Unit) Also known as a CSU/DSU. A combined channel service unit
`(CSU) and data service unit (DSU). See also CSU and DSU.
`
`In asynchronous transfer mode (ATM), the variation in actual cell trans-
`CDV (Cell Delay Variation)
`fer delay (CTD) and the expected transfer delay of an individual cell. CTV is a form of jitter, which can
`seriously degrade the quality of voice and video payloads. If cells arrive sooner than expected, the clump-
`ing can cause the peak cell rate (PCR) to be exceeded, and the excess cells to be discarded. If some cells
`arrive too late, the result may be gaps in the received information stream. Cell delay variation tolerance
`(CDVT) is a measurement of the maximum allowable CDV tolerance between two end stations. Peak-to-
`peak CDV is negotiated between the end station and the network, with peak-to-peak referring to the best
`case compared with the worst case, i.e., the difference between the earliest and the latest arriving cells on
`a connection. See also ATM, cell, CTD, jitter, payload, and PCR.
`
`In asynchronous transfer mode (ATM), a measurement of
`CDVT (Cell Delay Variation Tolerance)
`the maximum allowable cell delay variation (CDV) between two end stations. See also ATM, CDV, and cell.
`
`cell 1. In asynchronous transfer mode (ATM) and Switched Multimegabit Data Service (SMDS) net-
`works, a small protocol data unit (PDU) comprising 53 octets.The ATM cell consists of a header of 5 octets
`and payload of 48 octets.The small cell size offers the advantage of effectively supporting any type of data,
`including voice, fax, text, image, video, and multimedia, whether compressed or uncompressed and
`whether real-time or non-real-time. The fixed cell size offers the advantage of predictability, unlike the
`variable-length frames associated with services such as X.25, frame relay, and Ethernet, or the variable-
`length packets associated with the Internet Protocol (IP).This level of predictability yields much improved
`access control and congestion control. See also ATM, compression, Ethernet, frame relay, header, IP, non-real-time,
`packet, payload, PDU, real-time, SMDS, and X.25. 2. In radio systems, a relatively small geographical area
`
`

`

`cell tax
`
`92
`
`so the overhead accounts for approximately 10 percent of the cell. Additionally, there is overhead embed-
`ded in the payload attributable to Convergence Sublayer and Data Link Layer and Network Layer headers.
`See also ATM, Convergence Sublayer, Data Link Layer, header, Network Layer, octet, overhead, and payload.
`
`cell transfer delay (CTD) See CTD.
`
`Cellular Digital Packet Data (CDPD) See CDPD.
`
`cellular radio A radio system that positions numerous, low-power transmit/ receive antennas through-
`out a metropolitan area, thereby dividing a large area of coverage, or macrocell, into smaller microcells, or
`even smaller picocells. Allocated spectrum is divided into a number of bands and further subdivided into
`a number of voice grade channels.The bands are distributed among the cells and each frequency band can
`be reused in nonadjacent cells. The basic concept of cellular radio dates to 1947, when numerous, low-
`power transmit/ receive antennas were scattered throughout a metropolitan area to increase the effective
`subscriber capacity of specialized mobile radio (SMR) systems. The first prototype cellular radio system
`was developed by AT&T and Bell Labs in 1977. The first commercial cellular system was activated in
`Tokyo, Japan by Nippon Telephone and Telegraph (NTT) in 1979.The first commercial system in the United
`States was activated in Chicago in 1983.
`The coverage area of each individual cell overlaps those of neighboring cells, with the cell diameter
`generally a minimum of about one mile and a maximum of about five miles, sensitive to factors such as
`topography and traffic density.Approximately in the center of each cell is a fixed antenna known as a base
`station (BS) that establishes and maintains connections with mobile stations (MSs). As a mobile station
`moves out of the effective range of one cell, the call switches from one base station to another through a
`process known as handoff, in order to maintain connectivity at acceptable signal strength. The handoff is
`controlled through a mobile telephone switching office (MTSO), which is the functional equivalent of a
`central office in the public switched telephone network (PSTN).The MTSOs generally are interconnected
`and also provide connections to the PSTN. Cellular radio initially was analog in nature, although contem-
`porary systems are largely digital.Analog standards include Advanced Mobile Phone System (AMPS), Nar-
`rowband AMPS (N-AMPS),Total Access Communications System (TACS), and Nordic Mobile Telephone
`(NMT). Digital standards include Digital AMPS (D-AMPS), Global System for Global Communications
`(GSM), Personal Communications System (PCS), and Personal Digital Cellular (PDC). See also AMPS,
`analog, antenna, band, BS, channel, D-AMPS, digital, GSM, handoff, macrocell, microcell, MS, MTSO, N-AMPS,
`NMT, PCS, PDC, picocell, PSTN, SMR, TACS, and voice grade.
`
`CELP (Code Excited Linear Prediction) A family of voice compression algorithms used in voice
`over frame relay (VoFR), voice over Internet Protocol (VoIP), and in digital cellular radio systems based
`on cdmaOne and PDC standards. A key element of CELP and its variants is the construction and main-
`tenance of a codebook, which comprises binary descriptions of sets of voice samples. CELP gathers a set
`of 80 8-bit PCM voice samples, representing 10 milliseconds (ms) of a voice stream, in a buffer. CELP
`employs silence suppression to remove periods of silence and redundancy from the data set, normalizes the
`volume level, compares the resulting data set to a set of candidate shapes in the codebook, and selects the
`shapes that most closely match the actual data. (Note: CELP uses a stochastically overlapped codebook,
`with each entry sharing all but two samples with its neighboring entries.) CELP then transmits the index
`number of the selected code description and the average loudness level of the set of samples. Every 10 ms,
`the code is sent across the network in a block of 160 bits, yielding a data rate of 16 kbps, which is a com-
`pression ratio of 4:1, compared with toll quality PCM voice over the circuit-switched public switched tele-
`phone network (PSTN) at 64 kbps. At the receiving end of the transmission, the transmitted code is
`compared to the codebook, the PCM signal is reconstructed, and, eventually, the analog signal is recon-
`structed. See also algorithm, analog, binary, buffer, cdmaOne, circuit switching, compression, CS-ACELP, LD-
`CELP, PCM, µ/4 QPSK, PDC, PSTN, silence suppression, and toll quality.
`
`centimeter (cm) See cm.
`
`centralized attendant service (CAS) See CAS.
`
`

`

`175
`
`exchange
`
`access charge approved by the Federal Communications Commission (FCC) and billed by the incumbent
`local exchange carrier (ILEC), the EUCL is intended to compensate the ILEC for the costs of connect-
`ing a call to competitive local exchange carrier (CLEC) or an interexchange carrier (IXC) through local
`exchange facilities (the local loop, central office, and associated equipment), maintaining the equal access
`database, and other related costs.The EUCL applies to all ILEC local loops, but varies by type of facility
`(e.g., residence line, business line, and CO trunk). If the access circuit is digital in nature, a Digital Port
`Line Charge (DPLC) also applies. See also CLEC, DPLC, equal access, FCC, ILEC, and IXC.
`
`euphemism An agreeable, inoffensive, less offensive, or politically correct (PC) synonym for a word or
`phrase that is harsh, unpleasant, or offensive. For example, eccentric is a euphemism for someone who is
`crazy and rich, as opposed to being just plain crazy like the rest of us poor folks. See also Bless his heart,
`leverage, and PC.
`
`European Computer Manufacturers Association (ECMA) See Ecma International.
`
`European Conference of Postal and Telecommunications Administrations (Conférence
`Européenne des administrations des Postes et des Télécommunications or CEPT) See CEPT.
`
`European Radio Message System (ERMES) See ERMES.
`
`European Telecommunications Network Operators’ Association (ETNO) See ETNO.
`
`European Telecommunications Standards Institute (ETSI) See ETSI.
`
`EV (EVolution-Data Optimized) See EV-DO.
`
`EV-DO (EVolution-Data Optimized) Also known as 1xEV-DO (one carrier EV-DO). A high data
`rate (HDR) version of Code Division Multiple Access 2000 (CDMA2000). Revision 0 (Rev 0) employs
`16-QPSK modulation in support of a peak data rate of 2.4 Mbps on the downlink and 153 kbps on the
`uplink. In a fully loaded cell, 1xEV-DO supports average aggregate throughput of 4.1 Mbps on the down-
`links and 660 kbps on the uplinks. 1xEV-DO can run in any band and can coexist in any type of network.
`Rev A supports peak speeds of 3.1 Mbps on the downlink and 1.8 Mbps on the uplink, and average speeds
`of 450-800 Mbps and 300-400 Mbps, respectively. Rev B, still under development, is anticipated to yield
`peak downlink speeds up to 4.9 Mbps per carrier, with as many as 3 carriers linked for aggregate peak
`downlink speed of 14.7 Mbps. See also 16-QPSK, CDMA2000, downlink, modulation, throughput, and uplink.
`
`Evolution-Data Optimized (EV-DO or EV) See EV-DO.
`
`EVRC (Enhanced Variable Rate Vocoder) A speech encoding mechanism specified in Personal
`Communications System (PSC) digital cellular radio standard IS-95a. EVRC runs at 13 kbps at maximum
`speech activity and varies the rate downward to as low as one-eighth rate if the level of speech activity
`permits. See also cellular radio, encode, and PCS.
`
`In frame relay, the maximum amount of data that the network will accept in a
`Excess Burst Size (Be)
`block from a user and will attempt to deliver without discard, if bandwidth is available, and over a speci-
`fied time interval (T). In recognition of the bursty nature of LAN-to-LAN communications, the transmit-
`ting device may burst above the Committed Information Rate (CIR) and Committed Burst Size (Bc) for
`a brief period of time; and the network will attempt to accommodate those bursts.The network reserves
`the option to mark the excess data above Bc as discard eligible (DE) should the user CPE not have done
`so already. See also bandwidth, CIR, CPE, DE, frame relay, LAN, and Maximum Burst Size.
`
`Excess Information Rate (EIR) See EIR.
`
`exchange 1. A central office exchange (CO or COE) of the public switched telephone network
`(PSTN) and all of the equipment contained therein for the purpose of interconnecting (i.e., exchanging
`
`

`

`flow
`
`188
`
`flow 1. Movement in a manner suggestive of a liquid. Movement in a smooth and gentle manner, like
`water in a stream. See also stream-oriented. 2. In telecommunications, a sequence of bits, bytes, datagrams,
`or packets between common endpoints identified by features such as network addresses and port numbers.
`See also bit, byte, datagram, endpoint, packet, and port.
`
`flow control The process of controlling the rate of data transfer in order to prevent data loss due to
`congestion, flow control is an element of many data communications protocols. Between a PC and a local
`printer, for example, there is a simple flow control mechanism that throttles back the data transfer rate from
`the PC to ensure that the printer is not overwhelmed and that the printer buffer memory is not exceeded.
`ATM, frame relay IPv6, and TCP include more complex flow control mechanisms to ensure that switches
`and routers are not overwhelmed. A rate-based mechanism is an end-to-end flow-control scheme that
`considers resources edge to edge, communicating