Glossary

   

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1000BaseT:

Gigabit Ethernet on unshielded twisted pair wire.

100BaseT:

100 Mb/s Ethernet on unshielded twisted pair wire.

10BaseT:

10 Mb/s Ethernet on unshielded twisted pair wire.

2B+D :

Two 64 kb/s B channels and one 16 kb/s D channel are transported by basic rate ISDN.

2B1Q:

2-Binary 1-Quaternary line code is used for BRI and HDSL. Binary information is represented by four amplitude levels.

3B2T:

A baseband line code where three binary bits are encoded into two ternary symbols.

4B3T:

A baseband line code where four binary bits are encoded into three ternary symbols.

AAA:

Authentication, authorization, and accountingthree security functions that occur when a user gains access to a networked system.

AAL2:

ATM Adaptation Layer 2The ATM adaptation layer that is optimized for the transport of multiple simultaneous voice sessions.

AAL5:

ATM Adaptation Layer 5The ATM adaptation layer that is optimized for the transport of packet-based protocols such as IP.

ABCD parameters:

The transfer characteristics of a two-port network describing the input voltage and current to the output voltage and current.

ABR:

Available bit rate, an ATM quality of service class where the network dynamically controls that cell rate from the source.

ac:

Alternating current.

ADPCM:

Adaptive differential pulse code modulation, 32 kb/s voice coding using ITU Rec. G.726.

ADSL:

Asymmetric digital subscriber line simultaneously transports highbit-rate digital information towards the subscriber, lower rate data from the customer, and analog voice via one twisted-wire-pair. Relevant standards: T1.413, ITU G.992.1, ITU G.992.2.

AFE:

Analog front end, functions include the analog-digital conversion, analog filter, and line driver.

AGC:

Automatic gain control, receiver adaptation to the received signal level so as to reduce dynamic range of the signal input to the analog-to-digital converter.

Aliasing:

Sampling a signal at intervals greater than Nyquist rate, resulting in the inability to accurately reproduce the signal.

AMI:

Alternate mark inversion line code, aka "bipolar," used for T1 transmission systems. Binary information is represented by pulses with three possible amplitudes.

ANSI:

American National Standards Institute; accredits standards bodies, for example: committee T1 for telecommunications.

AP:

Access point, wireless LAN hub or gateway.

API:

Application program interface. A defined set of parameters for communication with a software application.

ARP:

Address resolution protocol translates physical layer address to IP address.

ASCII:

American Standard Code for Information Interchange: Binary coding of 128 alphanumeric characters as 7 bits plus an optional eighth parity bit. Extended ASCII, which uses 8-bit coding, is more widely used today.

ASP:

Application service provider, generally hosts software on a server or gateway function.

ATIS:

Alliance for Telecommunications Industry Solutions sponsors Standards Committee T1.

ATM:

Asynchronous transfer mode. Link layer using 53 byte cells .

Attenuation:

The signal loss resulting from traversing the transmission medium.

ATU-C:

ADSL transmission unit at the central office side of the subscriber line. The ATU-C performs transceiver functions, including modulation, coding, and equalization.

ATU-R:

ADSL transmission unit at the remote side of the subscriber line. The ATU-R performs transceiver functions, including modulation, coding, and equalization.

AWG:

American wire gauge measure of conductor diameter for wires.

AWGN:

Additive white Gaussian noise.

B8ZS:

Bipolar with 8 zero substitution line code use for T1 transmission. Ones are encoded as pulses of alternating polarity and eight consecutive zeros are represented by a pulse of the same polarity as the previous pulse.

Baseband:

Transmission using a technique that places signal energy in a frequency band starting at approximately zero.

Baud:

A symbol or element modulated for transmission.

B Channel:

A 64 kb/s bearer channel used for ISDN.

BER:

Bit error ratio, the proportion of bits that are altered from their correct value.

Binder Group :

A bundle of twisted wire pairs that maintain close proximity throughout a section of telephone cable.

Biphase:

A baseband line code, also known as the Manchester line code.

Bit:

Binary digit.

Bit Stuffing:

Extra bit(s) that are conditionally inserted into the frame to adjust the transmitted bit rate.

BLEC:

Building local exchange carrier which provides access service within a multitenant building.

BLES:

Broadband loop extension service.

BRI:

Basic rate ISDN provides 2B+D transport.

See also [2B+D]

See also [ISDN]

Bridged Tap:

A wire stub connected to the transmission path .

Broadband:

Digital communication at bit rates above 128 kb/s.

Byte:

A group of eight bits.

CAC:

Connection admission control, which means to deny a connection if network capacity does not exist.

CAP:

Carrierless AM/PM is a line code similar to QAM used for some DSL systems.

CAS:

Channel associated signaling. Call signaling is conveyed within the same bearer channel as the call.

CAT5:

ANSI/EIA/TIA-568 standard category 5 unshielded twisted pair cable for LAN bit rates up to 100 Mb/s.

CBR:

Constant bit rate, a quality of service to assure a fixed bit rate and delay.

CCS:

Common channel signaling.

CLASS:

Telephone services such as call forwarding and caller name ID.

Class 5 Switch:

A central officebased telephone switch that directly serves an end-user.

CLEC:

Competitive local exchange carrier. An access service provider other than the incumbent carrier in a region.

CO:

Central office, aka local exchange. A building where telephone lines terminate and connect to transmission and switching equipment.

Codec:

Coder -decoder.

Companding:

Compressing the dynamic range of a signal prior to transmission, with matching expansion at the receiver to regain the original signal.

Convolutional code:

A code that depends on the current bit sequence and the encoder state.

CRC:

Cyclic redundancy check. An error detecting or correcting code.

Crest factor:

The ratio of peak to RMS signal voltage, also called peak-to-average-ratio, PAR.

Crosstalk (XTLK):

The unintentional electromagnetic coupling of a signal to other wire pairs in a cable.

See also [ NEXT ]

See also [FEXT]

CSA:

Carrier Serving Area loop design rules specify the characteristics of loops served by digital loop carrier sites.

CSMA/CA:

Carrier sense multiple access with collision avoidance , a media access control used by IEEE 802.11 wireless LAN.

CSMA/CD:

Carrier sense multiple access with collision detection, a media access control method used by Ethernet.

Cyclic Code:

An error correcting code implemented with a feedback shift register, for example, CRC.

CVoDSL:

Channelized voice-over DSL.

DA:

Distribution area is a loop serving area for a feeder distribution interface (FDI).

dB:

Decibel; ten times of the common logarithm of the ratio of relative powers.

dBm:

dB relative to one milliwatt.

dBrnc.

The logarithmic power ratio of a C-message weighted filtered signal with respect to 1 picowatt.

dc:

Direct current.

D Channel:

A 16 kb/s channel used by basic rate ISDN lines to carry signaling and packet information.

DDS:

Digital data service. A tarried private line data service using AMI-type transmission of symmetric rates from 1.2 to 64 kb/s.

DFE:

Decision feedback equalizer.

DFT:

Discrete Fourier transform. A signal transformation that is often implemented as a fast Fourier transformation on a digital signal processor.

DHCP:

Dynamic host configuration protocol. A protocol for assigning an IP address for the duration of a session.

Diffserv:

A protocol for providing control of quality of service on an IP network.

Digital Duplexing :

a highly flexible and high-performance duplexing system used by DMT VDSL.

Digital Loop Carrier:

See [DLC]

Discrete Time Domain:

Signal values that are defined at periodic time intervals.

Distribution cable:

The portion of the telephone loop plant that connects the feeder cable to the drop wires.

DLC:

Digital loop carrier. A system that is often located remotely from the central office to multiplex the service from many customer lines on to a high-speed line between the central office and the DLC remote terminal.

DMT:

Discrete multitone is a multicarrier transmission technique that uses a fast Fourier transform (FFT) and inverse FFT to allocate the transmitted bits among many narrowband QAM modulated tones, depending on the transport capacity of each tone.

Downstream:

Information flowing from the network to the customer.

Drop Wire:

The section of the local loop connecting the distribution cable to the customer premises.

DS0:

A 64 kb/s bit rate.

DS1:

A 1.544 Mb/s bit rate.

DS3:

A 44.736 Mb/s bit rate.

DSL:

Digital subscriber line may be used to indicated the basic rate ISDN transceivers and the local loop to which they are connected. May also be used to indicate all types of DSL.

DSM:

Dynamic spectrum management can be used to allow DSL systems to self-improve as a function of binder situation.

DSP:

Digital signal processing performs filtering and other signal modifications in the digital domain by first converting analog signals to a digital representation.

DSSS:

Direct sequence spread spectrum. Modulation method used by IEEE 802.11 wireless LAN.

DSX-1:

DS1 Cross-connect. A 1.544 Mb/s AMI signal used for short distances to interconnect equipment within a CO.

DTMF:

Dual tone multifrequency: Signaling used by touch-tone telephone.

DWMT:

Discrete wavelet multitone. A version of DMT that uses a wavelet type transform in place of the FFT.

See also [DMT]

E1:

A 2.048 Mb/s bit rate.

E3:

A 34 Mb/s bit rate.

EC:

Echo cancellation is a DSP-time domain technique for removing echos.

ECH:

Echo- canceled hybrid is a 2-to-4 wire conversion with echo cancellation. A hybrid transform is often used to interface to the line.

EMC:

Electromagnetic compatibility prevents unintended radio frequency interference.

EMI:

Electromagnetic interference.

EMS:

Element management system.

Encapsulation:

The addition of a protocol header to a protocol data unit

ES:

Errored second. An interval of one second containing one or more bit errors.

Ethernet:

A link layer local access network protocol using CSMA/CD media access control.

ETSI:

European Telecommunications Standards Institute.

FCC:

Federal Communications Commission is the U.S. government agency that regulates the radio, television, and telecommunications industries.

FDI:

Feeder distribution interface is a cabinet that contains a cross-connect field used to connect feeder cables to distribution cables.

FDM:

Frequency division multiplexing permits more than one information stream to be sent over a line by subdividing the line into separate frequency bands.

FEC:

Forward error control. Errors are corrected by the receiver using redundant information sent by the transmitter.

Feeder:

Cable between the central office and the FDI point.

FEXT:

Far end crosstalk results from transmitted signals being coupled to another wire pair interfering with the reception at the far end of the line.

FFT:

Fast Fourier transform. An algorithm for efficiently implementing via digital signal processors the conversion from the time domain to the frequency domain.

FHSS:

Frequency hopping spread spectrum.

FIR:

Finite impulse response. A FIR filter utilizes a limited number of delay and multiplication elements.

FM:

Frequency modulation uses changes in frequency of a carrier signal to represent information.

Fourier Transform:

Using a sinusoidal expansion to represent a signal.

Fractionally Spaced Equalizer:

An equalizer using multiples of the symbol rate.

Frame Relay:

A low-complexity wide area network packet protocol.

FTP:

File transfer protocol.

Full duplex:

Simultaneous transmission in upstream and downstream directions.

Galois field:

A closed algebra field used to describe an encoder or decoder.

Gateway:

A device that enables different types of networks to interwork.

Gaussian distribution:

A bell shaped distribution function, aka a normal distribution.

GDFE:

Generalized decision feedback equalization is a canonical design method for DSL systems with ISI and/or crosstalk.

G.lite:

ITU Recommendation G.992.2 for ADSL operating up to 1.5 Mb/s in the downstream direction.

GR-303:

A Telcordia developed interface between a NGDLC/DLC and a class 5 switch.

Half-Duplex:

Transmission that alternates the upstream and downstream information flow.

Hamming Distance:

The number of bits having a different value for a pair of code words.

HDLC:

High level data link control, a layer 2 protocol.

HDSL:

High-bit rate digital subscriber line permits 1.544 or 2.048 Mb/s symmetric transmission over two or three wire pairs which meet CSA design rules.

HDSL2:

Second-generation HDSL uses one pair of wires for 1.544 Mb/s symmetric transmission over CSA loops.

HEC:

Header error correction.

HTML:

Hypertext markup language, used to describe World Wide Web information.

HTTP:

Hypertext transfer protocol: protocol for World Wide Web messages.

HTU-C:

HDSL transmission unit at the central office side of the line. The HTU-C performs transceiver functions, including modulation, coding, and equalization.

HTU-R:

HDSL transmission unit at the remote side of the line. The HTU-R performs transceiver functions, including modulation, coding, and equalization.

IAD:

Integrated access device, a customer premises device that includes a DSL modem with voice and data functions.

IDFT:

Inverse discrete Fourier transform. A discrete form of the IFFT.

IDSL:

A DSL that used BRI transceivers to convey 128 kb/s packet-mode transport via a local loop.

IEEE:

Institute of Electrical and Electronics Engineers.

IETF:

Internet Engineering Task Force, develops Internet specifications.

IFFT:

Inverse fast Fourier transform. An algorithm for efficiently implementing via digital signal processors the conversion from the frequency domain to the time domain.

ILEC:

Incumbent local exchange carrier, the telephone service provider that was originally the sole service provider in a region.

ILMI:

Integrated network management protocol.

Impedance:

The relationship between the voltage applied to the resulting current.

Impulse Noise:

An unwanted signal of short duration often resulting from the coupling of energy from an electrical transient from a nearby source.

Impulse Response:

The time-domain response of a network to a impulse input.

IN:

Intelligent networkadvanced telephone services that make use of the SS7 network.

IP:

Internet protocol. Layer 3 protocol used as part of TCP/IP; used in the Internet, as well as private networks.

IPSec:

Internet protocol security.

ISDN:

Integrated services digital network, provides end-to-end digital circuit switched and packet switched transport.

See also [BRI]

ISI:

Intersymbol interference. Signal energy of a symbol that transfers into nearby symbols due to channel dispersion.

ISP:

Internet service provider.

ITU:

The International Telecommunications Union develops international standards. The telecommunications sector, ITU-T, was previously called the CCITT.

IWD:

Interworking device.

JPEG:

Joint photographic experts group, method for compressed digital still images.

kft:

Kilofeet, a thousand feet.

L2TP:

Layer 2 tunneling protocol, used with PPP to convey many packet streams via one connection.

LAN:

Local access network, a means to interconnect many digital devices within a few hundred meters .

Latency:

The time for information to flow between two points of a network.

LES:

Loop extension service.

Lifeline POTS:

Commonly used to describe voice service that is powered from the network, so that service does not depend on customer premises power. This is distinct from the meaning of "lifeline" for regulators, meaning voice service for low-income persons.

Line Code:

A modulation method.

Loaded Loop:

A loaded loop contains series inductors, typically spaced every 6 kft, for the purpose of improving the voice-band performance of long loops. However, DSL operation over loaded loops is not possible due to excessive loss at higher frequencies.

LMS:

Least mean square. An algorithm used for adaptive filters.

Loop, also local loop:

Another term for the telephone line connecting the customer premises to the telephone network.

Loopback:

A diagnostic test method whereby the signal received by an element is replicated and retransmitted to the source of the signal. In some cases, the system is taken out of service to perform the loopback.

LT:

Line termination. The LT is the DSL transceiver at the network end of the line.

MAC:

Media access control, the means to control access to the physical medium.

Margin:

Signal-to-noise ratio in excess of that necessary to attain a reference bit error rate.

MCM:

Multicarrier modulation, for example, DMT.

MDB:

Modified duobinary. A baseband line code.

MDF:

Main distributing frame. A wiring cross-connect field in the central office used to connect outside lines to CO equipment.

MEGACO:

Media gateway control protocol.

MIB:

Management information base, an SNMP object used to define the characteristics of a network element.

ML:

Maximum likelihood is an optimum method by which to detect transmitted messages in a receiver.

Modem:

Modulator /demodulator, a device that converts digital signals for efficient transmission and reception over a certain physical media.

MPEG:

Motion picture experts group of ISO, develops video compression standards.

MPLS:

Multiprotocol label switching

NAP:

Network access provider. The entity that provides a broadband access network which allows a user to connect to a service network.

NAT:

Network address translation.

NEXT:

Near-end crosstalk results in the signal transmitted from a wire pair coupling into another wire pair and interfering with the reception of signals at a receiver located at the same end of the line as the disturbing transmitter.

NGDLC:

Next generation digital loop carrier.

NIC:

Network interface card, a communications interface circuit card for a PC.

NID:

Network interface device, a connection point located at the demarcation between the network and the customer installation.

NSP:

Network service provider. The entity that provides a network that support services that can be accessed by a user via an access network.

NT:

Network termination. The NT is the DSL transceiver at the customer end of the line.

Nyquist Interval:

The maximum time between equally spaced samples necessary for accurate representation of a signal.

OCn:

Optical carrier of n times 51.84 Mb/s.

OSP:

Outside plant, telephone cable, supporting infrastructure (poles, ducts), midspan equipment (loading coils, repeaters, DLC), and FDI

Overhead Information:

Information other than end-user data.

PAM:

Pulse amplitude modulation.

Passband :

The modulation of signals which permits the placement of the modulated signal in a specified frequency band, for example, CAP, DMT, QAM.

PC:

Personal computer.

PCM:

Pulse code modulation, used for voice coding.

PDH:

Plesiochronous digital hierarchy, used for asynchronous multiplexed transmission.

PDU:

Protocol data unit.

PHY:

The physical layer of a communications stack.

Ping:

TCP/IP message used to measure packet transport latency.

PLL:

Phase locked loop. A feedback loop with narrow bandwidth used to recover signal timing.

PM:

Phase modulation use changes in the phase of a carrier signal to represent information.

POTS:

Plain old telephone service, circuit switched analog voice.

POTS splitter:

See [Splitter]

PPP:

Point-to-point protocol, used for session control.

PPPoE:

PPP over Ethernet. A protocol that extends multiple PPP sessions over an Ethernet interface.

PSTN:

Public switched telephone network. The traditional circuit switched voiceband network.

PVC:

Permanent virtual circuit. A provisioned ATM or frame relay connection.

QAM:

Quadrature amplitude modulation is a passband modulation technique that represents information as changes in carrier phase and amplitude.

QPSK:

Quadrature phase shift keying. A passband modulation method.

QoS:

Quality of service. Virtual circuit characterization in terms of throughput, delay, and delay variation.

Quad Cable:

Cables where four wires are twisted as a unit. High crosstalk is experienced among the wires within a quad unit.

Quantization Noise:

The noise resulting from analog to digital conversion.

Quat:

A quaternary symbol representing two bits with four-level symbol.

RADSL:

Rate adaptive digital subscriber line is an ADSL, which adjusts its transmission rate to the capacity of the line.

Remote Terminal:

Digital loop carrier at a site remote from a CO.

RFI:

Radio frequency interference.

RJ-11:

A six-position modular plug/jack with four conductors commonly used to connect to two-line phones.

RJ-14:

A six-position modular plug/jack with two conductors commonly used to connect to single-line phones.

RJ-45:

An eight-position and conductor plug/jack commonly used for 10BaseT.

RS Code:

Reed-Solomon code. A code used for error detection or correction.

RT:

Remote terminal, equipment located distant from the central office. Often located in an outdoor cabinet or underground vault.

SDSL:

Variously used to describe symmetric DSLs and single-pair DSLs. May or may not carry POTS (voice) on the same loop.

SES:

Severely errored second, a one second interval with a bit error ratio greater than 10 ² .

SIP:

Session initiation protocol, IETF RFC 2543 method to initiate and manage Internet sessions.

SNMP:

Simple network management protocol. A network management protocol using TCP/IP to access management information base (MIB) information.

SNR:

Signal-to-noise ratio. A signal quality measure.

SONET:

Synchronous optical network.

Spectral Balancing:

Generally describes methods for adaptively determining the spectra of users in a common binder or cable of DSL systems.

Splitter:

Filter(s) used to combine voice-band and higher-band data signals to coexist in different frequency bands on the same pair of wires.

SS7:

Signaling system 7.

STP:

Shielded twisted pair. A metallic sheath is provided to reduce RFI.

SVC:

Switched virtual circuit. An ATM or frame relay connection established in real time via signaling messages.

T1 (Committee):

Telecommunications standards committee for the United States.

T1 (Carrier):

1.544 Mb/s symmetric AMI transmission.

T1E1.4:

The U.S. standards working group responsible for DSL standards. T1E1.4 is one of several Working Groups within Technical Subcommittee T1E1.

TCM:

Trellis coded modulation. A convolutional code that provides coding gain without increasing bandwidth.

TCM:

Time compression multiplexing, aka Ping-Pong, permits two-way transmission by the use of alternating short one-way transmission bursts.

TCP:

Transmission control protocol.

TDM:

Time division multiplexing.

Throughput:

The effective rate of information flow though a system.

TPS-TC:

Transport protocol specific transmission convergence.

TR-08:

A Telcordia developed Interface between a DLC and a class 5 Switch.

Unavailable Seconds:

A duration beginning with ten consecutive severely errored seconds and ending with ten seconds that are not severely errored.

UBR:

Unspecified bit rate, a best effort quality of service.

UNE:

Unbundled network element.

UNI:

User to network interface.

Upstream:

Information flowing from the customer to the network.

USB:

Universal serial bus, an interface supporting up to 12 Mb/s.

UTP:

Unshielded twisted pair.

V5.2:

An ITU-T specified protocol for connecting a digital loop carrier (remote terminal) to a telephone switch.

VC:

virtual circuit.

VCI:

virtual channel identifier used for ATM.

VDSL:

Very-high bit rate digital subscriber line systems transmit information at rates from 12 to 52 Mb/s.

Vectoring:

An optimum means of co-generating and/or co-receiving multiple DSL signals.

Viterbi:

An algorithm used for reception of trellis coded modulation.

VLSI:

Very large scale integration permits millions of transistors in one integrated circuit.

VoATM:

Voice-over ATM.

VoDSL:

Voice-over DSL.

VoIP:

Voice-over Internet protocol. Voice conveyed via IP packets.

VoSTM:

Voice-over synchronous transfer mode (CVoDSL).

VPI:

Virtual path identifier used by ATMVPN: virtual private network.

WAN:

Wide area network, covering more than one city.

Water-filling:

A procedure for determining best-transmitted spectra.

White Noise:

Noise with equal power at all frequencies.

XDSL:

A generic term that applies to all DSL technologies.

XML:

Extensible markup language, a more flexible version of HTML.

Zeptosecond:

10 ²¹ seconds, the time interval between a traffic signal turning green and a New York taxi driver honking the horn.

Zettasecond:

10 ²¹ seconds, about 300 years .

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