ATU-C
ADSL terminal unit central office. Terminal nearer the central office or remote network node.
ATU-R
ADSL terminal unit remote. ADSL terminal nearer to the subscriber.
Access
Point at which entry is gained into a circuit or a network interconnection; may be switched or dedicated.
Access charge
Fee paid by long distance carriers to local telephone companies for use of local facilities; amount paid by telephone subscribers to obtain access to local networks.
Active
Using electricity for generation or regeneration of signals.
Adjacent channel interference Refers to interference caused by the energy from a transmitting channel spilling over into an adjacent channel.
Advanced intelligent network (AIN) An advanced architecture for a telephone network. Its foundations are built on the evolution of computer-based switches and Signaling System 7.
Advanced mobile phone system (AMPS) The current analog cellular FM system in North America. It uses 30 kHz channels, and signaling is done superaudio.
Airtime Actual time spent talking on a cellular telephone. Most carriers bill customers based on how many minutes of airtime they use each month.
Alert Constant 10 kHz signaling tone sent on the reverse voice channel (by the mobile), in an analog conversation, while the mobile phone is ringing.
All-optical networks Networks that are entirely optical, thereby avoiding the cost and time delays inherent in converting optical signals to electric signals and vice versa.
Alphanumeric A message or other type of readout containing both letters (alphas) and numbers (numerics). In cellular, alphanumeric memory dial is a special type of dial-from-memory option that displays both the name of the individual and that individual's phone number on the cellular phone handset.
Alternate access carriers Local exchange carriers in direct competition with the regional Bell operating companies (RBOC). These carriers are normally found only in large metropolitan areas.
Alternative operator services Operator services provided by an authorized company other than a local exchange carrier, regional Bell operating company, or AT&T.
Amplitude modulation (AM) The simplest carrier modulation technique, where the radio frequency carrier's amplitude envelope is modulated.
Analog The traditional method of modulating radio signals so that they can carry information. Analog signals are measured by their frequency, or the number of times per second that an electromagnetic wave swings back and forth in a complete cycle. The higher the speed and frequency, the more cycles of waves are completed in a period of time. This speed is measured in hertz (Hz).
Asymmetric digital subscriber line (ADSL) A member of the digital subscriber line family of copper loop enhancing technologies (see DSL). ADSL is asymmetric, meaning that it provides faster transmission rates downstream than upstream. It is therefore well suited to fast Internet access, where requests for Web pages and e-mail sent generally require less bandwidth than the receipt of multimedia and Web pages. ADSL is not well suited for business applications that require symmetric communications, such as videoconferencing and two-way file transfer.
Asynchronous transfer mode (ATM) A high-bandwidth packet switching and multiplexing technique. Each cell in a stream is presented to the network on a start-stop basis (asynchronously), rather than having a circuit or a regular time slot reserved for the stream.
Asynchronous transmission Mode of data communications transmission in which time intervals between transmitted characters may be of unequal length.
Attenuation Weakening of the radio frequency signal due to being partially blocked or absorbed.
Automatic call back A feature that allows you to call back a number that just called you, simply by entering a code. Also called call return.
Automatic call distributor (ACD) Device that handles heavy incoming call volume.
Average revenue per user (ARPU) A primary element of valuation and analysis of wireless companies. It reflects the average amount of revenue generated by each subscriber.
Back-haul Routing of a call that appears to take an illogical path through a communications network.
Backbone Network of broadband connections between switches.
Bandwidth A measure of data sent through a connection.
Base station A multicircuit transceiver located at the center of a cell whose primary purpose is to handle all incoming and outgoing calls within the cell.
Bell operating company (BOC) The local, or regional, telephone company that owns and operates lines to customer locations and central office switches. BOCs have connections to other companies, tandem (class 4 toll) offices, and may connect directly to interexchange carriers like MCI WorldCom, AT&T, and Sprint.
Beta test A secondary product test performed by a selected set of early support end users or customers under special contract prior to the general availability of that product.
Block calls Prevents calls from being completed to the requested destination.
Bluetooth A short-range wireless connectivity technology with special focus on a specification that lends itself to a low-cost, low-power, and integrated implementation. Mobile users can use this short-range, wireless connectivity solution with computing and communication devices, such as personal digital assistants (PDA), notebook computers, pagers, and cellular and cordless phones. IBM Research is a major contributor to both infrared and radio-based standards and has developed a number of technologies in this area.
Bottleneck A system capacity constraint that may reduce traffic during peak load conditions.
Broadband Transmission facility having a bandwidth greater than 20 kHz; capable of high-speed data transmission.
Cable modem Offers high-speed, broadband access service over hybrid coaxial cable, providing up to 27Mbps of bandwidth.
Call detail record (CDR) Computer record that contains data unique to a specific call.
Call forwarding A feature that allows the subscriber to forward a call to another telephone number.
Call processing The complete process of routing, originating, and terminating cellular telephone calls, along with the necessary billing and statistical collection processes.
Call setup The call processing events that occur during the time a call is being established, but not yet connected.
Call waiting A feature that alerts the subscriber if another call comes in during a current conversation. The user can answer the call waiting, but cannot connect all parties (connecting all parties is considered a conference call).
Caller ID This feature displays the number of the person calling on a special display unit or screenphone.
Capacity The highest possible reliable transmission speed that can be carried on a channel, a circuit, or piece of equipment.
Carrier The operating frequency of a wireless system.
Carrier preselection A standard regulatory mechanism for allowing consumers access to a selected long distance operator's services through nomination.
Carrierless Amplitude Modulation/Phase Modulation
A technology that can be used in ADSL. Current standards put emphasis on discrete multitone (DMT) technology.
Cell The radio frequency coverage area in the cellular system resulting from operation of a single multiple-channel set of base station frequencies.
Cell splitting A means of increasing the capacity of a cellular system by subdividing or splitting cells into two or more smaller cells.
Cellular A term that refers to the radio antenna network of "cells" that allow users of mobile telephones to communicate with no physical connection.
Cellular digital packet data (CDPD) Sending digital data over the existing advanced mobile phone system by transmitting dense packets on vacant analog channels.
Cellular geographic service area (CGSA) The actual area in which a cellular company provides cellular service.
Central office (CO) The switching office that connects the mobile telephone switching office (MTSO) to the public switched telephone network (PSTN).
Centrex A service that offers features similar to those of a private branch exchange (PBX), except the equipment is located at the carrier's premises and not at the premises of the customer.
Centrex resale A means for competitive carriers to enter the local market, reselling the centrex switching service that the incumbent would typically provide.
Channel A unique radio frequency that is used for communication between subscriber unit and cell site base station.
Circuit switching Method of communications where an electrical connection between calling and called stations is established on demand for exclusive use of the circuit until the connection is released.
Clear channel Channel in which the full bandwidth (for example, 64 Kbps) is used for transmission; no portion of the channel is set aside for control, framing, or signaling.
Click tone A particular progress tone injected onto the forward voice channel (mobile unit receive, base station transmit) to indicate to the subscriber that the call has not been abandoned by the system.
Cloning Cellular cloning occurs when a criminal uses sophisticated equipment to capture a customer's phone and serial numbers when a call is being made. The criminal can program these numbers into another phone to make illegal calls.
Coaxial cable Cable capable of carrying much higher bandwidth than copper wire due to its fabrication with one or more pairs in a single sheath.
Cocarrier status A relationship between a CLEC and an incumbent LEC that gives each entity the same access to the other's network and provides access and services on an equal basis.
Cochannel interference The interference caused between two cells transmitting on the same frequency within a network.
Code division multiple access (CDMA) In a CDMA system, each voice circuit is labeled with a unique code and transmitted on a single-channel simultaneously with many other coded voice circuits. This allows for greater bandwidth.
Coder Transforms analog signals into digital signals.
Collocation The ability of a CAP to connect its network to the LEC's central offices.
Common carrier Government-regulated, private company that furnishes the public with telecommunications services and facilities; for example, telephone or telegraph companies.
Competitive access provider (CAP) A company, other than a local exchange carrier, regional Bell operating company, or AT&T, that provides its customers with an alternative to the local telephone company for local transport of private line, special access, and interstate transport of switched access telecommunications services. CAPs initially built their own facilities, requiring a great deal of capital expenditures. With the Telecommunications Act of 1996, competitive carriers were offered more options: building out their own facilities (what CAPs did) and reselling local service. Competitive carriers in the local market are broadly termed CLECs (competitive local exchange carriers).
Competitive checklist Fourteen points laid out by the U. S. Federal Communications Commission that the regional Bell operating companies (RBOC) must comply with before they are allowed to sell long distance services. This checklist is designed to ensure that the RBOCs have opened their networks to competition.
Competitive local exchange carrier (CLEC) A competitive access provider (see CAP) that also provides switched local telecommunications services.
Connection-oriented service The transport of packets of information from one network node to a destination node following an established network connection.
Connectionless service The transport of a single datagram or packet of information from one network node to a destination node or multiple nodes without establishing a network connection.
Constructive interference Interference that occurs when waves occupying the same space combine to form single stronger wave.
Consultative Committee for International Telegraph and Telephony (CCITT)
The primary international body for fostering cooperative standards for telecommunications equipment and systems. Currently known as the ITU-T (for Telecommunication Standardization Sector of the International Telecommunications Union).
Contention The process whereby multiple users make requests for transmission bandwidth across a transmission link but the pool of bandwidth is less than the aggregate amount of bandwidth the users could request.
Control channel A unique channel used by each base station dedicated to the transmission of digital control information from the base station to the mobile unit.
Copper twisted pair A standard phone line made up of two copper wires wrapped around each other.
Correlator The receiver component that demodulates a spread spectrum signal; a device that measures the similarity of an incoming signal and a stored reference code.
Coupler
A component used to combine or split an optical signal.
Cross-correlation A measure of the similarity of two different signals.
Cross-talk Interference of one phone call with another.
Customer premises equipment (CPE)
This equipment includes all telecommunications devices and wiring that are at a user's local site.
Data terminal equipment (DTE) The piece of equipment where a communications path ends.
Decoder
Transforms digital signals into analog signals.
Dedicated access
Connection between a customer's premises and a long distance carrier.
Dedicated lines
Telecommunications lines dedicated to or reserved for use by particular customers along predetermined routes (in contrast to telecommunications lines within the LEC's public network).
Dense wavelength division multiplexing (DWDM)
A high-speed version of wavelength division multiplexing. (See WDM)
Destructive interference
Interference that occurs when waves occupying the same space combine to form a single weaker wave.
Dial-up line
Communications circuit that is established by a switched circuit connection.
Dialing parity
Customers' ability to access their telecom vendor without having to dial extra digits.
Digital
A method of storing, processing, and transmitting information through the use of distinct electronic or optical pulses that represent binary digits (0 and 1).
Digital modulation
A method of encoding information for transmission is expected to eventually replace analog transmission.
Digital signal 0 (DS0)
A single voice-grade 64 KBPS circuit.
Digital signal 1 (DS1)
1.544MBPS with a payload of 1.536MBPS bidirectional.
Digital signal 2 (DS2)
6.312MBPS that can transport four DS1s asynchronously.
Digital signal processing (DSP)
Digital signal processing
Digital subscriber line (DSL)
A family of technologies that provides high-bandwidth transmission over standard twisted copper wires (regular telephone lines).
Digital transmission system
Information is transmitted in a series of pulses, and the signal can be regenerated.
Direct sequence
A pseudorandom code is added to the data signal that increases the modulation rate and signal bandwidth.
Discrete multitone (DMT)
A version of multicarrier modulation that allows allocation of payload data bits and transmitter power among more than one subchannel, depending on loss and interference among each subchannel. A candidate technology for ADSL.
Distribution plant
The interconnected group of cables that serves your house, feeds into a larger cable that feeds your street, feeds into the neighborhood cable, and ultimately into the telephone office. Sometimes referred to as outside plant (OSP).
Divestiture (AT&T)
On 8 January 1982, AT&T signed a consent decree with the U.S. Department of Justice. It stipulated that as of 1 January 1984, AT&T would divest itself of its 22 telephone operating companies, which were then formed into seven regional holding companies of roughly equal size.
Downstream transmission
The transmission coming into a consumer's residence or business. Often used with cable modems and DSLs to describe the data rate that can be achieved by the line coming into the home or office.
Drop
Portion of an outside telephone plant that extends from the telephone distribution cable to the subscriber's premises.
Drop out
A momentary loss of the carrier and sound, or a buildup of background noise when the transmitter is in a certain location in the room.
Drop wire
Last part of the loop connecting distribution cable to the customer premises.
Dual mode
Personal communication service (see PCS) telephone compatible with both analog and digital cellular phone systems.
Dual tone multifrequency (DTMF)
Commonly known as touch tones, this in-bank signaling is made up of two tones (out of a group of 8) and is used to translate dialed digits.
Echo canceler with hybrid (ECH)
Used in DSL and HDSL systems.
Electronic doped fiber amplifier (EDFA)
Concept made into law in 1984 Modified Final Judgement (MFJ) that all long distance carriers must have the same access to local facilities as AT&T
Electronic serial number (ESN)
A 32-bit code that is unique to each mobile unit. Used to validate mobile.
Enhanced specialized mobile radio (ESMR)
Digital mobile telephone services offered to the public over channels previously used only for analog two-way dispatch.
Equal access
Concept made into law by the 1984 Modified Final Judgment (MFJ) that all long distance carriers must have the same access to local facilities as AT&T has.
Erbium doped fiber amplifier (EDFA)
EDFAs are used for amplifying optical signals in long-haul optical networks. Unlike electro-optic repeaters, which convert light to electricity, amplify the signal, and then reconvert it to light, EDFAs amplify the light signal itself. EDFAs have advantages that make them critical components of optical networks: they are fast, very simple, and are not frequency-dependent, meaning that networks may be upgraded by installing new wavelength division multiplexing (WDM) equipment without changing fiber or amplifiers between nodes.
Eriang
A dimensionless quantity used in the measurement of traffic in the cellular system.
Ethernet
A proprietary bus network developed by Xerox, Digital Equipment Corporation, and Intel that provides fast transmission speeds.
European Telecommunications Standards Institute (ETSI)
The mission of ETSI is to produce the technical standards that are necessary to achieve a unified European telecommunications market.
Execute source
An order sent to a mobile on the Forward Voice Channel telling the mobile to change channels.
Execute target
An order sent to the cell that a mobile is being handed off to, informing the cell of a pending arrival of a mobile.
Fade
A drop in the received signal strength as a result of the transmission's interactions with the transmission environment.
Federal Communications Commission (FCC)
The government agency responsible for regulating telecommunications in the United States; located in Washington, D.C.
Fiber mile
The number of route miles installed (excluding pending installations) along a telecommunications path multiplied by the number of fibers along that path.
Fiber optics
Means of providing a high-speed transmission, using light to send images through a flexible bundle of glass fibers.
Fiber to the home (FTTH)
Deployment of direct fiber optic connections to consumers' homes, allowing for wide bandwidth connections. FTTH faces technical hurdles (amplification of signals in the upstream direction), but the most significant factor holding it back is the cost of laying fiber optic cables. As such, FTTH is not expected to be the only wideband access solution, but it will be deployed selectively and will coexist with DSL access solutions over copper pairs. FTTO (fiber to the office) is more prevalent, because large office buildings contain enough users and demand for services to justify the cost of laying fiber.
Flat network
Architecture in which every switch is connected to every other switch, enhancing routing options as well as survivability.
Follow-me roaming
The ability of the cellular system to automatically forward calls to a roaming mobile that has left its primary service area.
Forced disconnect
A call processing function that forces termination of a call, usually not at the mobile subscriber's request.
Forward control channel (FOCC)
A control channel used for the base station-to-subscriber direction, also known as the control channel downlink.
Forward voice channel (FVC)
A voice channel used in the base station-to-subscriber direction, also known as the voice channel downlink.
Four-wire line
A two-way transmission circuit using two pairs of conductors to allow full duplex (simultaneous) conversation without multiplexing.
Frame relay
Form of packet switching that employs statistical multiplexing over a shared network, intended for use between intelligent end points and implemented over high-quality transmission facilities that connect programmable switches.
Free space loss
The loss of a signal's power as a result of the signal spreading out as it travels through space.
Frequency division multiple access (FDMA)
Systems that transmit one voice circuit per channel. Each conversation gets its own unique radio channel.
Frequency hopping
The transmitter hops to one of many channels. The receiver knows the sequence of the frequency hopper and follows each hop.
Frequency modulation (FM)
Modulation of the radio frequency based on the frequency of signals (vs. the amplitude).
Frequency reuse
The ability to use the same frequencies repeatedly within a single system, made possible by the basic design approach for cellular.
Frequency shift keying (FSK)
The form of frequency modulation that uses two separate audio frequencies to transmit binary ones and zeros.
Front end
The first stage of filtering in a receiver. The first circuit stage following the antenna input to the receiver.
Full duplex
Refers to a communications system that uses two separate transmit and receive paths to allow simultaneous conversation in two directions. FVC (forward voice channel): A voice channel used in the base station-to-subscriber direction, also known as the voice channel downlink.
