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The Third Generation Partnership Project, set up to expedite the development of open, globally-accepted technical specifications for 3G services.

3G Services
Shorthand term for "third generation services." Generally applied to wideband mobile services.


In an antenna, the process within a poorly conducting material in which RF energy is absorbed and converted to heat energy.

The method, time, circuit, or facility used to enter the network.

Access Coordination
The design, ordering, installation, preservice testing, turn-up and maintenance on local access services.

Access Line
The circuit used to enter the communications network.

Account Codes
Also known as Project Codes or Bill-Back Codes. Account Codes are additional digits dialed by the calling party that provide information about the call. Typically used by hourly professionals (accountants, lawyers, etc.) to track and bill clients, projects, etc.

Address Mask
A 32-bit long mask used to select an IP address for subnet addressing. The mask selects the network portion of the IP address and one or more bits of the local LAN address.

Address Translation
The process of converting external addresses into standardized network addresses and vice versa. Facilities interconnection of multiple networks which each have their own address plan.

ADSL (Asymmetric Digital Subscriber Loop)
ADSL is a technology that allows data to be sent at rates as high as 6 Mbps through the conventional (analog, copper) telephone line, and is considered one of the most promising ways of connecting the "Information Superhighway" to the home. In collaboration with Aware, Inc. of Cambridge, Analog Devices has developed systems that support this standard.

Air interface
The radio communications between a mobile handset and the base station.

Stands for Alarm Indication Signal, usually all ones--F11111111. Also known as a Blue Alarm which signals that an upstream failure has occured.

Anti-Jam; a communication signal that is designed to resist interference or jamming.

A real-time indication or a signal of an abnormal situation or event. Usually includes a Priority or Severity Code.

Alternate Access
A form of local access where the provider is not the LEC, but is authorized or permitted to provide such service.

Alternate Access Carriers
Local exchange carriers in direct competition with the RBOCs. Normally found only in the larger metropolitan areas. Examples are Teleport and Metropolitan Fiber Systems.

Alternate Mark Inversion (AMI)
A line code used for T-1 and E-1 lines that has a 12.5% ones density minimum, and the one conditions of the signal alternate between positive and negative polarity.

Amplitude Modulation; the simplest carrier modulation technique where the RF carrier's envelope is modulated -- used today by broadcast band (BC) stations.

Stands for Advanced Mobile Phone System, which is the most common type of First Generation analog cell phone network. Because analog phones are suited for voice rather than data communications, AMPS networks are rapidly being supplanted by digital wireless networks. Operates in the 800 MHz frequency band and uses FDMA technology.

Amateur Service
A radio communications service that licensed operators with no pecuniary interest use for self-training, communications, and technical investigations.

AMI - Alternate Mark Inversion
A line code used for T-1 and E-1 lines that has a 12.5% ones density minimum, and the one conditions of the signal alternate between positive and negative polarity.

ANSI - American National Standards Institute
A United States-based organization which develops standards and defines interfaces for telecommunications.

The North American digital mobile standard previously known as Interim Standard IS-136 and used in TDMA (previously called D-AMPS) systems.

Answer Supervision
The off-hook indication sent back to the originating end when the called station answers.

AOA, or Angle of Arrival
A position identification technology that detects the direction of a signal received from a transmitter at only one point. In this system, the transmitter's location is determined from the receivers' antenna position and the AOA of the signals that are from the antennas.

The specifications of a system and how its subcomponents interconnect, interact and cooperate. Architectures are often described in multiple levels of abstraction from low-level physical to higher-level logical application and end-user views.

Area of Service - AOS
The geographical area supported by a communication service. For 800 numbers, if AOS is "CC", it is using Complex Call routing.

Automatic Room Identification (Hotel/Motel room number)

Association of Radio Industry Businesses, the standard-setting body for Japan.

ARP - Address Resolution Protocol under TCP/IP
Used to dynamically bind a high level IP address to a low-level physical hardware address. ARP is limited to a single physical network that supports hardware broadcasting.

Amplitude Shift Keying; a digital modulation of the RF carrier's envelope.

ASR - Access Service Request
A document (or data transaction) sent to the LEC to order the local access portion of a circuit.

Areas of Service State (list)

Asymmetric communications
Two-way communications in which the volumes of traffic in each direction are significantly different. For example, TV on demand.

Asynchronous (i.e. Not Synchronous)
A form of concurrent input and output communication transmission with no timing relationship between the two signals. Slower-speed asynchronous transmission requires start and stop bits to avoid a dependency on timing clocks (10 bits to send on 8-bit byte). (Contrast with Synchronous)

Asynchronous Transfer Mode Adaptation Layer - AAL
A series of protocols enabling to be made compatible with virtually all of the commonly used standards for voice, data, image and video.

An international ISDN high-speed, high-volume, packet-switching transmission protocol standard. ATM uses short, uniform, 53-byte cells to divide data into efficient, manageable packets for ultrafast switching through a high-performance communications network. The 53-byte cells contain 5-byte destination address headers and 48 data bytes. ATM is the first packet-switched technology designed from the ground up to support integrated voice, video, and data communication applications. It is well-suited to high-speed WAN transmission bursts. ATM currently accommodates transmission speeds from 64 Kbps to 622 Mbps. ATM may support gigabit speeds in the future.

These three types of high-speed fiber-optic systems (ATM switch interface, SONET/SDH network) are being deployed now in the LAN/WAN environment to connect workstations and to transport high bit-rate services.

A loss of signal strength in a lightwave, electrical or radio signal usually related to the distance the signal must travel (e.g. fiber optic transmission must be regenerated approx. every 30 miles). Fiber optic attenuation is caused by transparency of the fiber, bending the fiber at too small of a radius, nicks in the fiber, splices, poor fiber terminals, FOTs, etc. Electrical attenuation is caused by the resistance of the conductor, poor (corroded) connections, poor shielding, induction, RFI, etc. Radio signal attenuation may be due to atmospheric conditions, sun spots, antenna design / positioning, obstacles, etc.

The process of validating and identifying a caller as being a legitimate system user.

A measure of the similarity between a signal and a time-shifted replica of itself; a special case of cross-correlation; The auto-correlation function is the theoretical basis of direct sequence spread spectrum.

Automatic Number Identification
Originating Number
(1) The number associated with the telephone station(s) from which switched calls are originated (or terminated).
(2) A software feature associated with Feature Group D (and optional on Feature Group B) circuits. ANI provides the originating local telephone number of the calling party. This information is transmitted as part of the digit stream in the signalling protocol, and included in the Call Detail Record for billing purposes.
(3) ANI may also be used to refer to any phone number.

Automatic Ring Down (ARD)
A private line connecting a station instrument in one location to a station instrument in a distant location with automatic two-way signaling. The automatic two-way signaling used on these circuits causes the station instrument on one end of the circuit to ring when the station instrument on the other end goes off-hook. This circuit is sometimes called a "hot-line" because urgent communications are typically associated with this service. ARD circuits are commonly used in the financial industry. May also have one way signaling. Station "A" rings Station "B" when Station "A" goes off hook, but Station "B" cannot ring Station "A".

The probability of attaining a specified level of performance and maintaining that level for a scheduled period of time.

Additive White Gaussian Noise.

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