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Mobile Computing Glossary

[Index] [A - D] [E - H] [I - L] [M - P] [Q - T] [U - X] [Y - Z] [#'s & symbols]

A - D

A Band

... Duplex

A Band -- A non-wireline radio frequency spectrum. See also B Band.

Access Charge -- A flat monthly fee charged a subscriber for the use of a cellular system (whether the subscriber makes or receives any calls or not).

Access Number (cellular term)
The phone number that must be dialed by someone calling you when you are roaming outside of the National Network, prior to dialing the number of your phone. The access number gives the caller access to the facilities of the system in which you are roaming.

Adjacent Cell -- Two cells are adjacent if it is possible for an MES to maintain continuous service while switching from one cell to another.

ADPCM -- Adaptive Differential Pulse Code Modulation .

Air Link Interface -- The network interface between a MES and the CDPD service provider network.

AMPS (Advanced Mobile Phone Service)
The official name for the first commercial cellular system, which used 666 channels (A Band 333 and B Band 333). The standard for the analog cellular telephone service in use in North America. Developed by AT&T, this is the current standard for all North American cellular systems.

Analog Signal -- A transmission in which information is represented as physical magnitudes of electrical signals.

ANI -- Automatic Number Identification

ANSI (American National Standards Institute)
The coordinating body for voluntary standards groups within the United States that is a member of the International Organization for Standards.

APCO 25 -- Association of Public Safety Communications Officials
A set of standards for private radio networks designed specifically for public safety (police, fire, emergency services) applications in North America It includes standards for common air access, encryption, over the air reprogramming, data port interface, host data interface, trunking, inter-connection to PSTN and network management. APCO-25 was adopted in 1995 and is a digital standard, as compared to APCO-16 that was analog.

API -- Application Programming Interface

ARQ (Automatic Repeat Request) - Communication method where the receiver detects errors and request retransmissions.

ASCII -- American Standard Code for Information Interchange .

Asynchronous -- A process where overlapping communications operations can occur independently and do not have to wait for previous operation to be finished.

AUI (Attachment Unit Interface)
An IEEE 802.3 cable connecting the MAU (Media Access Unit) to the networked.

Attenuation -- Loss of communication signal energy.

ATMD (Asynchronous Time Division Multiplexing)
A method of sending information in which normal time division multiplexing (TDM) is used, except that to, slots are allocated as needed rather than specific transmitters.

AUC - Authentication Center

Band -- A portion of the radio frequency.

1. The range (band) of frequencies that are transmitted on a channel. The difference between the highest and lowest frequencies is expressed in hertz (Hz) or millions of hertz (MHz).

2. The range frequencies on the electromagnetic spectrum allocated for wireless transmission.

3. The wire speed of the transmission channel.

Base Station
The low power transmitter/receiver and signal equipment located in each cell in a cellular service area.

A transmission channel which carries a single communications channel, on which only one signal can transmit at a given time.

1. A unit of signaling speed represented by code elements (often bits) per second.

2. A French-language term that represents the transfer of one bit.

BCHO (Base Controlled Handoff) -- Cell transfer initiated by the network.

BOC (Bell Operating Companies)
The local telephone companies that existed prior to deregulation, under which AT&T was ordered by the courts to divest itself in each of the seven U.S. regions. See also RBOC.

Block (of frequencies)
A group if radio frequencies within a band set aside for a particular purpose. Cellular telephony uses four blocks of frequencies within the 800-MHz portion of the UHF band. Non-wireline and wireline carriers are assigned separate blocks of frequencies. See also Band.

Block A - The block of 800-MHz cellular radio frequencies assigned to the non-wireline or Block A carrier.

Block B - The block of 800-MHz cellular radio frequencies assigned to the wireline or Block B carrier.

This occurs when a subscriber tries to make a call but all channels at his nearest cell site are busy. Cell splitting becomes necessary when there is a high blockage percentage.

BPS - Bits per second. Also Kbps for kilo bits per second, and Mbps stands for million bits per second.

BPR (Business Process Reengineering)
Business Process Reengineering is the discipline of first analyzing and then redesigning current business processes and their components in terms of their effectiveness, efficiency and added value contribution to the objectives of the business.

BTS - Base Transceiver Station

Call Setup Time - The time required to establish a switched call between DTE and devices.

1. A company that provides telephone (or another communications) service. Also, and unmodulated radio signal. See also Non-wireline and Wireline.

2. A signal suitable for modulation by another signal containing information to be transmitted.

CCITT (Consultative Committee for International Telephone and Telegraph)
An international organization that makes recommendations for networking standards like X.25, X.400, and facsimile data compression standards. Now called the International Telecommunications Union Telecommunication Standardization Sector; this is abbreviated as ITU, ITU-T, or ITU-TSS.

CDMA - Code-Division Multiple Access (see chapter 8) .

CDPD (Cellular Digital Packet Data) - Uses idle moments on voice channels to send pure data over the channel, without affecting quality of voice transmissions.

The basic geographic unit of a cellular system and the basis for the generic industry term "cellular." A geographical area is divided into small "cells", each of which is equipped with a low-powered radio transceiver. The cells can vary in size depending on terrain and capacity demands. By controlling the transmission power and the radio frequencies assigned from one cell to another, a computer at the Mobile telephone switching office monitors the movement and transfers (or hands off) the phone call to another cell and another radio frequency as needed. The region in which RF transmission from one fixed transmission site can be received at acceptable levels of signal strength.

Cell Splitting
Dividing one cell into two or more cells to provide additional capacity within the original cell’s region of coverage.

1. Using cellular phone technology.

2. A reference to the wireless switched circuit network consisting of overlapping coverage cells that provides analog voice and CDPD.

An individual communication path that carries signals at a specific frequency. The term also is used to describe the specific path between large computers (e.g. IBM mainframes) and attached peripherals.

Channel Bandwidth
The frequency range of an RF channel. E.g. In a CDPD, it is 30 KHz.

Channel Hop
The process of changing the RF channel supporting a channel stream to a different RF channel on the same cell.

Channel Hopping
A radio frequency transmission method whereby transmissions hop from one channel to another. The channels are visited in a predefined order specified by a hopping sequence. Typically this uses the ISM band from 2.4000 to 2.4835 GHz with 85 one-megahertz channels or "hops," but at least 50 different frequencies must be used by FCC regulation. Also, CDPD uses frequency hopping on analog cellular systems to take advantage of unoccupied voice channels.

CHAP -- Challenge handshake authentication protocol .

CID -- Caller ID

Circuit Switching
An open-pipe technique that establishes a temporary dedicated connection between two points for the duration of the call. A switching system in which a dedicated physical circuit path must exist between sender and receiver for the duration of the "call". Used heavily in the phone-company network, circuit switching often is contrasted with contention and token passing as a channel-access method, and with message switching and packet switching as a switching technique.

Class of Service
An indication of how an upper layer protocol wants a lower-layer protocol to treat messages in terms of priority, assignment on physical bandwidth pipes, routing, etc. In SNA subarea routing, COS definitions are used by subarea nodes to determine the optimal route to establish a given session.

Code Division Multiple Access (CDMA)
1. A division of the transmission spectrum into codes, effectively scrambling conversations. Several transmissions can occur simultaneously with the same bandwidth, with the mutual inference reduced by the degree of orthogonality of the unique codes used in each transmission.

2. Wireless transmission technology that employs a range of radio-frequency wavelengths to transport multiple channel of communication signals. See also Spread-Spectrum Technology.

CO (Central Office)
The telephone-switching station nearest the customer’s location. A local telephone company office to which all local loops in a given area connect and in which circuit switching of subscriber lines occurs.

CODEC -- Coding/Decoding Device

CSU (Channel Service Unit)
A digital interface device that connects end-user equipment to the local digital telephone loop. The piece of equipment that terminates the long-distance circuit in the customer’s location. It is often paired with a digital service unit.

CSDS (Circuit Switched Data Service - a cellular term)
Developed for delivery vehicles to track packages (used by UPS). Services that carry data over conventional cellular where circuits are switched from call to call.

CSMA/CD (Carrier Sense Multiple Access With Collision Detection)
A communications protocol in which nodes contend for a shared communications channel and all nodes have equal access to the network. Simultaneous transmissions from two or more nodes results in random restart of those transmissions. Used in Ethernet protocol.

CT-2 - Digital Cordless Telephony (2nd generation)

CT-3 - Digital Cordless Telephony (3rd generation)

CTIA (Cellular Telecommunications Industry Association)
The organization created, in 1981, to promote the cellular industry, address the common concerns of cellular carriers and serve as a forum for the exchange of nonproprietary information.

A technical term indicating that stray signals from other wavelengths, channels, communication pathways, or twisted-pair wiring have polluted the signal. It is particularly prevalent in twisted-pair networks or when telephone and network communications share copper-base wiring bundles. A symptom of interference caused by two cell sites causing competing signals to be received by the mobile subscriber. This can also by generated by two mobiles causing competing signals that are received by the cellular base station. Crosstalk sounds like two conversations and often a distortion of one or the other or both.

CSMA/CA -- Carrier Sense Multiple Access With Collision Avoidance .

CSMA/CD -- Carrier Sense Multiple Access With Collision Detection .

CSU -- Channel Service Unit .

A U.K. system which allows callers with CT2 phones who are within 200 yards of a base station (or site) to make outgoing calls.

CTI -- Computer Telephone Integration .

CTIA -- Cellular Telecommunications Industry Association .

DACS -- Digital access and cross-connect systems .

Data Compression
A reduction in the size of data by exploiting redundancy. Many modems incorporate MNP5 or V.42bis protocols to compress data before it is sent over the phone line.

dB (Decibels)
A value expressed in decibels is determined as 10 times the logarithm of the value taken to base 10.

1. Data Communications Equipment.

2. In software architecture, it implies distributed computing environment.

Dead Spot
A location in a radio/cellular system where, for one reason or another, signals do not penetrate.

DECT - Digital European Cordless Telephone

De Facto Standard - A standard by usage rather than official decree; a default standard.

De Jure Standard - Literally, "from the law." A standard by official decree.

DES (Data Encryption Standard)
An encryption/decryption algorithm defined in FIPS Publication 46. The standard cryptographic algorithm developed by the National Institute of Standards and Technology

The restoration of redundant data that was removed through compression.

DECT (Digital European Cordless Telephone)
The specs for future European cellular, as yet not fully defined.

Dedicated Channel
An RF channel that is allocated solely for the use of a particular user or service. E.g. In CDPD, a channel may be dedicated to data.

The process of receiving information from a source computer. See also Download.

A software program that controls a physical computer device such as an NIC, printer, disk drive, or RAM disk.

DSU (Data Service Unit)
A device used in digital transmission for connecting data terminal equipment (DTE), such as a Router, to a digital transmission circuit (DTC) or service.

DTE (Data Terminal Equipment)
A computer terminal that connects to a host computer. It may also be a software session on a workstation or personal computer attached to a host computer.

DTMF - Dual Tone Multi Frequency

New cellular phones that work with both digital and analog switching equipment. Digital cellular offers the benefits of more channels, clearer-sounding calls, and ensured privacy.

Dual-NAM (cellular term)
Allows user to have two phone numbers with separate carriers. See also Multi-NAM.

1. The method in which communication occurs, either two-way as in full-duplex, or unidirectional as in half-duplex.

2. Cellular phones, using separate frequencies for transmission and reception, allow for duplex communications by allowing both parties to talk and listen at once. Push-to-talk systems are not duplex.

[Index] [A - D] [E - H] [I - L] [M - P] [Q - T] [U - X] [Y - Z] [#'s & symbols]

A - D

A Band

... Duplex



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