The range of frequencies, expressed in hertz (Hz),
that can pass over a given transmission channel. The
bandwidth determines the rate at which information can
be transmitted through the circuit.
ALSO: The information capacity of a communications resource, usually measured in bits
per second. Also see Narrowband, Wideband and Broadband.
A signal relay scheme in which a terrestrial-based
signal is sent to a satellite, which then relays the
signal back to Earth with minimal processing by the satellite.
Bluetooth is the term used to describe the protocol of a short range
(10 meter) frequency-hopping radio link between devices. It can be used to
connect wireless phones to computing devices, etc.
A classification of the information capacity or bandwidth of a communication channel.
Broadband is generally taken to mean bandwidth higher than 2 Mbps.
Code Division Multiple Access -- A way to increase channel capacity by using code sequences
as traffic channels in a common radio channel. This technology was originally
developed for military use over 30 years ago. Also -- A digital signal multiplexing technique
where each signal is split into many chips of data, each of which is tagged with a particular
code. During transmission, the chips are spread over a band of frequencies, then reassembled
at the receiving end. This technique permits many different signals to be co-located
in the same frequency band.
Cell: The basic geographical unit of a cellular communications system. Service coverage
of a given area is based on an interlocking network of cells, each with a radio base station
(transmitter/receiver) at its center. The size of each cell is determined by the terrain and
forecasted number of users.
The basis of telephone call handling, with a circuit connection being set up between caller
and called party. This connection is held open for the duration of the call, even when no
information (voice, data, images or video) is being transmitted. The alternative is packet
switching.
In an antenna, where the tip of the field vector, as viewed in the direction of
propagation, rotates either clockwise (right hand) or counterclockwise (left hand).
A technique Developed by Analog Devices that simplifies the job of synchronizing
data generated from disparate sampling rates. The technique resamples
and synchronizes modem, audio, and video data as needed, and it
eliminates the substrate noise and feedthrough problems.
In the context of mobile communications, convergence means many things. There is
convergence of industry sectors, including telecommunications, information, media and
entertainment; convergence of technologies, for example, of fixed and mobile communications
and of telecommunications and computing; and there is convergence between mobile communications
standard themselves.
The SS receiver component that demodulates a Spread Spectrum signal; a device that
measures the similarity of of an incoming signal and a stored reference code.
Digital AMPS, the digital wireless standard widely used throughout the Americas,
Asia Pacific and other areas. D-AMPS services can be introduced in the 800 MHz and 1900 MHz
frequency bands. Uses a TDMA-based air interface.
An industrial
measurement and control system routinely seen in factories and treatment plants
consisting of a central host or
master (usually called a master station, master terminal unit or
MTU); one or more field data gathering and control units;
and a collection of standard and/or custom software used to monitor
and control field data elements. Unlike similar SCADA systems,
the field data gathering or control units are usually located within
a more confined area. Communications may be via a local area network (LAN), and will normally
be reliable and high speed. A DCS system usually employs significant
amounts of closed loop control.
A generation of car telephones served by a cluster of
receiver-transmitter cell site receiver/transmitters; as the car travels, a telephone call
is activated by transferring it from cell site to cell site.
A second generation cell phone network employing digital technology to convert the sounds
of users' voices into streams of bits that are then used to modulate the wireless signals.
Digital networks can also be used for data communications. These networks came into use in the
1990s.
an enhanced radio modulation technique for GSM and TDMA (ANSI-136) networks
that expands radio timeslots to 48 kbit/s. When combined with GPRS, it gives a maximum bandwidth
of 384 kbit/s per subscriber. Currently being pursued by GSM networks in
Europe and AT∓T Wireless in the U.S.
In an antenna, the force field associated with the current distribution of an antenna
element, tangential to the element and expressed in volts per meter. It is mutually
perpendicular to the magnetic field.
Any electromagnetic disturbance that interrupts, obstructs, or otherwise degrades or limits
the effective performance of electronics/electrical equipment. It can be induced intentionally,
as in some forms of electronic warfare, or unintentionally, as a result of spurious emissions
and responses, intermodulation products, and the like. EMI is also an engineering term used
to designate interference in a piece of electronic equipment caused by another piece of electronic
or other equipment. EMI sometimes refers to interference caused by nuclear explosion. Synonym:
radio frequency interference.
European Telecommunications Standards Institute. A body formed by the European
Commission in 1998, which included vendors and operators. ETSI's purpose is to define
standards that will enable the European market (particularly for its citizens) for
telecommunications to function as a single market.
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