Stands for Frequency Division Multiple Access. This multiple access technique allows many
cell phone users to communicate with one base station by assigning each user a different
frequency channel. An AMPS network, for example, has 832 channels spaced
about 30 KHz apart. In digital networks, FDMA is used in conjunction with CDMA
or TDMA.
A radio link between an earth station and a satellite, conveying
information for a space radio communications service other than fixed satellite
service. In the broadcasting-satellite service, all feeder links are uplinks
(from the earth to the satellite), but in the mobile-satellite service, feeder
links can be both uplinks and downlinks.
A telephone system where subscribers are connected to the Public Switched Telephone
Network using radio signals rather than copper wire for part or all of the connection between
the subscriber and the switch. Includes cordless access systems, proprietary fixed radio
access and fixed cellular systems. Synonymous with Radio in the Loop and Wireless Local Loop
Systems.
Also called fixed cellular network. This apparent contradiction in terms
signifies a cellular network that is set up to support fixed rather than mobile
subscribers. Increasingly being used as a fast and economic way to roll out
modern telephone services, since it avoids the need for fixed wires.
In an antenna, the loss between two isotropic radiators in free space resulting
from the decrease in power density with the square of the separation distance.
A band of radio frequencies identified by an upper and lower frequency
limit earmarked for use by one or more of the 38 terrestrial and space
radiocommunications services defined by the International Telecommunication
Union under specified conditions.
The designation of portions of an allocated frequency band to individual
countries or geographical areas for a particular radiocommunication service;
for a satellite service, specific orbital positions may also be alloted to
individual countries.
Authorization given by a nation's government for a station or an operator
in that country to use a specific radio frequency channel under specified
conditions.
A ratio of output divided by input, expressed in decibels. In antennas, the
ratio of the radiation intensity, in a
given direction, to the radiation intensity that would be obtained if the power accepted
by the antenna were radiated equally in all directions (isotropically).
A planned improvement for GSM networks that implements packet switching for data communications.
Instead of sending data on dedicated circuits, a packet-switching network divides the
information into packets and transmits them on any of the network's available channels.
A circular orbit approximately 35,900 km above the earth, in the plane of
the earth's equator, in which a satellite revolves around the earth in the same
time that the earth rotates on its axis; thus the satellite appears
approximately stationary over one point on the earth.
The European standard for digital networks, which guarantees the compatibility of wireless
devices -- so that a German cell phone can be used on a French network, for example. Uses
TDMA technology and can be implemented in 900 MHz, 1800 MHz
or 1900 MHz frequency bands.
The term used by the International Telecommunications Union for the
specification for the projected third-generation wireless services. Formerly referred
to as FPLMTS, Future Public Land-Mobile Telephone Systems.
A capability in the public telecom network environment that allows new services such
as Freephone or televoting to be developed quickly and introduced on any scale, from a local
trail to network-wide. Also implies a well-developed network infrastructure.
Integrated Services Digital Network. A digital public telecommunications
network, in which multiple services (voice, data, images and video) can be provided
via standard terminal interfaces. Offers two times 68 kbps over the landline
network.
A hypothetical, lossless antenna having equal radiation intensity in all directions;
used as a zero-dB gain reference in pattern measurements or directivity calculations.
Any orbit around the earth substantially below the geostationary satellite
orbit, generally below the geostationary satellite orbit, generally within
several hundred km above the earth's surface and usually inclied to the
equatorial plane.
One consisting of a thin metallic conductor (patch) bonded to a thin grounded
dielectric substrate and fed by a coaxial probe or a microstrip transmission line.
A signal in the generic frequency range from above 1 GHz to an upper end of perhaps
30 or 40 GHz. This is the frequency range where coaxial cabled TEM mode signal propagation
is viable.
A radiocommunication service between mobile and fixed stations, or between
mobile stations. Depending on whether one or more of the earth stations are on
land, sea, or air, the service would be called land mobile, maritime mobile, or
aeronautical mobile.
A classification of the information capacity or bandwidth of a
communication channel. Narrowband is generally taken to mean a bandwidth of 64
kbps or below.
The acronym stands for Orthogonal Frequency Division Multiplexing, a modulation
technique for transmitting large amounts of digital data over a radio wave. In OFDM,
the radio signal is split into many smaller sub-signals which are transmitted
simultaneously at different frequencies to the receiver. OFDM reduces
the amount of crosstalk in signal transmissions. 802.11a WLAN technology uses OFDM.
For more information, see our OFDM Page.
