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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.

Forward Error Correction (coding / decoding technique).

Feeder Link
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.

First-In First-Out.

First Generation
Refers to early analog cell phone systems, those developed in the 1980s but still in use today.

Fixed Radio Access (FRA)
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.

Fixed-satellite service (FSS)
A radiocommunication service between earth stations at given fixed positions via one or more satellites.

Fixed service
A point-to-point radiocommunications service between specific fixed stations on the earth.

Fixed wireless network
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.

Frequency Moduation; modulation of the RF carrier frequency -- another very simple modulation, used today in the FM band.

Free-Space Path Loss
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.

The reciprocal of a signal's period is its frequency (units of Hertz -- or cycles per second -- actually 1/second, dimensionally).

Frequency allocation
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.

Frequency allotment
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.

Frequency assignment
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.

Frequency reuse factor (K)
A number based on frequency reuse to determine how many channels per cell.

Frequency Shift Keying; a digital binary modulation of the RF carrier frequency.


Gain, dB
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).

Gain, dBd
Antenna gain, expressed in decibels referenced to a half wave dipole.

Gain, dBi
Antenna gain, expressed in decibels referenced to a theoretical isotropic radiator.

Gain, dBic
Antenna gain, expressed in decibels referenced to a theoretical isotropic radiator that is circularly polarized.

GPRS: General Packet Radio Service
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.

Geostationary satellite orbit (GSO)
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.

GSM: Global System for Mobile Communications
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.


Half-Duplex Operation
Operating method in which transmission is possible in both directions, but only in one direction at a time.

A frequency channel will be changed to a new frequency channel as the vehicle moves from from one cell to another without the user's intervention.

High Frequency (HF)
A signal in the frequency range of from 3 to 30 MHz.

Horizontal Polarization
In an antenna, a linearly polarized electric field vector whose direction is horizontal relative to ground or some arbitrary coordinate system.


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.

Intelligent Network (IN)
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.

The name given to the worldwide collection of networks and gateways using the TCP/IP protocol that functions as a single virtual network.

Internet Protocol. (See also TCP/IP).

See TDMA (ANSI-136).

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.

Isotropic Radiator
A hypothetical, lossless antenna having equal radiation intensity in all directions; used as a zero-dB gain reference in pattern measurements or directivity calculations.

International Telecommunications Union. Based in Geneva, the ITU is an organisation of the UN that oversees cellular standards around the world.



The Constraint Length of a convolutional encoder or Viterbi decoder.


Land-Mobile-Satellite Service
A mobile satellite service in which mobile earth stations are located on land.

Land-Mobile Service
A mobile service between base stations and land-mobile stations, or between land-mobile stations.

Land Mobile Station
A mobile station in the land-mobile service capable of surface movement within the geographical limits of a country or continent.

Local Area Network (LAN)
A (usually wired or cabled) computer to computer data communications network.

Low earth orbit (LEO)
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.

Low Frequency (LF)
A signal in the frequency range of from 300 to 3000 kHz.


One million bits per second; a data rate.

Microstrip Antenna
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.

Mobile Cellular Systems
A high capacity system operating at 800-900 MHz using a frequency reuse scheme for vehicle and portable telephone communications.

Mobile-Satellite Service (MSS)
A service that links mobile earth stations with base stations and with one another via one or more satellites.

Mobile Service
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.

Mobile Station
A station in the mobile service intended to be used while in motion or during halts at unspecified points.

Monopole Antenna
One constructed above a ground plane producing a radiation pattern approximating that of a dipole in the half-space above the ground plane.

In the context of mobile communications, a service that may combine voice, data, graphics and video information.

Multiple Access
A method for accomodating more users in the same frequency band.


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.

Having properties that cause the appearance of true random noise.

In an antenna, near zero-level signals of sharp angular width seen in a radiation patterns. The opposite of lobes.


That property of an antenna exhibiting a non-directional pattern in a given plane.

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.

Offset Quadrature Phase Shift Keying; QPSK with an initial phase offset (of usually 45 degrees); OQPSK has less envelope AM than QPSK.

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