7E Communications
   

Glossary Terms Beginning G

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G.711
ITU-T specification for audio data coding using 64 kbps of bandwidth to provide 3 kHz telephone quality audio.
G.722
ITU-T specification for audio data coding using 64 kbps of bandwidth to provide 7.5 kHz audio over a 64 kbps circuit.
G.728
ITU-T specification for audio data coding using 16 kbps of bandwidth to provide 3 kHz audio of bandwidth.
G/T
See figure of merit.
Gain
Measure of amplification expressed in dB.
Gain step
The gain setting of a transponder, which can be varied in discrete steps from the TT&C ground station according to operational requirements.
GAN
Global Area Network: see M4.
GEO
Geostationary Earth Orbit.
Geostationary
Earth orbit GEO: describes a special geosynchronous orbit which is symmetrical above the Equator such that the satellite appears to remain stationary relative to a location on the surface of the Earth.
Geosynchronous orbit
Describes a circular orbit around the Earth, with an average distance from the centre of the Earth of about 42 000 km (26 000 miles) in which the satellite orbit has a period equal to the rotation period of the Earth.
GHz
Gigahertz: unit of frequency equal to one thousand million cycles per second, or 1 109 Hz (1 000 000 000 Hz).
Glitch
Imperfections in a digital signal.
GMDSS
Global Maritime Distress and Safety System: operated by INMARSAT as a life-saving service.
GMPCS
Global Mobile Personal Communication by Satellite.
GPRS
General packet radio services: wireless packet-data service; part of the thirdgeneration of digital cellular telephony (3G).
GPS
Global Positioning System: satellite-based navigation system.
Graveyard orbit
Orbital positions at 105W and 75E where satellites are moved or allowed to drift to at the end of their operational lives; thus this space junk can then be monitored to reduce the risk of debris damaging any active spacecraft.
Ground station
Generic term for satellite communications earth station.
GSM
Global System for Mobile Communications: digital cellular telephony standard.
Guard-band; guard-channel
Separation of signals in a transponder to minimize the risk of interference with each other.