G3G: Global Third Generation. The G3G proposal was developed by the OHG in order to harmonize the WCDMA systems being proposed by 3GPP and 3GPP2.

Gain. A measure of amplification - in decibels (dB).

Gateway. A device that connects two or more dissimilar networks and allows communication between them.

Gbs (Gigabits per second). The rate at which data can be transferred along a communications link. 1 Gbs is equal to one billion bits per second or approximately 125 million characters per second (where each character is equal to 8 bits).

Geostationary. Satellites orbit the earth 36,000 Km above the equator and rotate at the same relative speed and direction as the earth's surface, making them appear stationary.

GFC (Generic Flow Control). A field in the ATM header which can be used to provide local functions (for example, flow control). It has local significance only and the value encoded in the field is not carried end-to-end.

GGSN: Gateway GPRS Support Node. Interfaces GPRS networks to other networks. It is the main switch and control node for GPRS networks.

GHz. A unit of frequency equal to one billion hertz or one thousand megahertz.

GMSC (Gateway Mobile services Switching Center). GMSC acts as a gateway for incoming calls into a GSM network.

GPRS: General Packet Radio Service. GPRS is a packet based data service developed for mobile communications systems that will support data rates of up to 115 kbps.

GPS (Global Positioning System). GPS is a satellite-based navigation system operated by the US Department of Defense (DoD). The space segment of the GPS system consists of 24 satellites placed in 6 orbital planes that orbit the earth every 12 hours.

GSM service area. The GSM service area is the entire geographical area in which a mobile subscriber can access a GSM network.

Group 1 fax. An analog facsimile that can transmit a standard page within 6 minutes. Group 1 machines are no longer manufactured.

Group 2 fax. An analog facsimile that can transmit a standard page within 3 minutes by using data compression techniques.

Group 3 fax. A digital facsimile that can transmit a standard page in under 1 minute. Group 3 facsimiles are standard in business. They can detect the maximum transmission and reception capabilities of a group 1 or group 2 fax and alter its settings to suit.

GSM (Global System for Mobile communications). A digital system for cellular telecommunications.

GSM Bearer. Refers to the various mechanisms the GSM network uses to transmit voice and data.

GSM MAP: GSM Mobile Application Part. GSM MAP is the core network that supports the GSM air interface.

Guard tone. A feature of high speed modems that uses a special tone to detect if there is sufficient bandwidth available on a PSTN network for transmission.