Creativyst's Glossary of Industry Related Terms

Industry Terms

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(Creativyst™ Glossary)

G.711

	An ITU standard PCM codec that converts analog speech to a stream of digital data and back again. G.711 converts to and from analog and digital without compression of any kind and so requires a full 64Kbps of digital bandwidth
	See Also: G.729A PLC

G.729A

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An ITU standard PCM codec that converts analog speech to or from a stream of digital data. G.729A employs data compression techniques so that a voice conversation that would normally take 64Kbps of bandwidth (using G.711 can be transmitted using only 8Kbps.

Requiring a lower data-rate allows G.729A to utilize available bandwidth more efficiently but also makes the call much more fragile in the face of network transmission impairments such as packet loss. It also reduces the legibility, especially in situations where the signal is re-digitized multiple times (such as when a digital cordless phone is used).

See Also: PLC

General Packet Radio Service

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	A 2.5G digital cellular phone standard for data speeds up to 171 Kbps. This is an upgrade for GSM networks. GPRS reallocates serveral GSM time slots from voice to data uses, thereby increasing data rates but decreasing voice rates. GPRS services have recently been rolled out in variouus locations principally in China, Europe, and the US.
	See Also: GSM iDEN 2.5G

Geostationary

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	See: Geosynchronous

Geosynchronous

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Also known as geostationary. Describes the orbit of a satellite that remains stationary over a single geographic point on earth (i.e. synchronized to a geographic position on earth). This is accomplished by orbiting the satellite at a distance of 22,300 miles (35,900 km) above the equator. At this distance, an object orbits the earth at the same speed the earth rotates (approximately once every twenty-four hours) and so the object appears to remain stationary above the point.

Geosynchronous satellites are useful for many applications but not for two-way conversations. The reason for this is that it takes radio waves almost a quarter of a second to make the round trip (44,600 miles at 186,000 miles/second). This added to other delays in the normal transmission of digitized audio and video produces unacceptable latency during conversations.

LEO (Low Earth Orbiting) satellites orbit the earth at only a few hundred miles and so do not suffer from the latency problem.

See Also: Jitter LEO Latency

Global Positioning System

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	GPS - A system that uses radio signals between LEO satellites and ground based systems on Earth to pinpoint the location of the ground-based system. In the past the ground-based systems were large and used in planes, ships, and automobiles. Now they are routinely embedded in wristwatches and cell phone.

Glossary

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	A list of terms and their meanings. Usually relating to a specific industry or topic of interest. This is a glossary.

GPRS

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	See: General Packet Radio Service

GPS

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	See: Global Positioning System

Graphical User Interface

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	See: GUI

Ground Start

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Ground Start Signaling - Ground-start signaling for a two-way dial system is an old technology (introduced in the 1920s). It is used typically on two-way PBX central office trunks with direct outward dialing (DOD) and attendant-handled incoming call service. The ground-start line conductors transmit common battery-loop supervision, DTMF address signalling or loop dial pulses, alerting signals, and voiceband electrical energy.

	Global System for Mobile Communications � the world�s most popular 2G technology, implemented in much of Europe and Asia, is (like TDMA) based on time-division multiplexing but uses wider carrier frequencies and eight, rather than three, time slots.
	See Also: TDMA CDMA 2G

	Graphical User Interface - (Pronounced "gooey.") A software interface based on pictorial representations and menus of operations and files. Microsoft Windows is an example of a widely used GUI interface.
	See Also: User Interface