To use the glossary, simply click below on the first letter of the term of interest:

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

L

LAN

Local Area Network, usually used to connect workstations to a server or to each other, operating at modest speeds. Ethernet, available at 10-, 100- or 1000-Mbps is perhaps most widely used. In general, LANs do not provide guaranteed bandwith to users and may have significant latency depending upon system loading. Consequently, their use with VoIP and videoconferencing may be problematic.

LAP

Link Access Protocol (frame relay use, LAPD)

LATA

Local Access and Transport Area, a telecommunications tariff aspect in the USA.

Latency

The amount of delay in a LAN or WAN. For basic data where a small delay can be tolerated, latency is usually not an issue. However, for communications services used for videoconferencing or VoIP for example, latency can interfere with the audio and/or visual communications. In shared bandwidth transmission environments, it is possible to encounter latency which varies dynamically, caused by perhaps a single user accessing or originating multi-megabyte-sized files or accessing high bandwidth streaming signals.

LCD

Liquid Crystal Display. A very low-power device capable of displaying characters, words and symbols, often built into a telecommunications equipment control panels.

LCP

Link Control Protocol (PPP usage)

LCR

Least-Cost Routing.

LDAP

Lightweight Directory Access Protocol, developed at the University of Michigan as a front-end to the more complex ITU-T X.500 directory protocol, formalized in 1995 in RFC 1777. It includes five models: data, organization, security, function and topology. It is useful for a wide range of uses including simple dialing directories and indexing large databases.

LEC

Local Exchange Carrier

LEO

Low Earth Orbit, non-geosynchronous satellites used for communications and other purposes.

Lip Sync

The maintenance of sound (i.e., speech) exactly in step with movement in a visual image (e.g., talking heads). A common cause is different transmission paths and transmission technologies for the sound and image signals.

Within codec hardware, the processing time for the video portion of the signal is about 100 times longer than the audio processing time. Consequently, codecs usually incorporate adjustable audio delay circuitry to delay-equalize the two signals to maintain lip sync.

LMCS

Local Multipoint Communication System, another version of MMDS or "wireless cable TV"; a term used in Canada. Data rates can be as high as 155 Mbps compared to 64 Kbps cell phones and, depending on jurisdiction, may operate between 2-GHz and 42-GHz with up to 3-GHz of spectrum available.

LMDS

Local Multipoint Distribution Service, a broader-band, higher frequency, version of MMDS or "wireless cable TV". Data rates can be as high as 155 Mbps compared to 64 Kbps cell phones and, depending on jurisdiction, may operate between 2-GHz and 42-GHz with up to 3-GHz of spectrum available.

LMR

Land Mobile Radio

LMSS

Land Mobile Satellite Service

LNA

Low Noise Amplifier, an active device usually used in conjunction with an appropriate antenna to amplify and receive satellite microwave signals.

LNB or LNBC

Low Noise Block Converter, an active device used in conjunction with an appropriate antenna to convert a range of satellite signals to some intermediate frequency for processing by a receiver etc.

Loop Filter

H.261, H.263 video compression algorithm usage. See Spatial Filtering.

Luminance

The portion of a composite video signal that represents the monochrome or brightness part of the image.

LZW

Lempel-Ziv-Welch; a lossless data compression algorithm named after its developers.

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