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broadband definition - telecom
  1. In the Wide Area Network (WAN) domain, broadband is an imprecise term referring to a circuit or channel providing a relatively large amount of bandwidth. The ITU-T defines broadband in Recommendation I.113 as a transmission rate faster than the primary rate (referring to ISDN), which translates into 1.544 Mbps in North America and 2.048 Mbps in most of the rest of the world.The U.S. Federal Communications Commission (FCC) does not define broadband, but defines high-speed services as supporting a data rate of at least 200 kbps in at least one direction and advanced telecommunications capability as at least 200 kbps in both directions. Asymmetric digital subscriber line (ADSL) generally is described as a broadband access technology, even though many ADSL services operate at less than T1 and E-1 rates. In this context, ADSL certainly operates at much higher rates than the predecessor modem technology, which operates at narrowband rates of less than 64 kbps. Relatively speaking, ADSL is broadband in nature, even at very low operating rates. See also bandwidth, FCC, ISDN, ITU-T, narrowband, and wideband.
  2. In the Local Area Network (LAN) domain, broadband refers to a multichannel RF-based (Radio Frequency-based) LAN, with the channels derived through frequency division multiplexing (FDM).The workstations and other attached digital devices access analog channels through radio frequency (RF) modems that accomplish the digital-to-analog conversion process. Broadband LANs commonly use 75-ohm CATV-type coax, and use CATV-style connectors, taps, filters, and amplifiers in a tree and branch topology, which essentially is a variation of the bus with multiple branches off of a main root bus, much as there are branches off of the main trunk of a tree.The only broadband LAN to gain any significant following was 10Broad36, which has long been considered obsolete. All other LANs are baseband in nature. See also 10Broad36, baseband, B-ISDN, bus topology, CATV, channel, FDM, LAN, and tree topology.

Webster's New World Telecom Dictionary Copyright © 2008 by Wiley Publishing, Inc., Indianapolis, Indiana.
Used by arrangement with John Wiley & Sons, Inc.

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