ASYMMETRIC DIGITAL SUBSCRIBER LINE TECHNOLOGY

Asymmetric digital subscriber line (ADSL) uses existing twisted pair telephone lines to create access paths for high-speed data communications and transmits at speeds up to 8.1Mbps to a subscriber. This exciting technology is in the process of overcoming the technology limits of the public telephone network by enabling the delivery of high speed Internet access to the vast majority of subscribers’ homes at a very affordable cost. ADSL can literally transform the existing public information network from one limited to voice, text, and low-resolution graphics to a powerful, ubiquitous system capable of bringing multimedia, including full motion video, to every home this century. New broadband cabling will take decades to reach all prospective subscribers. Success of these new services will depend on reaching as many subscribers as possible during the first few years. By bringing movies, television, video catalogs, remote CD-ROMs, corporate LANs, and the Internet into homes and small businesses, ADSL will make these markets viable and profitable for telephone companies and application suppliers alike.

ADSL technology is asymmetric. It allows more bandwidth downstream---from an NSP's central office to the customer site---than upstream from the subscriber to the central office. This asymmetry combined with always-on access (which eliminates call setup), makes ADSL ideal for Internet/intranet surfing, video-on-demand, and remote LAN access. Users of these applications typically download much more information than they send. ADSL transmits more than 6 Mbps to a subscriber and as much as 640 kbps more in both directions (shown below). Such rates expand existing access capacity by a factor of 50 or more without new cabling.

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