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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, as
shown in the Figure. Such rates expand existing access capacity by a
factor of 50 or more without new cabling. ADSL can literally
transform the existing public information network from one limited
to voice, text, and low-resolution graphics to a powerful, universal
system capable of bringing multimedia, including full motion video,
to every home this decade.
ADSL will play a crucial role over
the next decade or more as telephone companies enter new markets for
delivering information in video and multimedia formats. 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 vendors alike.
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