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Asymmetric Digital Subscriber
Line, one of several BROADBAND technologies
designed to increase the BANDWIDTH available
over standard copper telephone wires (see also DSL).
ADSL'S design is based on the assumption that most homes and
businesses consume may theoretically provide an incoming (or downstream)
data speed of up to 8MBPS and an outgoing (or upstream) speed of less then
1mbps, although in practice ISPS are likely to
provide much slower connections than this (typically 512KBPS) to keep costs
down. the actual data transmission speeds possible depend on the quality and
integrity of the copper connection and associated equipment, as well as the
distance of the user from the exchange.
ADSL is suitable for one-way applications such as web browsing, video on
demand and software distribution, but much less so for those with two-way
needs such as VIDEOCONFERENCING. This makes it ideal for home users and
small businesses, who are slowly beginning to adopt it as ISPS and telecoms
companies broaden the reach of their broadband net-works and improve their
marketing. Most large ISPS in Europe now sell
ADSL connections for both home
and business use.
Because ADSL runs on standard copper wires with a direct one-to
one link to the exchange, rather than across shared cable, it will provide
much more consistent performance than most of the alternatives. It requires
only a special MODEM and, in some cases, a separate device to split the data
and voice channels. It is also much more widely available then equivalent
services from cable networks, which require expensive investment and
disruptive engineering work to extend their wires to people's doorsteps. But
many potential ADSL subscribers, especially those in rural areas, have been
disappointed to discover that they live or work too far from their nearest
exchange to receive it. This is one reason why only 9% of UK internet users
subscribed to broadband services in January 2003. |
