Asymmetric Digital Subscriber Line
Broadband Internet Glossary
Broadband Internet — Asymmetric Digital Subscriber Line
Information on Asymmetric Digital Subscriber Line
Asymmetric Digital Subscriber Line allows broadband data services
to be carried on conventional copper pair telephone cables.
Asymmetric Digital Subscriber Line
is based on an adaptive, multi-tone modulation system known as
discrete multi-tone (DMT). Each tone carries a part of either
the uplink or the downlink bitstream. Because the bitstreams are
split across a number of tones, the symbol rate on
the link is much less than the bit rate. An
important advantage of discrete multi-tone (DMT) is that it can
cope well with narrow-band interference, such as that generated by
an AM radio station.
The term "asymmetric" in Asymmetric Digital Subscriber Line refers
to the difference in uplink and downlink capacities; typically a
much higher capacity is provided for the downlink than for
the uplink. This means that a larger number of tones
are allocated for downlink data than for uplink data.
Asymmetric Digital Subscriber Line
supports upstream speeds between 16 and 64 kbps. Asymmetric Digital Subscriber Line
downstream speeds may be as high as 8 Mbps, with
1.5 Mbps available under good conditions at 5.5 km.
An advantage
of Asymmetric Digital Subscriber Line is that the Asymmetric Digital Subscriber Line modem is
powered from the same copper pair as carries the data,
which means that an Asymmetric Digital Subscriber Line link can operate even
if the mains power fails.
Other topics in our resources on Broadband Internet related to Asymmetric Digital Subscriber Line include:
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