ADSL
Broadband Internet Glossary
Broadband Internet — ADSL
Information on ADSL
ADSL (Asymmetric digital subscriber line) allows broadband data services
to be carried on conventional copper pair telephone cables.
ADSL
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 ADSL 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.
ADSL
supports upstream speeds between 16 and 64 kbps. ADSL
downstream speeds may be as high as 8 Mbps, with
1.5 Mbps available under good conditions at 5.5 km.
An advantage
of ADSL is that the ADSL modem is
powered from the same copper pair as carries the data,
which means that an ADSL link can operate even
if the mains power fails.
Other topics in our resources on Broadband Internet related to ADSL include:
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