| slovo | definícia |
digital subscriber loop
(foldoc) | Digital Subscriber Line
Digital Subscriber Loop
xDSL
(DSL, or Digital Subscriber Loop,
xDSL - see below) A family of digital telecommunications
protocols designed to allow high speed data communication
over the existing copper telephone lines between end-users
and telephone companies.
When two conventional modems are connected through the
telephone system (PSTN), it treats the communication the
same as voice conversations. This has the advantage that
there is no investment required from the telephone company
(telco) but the disadvantage is that the bandwidth available
for the communication is the same as that available for voice
conversations, usually 64 kb/s (DS0) at most. The
twisted-pair copper cables into individual homes or offices
can usually carry significantly more than 64 kb/s but the
telco needs to handle the signal as digital rather than
analog.
There are many implementation of the basic scheme, differing
in the communication protocol used and providing varying
service levels. The throughput of the communication can
be anything from about 128 kb/s to over 8 Mb/s, the
communication can be either symmetric or asymmetric (i.e. the
available bandwidth may or may not be the same upstream and
downstream). Equipment prices and service fees also vary
considerably.
The first technology based on DSL was ISDN, although ISDN is
not often recognised as such nowadays. Since then a large
number of other protocols have been developed, collectively
referred to as xDSL, including HDSL, SDSL, ADSL, and
VDSL. As yet none of these have reached very wide
deployment but wider deployment is expected for 1998-1999.
(http://cyberventure.com/~cedpa/databus-issues/v38n1/xdsl.html).
2Wire DSL provider lookup (http://2Wire.com/).
["Data Cooks, But Will Vendors Get Burned?", "Supercomm
Spotlight On ADSL" & "Lucent Sells Paradine", Wilson & Carol,
Inter@ctive Week Vol. 3 #13, p1 & 6, June 24 1996].
(2001-04-30)
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| | podobné slovo | definícia |
asymmetric digital subscriber loop
(foldoc) | Asymmetric Digital Subscriber Line
ADSL
Asymmetric Digital Subscriber Loop
(ADSL, or Asymmetric Digital
Subscriber Loop) A form of Digital Subscriber Line in which
the bandwidth available for downstream connection is
significantly larger then for upstream. Although designed
to minimise the effect of crosstalk between the upstream and
downstream channels this setup is well suited for {web
browsing} and client-server applications as well as for
some emerging applications such as video on demand.
The data-rate of ADSL strongly depends on the length and
quality of the line connecting the end-user to the telephone
company. Typically the upstream data flow is between 16 and
640 kilobits per second while the downstream data flow is
between 1.5 and 9 megabits per second. ADSL also provides a
voice channel.
ADSL can carry digital data, analog voice, and broadcast
MPEG2 video in a variety of implementations to meet customer
needs.
["Data Cooks, But Will Vendors Get Burned?", "Supercomm
Spotlight On ADSL" & "Lucent Sells Paradine", Wilson & Carol,
Inter@ctive Week Vol. 3 #13, p1 & 6, June 24 1996].
See also Carrierless Amplitude/Phase Modulation, {Discrete
MultiTone}.
ADSL Forum (http://adsl.com/).
(1998-05-18)
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