xDSL ==>
Digital Subscriber Line definition
<communications, protocol> (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://www.cyberventure.com/~cedpa/databus-issues/v38n1/xdsl.html.
2Wire DSL provider lookup.
["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)
Nearby terms:
Digital Simulation Language « Digital Simultaneous Voice and Data « DIGITAL Standard MUMPS « Digital Subscriber Line » Digital Subscriber Line Access Module » Digital Subscriber Loop » Digital Switched Network
| 
