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Asymmetric digital subscriber line (ADSL) is a type of digital subscriber line (DSL) technology, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voiceband modem can provide. ADSL differs from the less common symmetric digital subscriber line (SDSL).
The American National Standards Institute (ANSI) Telecommunications Committee created the first standardized ADSL specifications. They were published as ANSI T1.413-1995 and ANSI T1.413-1998 (sometimes called "issue 2") titled Network and Customer Installation Interfaces — Asymmetric Digital Subscriber Line (ADSL) Metallic Interface.
There are 2 competing standards for DMT ADSL - ANSI and G.dmt; ANSI T1.413 is a North American standard, G.992.1 (G.dmt) is an ITU (United Nations Telecom committee) standard. G.dmt is used most commonly today, throughout the world, but the ANSI standard was formerly popular in North America.
ITU G.992.3 is an ITU (International Telecommunication Union) standard, also referred to as ADSL2 or G.dmt.bis.It optionally extends the capability of basic ADSL in data rates to 12 Mbit/s downstream and, depending on Annex version, up to 3.5 Mbit/s upstream (with a mandatory capability of ADSL2 transceivers of 8 Mbit/s downstream and 800 kbit/s upstream). [1]
SDSL is a rate-adaptive digital subscriber line (DSL) variant with T1/E1-like data rates (T1: 1.544 Mbit/s, E1: 2.048 Mbit/s). It runs over one pair of copper wires, with a maximum range of 10,000 feet (3,000 m). It cannot co-exist with a conventional voice service on the same pair as it takes over the entire bandwidth. [1]
Digital subscriber line (DSL; originally digital subscriber loop) is a family of technologies that are used to transmit digital data over telephone lines. [1] In telecommunications marketing, the term DSL is widely understood to mean asymmetric digital subscriber line (ADSL), the most commonly installed DSL technology, for Internet access .
Tones are spaced apart by 4.3125kHz. In the Annex A, L and M frequency standards, POTS (analog PSTN voice) occupies (what would be) tones 0-3, tones 4-7 are reserved for a ‘guard band’, and the upstream DSL transmission band uses tones 8-31 in Annex A and L, or 8-56 in Annex M. In Annex B, ISDN occupies tones 0-31, DSL upstream uses tones ...
In telecommunications, ITU G.992.2 (better known as G.lite) is an ITU standard for ADSL using discrete multitone modulation. G.lite is designed to not require the use of a DSL filter . G.lite is a modulation profile which can be selected on a DSLAM port by an ADSL provider and provides greater resistance to noise and tolerates longer loop ...