Rate-adaptive digital subscriber line (RADSL) is a pre-standard
asymmetric digital subscriber line
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) solution.
RADSL was introduced as proprietary technology by AT&T Paradyne, later GlobeSpan Technologies Inc.,
in June 1996.
In September 1999, RADSL technology was formally described by
ANSI
The American National Standards Institute (ANSI ) is a private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organi ...
in T1.TR.59-1999.
RADSL supports
downstream
Downstream may refer to:
* Downstream (bioprocess)
* Downstream (manufacturing)
* Downstream (networking)
* Downstream (software development)
* Downstream (petroleum industry)
* Upstream and downstream (DNA), determining relative positions on DNA ...
data rates of up to approximately 8 Mbit/s,
upstream
Upstream may refer to:
* Upstream (bioprocess)
* ''Upstream'' (film), a 1927 film by John Ford
* Upstream (networking)
* ''Upstream'' (newspaper), a newspaper covering the oil and gas industry
* Upstream (petroleum industry)
* Upstream (software ...
data rates up to approximately 1 Mbit/s, and can coexist with
POTS voice on the same line.
RADSL allows rate-adaptation while the connection is in operation — rate-adaptation during connection setup is possible in many other DSL variants, including
G.dmt and its successors. Rate-adaptation while the connection is in operation is specified as an option in
ADSL2
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 ...
,
ADSL2+
G.992.5 (also referred to as ADSL2+, G.dmt.bis+, and G.adslplus) is an ITU-T standard for asymmetric digital subscriber line (ADSL) broadband Internet access. The standard has a maximum theoretical downstream sync speed of 24 megabits per second ...
, and
VDSL2
Very high-speed digital subscriber line (VDSL) and very high-speed digital subscriber line 2 (VDSL2) are digital subscriber line (DSL) technologies providing data transmission faster than the earlier standards of asymmetric digital subscriber line ...
, under the name ''seamless rate adaptation'' (SRA).
Technology
RADSL specifies two alternative modulation schemes,
quadrature amplitude modulation
Quadrature amplitude modulation (QAM) is the name of a family of digital modulation methods and a related family of analog modulation methods widely used in modern telecommunications to transmit information. It conveys two analog message signa ...
(QAM) and
carrierless amplitude phase modulation Carrierless amplitude phase modulation (CAP) is a variant of quadrature amplitude modulation (QAM). Instead of modulating the amplitude of two carrier waves, CAP generates a QAM signal by combining two PAM signals filtered through two filters desig ...
(CAP).
RADSL is not interoperable with
discrete multi-tone (DMT) modulation variants of ADSL, standardized in
ANSI T1.413 Issue 2 and
G.dmt (G.992.1).
Upstream and downstream are
frequency-division duplexed, the upstream and downstream transmit PSD masks are identical to those in ANSI T1.413.
In RADSL, the
baud rate
In telecommunication and electronics, baud (; symbol: Bd) is a common unit of measurement of symbol rate, which is one of the components that determine the speed of communication over a data channel.
It is the unit for symbol rate or modul ...
, center frequency, and constellation size of the downstream and upstream channels can be adjusted while the connection is in operation.
Using this technique the line is more tolerant of errors caused by
noise
Noise is unwanted sound considered unpleasant, loud or disruptive to hearing. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrations through a medium, such as air or water. The difference aris ...
and signal loss. As the parameters are adjusted, the bandwidth may be markedly decreased if there is a large amount of line noise or signal degradation.
See also
*
Etherloop Etherloop is a kind of DSL technology that combines the features of Ethernet and DSL. It allows the combination of voice and data transmission on standard phone lines. Under the right conditions it will allow speeds of up to 6 megabits per second o ...
—another DSL variant using single-carrier modulation (QAM)
*
High-bit-rate digital subscriber line High-bit-rate digital subscriber line (HDSL) is a telecommunications protocol standardized in 1994. It was the first digital subscriber line (DSL) technology to use a higher frequency spectrum over copper, twisted pair cables. HDSL was developed to ...
(HDSL)—another DSL variant using single-carrier modulation (CAP)
*
Multi-rate symmetric digital subscriber line Multi-rate symmetric DSL (MSDSL or MDSL) is a proprietary, non-standardized symmetric digital subscriber line technology with a maximum distance of . It is capable of multiple transfer rates, as set by the Internet service provider, typically base ...
(MSDSL)—another DSL variant using single-carrier modulation (CAP)
*
Very-high-bit-rate digital subscriber line
Very high-speed digital subscriber line (VDSL) and very high-speed digital subscriber line 2 (VDSL2) are digital subscriber line (DSL) technologies providing data transmission faster than the earlier standards of asymmetric digital subscriber line ...
(VDSL)—another DSL variant using single-carrier modulation (QAM)
References
{{DSL technologies
Digital subscriber line