High-bit-rate digital subscriber line 2 (HDSL2) is a standard developed by the
American National Standards Institute
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 ...
(ANSI) Committee T1E1.4 and published in 2000 as ANSI T1.418-2000.
Like its predecessor
HDSL 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 ...
, HDSL2 provides a symmetric data rate of 1,544 kbit/s in both the
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 ...
and
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 ...
directions at a
noise margin
In electrical engineering, noise margin is the maximum voltage amplitude of extraneous signal (electrical engineering), signal that can be algebraically added to the noise-free worst-case input level without causing the output voltage to deviate fr ...
of 5-6 dB.
Its primary purpose was also to provision a
T-1 line, only this technology relies on fewer wires - two instead of four - and therefore costs less to set up.
The modulation technique used in HDSL2 is
TC-PAM
Trellis-coded pulse-amplitude modulation (TC-PAM) is the modulation format that is used in HDSL2 and G.SHDSL. It is a variant of trellis coded modulation (TCM) which uses a one-dimensional pulse-amplitude modulation (PAM) symbol space, as oppos ...
, which is also used in
G.SHDSL, as opposed to
2B1Q in HDSL. Spectral shaping is applied to increase compatibility with ADSL and HDSL2 on the same bundle.
HDSL4 provides the same bitrate as HDSL2, but uses four wires instead of two, to increase robustness.
On an
AWG26 local loop, the reach of HDSL2 is , while that of HDSL4 is .
References
External links
*
Digital subscriber line
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