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, 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 directions at a noise margin 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 opposed ...

, which is also used in G.SHDSL, as opposed to

2B1Q Two-binary, one-quaternary (2B1Q) is a line code used in the U interface of the Integrated Services Digital Network (ISDN) Basic Rate Interface (BRI) and the high-bit-rate digital subscriber line (HDSL). 2B1Q is a four-level pulse-amplitude modulat ...

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 {{telecomm-stub