G.992.3

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] ADSL2 uses the same bandwidth as ADSL but achieves higher throughput via improved modulation techniques. Actual speeds may decrease depending on line quality; usually the most significant factor in line quality is the distance from the DSLAM to the customer's equipment.

G.992.3

Asymmetric digital subscriber line transceivers 2 (ADSL2)
Status	In force
Year started	2003
Latest version	(10/12) October 2012
Organization	ITU-T
Related standards	G.992.5, G.992.3 Annex J
Domain	telecommunications
License	Freely available
Website	https://www.itu.int/rec/T-REC-G.992.3/

Annex versions

ADSL2 has multiple modes for DSL providers to offer services for different needs. Below is a list of available features based on ADSL2 specs from the ITU standards.

Frequency plan for common ADSL standards and annexes

  POTS/ISDN

  Guard Band

  Upstream

  Downstream ADSL/ADSL2

  Additional Downstream ADSL2+

Annex version	Spec	Description
A	xDSL over POTS	xDSL service functioning over plain old telephone service.
B	xDSL over ISDN	xDSL Services running over Integrated Services Digital Network.
C	xDSL in ISDN	xDSL System operating in the same cable as ISDN as defined in ITU-T Rec. G.961 Appendix III (Currently[as of?] not implemented)
D	ATU-C and ATU-R state diagrams	See Annex D/G.992.3
E	POTS and ISDN-BA splitters	See Annex E/G.992.3. For operation according to Annexes A, B and I, the G.992.3 requirements applying over a frequency band up to 1104 kHz shall be met over a frequency band up to 2208 kHz.
F	ATU-x performance requirements for region A (North America)	F.1 Performance requirements for operation of ADSL over POTS (Annex A) F.2 Performance requirements for operation of All Digital Mode ADSL (Annex I) F.3 Performance requirements for operation of ADSL over POTS with extended upstream bandwidth (Annex L)
G	ATU-x performance requirements for region B (Europe)	G.1 Performance requirements for operation of ADSL over POTS (Annex A) G.2 Performance requirements for operation of ADSL over ISDN (Annex B) G.3 Performance requirements for operation of All Digital Mode ADSL (Annex I) G.4 Performance requirements for operation of All Digital Mode ADSL (Annex J) G.5 Performance requirements for operation of ADSL over POTS, with extended upstream bandwidth (Annex L)
I	All Digital mode ADSL with improved spectral compatibility with ADSL over POTS	Extending ADSL band to use the voice frequency range, 32 upstream tones for an additional 256 kbit/s upstream data rate over POTS lines.
J	All Digital mode ADSL with improved spectral compatibility with ADSL over ISDN	Extending ADSL band to use the voice frequency range, 64 upstream tones for an additional 256 kbit/s upstream data rate over ISDN Lines.
L	Reach Extended	Increases the range of the DSL service enabling the link to work at a distance of 7 kilometres (23,000 ft)
M	Increased Upload speeds	Upstream/downstream frequency split has been shifted from 138 kHz up to 276 kHz, allowing maximum upstream bandwidth to be increased from 1.4 Mbit/s to 3.3 Mbit/s.

See also

• ADSL
• ADSL2+
• List of interface bit rates
• Wetting current