View source for G.992.3

{{short description|ITU-T Recommendation}}
{{Infobox technology standard
| title             = G.992.3
| long_name         = Asymmetric digital subscriber line transceivers 2 (ADSL2)
| image             = 
| caption           = 
| status            = In force
| year_started      = 2003
| version           = (10/12)
| version_date      = October 2012
| preview           = 
| preview_date      = 
| organization      = [[ITU-T]]
| committee         = 
| base_standards    = 
| related_standards = [[G.992.5]], [[G.992.3 Annex J]]
| abbreviation      = 
| domain            = [[telecommunications]]
| license           = Freely available
| website           = https://www.itu.int/rec/T-REC-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 [[Asymmetric Digital Subscriber Line|ADSL]] in data rates to 12&nbsp;[[Mbit/s]] downstream and, depending on [[#ADSL2 Annexes|Annex version]], up to 3.5&nbsp;Mbit/s upstream (with a mandatory capability of ADSL2 transceivers of 8&nbsp;Mbit/s downstream and 800&nbsp;kbit/s upstream).<ref>{{Cite web|title=G.992.3: Asymmetric digital subscriber line transceivers 2 (ADSL2)|url=https://www.itu.int/rec/T-REC-G.992.3/|url-status=live|archive-url=https://web.archive.org/web/20210426165550/https://www.itu.int/rec/T-REC-G.992.3/|archive-date=2021-04-26|access-date=2021-04-26|website=www.itu.int}}</ref> 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 [[Digital subscriber line access multiplexer|DSLAM]] to the customer's equipment.

[[File:ADSL2 frequencies.png]]

==Annex versions==
<abbr>ADSL2</abbr> has multiple modes for <abbr>DSL</abbr> providers to offer services for different needs. Below is a list of available features based on <abbr>ADSL2</abbr> specs from the <abbr>ITU</abbr> standards.
[[File:ADSL annex overview.svg|thumb|500px|left|Frequency plan for common <abbr>ADSL</abbr> standards and annexes<br />
{{legend|#ff6600|<abbr>POTS</abbr>/<abbr>ISDN</abbr>}}
{{legend|#ffff00|Guard Band}}
{{legend|#00ee00|Upstream}}
{{legend|#d40000|Downstream <abbr>ADSL</abbr>/<abbr>ADSL2</abbr>}}
{{legend|#900000|Additional Downstream <abbr>ADSL2+</abbr>}}
]]{{clear}}
{| class="wikitable"
|-
! Annex version
! Spec
! Description
|-
|style="text-align: center;"| A
| <abbr>xDSL</abbr> over <abbr>POTS</abbr>
| <abbr>xDSL</abbr> service functioning over [[plain old telephone service]]. 
|-
|style="text-align: center;"| B
| <abbr>xDSL</abbr> over <abbr>ISDN</abbr>
| <abbr>xDSL</abbr> Services running over [[Integrated Services Digital Network]].
|-
|style="text-align: center;"| C
| <abbr>xDSL</abbr> in <abbr>ISDN</abbr>
| <abbr>xDSL</abbr> System operating in the same cable as <abbr>ISDN</abbr> as defined in <abbr>ITU-T</abbr> <abbr>Rec.</abbr> G.961 Appendix III (Currently{{as of?|date=May 2012}} not implemented)
|-
|style="text-align: center;"| D
| [[ADSL transceiver|ATU-C]] and <abbr>ATU-R</abbr> [[state diagram]]s
| See Annex D/G.992.3
|-
|style="text-align: center;"| E
| <abbr>POTS</abbr> and <abbr>ISDN-BA</abbr> [[DSL filter|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&nbsp;kHz shall be met over a frequency band up to 2208&nbsp;kHz.
|-
|style="text-align: center;"| F
| [[ADSL transceiver|ATU-x]] performance requirements for region A (North America)
| F.1 Performance requirements for operation of <abbr>ADSL</abbr> over <abbr>POTS</abbr> (Annex A)<br />F.2 Performance requirements for operation of All Digital Mode <abbr>ADSL</abbr> (Annex I)<br />F.3 Performance requirements for operation of <abbr>ADSL</abbr> over <abbr>POTS</abbr> with extended upstream bandwidth (Annex L)
|-
|style="text-align: center;"| G
| <abbr>ATU-x</abbr> performance requirements for region B (Europe)
| G.1 Performance requirements for operation of <abbr>ADSL</abbr> over <abbr>POTS</abbr> (Annex A)<br />G.2 Performance requirements for operation of <abbr>ADSL</abbr> over <abbr>ISDN</abbr> (Annex B)<br />G.3 Performance requirements for operation of All Digital Mode <abbr>ADSL</abbr> (Annex I) <br />G.4 Performance requirements for operation of All Digital Mode <abbr>ADSL</abbr> (Annex J)<br />G.5 Performance requirements for operation of <abbr>ADSL</abbr> over <abbr>POTS</abbr>, with extended upstream bandwidth (Annex L)
|-
|style="text-align: center;"| I
| All Digital mode <abbr>ADSL</abbr> with improved spectral compatibility with <abbr>ADSL</abbr> over <abbr>POTS</abbr>
| Extending <abbr>ADSL</abbr> band to use the voice frequency range, 32 upstream tones for an additional 256 [[kilobit|kbit]]/s upstream data rate over <abbr>POTS</abbr> lines.
|-
|style="text-align: center;"| [[G.992.3 Annex J|J]]
| All Digital mode <abbr>ADSL</abbr> with improved spectral compatibility with <abbr>ADSL</abbr> over <abbr>ISDN</abbr>
| Extending <abbr>ADSL</abbr> band to use the voice frequency range, 64 upstream tones for an additional 256&nbsp;kbit/s upstream data rate over <abbr>ISDN</abbr> Lines.
|-
|style="text-align: center;"| [[G.992.3 Annex L|L]]
| Reach Extended
| Increases the range of the <abbr>DSL</abbr> service enabling the link to work at a distance of {{convert|7|km|ft}}
|-
|style="text-align: center;"| [[ITU G.992.5 Annex M|M]]
| Increased Upload speeds
| Upstream/downstream frequency split has been shifted from 138&nbsp;kHz up to 276&nbsp;kHz, allowing maximum upstream bandwidth to be increased from 1.4&nbsp;Mbit/s to 3.3&nbsp;Mbit/s.
|}

==See also==
* [[Asymmetric digital subscriber line|ADSL]]
* [[G.992.5|ADSL2+]]
* [[List of interface bit rates]]
* [[Wetting current]]

==References==
{{reflist}}

==External links==
*[http://www.itu.int/rec/T-REC-G.992.3/en ITU-T Recommendation G.992.3]: Asymmetric digital subscriber line transceivers 2 (ADSL2)

{{DSL technologies}}

[[Category:Digital subscriber line]]
[[Category:ITU-T recommendations]]
[[Category:ITU-T G Series Recommendations]]
[[Category:Telecommunications-related introductions in 2002]]