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Fast access to subscriber terminals
StatusIn force
Year started5 December 2014 (2014-12-05)
Latest version(10/20)
October 2020
CommitteeITU-T Study Group 15
Base standards
  • G.997.2
  • G.9700
  • G.9701
LicenseFreely available
Sckipio 24port DPU
Sckipio 24-port DPU (Distribution point unit), provides service. is a digital subscriber line (DSL) protocol standard for local loops shorter than 500 meters, with performance targets between 100 Mbit/s and 1 Gbit/s, depending on loop length.[1] High speeds are only achieved over very short loops. Although was initially designed for loops shorter than 250 meters, Sckipio in early 2015 demonstrated delivering speeds over 100 Mbit/s at nearly 500 meters and the EU announced a research project.[2]

Formal specifications have been published as ITU-T G.997.2, G.9700, and G.9701, with approval of G.9700 granted in April 2014 and approval of G.9701 granted on December 5, 2014.[3][4][5][6] Development was coordinated with the Broadband Forum's FTTdp (fiber to the distribution point) project.[7][8][3]

The letter G in stands for the ITU-T G series of recommendations; fast is a recursive acronym for fast access to subscriber terminals.[9] Limited demonstration hardware was demonstrated in mid-2013.[10] The first chipsets were introduced in October 2014, with commercial hardware introduced in 2015, and first deployments started in 2016.[11][12][13]

Technology service is provided to users by DPUs (Distribution Point Units)[14][15] which are installed near the customer often at a distance of up to 100 meters[16] and connected via optical fiber to an internet service provider. DPUs can be installed in several locations such as multi-dwelling unit basements, utility poles, curb boxes, or manholes,[17] and can be powered by customer premises equipment called NTUs or network termination units, in what is called reverse powering or reverse power feeding.[18][19]


In, data is modulated using discrete multi-tone (DMT) modulation, as in VDSL2 and most ADSL variants.[20] modulates up to 12 bit per DMT frequency carrier, reduced from 15 in VDSL2 for complexity reasons.[21]

The first version of specifies 106 MHz profiles and the second version specifies 212 MHz profiles, compared to 8.5, 17.664, or 30 MHz profiles in VDSL2.[3] This spectrum overlaps the FM broadcast band between 87.5 and 108 MHz, as well as various military and government radio services. To limit interference to those radio services, the ITU-T G.9700 recommendation, also called, specifies a set of tools to shape the power spectral density of the transmit signal;[9] G.9701, codenamed, is the physical layer specification.[7][22] To enable co-existence with ADSL2 and the various VDSL2 profiles, the start frequency can be set to 2.2, 8.5, 17.664, or 30 MHz, respectively.[3]

Duplex uses time-division duplexing (TDD), as opposed to ADSL2 and VDSL2, which use frequency-division duplexing.[3] Support for symmetry ratios between 90/10 and 50/50 is mandatory, 50/50 to 10/90 is optional.[3] The discontinuous nature of TDD can be exploited to support low-power states, in which the transmitter and receiver remain disabled for longer intervals than would be required for alternating upstream and downstream operation. This optional discontinuous operation allows a trade-off between throughput and power consumption.[3]


GigaDSL is a frequency-division-duplex (FDD) version of Qualcomm believes GigaDSL offers a faster upgrade from VDSL in some regions like Korea and Japan. To date, however, it's the only chip supplier backing ITU standardization of GigaDSL. GigaDSL remains a transitional technology, and traditional TDD-based is expected to dominate larger post-VDSL growth.[23]

Channel coding

The forward error correction (FEC) scheme using trellis coding and Reed–Solomon coding is similar to that of VDSL2.[3] FEC does not provide good protection against impulse noise. To that end, the impulse noise protection (INP) data unit retransmission scheme specified for ADSL2, ADSL2+, and VDSL2 in G.998.4 is also present in[3] To respond to abrupt changes in channel or noise conditions, fast rate adaptation (FRA) enables rapid (<1 ms) reconfiguration of the data rate.[3][24]


Performance in systems is limited to a large extent by crosstalk between multiple wire pairs in a single cable.[20][21] Self-FEXT (far-end crosstalk) cancellation, also called vectoring, is mandatory in Vectoring technology for VDSL2 was previously specified by the ITU-T in G.993.5, also called G.vector. The first version of will support an improved version of the linear precoding scheme found in G.vector, with non-linear precoding planned for a future amendment.[3][20] Testing by Huawei and Alcatel shows that non-linear precoding algorithms can provide an approximate data rate gain of 25% compared to linear precoding in very high frequencies; however, the increased complexity leads to implementation difficulties, higher power consumption, and greater costs.[20] Since all current implementations are limited to 106 MHz, non-linear precoding yields little performance gain. Instead, current efforts to deliver a gigabit are focusing on bonding, power and more bits per hertz.


In tests performed in July 2013 by Alcatel-Lucent and Telekom Austria using prototype equipment, aggregate (sum of uplink and downlink) data rates of 1100 Mbit/s were achieved at a distance of 70 m and 800 Mbit/s at a distance of 100 m, in laboratory conditions with a single line.[21][25] On older, unshielded cable, aggregate data rates of 500 Mbit/s were achieved at 100 m.[21]

Service rate performance targets over 0.5 mm straight loops[A][26]
Distance Performance
target (Mbit/s)[B]
< 100 m, FTTB 900–1000
100 m 900
200 m 600
300 m 300
500 m 100[27]
A A straight loop is a subscriber line (local loop) without bridge taps.
B The listed values are aggregate (sum of uplink and download) data rates.

Deployment scenarios

The Broadband Forum is investigating architectural aspects of and has, as of May 2014, identified 23 use cases.[3] Deployment scenarios involving bring fiber closer to the customer than traditional VDSL2 FTTN (fiber to the node), but not quite to the customer premises as in FTTH (fiber to the home).[13][28] The term FTTdp (fiber to the distribution point) is commonly associated with, similar to how FTTN is associated with VDSL2. In FTTdp deployments, a limited number of subscribers at a distance of up to 200–300 m are attached to one fiber node, which acts as DSL access multiplexer (DSLAM).[13][28] As a comparison, in ADSL2 deployments the DSLAM may be located in a central office (CO) at a distance of up to 5 km from the subscriber, while in some VDSL2 deployments the DSLAM is located in a street cabinet and serves hundreds of subscribers at distances up to 1 km.[13][21] VDSL2 is also widely used in fiber to the basement.[29]

A FTTdp fiber node has the approximate size of a large shoebox and can be mounted on a pole or underground.[13][30] In a FTTB (fiber to the basement) deployment, the fiber node is in the basement of a multi-dwelling unit (MDU) and is used on the in-building telephone cabling.[28] In a fiber to the front yard scenario, each fiber node serves a single home.[28] The fiber node may be reverse-powered by the subscriber modem.[28] For the backhaul of the FTTdp fiber node, the Broadband Forum's FTTdp architecture provides GPON, XG-PON1, EPON, 10G-EPON, point-to-point fiber Ethernet, and bonded VDSL2 as options.[8][31]

Former FCC chief of staff Blair Levin has expressed skepticism that US ISPs have enough incentives to adopt technology.[32]


Multi-gigabit fast access to subscriber terminals
StatusIn force
Year started23 April 2021 (2021-04-23)
First published23 April 2021 (2021-04-23)
Base standards
  • G.997.3
  • G.9710
  • G.9711
LicenseFreely available

MGfast is the successor to The standard names are ITU-T G.997.3, G.9710, and G.9711. G.9711 was standardized on April 23, 2021.[33][34]

Before the standardization of MGfast, it was referred to as G.mgfast, XG-fast, and NG-fast.

Bell Labs, Alcatel-Lucent proposed the system concepts of XG-FAST, the 5th generation broadband (5GBB) technology capable of delivering a 10 Gbit/s data rate over short copper pairs. It is demonstrated that multi-gigabit rates are achievable over typical drop lengths of up to 130 m, with net data rates exceeding 10 Gbit/s on the shortest loops.[35] Real-world tests have shown 8 Gbit/s on 30-meter long twisted copper pair lines.[36][37]

The XG-FAST technology will make fiber-to-the-frontage (FTTF) deployments feasible, which avoids many of the hurdles accompanying a traditional FTTH roll-out. Single subscriber XG-FAST devices would be an integral component of FTTH deployments, and as such help accelerate a worldwide roll-out of FTTH services. Moreover, an FTTF XG-FAST network is able to provide a remotely managed infrastructure and a cost-effective multi-gigabit backhaul for future 5G wireless networks.[35][38][39]

ITU-T's new project MGfast (Multi-Gigabit fast) addresses functionality beyond Project objectives include:[26]

On October 15, 2019, Broadcom announced the BCM65450 series xDSL modems with support for upcoming G.mgfast modes with up to 424 MHz bandwidth.[40][41]

2021-2031 is the target date range for deployments.[42]

Terabit DSL (Waveguide over Copper)

Beyond MGfast lies a new concept now being studied by a group of Brown University and ASSIA researchers:[43][44] Waveguide over copper, which enables the Terabit DSL (TDSL). This exploits waveguide transmission modes, in particular transmission modes that are efficiently transported on the surface of a conductor such as copper wire. Waveguide over copper runs at millimeter frequencies (about 30 GHz to 1 THz) and is synergistic with 5G/6G wireless. A type of vectoring is applied to effectively separate the many modes that can propagate within a telephone cable. Preliminary analyses project that waveguide over copper should support about the following per-home data rates:

Distance Performance target
100 m, FTTB 1 Tbit/s (=1000 Gbit/s)
300 m 100 Gbit/s
500 m 10 Gbit/s

As of 2017, this technology remains an interest of research teams, as a working implementation is yet to be demonstrated.[43] Infrastructure Carriers

702 Communications
In 2016, 702 Communications announced that it began deploying services to multi-dwelling units throughout the Fargo-Moorhead metropolitan area.[45][46]
On 2016-10-18 Swisscom (Switzerland) Ltd launched in Switzerland after a more than four-year project phase. In a first step will be deployed in the FTTdp environment. Swisscom works together with its technology partner Huawei which is the supplier of the micro-nodes (DSLAMs) that are installed in the manholes.[47]
Frontier Communications
Nokia and Frontier Communications are to deploy in a pilot program in Connecticut.[48]
M-net Telekommunikations GmbH
The Bavarian operator M-net Telekommunikations GmbH announced on 2017-05-30 that it is launching services in Munich. M-net claims to be the first carrier running in Germany,[49] but availability of data rates remain unavailable to consumers,[50] even two years after the deployment to FTTB households.
On 2017-08-22 AT&T announced it is launching services in 22 US metro markets.[51]
An Openreach van in the UK countryside
On 16 January 2017 Openreach announced it is launching services to 46 locations in the UK.[52]
On 26 November 2018 Openreach announced it is launching services to 81 additional locations in the UK.[53]
On 24 June 2020 Openreach announced deployments will officially remain on pause until at least April 2021, as Fibre to the Premises (FTTP) takes priority. [1]
In 2016 CenturyLink announced that it had deployed to nearly 800 apartments in 44 multi-dwelling units in 2016.[54]
Iskon Internet d.d.
On 21 February 2018 Iskon announced first commercial implementation of G.Fast technology in Croatia, which, with FTTH, enables 200 Mbit/s internet speed in 250,000 Croatian households.[55]
Australia's NBN
In 2018 NBN Co announced that it would deploy services in future FTTC and FTTB deployments.[56]
Gigacomm delivers ultra-fast internet speeds up to 10x faster than the Australian download average and has recently launched its services in Sydney and Melbourne.[57]
KDDI delivers connections, marketed as "au Hikari Type G", to apartment buildings in Japan.[58]


  1. ^ ITU (2019-06-25). "Maximizing the telco sweats: at 1 Gigabit/sec". ITU News. Archived from the original on 2021-04-05. Retrieved 2021-04-05.
  2. ^ "100+ Mb/s 400 meters". News. Fast Net News. February 4, 2015. Archived from the original on March 9, 2017.
  3. ^ a b c d e f g h i j k l Van der Putten, Frank (2014-05-20). "Overview of Summary overview and timeline" (PDF). Summit 2014. Archived from the original (PDF) on 2014-10-15. Retrieved 2014-10-09.
  4. ^ "G.9700 : Fast access to subscriber terminals ( - Power spectral density specification". ITU-T. 2014-12-19. Retrieved 2015-02-03.
  5. ^ "G.9701 : Fast access to subscriber terminals ( - Physical layer specification". ITU-T. 2014-12-18. Retrieved 2015-02-03.
  6. ^ " broadband standard approved and on the market". ITU-T. 2014-12-05. Retrieved 2015-02-03.
  7. ^ a b "New ITU broadband standard fast-tracks route to 1Gbit/s". ITU-T. 2013-12-11. Retrieved 2014-02-13.
  8. ^ a b Starr, Tom (2014-05-20). "Accelerating copper up to a Gigabit in the Broadband Forum" (PDF). Summit 2014. Broadband Forum. Archived from the original (PDF) on 2015-04-02. Retrieved 2015-03-13.
  9. ^ a b "ITU-T work programme - G.9700 (ex - Fast access to subscriber terminals (FAST) - Power spectral density specification". ITU-T. 2014-01-29. Retrieved 2014-02-14.
  10. ^ Ricknäs, Mikael (2013-07-02). "Alcatel-Lucent gives DSL networks a gigabit boost". PCWorld. Retrieved 2014-02-13.
  11. ^ "Sckipio Unveils Chipsets". 2014-10-07. Retrieved 2014-10-09.
  12. ^ Hardy, Stephen (2014-10-22). " ONT available early next year says Alcatel-Lucent". Retrieved 2014-10-23.
  13. ^ a b c d e Verry, Tim (2013-08-05). " Delivers Gigabit Broadband Speeds To Customers Over Copper (FTTdp)". PC Perspective. Retrieved 2014-02-13.
  14. ^ Building the Network of the Future: Getting Smarter, Faster, and More Flexible with a Software Centric Approach. CRC Press. 26 June 2017. ISBN 978-1-351-80468-4.
  15. ^ Channel Modeling and Physical Layer Optimization in Copper Line Networks. Springer. 20 June 2018. ISBN 978-3-319-91560-9.
  16. ^
  17. ^ Bob, Dormon (2016-05-26). "How the Internet works: Submarine fiber, brains in jars, and coaxial cables". Ars Technica. Retrieved 2024-04-19.
  18. ^ "Request Rejected". doi:10.1109/MCOM.2016.7432157.
  19. ^ Broadband Communications Networks: Recent Advances and Lessons from Practice. BoD – Books on Demand. 19 September 2018. ISBN 978-1-78923-742-9.
  20. ^ a b c d " Moving Copper Access into the Gigabit Era". Huawei. Retrieved 2014-02-13.
  21. ^ a b c d e Spruyt, Paul; Vanhastel, Stefaan (2013-07-04). "The Numbers are in: Vectoring 2.0 Makes Faster". TechZine. Alcatel Lucent. Archived from the original on 2014-08-02. Retrieved 2014-02-13.
  22. ^ "ITU-T work programme - G.9701 (ex - Fast Access to Subscriber Terminals ( - Physical layer specification". ITU-T. 2014-01-07. Retrieved 2014-02-14.
  23. ^ "The Linley Group - Qualcomm's GigaDSL Uses FDD".
  24. ^ Brown, Les (2014-05-20). "Overview of Key functionalities and technical overview of draft Recommendations G.9700 and G.9701" (PDF). Summit 2014. Archived from the original (PDF) on 2015-03-13. Retrieved 2015-03-13.
  25. ^ Ricknäs, Mikael (2013-12-12). "ITU standardizes 1Gbps over copper, but services won't come until 2015". IDG News Service. Archived from the original on 2014-02-13. Retrieved 2014-02-13.
  26. ^ a b [bare URL PDF]
  27. ^ "Suddenly, is 500 meters, not 200 meters".
  28. ^ a b c d e Wilson, Steve (2012-08-14). " a question of commercial radio, manholes, prison sentences and indoor vs outdoor engineers". Retrieved 2014-02-13.
  29. ^ "Planning of Fibre to the Curb Using G. Fast in Multiple Roll-Out Scenarios - Volume 2, No.1, March 2014 - Lecture Notes on Information Theory". LNIT. Retrieved 2014-07-19.
  30. ^ Maes, Jochen (2014-05-20). "The Future of Copper" (PDF). Summit 2014. Alcatel-Lucent. Archived from the original (PDF) on 2015-03-13. Retrieved 2015-03-13.
  31. ^ Gurrola, Elliott (2014-08-01). "PON/xDSL Hybrid Access Networks". Optical Switching and Networking. 14. Elsevier Optical Switching and Networking: 32–42. doi:10.1016/j.osn.2014.01.004.
  32. ^ Talbot, David (2013-07-30). "Adapting Old-Style Phone Wires for Superfast Internet: Alcatel-Lucent has demonstrated fiber-like data-transfer speeds over telephone wiring—but will ISPs adopt it?". MIT Technology Review. Retrieved 2014-02-13.
  33. ^ "Up to 8 Gbit/s broadband with new ITU standard MGfast - ITU Hub". ITU Hub. 18 August 2021. Retrieved 23 October 2023.
  34. ^ tsbmail. "G.9711 : Multi-gigabit fast access to subscriber terminals (MGfast) - Physical layer specification". Retrieved 28 October 2023.
  35. ^ a b Coomans, W.; Moraes, R. B.; Hooghe, K.; Duque, A.; Galaro, J.; Timmers, M.; Wijngaarden, A. J. van; Guenach, M.; Maes, J. (December 2015). "XG-fast: The 5th generation broadband". IEEE Communications Magazine. 53 (12). 83–88. doi:10.1109/MCOM.2015.7355589. S2CID 33169617.
  36. ^ Anthony, Sebastian (October 18, 2016). " DSL does 10Gbps over telephone lines". Ars Technica.
  37. ^ "NBN attains 8Gbps speeds over copper in XG-FAST trial with Nokia". ZDNET.
  38. ^ "NBN Co shoots for faster copper speeds with XG.FAST trial".
  39. ^ "XG.FAST won't obviate need for copper replacement, says Internet Australia". September 2016.
  40. ^ "Broadcom Inc. | Connecting Everything". Retrieved 2019-10-23.
  41. ^ "Bcm65450". Retrieved 2019-10-23.
  42. ^
  43. ^ a b "DSL inventor's latest science project: terabit speeds over copper • The Register". The Register.
  44. ^ Cioffi, John M.; Kerpez, Kenneth J.; Hwang, Chan Soo; Kanellakopoulos, Ioannis (November 5, 2018). "Terabit DSLs". IEEE Communications Magazine. 56 (11): 152–159. doi:10.1109/MCOM.2018.1800597. S2CID 53927909 – via IEEE Xplore.
  45. ^ Wires, B. B. C. "Broadband Communities – News & Views / Calix Honors Three Innovation Award Winners at User Group Conference". Retrieved 2021-04-16.
  46. ^ 702 Communications - 2016 Calix Innovation Award, retrieved 2021-04-16
  47. ^ "Swisscom press release 2016/10/18".
  48. ^ "Nokia and Frontier Communications deploy technology to expand gigabit ultra-broadband access across Connecticut". Nokia. Archived from the original on 25 May 2017. Retrieved 21 June 2017.
  49. ^ M-net (2017-05-30). " Deutschlandpremiere in München".
  50. ^ " IT-News für Profis".
  51. ^ Sean Buckley (2017-08-22). "AT&T begins marketing Gfast services in 22 U.S. metro markets".
  52. ^ "Fibre for home". Archived from the original on 2017-11-22. Retrieved 2018-06-19.
  53. ^ "Openreach to roll out ultrafast Gfast services to 1 million customers". Totaltelecom. Retrieved 2018-11-26.
  54. ^ "CenturyLink completes largest deployment of technology in North America".
  55. ^ "Do pametnih tehnologija za domove može se i besplatno! - Iskon".
  56. ^ ltd., nbn co. "nbn set for launch in 2018 | nbn - Australia's new broadband access network". Retrieved 2018-07-13.
  57. ^ "About Gigacomm: A new non-NBN network for the Gigabit age".
  58. ^ "KDDI deploys Nokia gigabit solution to bring new services to its high-speed internet 'au Hikari' customers in Japan".