Page 675 - 5G Basics - Core Network Aspects

Transport aspects 2

Editorial note: This is a complete-text publication. Except for new Annexes S, T and X, modifications
introduced by this amendment are shown in revision marks relative to Recommendation ITU-T G.9701
(2014) plus Erratum 1, Corrigenda 1, 2 and 3, Amendments 1 and 2 and Cor.1 Erratum 1.

1 Scope
This Recommendation specifies the operation of a broadband access technology that exploits the existing
infrastructure of wire-pairs that were originally deployed for plain old telephone service (POTS) and, with
Amendment 3, adds support for operation over coaxial cables. This Recommendation supports
transmission at an aggregate net data rate (the sum of upstream and downstream rates) up to
approximately 2 Gbit/s.
Whilst asymmetric digital subscriber line transceivers 2 (ADSL2) – extended bandwidth (ADSL2plus) uses
approximately 2 MHz of the spectrum, and very high speed digital subscriber line transceivers 2 (VDSL2)
uses up to 35 MHz of the spectrum, this Recommendation defines profiles using spectrum up to 106 MHz
and 212 MHz and specifies all necessary functionality to support the use of far-end crosstalk (FEXT)
cancellation between ITU-T G.9701 transceivers deployed on multiple wire-pairs. The availability of
spectrum up to 106 MHz or 212 MHz allows ITU-T G.9701 transceivers to provide reliable high data rate
operation on very short loops. This Recommendation can be deployed from fibre-fed distribution points
located very near the customer premises, or within the buildings. This Recommendation is optimized to
operate over wire-pairs up to approximately 250 m of 0.5 mm diameter. However, it is capable of operation
over wire-pairs up to at least 400 meters of 0.5 mm diameter, subject to some performance limitations.
This Recommendation defines a wide range of settings for various parameters (such as spectral usage and
transmitter power) that may be supported by a transceiver. Therefore, this Recommendation specifies
profiles to allow transceivers to support a subset of the allowed settings and still be compliant with the
Recommendation. The specification of multiple profiles allows vendors to limit the implementation
complexity and develop implementations that target specific service requirements. This edition of the
Recommendation specifies transmission profiles for in-band spectral usage of up to 212 MHz and maximum
transmit power up to +8 dBm. This Recommendation operates in compliance with the power spectral
density (PSD) specification in [ITU-T G.9700].
As do ITU-T Recommendations in the ITU-T G.99x series, this Recommendation uses [ITU-T G.994.1] to
initiate the transceiver training sequence. Through negotiation during the handshake phase of the
initialization, the capability of equipment to support this Recommendation and/or ITU-T G.99x series
Recommendations (e.g., [ITU-T G.993.2] defining VDSL2) is identified. For reasons of interoperability,
equipment may support multiple Recommendations such that it is able to adapt to the operating mode
supported by the far-end equipment.

It is the intention of this Recommendation to provide, by negotiation during the initialization, U interface
compatibility and interoperability between transceivers complying with this Recommendation, including
transceivers that support different combinations of options.

The technology specified in this Recommendation provides the following key application features:
• Best aspects of fibre to the home (FTTH): up to 2 Gbit/s aggregate net data rate;
• Best aspects of ADSL2: customer self-install and operation in the presence of bridged taps,
avoiding operator truck-rolls to the customer premises for installation and activation of the
broadband access service;

• Coexistence with ADSL2 and VDSL2 on adjacent wire-pairs;
• Low power operation and all functionality necessary to allow transceivers to be deployed as part
of reverse powered (and possibly battery operated) network equipment and to adapt to
environmental conditions (e.g., temperature);

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