ITU-T Rec. G.9701 Amendment 2

398 Pages·2016·13.74 MB·English

I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n

ITU-T
G.9701

Amendment 2
TELECOMMUNICATION
STANDARDIZATION SECTOR
(07/2016)
OF ITU

SERIES G: TRANSMISSION SYSTEMS AND MEDIA,
DIGITAL SYSTEMS AND NETWORKS
Access networks – Metallic access networks

Fast access to subscriber terminals (G.fast) –
Physical layer specification
Amendment 2

Recommendation ITU-T G.9701 (2014) – Amendment 2
ITU-T G-SERIES RECOMMENDATIONS
TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS

INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS G.100–G.199
GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER- G.200–G.299
TRANSMISSION SYSTEMS
INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE G.300–G.399
SYSTEMS ON METALLIC LINES
GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS G.400–G.449
ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC
LINES
COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY G.450–G.499
TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS G.600–G.699
DIGITAL TERMINAL EQUIPMENTS G.700–G.799
DIGITAL NETWORKS G.800–G.899
DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900–G.999
MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER- G.1000–G.1999
RELATED ASPECTS
TRANSMISSION MEDIA CHARACTERISTICS G.6000–G.6999
DATA OVER TRANSPORT – GENERIC ASPECTS G.7000–G.7999
PACKET OVER TRANSPORT ASPECTS G.8000–G.8999
ACCESS NETWORKS G.9000–G.9999
Metallic access networks G.9700–G.9799
Optical line systems for local and access networks G.9800–G.9899
In premises networks G.9900–G.9999

For further details, please refer to the list of ITU-T Recommendations.
Recommendation ITU-T G.9701
Fast access to subscriber terminals (G.fast) – Physical layer specification
Amendment 2

Summary
Recommendation ITU-T G.9701 specifies a gigabit broadband access technology that exploits the
existing infrastructure of wire-pairs that were originally deployed for plain old telephone service
(POTS) services. Equipment implementing this Recommendation can be deployed from fibre-fed
distribution points (fibre to the distribution point, FTTdp) located very near the customer premises, or
within buildings (fibre to the building, FTTB). This Recommendation supports asymmetric and
symmetric transmission at an aggregate net data rate up to 1 Gbit/s on twisted wire-pairs using
spectrum up to 106 MHz and specifies all necessary functionality to support far-end crosstalk (FEXT)
cancellation between multiple wire-pairs, and facilitates low power operation.
Corrigendum 1 (2015) provides clarifications and corrects various errors in the Recommendation, and
in particular includes a change to the definition of DFT output samples.
Corrigendum 2 (2016) increases the number of RFI bands from 16 to 32, and provides clarifying text
on alignment between TIGA and SRA/FRA procedures, tone repetition, unavailable seconds, and byte
order in SOC and eoc messages.
Amendment 1 specified test parameters, some of which had previously been left for further study, and
specifies support for low power operation.
This amendment 2 includes a new annex on cross-layer traffic monitoring functions and link state
control to support low power operation. It also includes a new 106 MHz profile with increased
maximum transmit power, support for increased bit loading, Hlog reporting in both directions, and
Xlog reporting.
History
Edition Recommendation Approval Study Group Unique ID*
1.0 ITU-T G.9701 2014-12-05 15 11.1002/1000/12090
1.1 ITU-T G.9701 (2014) Cor. 1 2015-11-22 15 11.1002/1000/12541
1.2 ITU-T G.9701 (2014) Cor. 2 2016-05-07 15 11.1002/1000/12817
1.3 ITU-T G.9701 (2014) Amd. 1 2016-05-07 15 11.1002/1000/12542
1.4 ITU-T G.9701 (2014) Amd. 2 2016-07-22 15 11.1002/1000/12816

____________________
* To access the Recommendation, type the URL http://handle.itu.int/ in the address field of your web
browser, followed by the Recommendation's unique ID. For example, http://handle.itu.int/11.1002/1000/11
830-en.
Rec. ITU-T G.9701 (2014)/Amd.2 (07/2016) i
FOREWORD
The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of
telecommunications, information and communication technologies (ICTs). The ITU Telecommunication
Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical,
operating and tariff questions and issuing Recommendations on them with a view to standardizing
telecommunications on a worldwide basis.
The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes
the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
In some areas of information technology which fall within ITU-T's purview, the necessary standards are
prepared on a collaborative basis with ISO and IEC.

NOTE
In this Recommendation, the expression "Administration" is used for conciseness to indicate both a
telecommunication administration and a recognized operating agency.
Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain
mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the
Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other
obligatory language such as "must" and the negative equivalents are used to express requirements. The use of
such words does not suggest that compliance with the Recommendation is required of any party.

INTELLECTUAL PROPERTY RIGHTS
ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve
the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or
applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of
the Recommendation development process.
As of the date of approval of this Recommendation, ITU had received notice of intellectual property, protected
by patents, which may be required to implement this Recommendation. However, implementers are cautioned
that this may not represent the latest information and are therefore strongly urged to consult the TSB patent
database at http://www.itu.int/ITU-T/ipr/.

 ITU 2016
All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior
written permission of ITU.
ii Rec. ITU-T G.9701 (2014)/Amd.2 (07/2016)
Table of Contents
Page
1 Scope ............................................................................................................................. 1
2 References ..................................................................................................................... 3
3 Definitions .................................................................................................................... 3
3.1 Terms defined elsewhere ................................................................................ 3
3.2 Terms defined in this Recommendation ......................................................... 3
4 Abbreviations and acronyms ........................................................................................ 6
5 Reference models and system requirements ................................................................. 11
5.1 System reference models ................................................................................ 11
5.2 Application reference models ......................................................................... 14
5.3 FTU protocol reference model ....................................................................... 19
5.4 FTU functional model .................................................................................... 21
5.5 INP system requirements ................................................................................ 23
6 Profiles .......................................................................................................................... 23
6.1 Definition ........................................................................................................ 23
6.2 Profile compliance .......................................................................................... 25
7 Transmission medium interface characteristics ............................................................ 26
7.1 Duplexing method .......................................................................................... 26
7.2 Frequency band .............................................................................................. 26
7.3 Power spectral density .................................................................................... 26
7.4 Out-of-band PSD limit ................................................................................... 40
7.5 Termination impedance .................................................................................. 40
7.6 Maximum aggregate transmit power .............................................................. 40
8 Transport protocol specific transmission convergence (TPS-TC) function ................. 40
8.1 Functional reference model ............................................................................ 40
8.2 Generic DTU format ....................................................................................... 49
8.3 Packet-based TPS-TC (PTM-TC) .................................................................. 51
8.4 Network timing reference (NTR) ................................................................... 54
8.5 Time-of-day (ToD) ......................................................................................... 56
9 Physical media specific transmission convergence (PMS-TC) sub-layer .................... 60
9.1 Functional reference model ............................................................................ 60
9.2 DTU scrambler ............................................................................................... 63
9.3 DTU encoder .................................................................................................. 63
9.4 Interleaver ....................................................................................................... 64
9.5 Data frame multiplexer ................................................................................... 65
9.6 RMC ............................................................................................................... 68
9.7 Acknowledgement .......................................................................................... 79
9.8 Retransmission function ................................................................................. 81
Rec. ITU-T G.9701 (2014)/Amd.2 (07/2016) iii
Page
10 Physical media dependent (PMD) function .................................................................. 89
10.1 PMD functional reference model ................................................................... 89
10.2 Symbol encoder .............................................................................................. 93
10.3 Precoder (downstream vectoring) ................................................................... 115
10.4 Modulation ..................................................................................................... 129
10.5 TDD frame structure ....................................................................................... 132
10.6 Superframe structure ...................................................................................... 135
10.7 Normal and discontinuous operation intervals ............................................... 136
10.8 Alignment of transmissions in vectored group ............................................... 141
11 Operation and maintenance (OAM) ............................................................................. 141
11.1 OAM functional model ................................................................................... 141
11.2 Management functions and procedures over eoc ........................................... 144
11.3 OAM primitives .............................................................................................. 188
11.4 OAM parameters ............................................................................................ 191
12 Link activation methods and procedures ...................................................................... 217
12.1 Overview ........................................................................................................ 217
12.2 Special operations channel (SOC) .................................................................. 234
12.3 Initialization procedure ................................................................................... 238
12.4 Loop diagnostics mode ................................................................................... 305
13 Online reconfiguration (OLR) ...................................................................................... 306
13.1 Overview ........................................................................................................ 306
13.2 Eoc-based procedures ..................................................................................... 307
13.3 RMC-based procedures .................................................................................. 321
13.4 Low power link states ..................................................................................... 326
14 Electrical requirements ................................................................................................. 344
14.1 Balance ........................................................................................................... 344
14.2 Differential port impedance ............................................................................ 345
Annex A to Annex X ............................................................................................................... 346
Annex Y – Upstream dynamic resource reports ...................................................................... 347
Annex Z – Cross-layer traffic monitoring functions and link state control ............................. 349
Z.0 Introduction .................................................................................................... 349
Z.1 Definition of Terms ........................................................................................ 349
Z.2 Abbreviations and acronyms .......................................................................... 349
Z.3 Reference models ........................................................................................... 350
Z.4 Generic traffic monitoring functions .............................................................. 351
Z.5 Generic information flows .............................................................................. 353
Z.6 Link state specific functions ........................................................................... 356
Z.7 Link state management and reporting parameters .......................................... 360
Appendix I – Wiring topologies and reference loops .............................................................. 362
iv Rec. ITU-T G.9701 (2014)/Amd.2 (07/2016)
Page
I.1 Wiring topologies ........................................................................................... 362
I.2 Reference loops .............................................................................................. 362
Appendix II – Example OLR use cases ................................................................................... 371
II.1 Transmitter initiated gain adjustment (TIGA) ................................................ 371
Appendix III – Motivation of MTBE accelerated test ............................................................. 373
Appendix IV ............................................................................................................................. 375
Appendix V – Retransmission buffer size and the achievable bit-rate .................................... 376
V.1 Case 1: NSYMret+NSYMack+1 ≤ Mus ............................................................ 376
V.2 Case 2: NSYMret+NSYMack+1≥Mus........................................................... 377
V.3 Case 3: Lower bound for the achievable net data rate .................................... 377
V.4 Memory size example ..................................................................................... 378
Appendix VI – Example applications of discontinuous operation .......................................... 379
VI.1 Discontinuous operation with vectoring disabled .......................................... 379
VI.2 Examples of discontinuous operation with vectoring enabled ....................... 380
Appendices VII to YX ............................................................................................................. 386
Appendix YY – Calculation of loop attenuation (LATN) ....................................................... 387
Bibliography............................................................................................................................. 388

Rec. ITU-T G.9701 (2014)/Amd.2 (07/2016) v

Recommendation ITU-T G.9701
Fast access to subscriber terminals (G.fast) – Physical layer specification
Amendment 2
Editorial note: This is a complete-text publication. Modifications introduced by this amendment are
shown in revision marks relative to Recommendation ITU-T G.9701 (2014) plus Erratum 1,
Corrigenda 1 and 2, and Amendment 1.
1 Scope
This Recommendation supports transmission at an aggregate net data rate (the sum of upstream and
downstream rates) up to approximately 1 Gbit/s on twisted wire-pairs. 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).
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 30 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 the profile for in-band spectral usage of
up to 106 MHz at 4dBm maximum transmit power. A second profile for in-band spectral usage up to
212 MHz is for further study. 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., [b-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 one gigabit per second aggregate net data
rate;
Rec. ITU-T G.9701 (2014)/Amd.2 (07/2016) 1
• 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);
• Management capabilities allowing transceivers to operate in a zero touch deployment,
avoiding truck-rolls to the network equipment for installation and activation of new or
upgraded broadband access service;
• Control of the upstream vs downstream transmission time to adapt net data rates to the needs
of the business and the residential customers;
• Vectoring (self-crosstalk cancellation) for increased net data rates on wire-pairs that
experience far-end crosstalk from ITU-T G.9701 transceivers in the same vectored group
operating on other wire-pairs in the same cable or operating on other wire-pairs originating
from the same network equipment;
• Network timing reference (NTR) and time-of-day (ToD) transport for network frequency and
time synchronization between network and customer premises equipment;
• Configuration of spectrum use, including configuration of the transmit power spectral density
(PSD) limitations and notches to meet electromagnetic compatibility (EMC) requirements.
The technology specified in this Recommendation uses the following key functionalities and
capabilities:
• Transparent transport of data packets (e.g., Ethernet packets) at an aggregate (sum of
upstream and downstream) data rate of up to 1 Gbit/s;
• In-band spectral usage up to 212 MHz, with this edition of the Recommendation specifying
one profile up to 106 MHz at 4dBm transmit power;
• Configurable start and stop frequencies, PSD shaping and notching;
• Discrete multitone (DMT) modulation (2 048/4 096 subcarriers with 51.75 kHz subcarrier
spacing);
• Time-division duplexing (sharing time between upstream and downstream transmission);
• Low latency retransmission, facilitating impulse noise protection (INP) between the V and T
reference points at all data rates to deal with isolated erasure events at the U reference point
of at least 10 ms, without loss of user data;
• Forward error correction based on Trellis coding and Reed-Solomon coding;
• Vectoring (self-FEXT cancellation), where this edition of the Recommendation uses linear
precoding;
• Discontinuous operation where not all of the time available for data transmission is used;
• Online reconfiguration (OLR) for adaptation to changes of the channel and noise
characteristics, including fast rate adaptation (FRA).
With these functionalities and capabilities, the technology specified in this Recommendation targets
the following aggregate net data rates over a 0.5 mm straight wire-pair:
• 500 to 1000 Mbit/s on a wire-pair shorter than 100 m;
• 500 Mbit/s at 100 m;
• 200 Mbit/s at 200 m;
• 150 Mbit/s at 250 m;
2 Rec. ITU-T G.9701 (2014)/Amd.2 (07/2016)