Committed to connecting the world

Executive Summary

​8-19 October 2018
ITU-T Study Group 15
Networks, Technologies and Infrastructures for Transport, Access and Home
Study Group 15 Chairman: Stephen Trowbridge

​​Study Group 15 held its third meeting of the 2017-2020 study period in Geneva from 8-19 October 2018, attended by 289 delegates representing 37 countries.
The meeting received 403 contributions and 439 TDs, a substantial increase from the previous meeting. The meeting observed the 12-day contribution deadline of revised Recommendation ITU-T A.1, and nearly all of the contributions to this meeting were submitted using Direct Document Posting (DDP).

Some important results of the SG15 meeting include:

​​​​​​​​​​Transport Network support of 5G:  An updated version of Technical Report GSTR-TN5G, Transport network support of IMT-2020/5G, was agreed. This report captures requirements for Transport Network support of 5G mobile fronthaul, middle-haul, and backhaul networks. A new Recommendation was completed on Radio over fiber systems, and a new Supplement on 5G Wireless Fronthaul Requirements in a PON Context.  New Recommendations G.8262.1 and Amendment 2 to G.8273.2 that specify new clocks to support synchronization for IMT-2020/5G were consented.
Coherent Line Interfaces: A revision of Recommendation G.698.2 was completed, adding new 100G DWDM application codes using DP-DQPSK modulation format in two different application areas: new codes have been specified for operation over point-to-point WDM systems for reaches of approximately 80 km (typical data-center-interconnect use case), and for operation over amplified metro ROADM networks with reach up to about 450 km. This is the first industry standard specifying multi-vendor interoperable coherent DWDM line interfaces. Work has been initiated for a future revision of G.698.2 to specify 200G and 400G application codes, with DP-16QAM provisionally agreed as the modulation format for 400G applications. An amendment to G.709.3 provides a flexible OTN frame format for operation over some 200G and 400G interfaces with a higher-gain forward error correcting code (FEC) than that required for 100G applications.
Visible Light Communications: In extending the in-premises (home networking) series of Recommendations, a new Recommendation G.9991 has been prepared on transceivers for visible light communications and a new Recommendation G.9992 on transceivers for indoor optical cameras.
Optical fibre cable installation with minimal existing infrastructure: A new Recommendation L.163 was completed, specifying criteria for installation of direct surface application (DSA) cables which can allow rapid deployment to establish communication to remote areas, particularly in developing countries.

SG15 determined one revised Recommendation, consented 55 texts (6 new Recommendations, 33 revised Recommendations, 14 Amendments, and 2 Corrigenda). Agreement was reached on two new and three revised Supplements, two Implementer's guides, two Technical Reports, and a Technical Paper.

SG15 authorized 14 interim face-to-face Rapporteur group meetings to be held prior to the fourth SG15 plenary of the 2017-2020 study period, 24 virtual meetings, and generated 37 liaison statements. The fourth plenary meeting of SG15 in the 2017-2020 study period is scheduled 1-12 [1] July 2019 in Geneva.

SG15 agreed to the disbanding of Q9/15, reassigning responsibility for packet protection mechanisms to Q10/15, circuit protection to Q11/15, and SDN or ASON control-plane based restoration to Q12/15.

In fulfilling its lead study group responsibilities, SG15 revised the Access Network Transport (ANT) standards overview and work plan, the Home Network Transport (HNT) Standards Overview and Work Plan, and the Smart Grid standards overview and work plan. Due to lack of time, update of the Optical Transport Networks and Technologies (OTNT) standardization work plan was not completed during the meeting: this update will be completed by correspondence prior to the December meeting of TSAG.

[1] Pending resolution of room availability, there is a possibility that a Saturday closing plenary will be necessary and the meeting dates would be 1-13 July 2019. This uncertainty should be resolved before year end 2018.

Executive reports from WP Chairmen

WP1/15 – Transport aspects of access, home and smart grid networks
WP1 Chairman: Tom Starr; WP1 Vice-Chairman: Hubert Mariotte

Hubert Mariotte was thanked for his five years of service as WP1/15 Vice Chairman.  Following this meeting, Ian Horsley has been appointed the new WP1/15 Vice Chairman.

Q1/15 updated the Access Network Transport (ANT) Standards Overview and Work Plan documents. The Home Network Transport (HNT) Standards Overview and Work Plan document was revised. The list of CIT activities in other organizations related to the WP1/15 Recommendations was updated.

Q2/15 worked on Passive Optical Networks (PON), with work on the OMCI, the NG-PON2 series, the XGS-PON series, the higher speed PON series, and bidirectional optics.  Five documents were forwarded for consent, and one for agreement.

Q4/15 worked on access via metallic conductors, focusing on, the next-generation MGfast, and VDSL2.  Ten texts were prepared for consent, one for determination, and one for agreement.  Work on a new Recommendation for DPU backhaul using bonded was started. 

Q15/15 discussed plans for future standards activities for Smart Grid.

Q18/15 worked on the family of Recommendations and the evolution to the next generation of Two new draft Recommendations were prepared for consent addressing Visible Light Communication (G.vlc) and Optical Camera Communication (G.occ). A joint session with Q4/15 addressed the possible coordination between access and in-home standards.

WP2/15 – Optical technologies and physical infrastructures
WP2 Chairman: Noriyuki Araki; WP2 Vice-Chairman: Pete Anslow

WP2 made good progress on the development of a number of Recommendations and produced one new, five revised Recommendations and one corrigendum for consent, as well as two supplements, one technical report and one questionnaire for agreement at this meeting. WP2 produced two Liaisons and updated its work programme including one new work item on management of telecommunication infrastructures. WP2 also scheduled one interim meeting and a number of correspondence activities to progress the work.

Q5/15 worked on characteristics and test methods of optical fibres and cables and consented revised Recommendation G.651.1, which contains characteristics of multi-mode fibre, and agreed revised G.suppl.40 optical fibre and cable Recommendations and standards guideline. Progress was also made on study on attenuation coefficient of G.654.E fibre at C-L band.

Q6/15 consented revised Recommendation G.698.2 with sets of parameters and associated values to enable multi-vendor interoperability for coherent 100G application codes as well as a Corrigendum to G.698.4. Q6 also made progress towards a future revision of G.698.2 that considered suitable modulation formats in relation to reach for 200G and 400G application codes.

Q7/15 worked on optical component specifications and subsystems and consented revised G.672 Characteristics of multi-degree reconfigurable optical add/drop multiplexers.

Q8/15 made progress on new Recommendation G.977.1, Longitudinally compatible DWDM applications for repeatered optical fibre submarine cable systems, including issues related to open cable characterization and commissioning and agreed a questionnaire on cable ship and submersible equipment.

Q16/15 consented new Recommendation L.163 (ex L.cci), which can be applied to installation of optical fibre cables in a location with minimal telecommunication infrastructure, and revised Recommendation L.109 related to construction of optical/metallic hybrid cables. Progress was also made on new Recommendations related to optical fibre distribution box and optical fibre cables for in-home application.

Q17/15 worked on maintenance and operation of optical fibre cable networks and consented revised Recommendation L.314 that deal with requirements for optical fibre identification and started new work item on L.tifm Telecommunication infrastructure facility management.

WP3/15 – Transport network characteristics
WP3 Chairman: Malcolm Betts; WP3 Vice-Chairman: Glenn Parsons

​Highlights of WP3 work include:

  • WP3/15 completed a revision of a Technical Report (GSTR TN5G) on “Transport network support of IMT-2020/5G". This report provides a framework that allows the Questions of SG15 to work independently and engage wireless SDOs. Q11/15 started two new work items directed at the support of IMT-2020/5G.
  • WP3/15 consented new Recommendations G.8262.1 and Amendment 2 to G.8273.2 specifying new clocks to support Sync for IMT-2020/5G. Some of the key driving requirements have been included into Amendment 2 to G.8271. 
  • Q14/15 is continuing to working in cooperation with IEEE 802.1, IEEE 802.3, ONF, MEF, BBF, and IETF to provide consistent information models and YANG data models for Ethernet.

Q9/15 consented an amendment to G.8131 “Linear protection for MPLS transport profile" to align with the most recent RFCs, and continued work on the revision of G.808.2 “Generic protection switching – ring protection" and new Recommendation G.mtdh “MPLS-TP dual-homing protection".  Considering the decline in work with the scope of Q9/15, SG15 agreed to propose the deletion of Q9/15 with the responsibilities for protection and restoration work being moved to Q10/15, Q11/15, and Q12/15.

Q10/15 consented revised G.8011/Y.1307, G.8013/Y.1731 (2015) Amd.1 (amending the one-way frame delay description), revisions of the three G.8121/Y.1381 series Recommendations (in part adding Client Signal Fail and MPLS-TP Shared Ring Protection support), and initiated repatriation of definitions from former Q3/15 Recommendations by agreeing Implementers' Guides to both G.8001/Y.1354 and G.8101/Y.1355. Q10/15 also initiated work to revise G.8021/Y.1341. Future work is planned to revise G.8011 and G.8021.

Q11/15 focused much of the meeting on topics related to IMT2020/5G transport networks, and approved three new work items including two related to that area.  The new IMT-2020/5G Transport-related work items are both targeted at metro networks, including transport of RAN traffic.  They are “Interfaces for a metro transport network," which is a new transport technology, and G.709.25-50 “25G and 50G OTN interfaces" that is an extension to the OTN.  The other new work item is G.Sup.sub1G "Sub 1 Gbit/s services transport over OTN" that describes existing and new mappings for sub-Gbit/s clients over OTN. 
Q11/15 consented three amendments and one corrigendum, and agreed one supplement revision.  One of the new amendments defines a hard-decision FEC with higher coding gain for the G.709.3 FlexO interfaces that are used for OTN signals with rates higher than 100 Gbit/s.  Amendments to G.709 and G.709.1 were consented, along with a corrigendum to G.8023 and the agreed revision to G.Sup58. 
Q11/15 plans two interim meetings in February 2019 and April 2019 to progress work on IMT2020/5G transport and other work items.

Q11/15 and Q12/15 completed a revision to Technical Report (GSTR TN5G) on “Transport network support of IMT‑2020/5G.

Q12/15 made progress on its work on the architecture for optical media networks that describe constructs used for propagating optical signals. Management aspects of media networks was progressed with Q14/15. Work was initiated to update G.8080 “Architecture for the automatically switched optical network" to synergize with control components in G.7701 and the SDN architectural approach in Recommendation G.7702. These Recommendations provide the foundation for SG15 to define the interface from the Transport Network to the 3GPP management system and, in particular, support 5G network slicing. The Optical Transport Networks & Technologies Standardization Work Plan (OTNT SWP) will be completed in a correspondence activity that will complete its work 6th December, 2018.

Q13/15 completed the investigation on the requirements for networks synchronization to support IMT-2020/5G. These have been collected in an Amendment (Amd.2) to G.8271 that has been consented at this meeting. This has been used as input to several other work items addressed by SG15. On a related topic, Q13/15 has initiated the analysis of the synchronization for the fronthaul network. This work is planned to be included in G.8271.1.
The new clock to support enhanced distribution of frequency synchronization over the physical layer has been consented in G.8262.1 (Timing characteristics of enhanced synchronous equipment slave clock).
Another major achievement concerns the specification of new time sync clocks in Amendment 2 to G.8273.2: “class C" and “class D" clocks. Both clocks are expected to become an important reference for building future synchronization networks. 
Work is progressing on the “coherent network PRTC", with high level architecture included in an Amendment to G.8275 (Amd1) consented at this meeting.
Progress has been made on the clock for partial timing support, G.8273.4 (planned for consent in July 2019).
The Recommendation G.8272 specifying the Primary Reference Time Clock, G.8272, was revised to include a new more accurate type of PRTC, the PRTC-B.
Overall, 10 documents were consented. The Supplement G.Supp.Sim went for Agreement. It includes work on simulation performed over the last few years for the transport of time synchronization over packet networks.
Q13/15 plans to hold an interim meeting in March 2018.

Q14/15 consented one new Recommendation G.7721 (ex. G.sync-mgmt) and four revised Recommendations, namely G.875 (ex. G.874.1) on OTN management, G.8052 on Ethernet management, and G.8151 & G.8152 on MPLS-TP management. Good progress was made on the other nine active work items. Q14/15 also initiated four new work items. Two of them are MPLS-TP information/data model for specific functions, namely G.8152.1 on OAM and G.8152.2 on resilience. The other two work items are revision to Recommendations with significant extended scope. They are G.7718 Framework for the management of MCC components and functions and G.7719 (ex. G.7718.1) Management information model for MCC components and functions. Q14/15 plans to hold two face-to-face interim meetings and monthly vMeetings until June 2019, with invited experts from IEEE 802.1, IEEE 802.3, ONF, MEF, IETF, and BBF to coordinate on Ethernet information and YANG modelling.



WP1/15 – TAP Approval
WP2/15 - TAP Approval
WP3/15 - TAP Approval

WP1/15 - AAP Approval
WP2/15 - AAP Approval
WP3/15 - AAP Approval


WP1/15 - Determination:

Recommendations N=new/  R=rev. Title Text in  Doc(s)
G.9700RFast access to subscriber terminals ( – Power spectral density specification TD284R2/P

WP2/15 - Determination:
WP3/15 - Determination:


WP1/15 - Consent:

Recommendations N=new/  R=rev. Title Text in  Doc(s)
G.988 Amd1NONU management and control interface (OMCI) specification: Amendment 1 TD307R1/P
G.989.2R40-Gigabit-capable passive optical networks 2 (NG PON2): Physical media dependent (PMD) layer specification TD320R2/P
G.989.3 Amd2N40-Gigabit-capable passive optical networks (NG PON2): Transmission Convergence (TC) layer specification: Amendment 2 TD313R2/P
G.993.2RVery high speed digital subscriber line transceivers 2 (VDSL2) (for consent) TD229/P
G.993.5RSelf-FEXT cancellation (vectoring) for use with VDSL2 transceivers (for consent) TD230/P
G.994.1RHandshake procedures for digital subscriber line transceivers (for consent) TD243R1/P
G.996.2RSingle-ended line testing for digital subscriber lines (DSL) (for consent) TD242R1/P
G.997.1RPhysical layer management for digital subscriber line transceivers (for consent) TD244R2/P
G.997.2RPhysical layer management for transceivers (for consent) TD245R1/P
G.998.2REthernet-based multi-pair bonding (for consent) TD327/P
G.998.4RImproved impulse noise protection for digital subscriber line (DSL) transceivers (for consent) TD231R1/P

Interface between the link layer and the physical layer for digital subscriber line (DSL) transceivers (for consent)
A.5 justification for references to IEEE 802.3

A.5 in TD339/P
G.9701RFast access to subscriber terminals ( - Physical layer specification (for consent) TD285R1/P
G.9807.2 Amd1N10 Gigabit-capable symmetrical passive optical networks (XG(S)-PON): Reach extension: Amendment 1 TD305R1/P
G.9960RUnified high-speed wire-line based home networking transceivers – System architecture and physical layer specification TD287R1/P
A.5 in TD341/P
G.9961RUnified high-speed wireline-based home networking transceivers – Data link layer specification TD288R1/P
A.5 in TD342/P
G.9962RUnified high-speed wireline-based home networking transceivers – Data link layer specification TD336/P
A.5 in TD340/P
G.9963RUnified high-speed wireline-based home networking transceivers – Multiple input/multiple output specification TD289R1/P
G.9979RImplementation of the generic mechanism
in the IEEE 1905.1a-2014 Standard to include applicable ITU-T Recommendations
A.5 in TD343/P
G.9991 (ex G.vlc-hs)NHigh speed indoor visible light communication transceiver – System architecture, physical layer and data link layer specification TD291R1/P
G.9992 (ex G.occ)NIndoor optical camera communication transceivers – System architecture, physical layer and data link layer specification TD292R1/P
A.5 in TD344/P
G.9978RSecure admission in network TD296R1/P
G.9803 (ex. G.RoF)NRadio over fiber systems TD298R1/P


WP2/15 - Consent:

Recommendations N=new /  R=rev. Title Text in Doc(s)
G.651.1RCharacteristics of a 50/125 µm multimode graded index optical fibre cable for the optical access network TD232R1/P
G.698.2RAmplified multichannel dense wavelength division multiplexing applications with single channel optical interfaces TD293R1/P
G.698.4 Cor.1NMultichannel bi-directional DWDM applications with port agnostic single-channel optical interfaces TD324/P
G.672RCharacteristics of multi-degree reconfigurable optical add/drop multiplexers TD318R1/P
L.163 (ex L.cci)NCriteria for optical fibre cable installation with minimal existing infrastructure TD286R2/P
L.109 (ex L.60)RConstruction of optical/metallic hybrid cables TD316R1/P
L.314 (ex L.85)ROptical fibre identification for the maintenance of optical access networks TD317R1/P


WP3/15 - Consent:

Recommendation N=new /   R=rev. Title Text in Doc(s)
G.8131 Amd.3NLinear protection switching for MPLS transport profile TD225/P
A.5 in TD323/P
G.8011/Y.1307REthernet service characteristics TD224R2/P
A.5 in TD330/P
G.8013/Y.1731 Amd.1NOperation, administration and maintenance (OAM) functions and mechanisms for Ethernet-based networks TD308R1/P
A.5 in TD335R2/P
G.8121/Y.1381RCharacteristics of MPLS-TP equipment functional blocks TD309R1/P
A.5 in TD334/P
G.8121.1/Y.1381.1RCharacteristics of MPLS-TP equipment functional blocks supporting ITU-T G.8113.1/Y.1372.1 OAM mechanisms TD310R1/P
G.8121.2/Y.1381.2RCharacteristics of MPLS-TP equipment functional blocks supporting ITU-T G.8113.2/Y.1372.2 OAM mechanisms TD311R1/P
A.5 in TD331/P
G.709/Y.1331 (2016) Amd.3NInterfaces for the optical transport network (OTN): Amendment 3 TD325R1/P
A.5 in TD328/P
G.709.1/Y.1331.1 (2018) Amd.1NFlexible OTN short-reach interface - Amendment 1 TD315R1/P
G.709.3/Y.1331.3 Amd.1NFlexible OTN long-reach interfaces – Amendment 1

A.5 in TD326/P
G.8023 (2018) Cor.1NCharacteristics of equipment functional blocks supporting Ethernet physical layer and FlexE interfaces - Corrigendum 1 TD227/P
G.8251RThe control of jitter and wander within the optical transport network (OTN) TD319R1/P
A.5 in TD282/P
G.8260 (2015) Amd.2NDefinitions and terminology for synchronization in packet networks: Amendment 2 TD235R1/P
G.8262RTiming characteristics of synchronous equipment slave clock TD239R1/P
G.8262.1/Y.1362.1NTiming characteristics of enhanced synchronous equipment slave clock TD238R1/P
A.5 in TD329/P
G.8271 Amd 2NTime and phase synchronization aspects of telecommunication networks - Amendment 2 TD236R1/P
G.8271.2 Amd.2NNetwork limits for time synchronization in packet networks with partial timing support from the network - Amendment 2 TD237R1/P
G.8272RTiming characteristics of primary reference time clocks TD297R1/P
G.8273.2/Y.1368.2 Amd.2NTiming characteristics of telecom boundary clocks and telecom time slave clocks - Amendment 2 TD240R1/P
G.8273.3/Y.1368.3 Amd.1NTiming characteristics of telecom transparent clocks - Amendment 1 TD241R1/P
G.8275/Y.1369 Amd.1NArchitecture and requirements for packet-based time and phase distribution Amendment 1 TD322R1/P
(ex G.874.1)
ROptical transport network: Protocol-neutral management information model for the network element view TD246R1/P
G.8052/Y.1346RProtocol-neutral management information model for the Ethernet Transport capable network element TD247R1/P
G.8151/Y.1374RManagement aspects of the MPLS-TP network element TD312R1/P
G.8152/Y.1375RProtocol-neutral management information model for the MPLS-TP network element TD248R1/P
(ex G.sync-mgmt)
NManagement Requirement and Information Model for Synchronization TD300R1/P
A.5 in TD337/P


WP1/15 - Agreement:

Doc. #/  Ref. N=new /  R=rev. Title Text in Doc(s)
G.sup.5GPN5G Wireless Fronthaul Requirements in a PON Context TD299R2/P
 NQ4/15: Technical Paper on NT software upgrade for one image TD314R1/P

WP2/15 – Agreement:

Doc. #/  Ref. N=new /  R=rev. Title Text in Doc(s)
G.suppl.40ROptical fibre and cable Recommendations and standards guideline TD302R1/P
G.suppl.42RGuide on the use of the ITU-T Recommendations related to optical fibres and systems technology TD304R1/P
TR-GLSRRGuide on the use of ITU-T L-series Recommendations related to optical technologies for outside plant TD228R1/P
--Questionnaire on cable ship and submersible equipment TD303/P

WP3/15 - Agreement

Doc. #/  Ref. N=new / R=rev. Title Text in Doc(s)
G.8001 Implementers' Guide NImplementers' Guide for G.8001/Y.1354 TD332/P
G.8101 Implementers' GuideNImplementers' Guide for G.8101/Y.1355 TD333/P
G.Suppl.58ROptical transport network (OTN) module frame interfaces (MFIs) TD233R1/P
GSTR-TN5GRTransport network support of IMT-2020/5G TD338/P
G.Suppl.simNSimulations of transport of time over packet networks TD321R1/P