Title: GSC-8 CONTRIBUTION DRAFT
Author: David Clemis, TSACC
Last saved by: ttacanival

GSC9/Joint_020
Page  of 

GSC-9/GTSC-2/GRSC-2
Seoul, Korea
9-13 May 2004

SOURCE: | ATIS Committee T1E1
TITLE: | Status Report of Digital Subscriber Line (DSL) Work
AGENDA ITEM: | Joint GTSC/GRSC ; #4.4

Decision |
Discussion |
Information | X
DOCUMENT FOR:

1.	Decision or Action Requested
None.  This report summarizes the current activities of Committee T1’s Technical Subcommittee T1E1 on Digital Subscriber Line (DSL) and highlights work on VDSL, SHDSL, ADSL, spectrum management, filters and splitters, and a new project on bandwidth on demand (bonding).

2.	References
Recently Published Standards:
T1.417-2003, Spectrum Management for Loop Transmission Systems, Issue 2
T1.TRQ.10-2003, Technical Requirements for Splitters for Line Splitting and Line Sharing Applications

3.	Issues for Discussion
Committee T1’s Technical Subcommittee T1E1 (Interfaces, Power, and Protection of the Network) has, as one of its mandates, the development of Digital Subscriber Line (DSL) standards as well as the development of standards enabling the application of DSL technology in the marketplace.  In this latter category are efforts to specify guidelines to facilitate a spectral environment in metallic loop cables such that DSL technologies can be deployed without impaired operation due to crosstalk with existing carrier technologies and to develop DSL filter and splitter specifications facilitating the deployment of DSL systems.  Work this past year continued on a number of fronts, VDSL and other variants of xDSL, enhancement to spectrum management, dynamic spectrum management, network-end line sharing splitters, and new work on multi-rate multi-pair DSL using bonding techniques.

VDSL:
Since the last GSC meeting, T1E1 has continued its leadership in the development of xDSL Physical Layer standards.  Following several years of discussion and evolving from the publication of Trial Use standard for DMT and QAM as linecodes for VDSL, T1E1 held a ‘bake-off’ to compare the performance of the two linecodes under controlled conditions.  The bake-off was held during May and June of 2003 and the results reported out to the group on June 19, 2003, when, after discussion, the group reached a decision on line selection as we had promised the telecommunications community.  The consensus decision from T1E1 was to develop an American National Standard for VDSL specifying DMT as the linecode and a Technical Requirements (TRQ) document for VDSL specifying the QAM linecode.  One of the prime recipients of this news was IEEE 802.3ah (Ethernet in the First Mile, EFM) who received the notice of our decision via liaison and incorporated it into their specification process.  For our own part of the process, T1E1 has proceeded through the balloting process and has approved for publication both of the documents mentioned above, an ANS entitled, Very-high-bit-rate Digital Subscriber Lines (VDSL) Metallic Interface (DMT-based), and a TRQ entitled, Very-high-bit-rate Digital Subscriber Lines (VDSL) Metallic Interface (QAM-based).  The results were also shared with ITU-T Q.4/15.  The VDSL Trial Use Standard, T1.424, has been withdrawn and the number used by the DMT VDSL version.

The group has begun discussion on the next version, VDSL2.

SHDSL:
The group initially began a discussion on Enhanced SHDSL but found their goals were very similar to those of ITU-T Q.4/15.  In light of that, the group decided to pursue a path of referencing the ITU-T document known as G.shdsl.bis in the spirit of harmonizing versions specifying the same technology.  Our pointer document is out for Letter Ballot.

ADSL:
The draft for ADSL, Issue 3, incorporating T1.413 and T1.413a, including text on ADSL filters, and providing updates to some of the Annexes has been sent out for Letter Ballot.

There is potential interest in evaluating ADSL2plus performance using premises wiring with HPNA devices attached.

Spectrum Management, Issue 2:
The enhancement of Spectrum Management for Loop Transmission Systems, T1.417, Issue 2, addressing spectral compatibility of repeaters and intermediate transceiver units and providing guidelines for deployment of remote terminals and managing spectral compatibility with systems deployed from the CO  (per NRIC-V directive), was published.  

Spectrum management is the administration of the loop plant in a way that provides spectral compatibility for services and technologies that use pairs in the same cable.  In order to achieve spectral compatibility, the ingress energy that transfers into a loop pair, from services and transmission system technologies on other pairs in the same cable, must not cause an unacceptable degradation of performance.  In addition, the egress energy from a particular loop pair must not transfer into other pairs in a manner that causes an unacceptable degradation in the performance of services and technologies on those pairs. 

This standard was also developed to assist carriers, manufacturers, and users of products connected to local loops, to understand the characteristics of twisted-pair loop cables.  In addition, this standard can be used to determine if new services and loop transmission system technologies are spectrally compatible with the basis systems that are defined in this standard.  This standard is intended to be consistent with technical criteria adopted by the Administrative Council for Terminal Attachments (ACTA) to protect the network from harm caused by customer installed terminal equipment.  

Dynamic Spectrum Management (DSM):
The goal of Dynamic Spectrum Management is to enhance spectrum-management value by improving reliability and increasing data rates through measurement and/or dynamic management of DSL spectral compatibility.  Dynamic management incorporates parameters of the loop plant environment and loop transmission systems that are time or situation dependent and which are not incorporated in the current issue of T1.417 Spectrum Management for Loop Transmission Systems.  Using physical-layer performance information provided to the service provider’s maintenance entity, the service provider may use this information to improve service provisioning, reliability, and/or data rates.  DSM defines methods and/or tests that determine the spectral compliance of dynamic-spectra DSL systems with themselves and with the static DSL systems of T1.417.  Specifications may thus allow situation-dependent (i.e., adaptive or dynamic) assignment of lines, signals, spectra, and operation of DSL modems that are found spectrally compliant.  Text has been included to cover band preference bounding and an optimum spectrum management algorithm.  This work is under discussion.

Network End Line Sharing Splitter:
This document describing the electrical characteristics of four network equipment facility line sharing splitters that may be used to facilitate the deployment of various DSL technologies over metallic lines that are also being used to provide voice band service has now gone to publication.  Protection is provided for DSL signals from the high frequency transients and impedance effects that occur during PSTN operation, namely ringing transients, ring tip transients, off-hook transients.  The filter Types A, B, C, and D respectively cover splitters for T1.413, Annex E; filters with added consideration of envelope delay and DSL band attenuation; filters intended to accommodate VDSL and covering the entire 998 spectrum plan; and filters addressing ISDN BRI service.  Test methodologies to ascertain compliance are also included in this standard.  

M^2DSL (Multi-rate Multi-pair Digital Subscriber Line):
The project on M^2DSL is striving to develop a standard for a broadband DSL that will support bit rates up to at least 10 Mb/s symmetric on short loops decreasing to lower rates on longer loops.  The scope includes use of bonding techniques, i.e., the use of multiple pairs of wires to achieve higher aggregate bit-rates, enabling multi-megabit rates to all customers on non-loaded loops using multiple pairs of wires to meet a range of rate-reach objectives.  This project has addressed symmetric bit-rate transmission first, but may also address asymmetric bit-rate operation.  Three drafts have been produced covering ATM over DSL, Ethernet over DSL and Time Division Inverse Multiplexing over DSL.  The bonding specifies transmission over 2-32 pairs, is PHY independent, and includes automatic dynamic removal and restoration of pairs.  Optional initialization procedures are used to facilitate spectral optimization.  The Ethernet version builds on methods from IEEE P802.3ah and extends Ethernet transport over other xDSL technologies, including ADSL.  The drafts are currently in the comment resolution stage of the initial Letter Ballot.

T1E1 expects to continue its traditional cooperation with ITU-T SG 15 and their instantiation of this effort known as G.bond.  One overarching issue of this DSL development work concerns the applicability of the technology and whether the application necessitates symmetric or asymmetric bit rates upstream and downstream; the resulting decision point evolves with the marketplace.  

Liaisons:
T1E1’s traditional of international cooperation is exemplified by the list of liaison partners from this past year:  the DSL Forum, IEEE 802.3ah, FS-VDSL, and ETSI TM6.  T1E1 also forwarded 16 and 37 contributions respectively to the two ITU-T SG15 meetings in October 2003, and April 2004, on DSL related matters.

________________________________

* Contact:

Rick Townsend, T1E1 Chair

Tel:	+1 732-949‑8667
E-mail:	rltownsend@lucent.com