CSR Volume 13 #4, Feb. 21, 2002

COMMUNICATIONS STANDARDS REVIEW

Volume 13, Number 4 February 21, 2002

REPORT OF ETSI TM6 #25, ACCESS TRANSMISSION SYSTEMS ON METALLIC CABLES, FEBRUARY 4 – 8, 2002, TORINO, ITALY The following report represents the view of the reporter and is not the official, authorized minutes of the meeting. ETSI TM6 #25, Access Transmission Systems on Metallic Cables, Feb. 4 – 8, 2001, Torino, Italy.3 Future of ETSI TM6...... 4 Liaison from ETSI TC STQ...... 4 Liaison from ETSI TC AT...... 4 Report from ITU-T Q4/15...... 4 Report from T1E1.4...... 5 Joint CENELEC ETSI Coordination Meeting...... 5 SDSL...... 5 Deactivation/Warm Start...... 6 Test Noise...... 8 Multi-Pair...... 8 Wetting Current...... 10 Summary of the Status of Study Points for TM-06022...... 10 New WI TM-06032, TS 101 524 Extension to SDSL Working Over Multiple Pairs...... 12 VDSL...... 12 Part 1. VDSL Functional Requirements, Revision of TS 101 270-1 (TM-06026-1)...... 12 FS-VDSL Liaison...... 12 PSD Mask Issues...... 13 Upstream Power Backoff...... 16 Packet Transport Mode...... 16 Simulation Parameters...... 17 VDSL Splitter Issues...... 17 TM-06026-1 Living List...... 17 Part 2. VDSL Transceiver Requirements, Revision of TS 101 270-2 (TM-06023)...... 18 Study Points for the Revision of TS 101 270-2 (TM-06023)...... 18 ADSL...... 18 Testing Configuration...... 19 Performance Objectives...... 20 Deployment Issues...... 23 Splitter Issues...... 23 All Digital Loop...... 24 TM-06025 Living List...... 25 Spectral Management...... 26 TM-06029 (rev of TR 101 830-1), Part 1: Definition of signals...... 26 Part 1 Living List...... 27

TM-06030 (rev of TR 101 830-2), Part 2, Technical Methods for Performance Evals...... 27 Part 2 Living List...... 29 TM-06031 (TR 101 830-3), Part 3, Construction Methods for Spectral Mgmt Rules...... 29 Part 3 Living List...... 30 TM6(01)17 European Approaches to Spectral Management...... 30 VoDSL...... 30 VoDSL Living List...... 30 European Specific Splitter Requirements...... 31 SP1, ADSL-friendly PSD Mask...... 31 Splitter Testing...... 32 STF 215...... 33 Draft TS 101 952-1-2 (High Pass ADSL/POTS Splitters)...... 33 Draft TS 101 952-1-3 (ADSL/ISDN Splitters)...... 33 DSL Splitter Living List...... 34 Liaisons...... 34 Work Plan...... 34 DSL Testing and Interoperability...... 34 Testing Methods for DSL Splitters...... 35 TM6 #25 Meeting Roster, February 4 – 8, 2002, Torino, Italy...... 36 Acronym Definitions...... 38 Communications Standards Review Copyright Policy...... 40

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REPORT OF ETSI TM6 #25, ACCESS TRANSMISSION SYSTEMS ON METALLIC CABLES, FEBRUARY 4 – 8, 2001, TORINO, ITALY M. Gindel (Telekom Austria) is the TM6 chair. TD-00 contains the list of TDs and their abstracts. TD-01r1 is the meeting agenda. TD-02 shows the status of TM6 WIs (published WIs not included). M. Gindel had informed TM6 delegates by email prior to the meeting that his term as TM6 Chair would end by December 2002, and that it was necessary for the committee to indicate its wishes for the next period of chairmanship before the forthcoming TC TM meeting. There was unanimous support by email supporting M. Gindel as the TM6 Chair for another term; hence, he will offer his candidature as TM6 Chair for the following period. He also indicated that he will be able to dedicate more time to TM6 from the end of the year, as he will retire from his other activities with Telekom Austria. TM6 discussed choosing meeting places outside of Europe. It was decided to postpone to the year 2003 any TM6 meeting outside Europe. The following table shows the work items assigned to TM6 for this meeting:

ETSI no. WI Title DTS/TM-06021 TM; Access networks; Reqs. for the support of VoDSL TS 101 524 RTS/TM-06022 TM; Access networks; SDSL TS 101 270-2 RTS/TM-06023 TM; VDSL; Part 2: Transceiver Specification issue 2 TS 101 388 RTS/TM-06025 TM; ADSL - European specific requirements TS 101 270-1 RTS/TM-06026-1 TM; VDSL; Part 1: Functional requirements TR 101 953-1-2 DTR/TM-06027-1-2 Test Methods for High Pass part of ADSL/POTS splitters TR 101 953-1-3 DTR/TM-06027-1-3 Test Methods for ADSL/ISDN splitters TR 101 953-2-2 DTR/TM-06027-2-2 Test Methods for high pass part of VDSL/POTS splitters TR 101 953-2-3 DTR/TM-06027-2-3 Test Methods for VDSL/ISDN splitters. TR 101 953-2-4 DTR/TM-06027-2-4 Test Methods HP part of VDSL/”Other services” splitters. TS 101 952-1-2 DTS/TM-06028-1-2 DSL Splitter Reqs.; High Pass part ADSL/POTS splitters TS 101 952-1-3 DTS/TM-06028-1-3 DSL Splitter Reqs.; ADSL/ISDN splitters TS 101 952-2-2 DTS/TM-06028-2-2 DSL Splitter Reqs.; HP part VDSL/POTS splitters TS 101 952-2-3 DTS/TM-06028-2-3 DSL Splitter Reqs.; VDSL/ISDN splitters. TS 101 952-2-4 DTS/TM-06028-2-4 DSL Splitter Reqs.; VDSL/”Other services” splitters. TR 101 830-1 RTR/TM-06029-1 TM; Spectral management; Part 1: Def. of signals TR 101 830-2 RTR/TM-06030 TM; Spectral management; Part 2: Technical methods for performance evaluations TR 101 830-3 RTR/TM-06031 TM; Spectral management; Part 3: Construction methods for SM rules TS 101 524 RTM/TM-06032 TM; Access networks; SDSL

The Chair asked if there were any essential IPR to declare in this meeting; none was declared.

Future of ETSI TM6 Several options are available for the future of TM4 and TM6. The variant preferred by the TM6 Chair (and also by TM4) is that TM continues as a Technical Committee, albeit with only two working groups. One alternative that was rejected by the TM6 Chair and the meeting as a whole was to incorporate TM6 (together with TC AT) into SPAN, although it might be acceptable to merge TM and AT under the current AT Chair. (It is believed that TM4 is not in favor of merging with ERM.) The TM6 meeting strongly felt that it is important that the name “TM6” continue to exist, as it has achieved a high level of international recognition, and a change in name would have negative repercussions in ETSI’s relationship with external bodies such as ITU-T and T1E1. The meeting was prepared to accept any organizational change to streamline the internal ETSI organization, provided that such re-organization does not adversely affect the TM6 working methods and external image. TM6 will discuss the future of TM at a meeting scheduled for April 9-11.

Liaison from ETSI TC STQ TD-05 is an STQ liaison to TM6 including a copy of STQ’s latest draft of DTR 201 769-3, QoS parameter definitions and measurements for use in network to network interconnection; Part 2: Physical unbundling of metallic local loops. STQ hopes to be able to approve this TR at their April meeting. They welcome any comments or suggestions that TM6 might have about this draft. No comments to this liaison were raised; a liaison to that effect was drafted in reply (WD-27).

Liaison from ETSI TC AT TD-04 is a liaison from TC AT informing that AT WG Digital has drafted ES 201 910 (v.1.2.2), Line power requirements for IP terminals. This draft standard specifies the line powering requirements for IP terminals that are powered by a LAN network (802.3 data interface). IP terminals could range from card readers, line powered security cameras to IP telephone terminals. The characteristics of the power provided at the 802.3 interface, as well as the terminals that will draw the power, is in accordance with IEEE Draft P802.3af/D1.2 (Data Terminal Equipment [DTE], Power via Media Dependent Interface [MDI]). In addition to the IEEE requirements, the ETSI standard also specifies requirements to cater for the provision of emergency power in the event of power failure of primary power of the PSE (Power source element providing power to the MDI interface). Since the additional requirements in the ETSI standard pertain to PSE only, AT WG Digital feels that the scope of this work now also covers some of the areas that pertain to the work done in TM6. AT WG Digital intends to approve this standard at the April meeting of TC AT. P. Golden (LEA) reported that the low-pass part of the ADSL over POTS splitter had been addressed in a Rapporteurs meeting and in email discussions. A draft is available on the server. It is hoped to have it approved by mid-April so that the full ADSL specification will be available for ITU-T Q4/15.

Report from ITU-T Q4/15 N. King (Infineon), assisted by P. Eriksson (Ericsson), gave a summary of the December 2001 Q4/15 Rapporteurs meeting held in Clearwater, Florida (see also CSR 12.50).

• ADSL: Still plan to complete the second version of ADSL (G.dmt.bis, G.lite.bis) in April 2002. A new project called G.bond is under consideration, generally aimed at multi-pair xDSL, but with most attention focused on ADSL. This is a separate project from G.dmt.bis or G.lite.bis. • VDSL: G.vdsl.f has been approved for publication (with no modulation specified). • SHDSL: 1) Multi-pair: Agreements were reached that: a) G.shdsl.bis shall include an optional M-pair mode; b) this should be compatible with the existing four-wire mode when M = 2, unless a substantial benefit can be shown for a more complex approach. There is a feeling that failure-handling procedures will be needed for larger numbers of pairs. There is also a feeling that optimizing the bitrates for different pairs in the group would be an enhancement that could come later. 2) Voice over SHDSL, Dynamic rate repartitioning (DRR): There are two main proposals which are being compared on the grounds of simplicity and robustness. There is a goal to make a decision between them at the next meeting.

Report from T1E1.4 There was no official written liaison from T1E1.4 to TM6. N. King (Infineon) gave a brief oral report of the T1E1.4 November 2001 meeting. In summary: • “Technical requirements for single-pair high-speed digital subscriber line (SHDSL) terminal equipment to prevent harm to the telephone network” has been approved for publication. • The T1E1 specification that is a pointer-document to G.dmt has been approved. • The HDSL2 specification has been sent out for default letter ballot. • The three-part VDSL specification has been sent out for a second default letter ballot, due to substantive changes during ballot resolution. • “Technical requirements for EtherLoop terminal equipment to prevent harms to the telephone networks” is undergoing letter ballot, after post-meeting modification. • Comment resolution on the network-end line-sharing splitter is continuing; it is expected to reach conclusion at the next meeting. • Issue 2 of the spectrum management document is still being developed, with a goal of completion by April 2002. In the meantime, SHDSL has been agreed as a “basis system” for spectrum management, and 2B1Q SDSL has been removed from the list of basis systems. • Consideration of the dynamic spectrum management topic is still underway. • The next T1E1 meetings are scheduled for February 18-22 in Vancouver, British Columbia, Canada, and April 8-12 in Atlanta, Georgia.

Joint CENELEC ETSI Coordination Meeting A meeting of the joint CENELEC / ETSI working groups is to be held February 8 in Brussels. The agenda includes the preparation of a joint CENELEC/ETSI position on EC Mandate M313, which, among other things, addresses harmonized EMC standards for xDSL technology. SDSL S. Schmoll (Alcatel) is the Rapporteur for TM-06022, Revision of TS 101 524, SDSL. In his absence, M. Kimpe (Adtran) served as Rapporteur for this session. WD-06 contains the agenda for the SDSL session. Work continued on the enhancement of TS 101 524. TM6 Approval is planned for November 2002.

Deactivation/Warm Start TD-11 (B. Heise, Infineon) presents simulation results that indicate the number of activation faults and the distribution of the warm start-activation times of the NTU on different lines. The minimum activation time given by the implementation and the way of detecting WSL is 20 msec; this time was reached in each configuration during at least one simulation. The maximum activation times are generally higher using the unprecoded transmission signal. Furthermore, a significant portion of these activations could not be successfully finished. It shows that without Tomlinson precoding the probability of activation faults is higher and the activation time of the successful activations is increased. The simulations were performed with a fully trained echo canceler; the results are therefore independent of the kind of wakeup tone and the existence of half-duplex segments. TD-11 does not recommend using a warm start sequence (which sometimes cannot activate on-line configurations even though the previous coldstart was successful). It does propose to use Tomlinson-precoded signals for signals WSL, WSN, WOKN, and WOKL. TD-10 (B. Heise, Infineon) presents simulation results that indicate the range and distribution of warm start-activation times of the NTU at 192 kbit/s. Earlier simulations showed that a clear relationship exists between activation time, symbol rate, and loop length: Activation time is directly and proportionately inverse to the symbol rate. Activation time increases on longer loops rather than at more noise interference. Concentrating on that worst case scenario, TD-10 shows that the maximum synchronization time of the NTU can come near to 500 msec, but in 95% of the cases the value remains below 350 msec. Thus, there is a sufficient margin of 150 msec, enough for processes during the activation that are invariable in time. TD-10 proposes to keep tWsactmax=500 msec as the maximum activation time that shall not be exceeded in 95% of the warm starts when there are no changes either in equipment or environment since the previous activation. TD-16 (B. Heise, Infineon) proposes modifications to the half duplex segments in the warm start sequence to improve the activation procedure in case that the transmission line characteristics have changed since the last activation. The modifications are: • For the NTU there is no half duplex segment. • For the LTU the half duplex segment is mandatory. • The LTU starts the transmission with the new signal WECL. Waveform WECL shall be generated by connecting logical zeros to the input of the LTU scrambler. The transmit power, symbol rate and PSD mask for WECL, shall be as for signal WSN. The procedure is as follows:

• After the wakeup sequence, the LTU starts the transmission with sending WECL • At the same time the NTU starts synchronizing on the LTU signal • When the LTU is ready to receive the signal from the NTU, then the LTU starts sending WSL • When the NTU is synchronized and has recognized WSL then it starts sending WSN • When the NTU is ready to go to data mode it starts sending WOKN • When the LTU is synchronized and can recognize WOKN then it sends WOKL for 256 symbols and the NTU and the LTU go to data mode hereafter This modification is very similar to the sequence discussed in TD-15 (below). The main advantage is that the half duplex segment can be rather short if no adaptation is needed. If the line characteristic has changed, each transceiver has time periods where it is possible either to separately readjust the echo canceler or to synchronize and to readjust the receive filters. The time used for possible readjusting can be made as long as is needed.

TD-15 (B. Heise, Infineon) is a revised version of TD-10, Deactivation and warm start (B. Heise, Infineon Technologies), from the TM6 November 2001 meeting (CSR 12.44). It proposes a complete text for the all power down mode, deactivation and warm start related items. Besides some editorial amendments, it includes the following major changes: • Deactivation can be initiated from NTU and LTU • Timeouts removed or changed to coldstart values • M-sequences have been removed as an option • Tomlinson precoding is used during activation WD-23 (B. Heise, Infineon) contains the results of the ad hoc group on power down mode (warm start activation/deactivation). The ad hoc was attended by representatives of Alcatel, Conexant/Mindspeed, Tioga, Metalink, Adtran, Paradyne, Deutsche Telekom, Siemens, Analog Devices, and Infineon. The following questions were discussed, and resolved, as follows: Is there a real need for the warm start? Concerns were raised as to the advantage of the power down compared to possible risks for interoperability. Deutsche Telekom indicated a strong interest in the power saving mode (power down). It was pointed out that although the main target of SDSL is business customers, these lines are idle a good deal of the time during a week. Therefore, the warm start is expected to have a clear effect on the power costs. The ad hoc decided to continue the work on warm start activation and deactivation. Shall the signal during synchronization be Tomlinson-precoded? The architectures of the existing transceiver implementations are significantly different; the effect of using Tomlinson precoding is implementation-dependent. Since none of the transceiver manufacturers attending the ad hoc were suffering any drawback from Tomlinson precoding, it was preliminarily agreed to use the Tomlinson precoded signal during warm start activation. Shall PACC-tones or m-sequence signals be used for wake-up? It was preliminarily decided to use the PACC-tones. The manufacturer must take care to reliably distinguish between the wake-up signal and the PACC-tones by the different duration. Shall the half-duplex segments in the NTU be used? All participants agreed that using the half- duplex segments will improve the robustness of the warm start in case of small changes of the line characteristics, e.g., variations in temperature. On the other hand, the half-duplex segments increase the activation time even when the line characteristics have not changed at all. It was decided for the sake of robustness to use a non-optional half-duplex segment for the NTU with a fixed time. Shall the half-duplex segments in the LTU be used? No decision was reached on how to specify the half-duplex segment for the LTU. Two positions were maintained: 1. The LTU shall have a fixed time while the NTU shall not transmit. The duration of the segment is to be defined and should be in the range of 100–200 msec. 2. The LTU shall use a signal (WECL) to prohibit the NTU transmitting. The minimum duration of the half duplex segment is thus under full control of the LTU. The ad hoc participants will evaluate the two solutions of a half-duplex segment for the LTU. Shall the NTU be allowed to refuse a request for deactivation from the LTU? The rationale behind this question is the possibility of the NTU transceiver software being hacked. No conclusion was reached on this issue. All interested parties were invited to contribute to this question.

Definition of the code points for the warm start in the PACC-sequence: Appropriate code point shall be identified before the next meeting. Which tests shall be defined to prove conformance with the warm start specification? Several tests were discussed, e.g., activation (different loops, noise models, bitrates), timing of the segments of the sequence. All interested parties were invited to contribute to this question. WD-24 (B. Heise, Infineon) is the updated text proposal for power down mode, deactivation and warm start. It is based on TD-15 and on the discussion of the power down mode ad hoc group. It is intended to be included in the next revision of Part 1 of the ETSI SDSL specification.

Test Noise TD-14 (M. Kimpe, Adtran; A. Carrick, Ascom; T. Nordström, FTW; L. Dreier, Alcatel) proposes an informative annex describing the noise profile values for all of the possible 280 test cases of test sets 1 to 7, for inclusion in the next revision of SDSL. This was provisionally agreed. TD-20 (A. Carrick, Ascom) presents the status of SDSL Study Point 17, description of test noise profiles: • Since the previous meeting considerable work was put into tabulating and proof-reading the noise profiles and a consensus was reached on the values. This exercise demonstrated the need for such tables, as even the ETSI experts had initial problems arriving at agreed values. Draft text is now available for this annex (TD-14). • The length of time required for a complete test sequence (even in the ideal case) is a cause for concern. • The possibility of identifying noise shapes that are very similar to reduce the total number of noise shapes is worthy of consideration. • The need to specify how closely the test equipment must be to the theoretical noise was identified, as well as the need to clarify the methods for injecting and measuring the noise. (ADSL has two methods for noise calibration: a modified noise shape into a resistance or the original noise shape into a complex impedance; the same issue arises with SDSL.) • The required “noise-floor” for practical test equipment needs to be addressed; some manufacturers have indicated that the value of -140 dBm/Hz for the noise generator (or -150 dBm/Hz for the line simulator) is problematic. However, simulations show that in some cases increasing the noise floor to, say, -120 dBm/Hz, will result in 0.5 dB degradation of margin. This should be studied in more detail. TD-20 proposes that Study Point 17 be split into the following several individual study areas: • Analysis of test times and generation of proposals for reducing them • Generation of a specification for the accuracy with which performance test equipment is required to fulfil the loop frequency responses and the tabulated noise profiles • Analysis of an appropriate noise floor for practical test purposes • Generation of descriptive text for the noise injection and calibration method After some modification of the scope of the study point addressing noise injection and calibration methods, four new study points were created (SP19–22; see below).

Multi-Pair TD-12r1 (D. Daecke, Infineon) proposes the generalization of the SHDSL/SDSL four-wire mode for two or more wire pairs. The proposed technique allows transmission over up to (TBD) wire

8 Vol. 13.04 Copyright © CSR 2002 February 21, 2002 COMMUNICATIONS STANDARDS REVIEW pairs. A major characteristic of this proposal is that, as a generalization of the current four-wire mode, it is consistent with that and with the SDSL TPS-TC layer. This plain multi pair mode should be agreed in a first step, as this mode is already defined and standardized for the 2-pair case. A more sophisticated multi pair mode should then be developed in a further step. New features like “operation in case of failure of one or more pairs” or “new TPS-TCs for unequal data rates” should be included. TD-13 (D. Daecke, Infineon) discusses the number of wire pairs as well as possible applications of multi-pair systems. It proposes that the number of wire pairs M in the SDSL multi-pair mode can be 2, 3, 4, … 16. WD-01 (A. Almog, Orckit) proposes requirements for multi-pair use of SDSL including aggregation of pairs with different rates and low latency. The extension of the four-wire mode of ITU-T G.shdsl to support multi-pair operation has some weaknesses. While working with several DSL pairs there are likely to be physical differences between the pairs, resulting in different rate performance (See TD-57, Influence of SDSL on ADSL performance—the effect of pair position, G. Vanhoutte, P. Vandendriessche, M. Zekri, Belgacom, TM6 #23). To avoid forcing a multi-pair SDSL system to operate at the rate of the pair with the worst characteristics, the solution should support aggregation of pairs with different rates; achievement of this is not straightforward with the extension of the SDSL four-wire standard. Implementation of the extension of the four-wire mode requires a new chipset, which will increase time to market. This solution is also SDSL specific and cannot be used as is for any other physical layer technologies. Other known protocols as MLFR (Multi Link Frame Relay, FRF), IMA (Inverse Multiplexing for ATM, ATMF) and MLPPP (Multi Link PPP, IETF RFC 1990) have different disadvantages. They imply large overhead, suffer from high latency, and are not appropriate for TDM streams. In addition, IMA supports only the same data rate for all sub-links. WD-04 (J. Frimmel, M. Sorbara, GlobeSpan) proposes objectives for multi-pair SDSL. At the November 2001 meeting, TD-21, Multi-pair SDSL with multiple symbol rates (F. Reuven, Tioga), proposed a list of requirements for multi-pair transmission. WD-04 proposes that these be relabeled as objectives, to guide the development of the specification. It presents the reorganized list (below), and includes suggested changes. Many of these would be restated as actual requirements later, in the baseline text. Phase 1 objectives: • Multi-pair transmission mode shall be compatible with ITU-T G.shdsl four-wire mode. • Operation with up to 16 pairs will be possible. • Multiplexing will be performed byte by byte. The mapping of the multiplexed timeslots shall be identical for every subframe. • The multiplexing function will be derived solely from the bit rates. Multiplexing will not depend on the physical modulation (this needs clarification). • The symbol rates of links shall be user-configurable, and shall be the same for all links. • Operation shall be protocol-independent and transparent. It shall not depend on the encoding or format of payload. • Multipair transmission mode will optionally handle link failure. • The addition and deletion of links during operation shall be possible. • Normal, independent EOC operation shall be the default. Duplication of overhead shall be allowed for fallback interoperability with G.shdsl four-wire mode only. • At a minimum, any multi-pair transmission will be able to handle differential delay of 50 msec +6 symbols. (This requirement is taken from ITU-T G.shdsl. The symbol period should corresponds to the link of the lowest rate.)

• Latency inherent in multi-pair SDSL multiplexing will be minimized. • Disruption of customer data due to reconfiguration of rates or addition/deletion of links shall be minimized (but not eliminated). Phase 2 objectives: • The symbol rates of each link shall be individually user-configurable. • Optionally, the multiplexing of different rates on links within the same multi-pair system shall be possible. • The multi-pair transmission mode shall optionally allow automatic selection of symbol rate with full resolution (that is, the number of time slots ni will be set to 3 to 36 according to channel conditions). • Multi-pair transmission mode will include an optional protocol for adding and deleting links while maintaining seamless (hitless, no payload errors inserted) operation. WD-04 concludes that independent operation of each individual SDSL channel should be adopted as the default behavior, that their capabilities might be fully utilized if needed. The functional model should reflect this independent operation. With the current M-wire mode as a basis for multi-pair SDSL, a limited, but useful, standard may be achieved quickly. However, to achieve such goals as “seamless” add/delete, the ITU-T model requires some enhancement. Some potential users may not care about the “seamless” reconfiguration, nor about automatic rate assignment; they may be satisfied with limited or no EOC, either because of their application or because in-band management is available. On the other hand, some will want a complete, well-managed and high-availability solution. Therefore, to address both classes of users, WD-04 proposes to split development into the two phases outlined above. In discussion of these contributions, DTAG and BT both expressed an interest in high bit rates, but with a maximum number of pairs of 16. It was agreed that the first step in the new project is to identify the requirements for such a system. Two new study points were created for the multi-pair annex to TS 101 524 (See below: New WI TM-06032)

Wetting Current TD-06 (G. Keratiotis, BTexact) describes an experiment being conducted by BTexact Technologies to evaluate the effect of contact resistance fluctuations on the performance of SDSL transceivers when various levels of wetting current flow through the loop. Preliminary results from this experiment demonstrate the effectiveness of wetting current in curing degraded copper joints. The first part of the experiment shows that the level of wetting current that can cure a degraded joint depends on the level of the degradation and the type of the joint. When the current is adequate to trigger the healing process, the resistance exhibits significant fluctuations and the joint eventually gets healed. The noise signatures captured during the healing process will be used to examine the robustness of typical SDSL transceivers. Results from this work will appear in a future contribution.

Summary of the Status of Study Points for TM-06022 The following summarizes the status of the living list, permanent document TM6(00)17: • SP1, Definition of Impulse noise test (deleted; TM6 #25) • SP2, AM Broadcast ingress RF noise generator (partitioned; TM6 #20) • SP3, Requirements for return loss specification (agreed; TM6 #24) • SP4, Warm start and deactivation capabilities (under study) • SP5, Additional optional asymmetric PSD masks (deleted; TM6 #20)

• SP6, Investigation of common noise floor for all DSL (agreed; TM6 #21) • SP7, Four-wire transmission mode (agreed; TM6 #25) • SP8, Micro-interruption test (deleted; TM6 #25) • SP9, Transmit power testing (deleted; TM6 #25) • SP10, Dynamic configuration of narrowband channels (under study) • SP11, Modulation methods for RFI Ingress noise test. (Take text from ADSL; provisionally agreed; TM6 #24) • SP12, Noise levels for RFI Ingress noise test (under study) • SP13, Test methods for RFI Ingress noise test (deleted; TM6 #25) • SP14, Wetting Current implementation details (under study; TM6 #21) • SP15, Accuracy of margin measurements (merged with SP22; TM6 #25) • SP16, TPS-TC for LAP V5 enveloped POTS or ISDN (agreed; TM6 #24) • SP17, Description of noise specifications (provisionally agreed; TM6 #25) • SP18, IMA for SDSL (agreed; TM6 #25) New study points created at this meeting: • SP19, Possibilities for reduction of the performance test time • SP20, Test equipment accuracy for performance tests • SP21, Practical noise floor for performance tests • SP22, Noise injection and calibration methods It was provisionally agreed to use the text agreed for ADSL as the text for SP11, Modulation methods for RFI Ingress noise test. A short debate was held as to the status of SP12 (Noise levels for RFI ingress noise test) as no contributions had been received for some time. It was agreed to keep it under study and remove the existing table from the draft to emphasize the need for values to be generated as an output of this work. Following this, WD-12 was produced. WD-12 (R. van den Brink, KPN; supported by BT, Deutsche Telekom, France Telecom, Swisscom, Telecom Italia Lab, Telekom Austria, and Czech Telecom) contains the position of several operators on RFI tones for SDSL. Since it was first published in April 2000, ETSI TS 101 524 has specified synthetic ingress noise by means of RFI tones. While concerns have been raised that these numbers are not perfect, they are much more realistic than no tones at all, and better than the RFI tones defined years ago for ADSL. The fact that improvement of these numbers cannot be progressed should not be used as an argument to delete them all from the current TS 101 524. The current numbers for RFI tones published in TS 101 524 should not be deleted. Furthermore, the way these RFI tones are to be modulated with noise has been discussed and agreed in the past for ADSL and SDSL. The proposed text was not included in the SDSL August 2001 revision (v.1.1.2) nor in the November 2001 revision (v.1.1.3). The current RFI tones with the agreed modulation method should be extended as agreed, and included in the next revision of TS 101 524. In a later session (with S. Schmoll in the chair as Rapporteur), the debate on whether or not to delete the current values in the draft was reopened. It was decided to reverse the earlier decision and keep the current values, different from those agreed for ADSL. Some delegates felt that this procedure was inappropriate. The Rapporteur asked delegates to bring proposals to the next meeting to move this subject forward, and emphasized that the values kept in the draft should only be considered as a provisional starting point. The meeting also decided that notes should be added to the relevant parts of the ADSL, VDSL, and SDSL documents explaining that the long-term aim is to have identical RFI disturber definitions for all TM6 DSL specifications.

New WI TM-06032, TS 101 524 Extension to SDSL Working Over Multiple Pairs Work started on this work item. TM6 Approval is planned for September 2003. The living list has been assigned to permanent document TM6(01)19. The following summarizes the study points created for this new work item: • SP1, Requirements for multi-pair SDSL • SP2, Method of extension from two to multi pairs VDSL B. Waring (Infineon) is the Rapporteur for TM-06023 and 06026, Revision of TS 101 270, VDSL (Parts 1 and 2). WD-02 is the work plan for the VDSL session. Work progressed on these work items. TM6 Approval is planned for September 2002 for both parts, but it may be delayed until November.

Part 1. VDSL Functional Requirements, Revision of TS 101 270-1 (TM-06026-1) FS-VDSL Liaison J. MacDonald (BT) reported that a full FS-VDSL specification should be available for publication in May. TD-03 is a liaison from FS-VDSL to TM6 concerning open PSD issues raised by TM6 in their liaison WD-21 from the November 2001 meeting. FS-VDSL discussed these issues in their December meeting; the following is a summary of those discussions: Issue 1 (PSD mask interpolation): It appears there is agreement on this issue; therefore, it was not discussed. Issue 2 (Constant in-band values for the boosted PSDs) and Issue 4 (PSD masks and PSD templates): These two issues have been frequently linked and they were widely explored during the FS-VDSL discussions. FS-VDSL recognized a large number of conflicting interests associated with these issues. The important ones are identified as follows: • The PSD masks from TS 101 270-1 were established by operators in response to EMC concerns, and were set as upper bounds on peak PSD after careful measurements and lengthy discussions. There was considerable reluctance to see these bounds changed. • The use of such “hard” PSD masks in the absence of a corresponding PSD template was recognized as contentious in that it was perceived as detrimental to the interests of one of the contending line codes. • The setting of a PSD template 3–3.5 dB below the existing masks would represent a considerable adverse impact on VDSL performance which is limited by noise floor considerations toward the end of its useful range. It was also understood that recent requests for “flat tops” for the band PSD were as much motivated by a desire to see a higher in-band PSD as by any need for the band tops to be flat. In recognition of these facts, the following compromise proposal (which seems to have received broad- based support) was made: a) “Hard” PSD masks are re-established at a level 1 dB higher than the existing masks set out in ETSI TS 101 270-1. b) New PSD templates are established at a level 1 dB lower than the existing masks set out in ETSI TS 101 270-1 (i.e., 2 dB below the re-established masks).

These suggestions effectively involve a small compromise on all the issues identified above, while involving the minimum changes from ETSI TS 101 270-1. Concern was expressed that if any further changes were permitted, then all of the work done so far on VDSL PSDs, including even the band planning agreements, could become open to renewed debate. Issue 3: Shall the use of the band (0, 138 kHz) be allowed for VDSL? Shall this band (or part of it) be used for upstream or downstream? Shall it be optional or mandatory? What should the PSD masks have to be in the downstream and upstream directions in the band below 138 kHz? The optional use of the 25-138 kHz band for upstream or downstream transmission was accepted (but see question above). For FTTEx (fiber to the exchange) deployment, a peak, flat PSD of -34.5 dBm/Hz was proposed for upstream transmission and a peak, flat PSD of -6.5 dBm/Hz was proposed for downstream transmission. Issue 4 (Use of the band 0–138 kHz): There was considerable interest among operators in using this band in the upstream direction. As to the allowable PSD, this was subject to further study, although it was agreed that the PSD should not be any higher than the existing ADSL mask for this band. It should be noted that some operators are considering the use of this band in this way in both FTTCab (fiber to the cabinet) and FTTEx deployments. Among the operators at the FS- VDSL meeting, none had any current plans to use this band in the downstream direction, so it was not possible to consider a PSD bound for its use in this direction. Issue 5 (Total power relaxation): FS-VDSL discussed this issue extensively. In the case of upstream power, while acknowledging the potential reach benefit of increasing the transmitted power, it was considered that the magnitude of the increase in the upstream PSD masks that would be needed to realize any significant benefit was far in excess of what could be contemplated for EMC reasons in Europe. However, in the case of downstream in the FTTEx configuration, it was considered that more simulation work is required before the issue can be resolved. This work was scoped and results were expected by the end of December 2001, to be discussed by FS-VDSL in emails or a teleconference in January 2002. TD-03 was considered by an ad hoc group. The Rapporteur emphasized that the scope of the work item was to rationalize the existing specification where possible, but not to spend too much time on introducing new aspects. He asked whether the values proposed for mask M1 (strong EMC environment) could be provisionally agreed. After some debate (including a proposal for a third mask, M3), the proposal in TD-03 for M1 was provisionally agreed, with the proviso that this did not exclude contributions being brought to the next meeting with further proposals. TD-07 is a liaison from FS-VDSL to ETSI highlighting PSD differences between the ANSI and ETSI VDSL specifications, and providing an update on time scales for FS-VDSL specification work. During this meeting, FS-VDSL strongly encouraged TM6 to give a high priority to the vitally important issues of PSD and UPBO. The Rapporteur made the point that the FS-VDSL group is in a better position than TM6 to explain why ANSI has differences in its specification compared with the (earlier) ETSI specification, as both European and American operators are represented there. However, TM6 does have the opportunity to align the two specifications sufficiently to allow hardware compatibility. PSD Mask Issues TD-39 (S. Schelstraete, Alcatel) assesses the validity of the claim that -60 dBm/Hz was established as an EMC limit, and discusses a number of problems with the current definition of the VDSL PSDs. Looking into the history of PSD definitions and the available studies to assess this claim, it finds no evidence that -60 dBm/Hz was intended for EMC purposes. Even more, the relation between this level and possible RF interference with radio spectrum users has never been studied outside of the radio amateur bands! Therefore it would be justified to interpret this value as a

February 21, 2002 Vol. 13.04 Copyright © CSR 2002 13 COMMUNICATIONS STANDARDS REVIEW nominal PSD rather than as a mask, as is done in “VDSL Metallic interface, Part 1: Functional requirements and common specification,” ed. Q. Wang, T1E1.4/2001-009R5. While egress is an important concern, there is no evidence that -60 dBm/Hz has any special meaning in terms of egress control. With no supporting evidence, the conclusion that -60 dBm/Hz is a peak value is not justified and even harmful to VDSL performance. To not complicate revision of the standard, TD- 39 proposes to keep the value for the time being, but interpret it as a nominal value. The complete PSD definition (including egress issues) could be done as proposed in TD-38. There was some discussion as to whether or not the PSD limits were solely based on EMC limits, but it was felt that there was insufficient ground to dispute them, especially as the values had been agreed at previous meetings. Also, there are regulatory issues that may end up being European country dependent. TD-39 was taken as background for the mask versus template debate. TD-38 (S. Schelstraete, Alcatel) revisits an earlier proposal (TD-46, Transmit PSD masks and ripple, S. Schelstraete, Alcatel, TM6 #23, Stockholm September 2001, CSR 12.35) to define the PSD of a VDSL system in terms of a PSD template and a PSD mask. It modifies the earlier proposal to take into account egress concerns. It proposes to: • Clarify that the PSDs in TS 101 270-1 are PSD templates. • Define a PSD mask as being TBD dB above the template (suggested value is 3.5 dB to be in line with VDSL Metallic interface, Part 1: Functional requirements and common specifications [T1E1.4/2001-009R5] and ADSL practice). • Define an egress mask. This mask will depend on deployment scenario (M1 vs. M2, weak EMC environment), country, etc. The value could be determined by the regulator or by TM6 based on results from the EMC working group. Following extensive debate, the concept of two masks was accepted in principle, but the decision to change the specification was deferred, pending results of further contributions proving that such a change will bring clear advantages. TD-45 (E. Barnea, A. Leshem, Metalink) proposes to decouple the use of RFI egress notches from the definition of the PSD mask. The support of notches shall be mandatory for both masks, but the use of notches will be optional, and determined by the operator, according to local regulations. There was no clear support for this proposal, so a study point was created to study this topic further. TD-08 (V. Oksman, Broadcom) presents a detailed analysis of the impact of the transmit PSD mask on the performance of a VDSL loop for ETSI spectral plans 997 and 998. It concludes the following: Increasing of the transmit PSD in any band of both upstream and downstream direction improves performance of the VDSL loop. A 6 dB PSD boost relatively to M1 in upper bands already leads to significant performance improvements: • A boost in the first upstream band (U1) improves the loop length of about 10%. • A boost in the second upstream band (U2) improves the channel capacity for 3–4 kft loops up to 30%. • A boost in the second downstream band (D2) improves the channel capacity for 3–4.5 kft loops up to 15%. The first downstream band PSD has less impact on the overall capacity. It increases by only 1.5 Mbit/s (less than 10% for 998 and less than 12.5% for 997) for each 6 dB step between -52 dBm/Hz to -40 dBm/Hz.

Since performance gradually improves as PSD increases, the only limiting factor to select the transmit PSD is the total transmit power. The PSD should be defined such that for the given transmit power the maximum performance could be achieved. Analysis of the sensitivity of the upstream and downstream performance to the PSD variations leads to the following list of priorities for transmit power distribution: • The first priority, to increase the maximum PSD, should be given to the first upstream band as it leads to the reach improvement (the reach of both 997 and 998 is limited by the upstream, especially 998). • The second priority, to increase the maximum PSD, should be given to the second upstream and second downstream bands, as both significantly improve the number of customers getting high speed symmetric services (more than 10% reach improvement). The second downstream is even more important for FTTCab deployments where D1 is significantly cut to avoid crosstalk into ADSL. • The third priority, to increase the maximum PSD, should be given to the first downstream. TD-40 (VDSL Coalition) addresses the definition of the PSD mask M2. The current VDSL PSD masks for spectral plans 997 and 998 show some looseness due to a big difference between the “fill-up” power and the transmit power limit. Also, some non-optimality in the distribution of the transmit power over the frequency band was found. Contribution TD-24 (B. van den Heuvel, KPN; R. Persico, Telecom Italia Lab) from the September 2001 Stockholm meeting(CSR 12.35), suggested to increase the downstream transmit power limit by 9.5 dB, and to reduce the PSD on all frequencies above 1.1 MHz to improve the situation. This suggestion, however, requires a very high transmit power and increases dynamic range of the receive signal, leading to serious complications in the AFE of the modem. TD-40 proposes an alternative approach, based on more balanced distribution of the transmit power among the frequency bands. It proposes PSD mask definitions for the updated ETSI mask M2 in the frequency range above 138/276 kHz, and it proposes the following changes in the transmit power limit for both PSD masks (M1 and M2): • CPE (FTTEx and FTTCab, NT): 14.5 dBm • ONU (FTTCab, LT): 11.5 dBm • Exchange (FTTEx, LT): 14.5 dBm TD-55 (S. Schelstraete, Alcatel) proposes a method to improve the reach of the lower upstream data rates by raising the upstream transmit PSD. It proposes the following (boosted) PSDs for VDSL, to be used in an environment where egress is of no concern:

First upstream band Second upstream band Plan 997 -52 dBm/Hz -57 dBm/Hz Plan 998 -50 dBm/Hz -55 dBm/Hz

Outside of the upstream bands, the agreed out-of-band PSD definition applies. It is understood that the modem is allowed to completely “fill” the PSD template. This will limit the total power to 13.6 dBm and 14 dBm for Plan 997 and Plan 998, respectively. The Rapporteur asked the operators present if they were prepared to consider modifications to mask M2 as proposed in these contributions. The general feeling was that a compromise was beyond the reach of the group at that time. An ad hoc group was formed to continue the debate off- line, to attempt to establish a new set of masks related to M2 that will allow improved performance. WD-26 is the TM6 liaison reply to TD-03 and TD-07 from FS-VDSL. TM6 informs FS-VDSL that they reached provisional agreement on the proposal in TD-03 to establish a “hard” mask at a level 1dB higher than the levels in their requirements specification, and to establish a “nominal”

February 21, 2002 Vol. 13.04 Copyright © CSR 2002 15 COMMUNICATIONS STANDARDS REVIEW mask at a level 1dB lower than the levels in their requirements specification. This provisional agreement was only achieved for Mask set M1. Mask M1 is intended for use in deployments where strong EMC effects are expected. This provisional agreement was based on the rationale given in TD-03 relating the PSD masks to EMC limits. TD-39 questions the validity of this rationale; TM6 requests FS-VDSL comments on TD-39 before finally agreeing on the new mask set for M1. For Mask set M2, which is intended for use in deployments where EMC effects are expected to be weak, an ongoing debate attempted to determine what the maximum acceptable PSD levels could be. Some network operators expressed concerns at raising the PSD levels above those proposed in TD- 03. To try to finalize their discussions on mask set M2, TM6 requests the views of FS-VDSL on TD-40 in so far as it relates to M2. The PSD proposals in TD-40 are thought to be capable of economic implementation by manufacturers of SCM and MCM technologies. In addition, the proposals show significant performance improvements and also align with the PSDs agreed in the ANSI trial use standard. However, as mentioned, some network operators are nervous at the prospect of increasing the PSD levels even in a benign EMC environment. Upstream Power Backoff TD-41 (VDSL Coalition [supports SCM]) addresses the proposal to restrict the receive PSD in the upstream direction. WD-17 (Text proposal for UPBO specification, S. Schelstraete, Alcatel; BT, Texas Instruments) from the November meeting (CSR 12.44) proposed to add a requirement into the current VDSL transceiver specification TS 101 270-2 restricting PSD of the receive signal in the upstream direction. The rational for that was to avoid ambiguity in the way UPBO is specified. The main reason for the ambiguity, as stated in WD-17, is the lack of clear specification on how the estimation of the electrical length should be performed. TD-41 shows that restriction of the receive PSD still allows ambiguity and is actually misleading. It proposes to not require restriction of the receive PSD, but to instead specify a clear and unambiguous method of electrical length estimation. This was accepted. TD-43 (VDSL Coalition [supports SCM]) discusses estimation of electrical length for VDSL loops. It is based on the results obtained in two contributions from the September 2001 Stockholm meeting (CSR 12.35), TD-48, Open issues in UPBO (S. Schelstraete, Alcatel) and TD-21, On estimation of the electrical length for upstream power backoff in VDSL (V. Oksman, Broadcom). It proposes a simple method of electrical length estimation that could be successfully used for all kind of loops. For European loops the accuracy of estimation is even better as bridged taps are not an issue. An ad hoc group used TD-43 as a basis for generating a text proposal which, after further discussion and textual enhancements, was accepted by the meeting in the form presented in WD-15, Revised UPBO text defining electrical length (R. Kirby). In particular, the UPBO definition in the standard was extended by adding a definition of the quantity kl0 (formerly known as electrical length). WD-15 was provisionally agreed. In WD-26, the TM6 liaison to FS-VDSL, TM6 reports of the progress made on upstream power backoff and the provisional agreement reached on WD-15. TM6 work on this topic will now concentrate on establishing a suitable test procedure to check transceiver performance. Packet Transport Mode TD-25 (P. Kunnas, VDSL Systems Oy) proposes working text to introduce a packet transport mode (PTM) into Part 1 of the VDSL specification TS 101 270-1. This was provisionally agreed for inclusion in a revision of Part 1.

Simulation Parameters TD-33 (T. Nordström, FTW) suggests that a common set of simulation parameters should be used when simulating VDSL performance requirements, and proposes a first set of such simulation parameters. In discussion, the following questions and comments were raised: Should the same parameters be used for both coding schemes? How are the results going to be used? The goals of the whole exercise need to be better defined. It was agreed to use TD-33 as a basis for further discussion and improvements. Updated proposals will be discussed via email to achieve provisional agreement before the next meeting. VDSL Splitter Issues TD-49 (D. Heumann, J. Binkofski, Vacuumschmelze GmbH) proposes requirements for three types of VDSL splitters: 1) VDSL over POTS splitters 2) VDSL over POTS/4B3T-ISDN splitters 3) VDSL over POTS/2B1Q-ISDN splitters It was agreed to use this, as well as the existing text in TS 101 270-1 as a basis for the VDSL part of TS 101 952, which will then be referenced by TS 101 270. The frequency bands will be adjusted to match the VDSL specification. TM-06026-1 Living List The current status of the living list TM6(01)5 for revision of Part 1 is as follows: SP1-1, Reach values in Tables 7 and 8 (under study) SP1.2, Additional PSD Mask for FTTCab (agreed) SP1.3, Power dissipation for remotely located transceivers (deleted; TM6 #24) SP1-4, Power dissipation and volume requirements for exchange based VDSL transceivers (deleted; TM6 #24) SP1-5, Need to specify allowed ripple in transmit PSD mask (under study) SP1-6, Is there a need for a notch at 10.7 MHz (deleted; TM6 #24) SP1-7, Rationalization of PSD masks (under study) SP1-8, Implications of increasing the wideband power for FTTx (under study) SP1-9, Frequency band below 138 kHz (use of) (agreed; TM6 #25) SP1-10, Study of single power back off algorithm (was 2-1) (provisionally agreed; TM6 #25) SP1-11, Dealing with measurement errors in UPBO (was 2-5) (under study) SP1-12, TPS-TC for Packet over VDSL systems (provisionally agreed; TM6 #25) SP1-13, Need for specification of nominal PSD masks (under study) SP1-14, Proposals for boosted PSD mask (under study) SP1-15, Review of requirements for high-pass section of VDSL splitters (moved; TM6 #25) Two new study points were created at this meeting: • SP1-16, Requirements for optional notches on mask M2 • SP1-17, Appropriate test procedure for upstream power backoff SP1-15, the review of the requirements for the high-pass section of VDSL splitters, will be taken over into work item TM-06028, European specific requirements for DSL splitters (Parts of TS 101 952).

Part 2. VDSL Transceiver Requirements, Revision of TS 101 270-2 (TM-06023) TD-42 (VDSL Coalition [supports SCM]) proposes changes in the single-carrier sections of the VDSL transceiver specification (TS 101 270-2 V1.1.5). The changes correct typos and inconsistencies, as well as add some new and adjust some existing technical parameters to improve the VDSL specification and align it with the latest work done in T1E1.4 and ITU-T. These proposed changes were provisionally agreed for incorporation into the draft. TD-23 (J. Väänänen, Tellabs Oy; Tioga) provides Chapters 1 and 2 for a text proposal for optional Tomlinson – Harashima precoding for single carrier modulated (SCM) VDSL. The meeting proposed various editorial corrections and enhancements; these will be discussed off-line before the next meeting. The constellations were provisionally agreed. TD-34 (J. Väänänen, Tellabs Oy) provides a text proposal for “Continuous update of precoder filter parameters” for optional Tomlinson – Harashima precoding for single carrier modulated (SCM) VDSL. The meeting did not accept this proposal. TD-53 (R. Verbin, Tioga; J. Väänänen, Tellabs Oy) defines the new VOC and EOC commands needed to support the implementation of the optional Tomlinson – Harashima precoding. It relates to SCM VDSL. This text proposal was provisionally agreed. Study Points for the Revision of TS 101 270-2 (TM-06023) The following permanent documents have been allocated: • TM6(00)15, Living List for revision of VDSL Part 2 • TM6(00)16, Working draft of the revision of VDSL Part 2 (not yet available) The current status of the study points is as follows: • SP2-1, (moved to Part 1) • SP2-2, Behavior of option dynamic power savings mode (deleted; TM6 #24) • SP2-3, Resolution of technical comments (deleted; TM6 #24) • SP2-4, Performance of alternative band plans (provisionally deleted; TM6 #25) • SP2-5, (moved to Part 1) • SP2-6, Measurement techniques for electrical length (provisionally deleted; TM6 #25) • SP2-7, TPS-TC for Packet over VDSL systems (provisionally agreed; TM6 #25) • SP2-8, Text proposal for optional Tomlinson precoder for SCM VDSL (under study) • SP2-9, Constellation for precoder use for SCM VDSL (provisionally agreed; TM6 #25) • SP2-10, Requirements for an optional Tomlinson precoder for SCM (under study) No new study points were created at this meeting. ADSL R. Jonsson (Conexant) is the Rapporteur for TM-06025, Revision of TS 101 388, ADSL (European-specific requirements). The work plan for the ADSL session is contained in WD-05. The draft of TS 101 388 that was finalized during the meeting was presented by the Rapporteur. After some discussion for clarification, and various minor editorial changes, the draft was approved unanimously for forwarding to TM for the AbC (Approval by Correspondence) procedure.

TD-46 (R. Jonsson, Conexant) summarizes the off-line work on ADSL in the interim since the November 2001 meeting. Five teleconferences were held and there was active email discussion. Teleconference discussion focused mainly on generating performance requirements for ADSL. The noise calibration provisionally agreed at the November 2001 meeting resulted in readjustment of the performance numbers. Teleconference and email discussions also resulted in several incremental refinements to the performance numbers, but no major adjustments. Coming into this meeting, a majority of the performance numbers had reached stable state, but some minor adjustments are still needed in a few isolated cases. There was considerable off-line discussion about noise injection for same pair ISDN noise. Two approaches were discussed: 1) Use arbitrary splitter for the noise injection, but compensate for variations in splitters by calibrating the noise injection. 2) Use a reference splitter design for the noise injection. Approach 1 received more support than Approach 2. There was no clear agreement on how to accomplish same pair ISDN noise injection, mainly due to the lack of a comprehensive proposal on the issue. Initial text on noise calibration has been included in the current ETSI ADSL draft. There is still no text available about power level at other end during testing, but a contribution is expected on the issue.

Testing Configuration TD-27 (K. Jacobsen, Texas Instruments) proposes to add primary parameters of frequencies up to at least 2200 kHz to Tables A.1–A.5 in the revision of TS 101 388. The granularity of the additional table entries does not need to be as fine as it currently is from 0–1100 kHz. Inclusion of values at 1104 kHz, 1500 kHz, 2000 kHz, and 2200 (or 2208) kHz should be sufficient to ensure a reasonable level of accuracy in loop and noise simulations that use the primary parameters. Currently, the tables of primary parameters (used to generate test loops) for various cables in Annex A of the ADSL draft specification specify the primary parameters from DC to 1100 kHz. A minor problem arises because the downstream ADSL band extends to 1104 kHz, which means the tables do not allow an entirely accurate simulation of the loop at all relevant frequencies. Furthermore, if for any reason (i.e., accurate modeling of the channel and noise in time-domain system simulations) the primary parameter values above the ADSL band are required, extrapolation from the given values is necessary. The extrapolation process may not result in exactly the correct insertion loss above the band edge, which could in turn jeopardize the quality of simulation results. TD-32 (T. Nordström, S. Trautmann, FTW) suggests the use of parametric cable models that match the tables as well as possible but have realistic (causal) time-domain behavior (a MAR model), instead of the primary cable parameter tables currently in use. It establishes some parametric models and compares them to the current tables. The MAR model is described in Heylen, L., J. Musson, “Cable models predict physically impossible behavior in time domain”, ETSI TM6 TD53, Amsterdam, Netherlands, Nov. 1999 (CSR 10.11). This TD generated some discussion. It was asked, Why is there a need to change the interpolation model? The so called “Mossun model” was initiated by ETSI, and ITU-T seems to have picked it up without due reference. The BT model seems reasonable, while the DT model seems the poorest. Although there was a general acceptance of the need for improved parameter modeling, more off- line work is required. It was agreed to convene an ad hoc group to discuss this subject.

TD-30r1 (T. Nordström, FTW; O. van de Wiel, Broadcom; J. Shah, Cisco) analyses the importance of same pair ISDN noise on the performance figures calculated for all ADSL over ISDN configurations. It proposes that the “same pair ISDN” noise be injected by the same noise injection device as used for the crosstalk noise. This will provide the advantage of reducing the amount of calibration to be performed. Also, performance figures have been produced with this model, and they do not include the possible effects that alternative injection methods might have. TD-30r1 further proposes that a number of tests involving a more complex setup be defined to tackle this problem. This could be associated with higher tolerances on the nominal performance if needed. Further study is needed to have a stable test definition, as the ISDN signal might be poorly modeled by the current proposals. TD-57 (P. Reusens, Alcatel) proposes that, in the direction opposite to the direction under test, the ADSL bitrate should be specified at some agreeable rate and the PSD should be at nominal level. This is needed to prevent unfair and/or unrealistic performance claims. When measuring the ADSL performance requirements in the ETSI TM6 way, the TX power used in the opposite direction is not yet specified. This can allow “cheating” for ADSL. Indeed, the ETSI standard specifies single ended tests. Moreover, the bitrates (or the power) of upstream and downstream are never linked for ADSL, neither in actual installations nor in the test environment. It is therefore possible to reduce the bitrate and also the power in an unfair way at the transmitter collocated with the receiver under test. There is a clear need to specify the behavior of the transmitter in the opposite direction, while performing a test of the receiver. This proposal was accepted. TD-58 (P. Reusens, Alcatel) proposes the use of a realistic same pair ISDN noise injection model for the performance tests of ADSL over ISDN. It is difficult to model the 13.5 dBm power of the same pair ISDN noise during the ADSL performance tests. The only viable solution seems to be the use of a voltage source with the agreed spectrum, injecting the 22.5 mW signal with a 150 Ohm impedance, and coupled to the line with an actual splitter lowpass. For the ADSL over ISDN downstream with FDD, the same pair ISDN could be limited to signals above some frequency, and an injection method using the existing NEXT and FEXT noise injection could be an approximating alternative. Such approximation for upstream seems not recommendable. The same pair ISDN noise could be removed completely. The authors of TD-58 do not actively seek this to be accepted, but would support any proposal in this line. WD-19 contains the report of an ad hoc group that met to address this issue of same-pair ISDN noise. It was agreed that the description of the same-pair ISDN noise injection method is for further study. A note will be added to indicate that the effect on performance figures is for further study.

Performance Objectives TD-31 (T. Nordström, FTW) proposes an updated set of ADSL performance requirement tables for inclusion in RTS/TM-06025. It suggests that any reach below 300 m be deleted from the tables before inclusion into the standard. The currently open issue on these numbers is the influence of ISI (inter-symbol interference) and ICI (inter-carrier interference). This has been shown by one manufacturer to reduce the reach for the case “FDD ADSL over ISDN” compared to the numbers given in TD-31. It seems to be mostly an issue for the highest bit-rates (384–640 kbit/s) in the upstream direction. This is most visible if no other external noise is injected, that is, for noise model FD (EC ADSL over ISDN downstream). This effect is, however, dependent on the ISDN splitter high pass filter, the FDD filters used, and the implementation of the time domain equalizer. Thus, this is clearly manufacturer-dependent. Unfortunately, at this point there exists no agreed way to simulate such effects (actually, there is no proposal to address this at all).

TD-59 (P. Reusens, Alcatel) discusses FDD ADSL performance specifications. The ADSL performance figures are based on models using a capacity calculation in the frequency domain. This agreed FTW model from the TelecommunicationsResearch Centre, Vienna, ignores the effect of ISI and ICI. As a result, the present performance specifications favor echo-canceler (EC)-based ADSL implementations and not those using filters. This is especially an issue in FDD systems implemented with filters. The ISI and ICI of the TX and RX filter reduce the performance on shorter lines, but the same filters improve the sensitivity on longer lines. On the other hand, the EC implementations have much less ISI and ICI noise on short lines, while the FTW simulation models already include the reduced sensitivity of the EC-based implementations with a simple (but for FDD systems unnecessary) increased noise floor. The quantitative effect of the missing noise became clear when an extensive FDD model (including filters) was completed at Alcatel. For fairness, the FTW model should include an ISI and ICI modeling FDD separation filters, to not be unfavorable for the filtered implementations on short loops with high bitrates. This is for both upstream and downstream. Also, the interoperation between EC and filtered implementations can have ISI and ICI issues. Moreover, the ISI and ICI are not only limited to the pure filtered ADSL implementations. The high pass part of the splitter/combiner introduces ISI and ICI even for pure EC-based implementations. This high pass introduces issues in the upstream band again for shorter loops and high bitrates. The last missing filter effect, which is not modeled in the FTW model, is the impulse response lengthening caused by terminating the ADSL line loop with 100 Ohm. This causes again too optimistic a rate prediction, again on upstream for shorter loops with high bitrates. TD-60 (P. Reusens, Alcatel) asserts that current ADSL performance specifications are too optimistic on short lines. The performance specifications are based on models using a capacity calculation in the frequency domain, ignoring the effect of the downstream power cutback. As a result, data rates are predicted that are not actually achievable on short lines. Caution must be taken in the attempt to simply copy the results from the agreed simulation model into the ETSI ADSL specification. Only when the model includes also the power cutback rule can the results be fully trusted. TD-61 (P. Reusens, D. Van Bruyssel, Alcatel) asserts that the preliminary ADSL performance numbers generated with the common simulation model tend to be too optimistic in some cases, e.g., on short loops, where ISI and ICI dominate, and/or where downstream cutback is active. Discrepancies also appear for filtered implementations, because filtered implementations tend to trade the “ultimate” high bitrates on short loops for a better sensitivity and a somewhat higher bitrate on the longest lines. The Alcatel FDD model, asserts TD-61, is a much more extensive model than the agreed common models using a capacity calculation in the frequency domain. It includes hybrid mismatch, downstream power cutback, filters, inter-symbol and inter-carrier interference, and same pair ISDN noise injection with lowpass. While the agreed common performance model of ADSL has been improved a great deal, in extreme cases, such as high bitrates on short loops or medium length under noise model D (very little noise), the expectations of the agreed model are too optimistic. Also, other degradation effects are yet to be modeled. Alcatel still sees problems in specific loops and circumstances, probably related to the more simple nature of the model, which predicts an implementation based on better echo-canceling. Indeed, it misses the inter-symbol and inter-carrier interference, which will be more harmful for filtered implementations. The FTW model is also missing other elements, e.g., the lack of the downstream power cutback (also called the “politeness rule”). This causes sometimes a reduction of data rate (e.g., for a shorter line in some particular noise profiles) and 6 Mbit/s might not be reached,

February 21, 2002 Vol. 13.04 Copyright © CSR 2002 21 COMMUNICATIONS STANDARDS REVIEW although the FTW model predicts it. Also missing seems to be the impulse response lengthening by mismatch between the Zline and the 100 Ohm ADSL termination and input filter. This effect is more pronounced on short lines, where the signal will bounce back repeatedly, causing bad ISI and ICI (missing in the model). Some other degrading effects not accounted for include, for example, some G.992.1 initialization imperfections: • Non randomness of MEDLEY, leading to an incorrect SNR estimation in cases with high level of ISI/ICI (See CF-059, G.gen.bis: A requirement for the U/S pseudo-random (PR) generator for SNR estimation, A. Ginesi, A. Deczky, Catena Networks, Q4/15 Clearwater, Florida, January 2001, CSR 12.03). • Rate negotiation process: The ATU-C has to propose four data rate options to the ATU-R. For this the ATU-C needs to make some assumptions on the decoder implementation/settings. This leads to a first inefficiency. Further, the ATU-R selects the highest data rate options lower than the ATU-R determined attainable data rate. This leads to a flooring effect (downward truncation) on downstream data rates, resulting in another inefficiency. Other derating could be needed because of interoperability losses between equipment of different vendors. All this requires further refinement of the model, leading to a reduction of some performance numbers or the simple deletion of other erroneous (i.e., too optimistic or impossible) performance numbers. TD-61 includes a list of performance corrections absolutely needed in some cases to arrive at fairness toward filtered FDD implementations. However, even with the correction of the model with power cutback and ISI/ICI, some performance figures will give overly optimistic results for the extreme cases because some degradation effects remain yet to be modeled. The modified numbers to include the ISI model were then presented to the meeting in WD-20, Updated set of ADSL performance requirement tables (T. Nordström, FTW), for detailed discussion. A few discrepancies with simulations by other delegates were highlighted, so an ad hoc group was formed to address these issues as well as to rationalize the proposals in the above documents. WD-17 (R. Jonsson, Conexant) is the report on the ADSL editing ad hoc group, which made several editorial changes to the ADSL document. Additionally, the following issues were identified as needing further clarification: 1) Fix formula for 80–120 kHz in Tables 1 & 2 2) Clarify note on page 17 3) Change name of Zx to more descriptive name 4) Fix text around Figure 8 to make it consistent with revised figure 5) Find appropriate name for “line sharing noise” (same pair ISDN noise) 6) Should PG8(f) be included in the sum for Pxn (f) (see text below Figure 8)? 7) How can switches S1–S8 in Figure 8, be captured in the text? 8) Text for new clause 5.3.3.8 9) Delete reference to 135 Ohm from Tables 7–14, and the associated text 10)Should the noise in Table Y be equal to -140 dBm/Hz above 215 kHz? 11)Reword text associated with Table 18 12)Reword Table 18 13)Look into text in Annex E 14)Align the text in Annex B with the rest of the document

15)Align aggregate transmit power in Table E.4 with values in G.dmt.bis The revised ADSL performance figures were presented to the meeting in TD-31r1 (T. Nordström, FTW); after some modification they were accepted. It was suggested that information regarding the generation method of these performance figures could be of value to the Spectrum Management Project. TD-26 (P. Eriksson, Ericsson) proposes that TM6 recommend the agreed performance tables in the new revision of TS 101 388 for use by the ITU-T in G.dmt.bis Annex G as the text describing the performance tests for Region B (Europe). This was agreed, and a liaison to that effect was drafted (WD-29).

Deployment Issues TD-21 (M. Jonsson, Telia) presents some recent statistics of the traffic behavior of Telia’s ADSL customers. In contrast to the common assumption that the downstream traffic for residential customers will be much higher than traffic in the upstream, Telia has found the total amount of upstream traffic in their network is continuously increasing and will soon reach the total amount of downstream traffic. Telia believes the main cause for this to be peer-to-peer communication, and notes that this degree of symmetry was not expected until digital video cameras and picture telephones become more common. Telia notes that it is hard to say whether service offerings like video-on-demand, personal TV, and others will change this trend. Nonetheless, they strongly believe that symmetry is of value to their customers. While video-on-demand will benefit from higher downstream performance, other services will not. Finally, Telia notes that the relevance of TD-21 concerns not only ADSL but also other xDSL systems, not the least when it comes to the important choice of bandplan to use for VDSL.

Splitter Issues TD-51 (P. Golden, LEA) proposes an ADSL band noise requirement for TS 101 952-1-1, Specification of the low pass part of ADSL/POTS splitters, and for TS 101 952-1-3, Specification for ADSL/ISDN splitters. Protection of the DSL transmission is a fundamental role of the splitter filter; requirements for the splitter must take this into account. One of the critical metrics in DSL performance is the signal to noise ratio of the transmitted/received signal. Thus, any effect due to the splitter on this signal parameter must be considered and limited. In particular, the maximum acceptable noise produced by the splitter in the frequency band used for DSL transmission must be specified. TD-51 proposes to include the following text in the draft of TS 101 952 (Technical specification of DSL splitters for European deployment): From the noise floors given in WD-26 [Proposed ADSL performance requirements, R. Jonsson, Conexant] from the [September 2001, CSR 12.35] Stockholm meeting, the upstream acceptable noise level be set at -125 dBm/Hz, with the downstream at -140 dBm/Hz. This requirement is applicable to both ADSL/POTS and ADSL/ISDN splitters. The acceptable splitter noise level should be better than that assumed for the ADSL receiver, then the distinction between upstream and downstream should be made between CO and CPE splitters. The CPE will receive the downstream, and a low noise floor is assumed for the downstream (worst case -140 dBm/Hz), due to the fact the CPE splitter will most likely have far fewer interferers in its neighborhood. The sensitivity of the receiver is typically very high, thus the noise floor of the splitter should be very low. Considering the possibility of an EC system, this floor should be for the entire band.

In the case of the CO however, the upstream receiver is typically subject to far more interferers, is less sensitive, and thus has a higher expected noise floor. Thus, -125 dBm/Hz for the CO at upstream frequencies can be considered. For the case of higher frequencies at the upstream, the noise should not affect the CO modem, but it could still travel along the line to the CPE side. In this case, it must be assumed that the line presents 15 dB attenuation to the noise, and thus the - 125 dBm/Hz (limit) noise at the CO should not affect the CPE (which expects -140 dBm/Hz).

In the case of measurements at the ADSL port, ZRHF is used to terminate the LINE and telephony ports. In the case of LINE port measurements, a purely real 100 Ohm impedance is used at these ports for ease of measurement. After some minor editorial changes, the ADSL session recommended that this text be adopted during the work on TS 101 952. TD-52 (P. Golden, T. Fernandez, T. Doligez, LEA) addresses the issue of the robustness of LT (CO) side splitters regarding high transient currents that can originate from POTS services. TR 101 728 v.1.1.2z contains an “Immunity to high level POTS signals” test that measures the step response of the splitter. This test measures the voltage produced at the ADSL port due to local on/off hook transitions; it does not consider the non-linearity that can occur in the splitter magnetic components when a large DC current passes through. Due to the randomness of ringing signal phase at the moment the handset goes off-hook, this parameter can be quite difficult to measure in an actual configuration. TD-52 proposes a standard test set-up to measure the maximum value of the DC and ringing voltages to prevent non-linear effects appearing in the ADSL band. It also proposes that the issue of immunity to high level POTS ringing currents be studied for possible consideration in later revisions of TS 101 952.

All Digital Loop TD-24 (Deutsche Telekom, supported by Infineon) studies the spectral compatibility of ADL with SDSL. It finds that ADL with an overlapped downstream spectrum as proposed by Alcatel and Ericsson in the November 2001 meeting has a severe influence on SDSL. (See TD-40, Tutorial on the spectra of the ADSL based all digital loop, P. Reusens, Alcatel, and TD-09, All digital loop downstream PSD mask for overlapped operation, P. Eriksson, Ericsson, CSR 12.44.) In TD-09 and TD-41 (Spectral compatibility of the ADL spectra with non-ADSL xDSL (P. Reusens, Alcatel) from the November meeting, the compatibility of ADL was shown by applying the Telcordia tool. Apart from the general non-applicability of the tool in Europe, the tool does not calculate the margin for ETSI SDSL victim systems. Since the compatibility between ADL and SDSL is considered critical, this was analyzed by measurements. The ADL downstream channel affects the SDSL upstream channel at central office site. Therefore, the performance of SDSL was measured when overlapped ADL was the disturber. For studying the spectral compatibility, a reference method was applied which will be specified in ETSI for this purpose (TD-22, Reference methods for performance calculations, R. van den Brink, KPN Research, TM6 #24, November 2001, CSR 12.44). Instead of ETSI references, configurations and cable conditions for the German access network were used, i.e., real cables of a cable plant, an average NEXT coupling function, and worst-case scenarios. The compatibility evaluation was done by comparing the results. Overlapped ADL affects SDSL more than ADSL over ISDN does (by 4.0 dB). Overlapped ADL is a more severe disturber than SDSL itself (by 2.3 dB). FDD ADL-64 friendly to ADSL over ISDN (downstream above 276 kHz) is expected to affect SDSL as much as ADSL over ISDN. Therefore, this disturbance is acceptable. SDSL will suffer from FDD ADL-32 friendly to ADSL over POTS (downstream above 138 kHz) more than

24 Vol. 13.04 Copyright © CSR 2002 February 21, 2002 COMMUNICATIONS STANDARDS REVIEW from FDD ADL-64 with downstream above 276 kHz. Furthermore, FDD ADL-32 with downstream above 138 kHz is not compatible with ADSL over ISDN. TD-24 recommends to not specify overlapped (EC) ADL, and to not specify FDD ADL with a downstream cutoff frequency below 276 kHz. The only new system variant to be introduced should have little spectral overlap with SDSL to exploit their compatibility. Although the specific conclusions presented in TD-24 were not queried, there was some discussion as to their general validity. The examples given were considered by some not necessarily appropriate in the light of potential deployment scenarios. The meeting agreed to move the text in the annex to agreed status, but to add a note outlining these concerns. This note was produced, and agreed with the proviso that an additional note be inserted in the meeting report as follows: If these problems can not be resolved by applying access restrictions, it may be necessary to alter the ADL PSD.

TM-06025 Living List The Living List for TM-06025 is contained in permanent document TM6(01)08. • SP1, Performance objectives (agreed*; TM6 #25) • SP2, All digital loop coexisting with POTS (agreed*; TM6 #25) • SP3, All digital loop coexisting with ISDN (agreed*; TM6 #24) • SP4, All digital loop coexisting with both POTS and ISDN (agreed*; TM6 #24) • SP5, Out of band PSD limits for ISDN-BA and ADSL (deleted; TM6 #25) • SP6, Method of specifying ISDN degradation with splitter (deleted; TM6 #25) • SP7, RFI injection method including common mode (moved; TM6 #25) • SP8, Implementation methods to allow spectral coexistence of ADSL over POTS with ADSL over ISDN (deleted; TM6 #24) • SP9, General mechanism to support ditched PSD masks (deleted; TM6 #25) • SP10, Tone levels for RFI Ingress noise test (moved; TM6 #25) • SP11, Test methods for RFI Ingress noise test (moved; TM6 #25) • SP12, POTS interference test (deleted; TM6 #24) • SP13, Normalization of performance figures for FDD (closed; TM6 #24) • SP14, Carrier masking (moved; TM6 #25) • SP15, Spectral compatibility carrier masking (deleted; TM6 #24) • SP16, Co-existence problems between ISDN and ADSL-over-ISDN (deleted; TM6 #25) • SP17, Noise injection methods (agreed; TM6 #24) • SP18, Mandatory capability for tones below 33 (deleted; TM6 #25) • SP19, Noise impairment model for noise from ISDN DTAG (agreed*; TM6 #25) * These were agreed conditional on notes or text modifications being acceptable to the meeting No new study points were created at this meeting. The following study points are being kept for a potential revision: • SP7, RFI injection method including common mode • SP10, Tone levels for RFI ingress noise test • SP11, Test methods for RFI ingress noise test • SP14, Carrier masking The following study points are considered relevant to potential future spectral management work:

• SP8, Implementation methods to allow spectral coexistence of “ADSL over POTS” with “ADSL over ISDN” • SP9, General mechanism to support ditched PSD masks • SP14, Carrier masking • SP15, Spectral compatibility carrier masking The Rapporteur will maintain an unofficial living list to capture these study points until a decision is made to produce a revised version of TS 101 388. Spectral Management R. van den Brink (KPN) is the Rapporteur for TM-06029, Revision of TR 101 830-1, Spectral management Part 1: Definition of signals, and TM-06030 (TR 101 830-2), Spectral management Part 2, Technical methods for performance evaluations. WD-03 contains the work plan for Spectral management Parts 1 and 2. T. Kessler (T-Systems Nova GmbH) is the Rapporteur for TM-06031 (TR 101 830-3), Spectral management Part 3, Construction methods for spectral management rules. WD-14 contains the work plan for Spectral management Part 3.

TM-06029 (rev of TR 101 830-1), Part 1: Definition of signals TD-37 (R. van den Brink, KPN) proposes to define some of the spectral management terminology. At the last TM6 meeting on spectral management, confusion ensued from the fact that, in discussion, terms used often had different meanings. The meeting supported this goal, but suggested that before finalizing terms used in TM6 the Rapporteur should check for European guidelines on the subject. The meeting then considered the individual definitions proposed: Change “network owner” to “loop operator” (the company that manages the cable is not necessarily the owner) After some discussion, the term “loop provider” was accepted to describe the company owning the telecommunication access network (mostly incumbent telecommunication network operators). Specify three distinct concepts for spectral management rules: (Spectral) access rule: Mandatory rule for achieving access to the local loop wiring, equal for all network operators that make use of the same network cable, that bounds the spectral pollution in that network cable. (Spectral) deployment rule: Voluntary rule, irrelevant for achieving access to the local loop wiring and proprietary for individual network operators. Deployment rules reflect the private view of network operators about what maximum length or maximum bitrate they prefer for offering their transmission service to ensure a chosen minimum quality of service. (Spectral) sanity rule: Voluntary rule, irrelevant for achieving access to the local loop wiring and proprietary for individual loop operators. Sanity rules reflect the private view of the loop operator about what wire pair selection or manipulation he prefers to keep the spectral pollution as low as possible, for offering access to the local loop wiring he manages. The meeting considered this a sensible approach. The detailed wording was discussed. The point was made that only government bodies can specify enforceable rules, and TM6 can only produce technical specifications or reports with normative or informative content. Further study of these issues is required. A study point (SP1-9) was created to generate the relevant text.

Specify three distinct concepts for PSD definitions: Peak mask of a PSD: This is the maximum level of a PSD, measured within relatively narrow resolution bandwidths, for instance 10 kHz for signals up to 1 MHz. The purpose of specifying peak masks is often to bound the “worst case” values of a PSD. Nominal mask of a PSD: This is the maximum level of a PSD, measured with in relatively wide resolution bandwidth, for instance 100 kHz for signals up to 1 MHz. The purpose of specifying nominal masks is often to bound the “average” values of PSDs in the pass band. On the edges of PSDs, however, the nominal masks tend to be more capacious, due to the wide nature of the resolution band, and their value has often a limited meaning. Template of a PSD: These levels represent the “average” values of PSDs over the full frequency band, being close to the nominal mask in flat frequency bands and close to the real PSD near the edges of PSDs. This too was considered to be a sensible goal. It was proposed to adopt definitions from, for example T1E1, so as to have harmonized definitions for these concepts. A study point (SP1-10) was created to generate the relevant text.

Part 1 Living List TM6(99)8 is the living list for revision of Part 1: • SP1-1, Complete signal description for ADSL FDD over POTS (under study) • SP1-2, Complete signal description for ADSL FDD over ISDN (under study) • SP1-7, Review of power feeding issues (agreed; TM6 #24) • SP1-8, Complete signal description for ADSL-ADL (under study) • (SP1-3 – SP1-6 deleted) The following two new study points were created at this meeting: • SP1-9, Harmonization of spectral management technology • SP1-10, Definition of PSD terminology

TM-06030 (rev of TR 101 830-2), Part 2, Technical Methods for Performance Evaluations The Rapporteur presented a first draft of TR 101 830-2 and went through the Table of Contents for comment from the floor. It was asked how new or existing proprietary systems will be dealt with. Provided that models for such proprietary systems are available, they will be included in the document. The scope of the Part 2 document highlights the following objectives: • Study access rules, for the purpose of bounding the spectral pollution in unbundled networks. • Study deployment rules, for the purpose of offering uninterrupted transmission services in spectrally polluted access networks. • Study spectral compatibility within different scenarios, for the purpose of designing new xDSL equipment. Reporter’s note: this is an important step for ETSI in the field of spectral compatibility. The Rapporteur emphasized that the scope of the Part 2 work is to describe technical methods for analyzing the behavior of systems in the context of spectral management, rather than to make

February 21, 2002 Vol. 13.04 Copyright © CSR 2002 27 COMMUNICATIONS STANDARDS REVIEW judgements. The meeting discussion of this first draft of Part 2 yielded a number of changes and corrections. Following these modifications, the meeting approved the draft Scope and Table of Contents. TD-50 (V. Buyck, Siemens ATEA) proposes a number of requirements for performance calculations methods for Part 2 of the spectral management deliverable to ensure that these methods will be useful for Part 3 of this deliverable. A study point was requested to study the requirements to be addressed as prerequisites for Part 3, but this was deemed unnecessary as the Scope of Part 2 has already covered these aspects. TD-35 (R. van den Brink, KPN) provides the literal text for two related calculation blocks, one modeling the equivalent SNR and another modeling the “echo loss.” Part 2 of the spectral management report requires the description of performance models consisting of a range of individual calculation blocks. All these blocks together will enable reproducible and well-defined performance evaluations of (noisy) scenarios. TD-35 formalizes a commonly used concept to evaluate the performance of an xDSL receiver into a straightforward calculation model. This concept results in the evaluation of the SNR (signal to noise ratio) of the received signal, as intermediate result, followed by a linecode-specific detection block. The SNR of the input signal is deteriorated by internal receiver noise and echo. TD-35 describes this approach as a model of a block, and defines a naming convention of various flows. Most of this approach is very common, but it has been extended by modeling echo suppression as well. For many situations this addition is less relevant, because state-of-the-art echo-cancelers are quite sophisticated and effective. The importance of including echo cancellation in this building block is mainly to cover the case that lacks echo cancellation, such as for FDD systems like ADSL and VDSL. Residual frequency overlap in the guard bands between up and downstream spectra may cause some problem. By tweaking the value for echo suppression h, the absence or presence of echo cancellation can be controlled. The model proposed in TD-35 is a 100% linear model. In case the receiver gain is controlled, to enable a high dynamic range, the equivalent internal receiver noise PRN0 may vary with the signal level. For many situations this can be ignored (when crosstalk noise dominates the internal receiver noise), but in case this effect has a significant effect, a more advance non-linear calculation model is required. Such a non-linear model is beyond the scope of this proposal, but can always be added to the spectral management report Part 2. TD-35 also includes a model of echo loss that models the suppression caused by the analog hybrid used for “isolating” received and transmitted signal in a transceiver. When this hybrid is perfectly balanced (loaded by the design impedance) no echo will flow into the receiver. When the cable impedance differs from this design impedance Rv the hybrid will be out of balance and some transmitted signal reflects into the receiver. In the proposed model for echo loss the hybrid is modeled as a Wheatstone bridge, which is perfectly balanced when one branch is terminated with Rv. More advanced models for echo-loss are beyond the scope of TD-35, but can always be added to the spectral management report Part 2. The meeting asked whether this model is too complex. The Rapporteur pointed out that this is a first proposal, and welcomed further contributions on this topic. A study point (SP2-2) was created to explore possible improvements. TD-36 (R. van den Brink, KPN) provides the literal text for the calculation blocks, to build topologies in which all disturbers are co-located at only two nodes. It combines a few commonly used concepts to evaluate the crosstalk noise in a cable. The primary assumption within this concept is that all customers are virtually co-located, so the model requires only two nodes (one on the LT side, and another one on the “common” NT side) connected by a multi wire pair cable.

This approach is often used when modeling ADSL, HDSL, and SDSL performance. For modeling VDSL, where customers are distributed along the line, or for modeling repeatered HDSL, where repeaters act as disturbers somewhere in the middle of a line, a more advanced multi-node approach is required. This proposal is dedicated to the two-node case. A study point (SP2-3) was created to explore possible improvements.

Part 2 Living List TM6(01)21 is the living list for Part 2. SP2-1, Spectral management rules for non-stationary signals, was provisionally deleted. Two new study points were created at this meeting: • SP2-2, Basic model of receiver input block • SP2-3, Basic model of 2-node crosstalk

TM-06031 (TR 101 830-3), Part 3, Construction Methods for Spectral Management Rules T. Kessler (T-Systems Nova GmbH), Rapporteur, presented his proposed Scope and Table of Contents (TD-28). An ad hoc group studied this, but was unable to produce a proposal to the meeting, so the precise wording of the Scope was left for further study. TD-17 (P. Donaldson, WorldCom) proposes creation of a new study point, Basic objectives for spectral management plans. It also proposes text for basic objectives and principles of spectral management plans for inclusion in Spectral management Part 3. Many of these principles were considered as the basis for the Access Network Frequency Plan (ANFP) adopted in the UK. Currently, regulatory activity in many countries throughout the world is unbundling the local loop. With this unbundling and the shared nature of the local loop plant by many competitive carriers, an inherent need arises for a plan to manage the crosstalk environment resulting from the various digital subscriber loop (DSL) technologies deployed in a given loop plant. It was agreed to create a new study point (SP3-5). There was no consensus on the proposed text, which requires re- drafting. WD-10 (M. Sorbara, GlobespanVirata, T1E1.4 Chair) is an overview of T1E1.4 spectrum management activities. The spectrum management standard (T1.417-2001) only defines the guidelines for deploying signals from the CO. Regenerated and Remote Terminal signals are not addressed. The second issue of T1.417 will address the spectral compatibility and deployment guidelines for: · Repeatered DSL systems · Intermediate Transceiver Units – DSLs deployed from a location remote from the central office, such as: DLC or RT TD-18 (V. Buyck, Siemens ATEA) proposes that TM6 endorse the T1E1.4 document, Spectrum management for loop transmission systems (revision of T1.417), taking into account the required adaptations for Europe, which are proposed to be identified in an ETSI delta document. It begins with the adaptation of the T1E1.4 document to make it suitable for use in ETSI, by identifying the basis systems and legacy systems applicable for Europe. One open issue is which HDSL system variants should be on the basis systems list. BT was strongly against this proposal as presented; other delegates also saw disadvantages with this approach. The point was made that TM6 has no mandate to impose restrictions on the use of the access network, and therefore should not endorse any particular method. The author of TD-18 clarified that his intention was not to impose any restrictions, as the document is in any case only a technical report.

TD-54 (M. Gindel, Telekom Austria) is an overview of present regulation for the unbundled local loop (ULL) in Europe. It is the same as WD-10 (Siemens ATEA) from the November 2001 meeting (CSR 12.44), amended to include relevant data from the Austrian network. TD-29 (V. Buyck, Siemens ATEA) provides an overview of the remote deployment spectrum management studies in T1E1.4, which have identified that the major issue is RT-deployed ADSL. RT-based ADSL is spectrum compatible with everything except CO-deployed ADSL. Some techniques (PBO and notching) allow RT-deployed ADSL to become spectrum compatible with CO-deployed ADSL at the expense of the RT ADSL performance. Since the probability of the presence of RT- and CO-deployed xDSL technologies in the same cable binder is so low, TD-29 recommends not to apply those techniques (unless automatically applied, such as PBO). TD-29 suggests the following items for TM6 further study: • Verify whether the probability studies are valid also for the European case • Impact of central-deployed technologies on remote-deployed technologies • VDSL remote deployment (VDSL from the cabinet) • Keep track of T1E1.4 evolution/decision on remote deployment There was insufficient time to address TD-29; it was accepted for information.

Part 3 Living List • SP3-1, Limits for noise that may leak into the local loop wiring (provisionally deleted) • SP3-2, Wetting current requirements (under study) • SP3-3, Interworking issues in case of line sharing (under study) • SP3-4, Methods for constructing spectral management plans (under study) One new study point was created at this meeting: SP3-5, Review of text for basic objectives and principles of plans.

TM6(01)17 European Approaches to Spectral Management This permanent document (ed. V. Buyck, Siemens ATEA) gives an overview of the regulation in European countries related to spectrum management issues. It will be updated with information on VDSL band plans and the information about the situation in Austria contained in TD-54. VoDSL N. King (Infineon) is the Rapporteur for TM-06021, In-band support of voice and narrowband data over DSL systems. WD-25 contains the work program for the VoDSL session. The Rapporteur distributed copies of the current living list and highlighted the various changes that had been made to the document since the last meeting. Work progressed on this work item. TM6 Approval has been postponed until November 2002. TD-22 (M. Lahti, M. Jonsson, Telia) presents Telia’s answers to VoDSL-specific questions to operators compiled at the November 2001 meeting. Telia answers support the use of VoDSL. Other operators were encouraged to contribute to this catalogue. BT hopes to have a response for the next meeting.

VoDSL Living List The following permanent document numbers have been allocated to this project:

• TM6(00)13, Living list • TM6(00)14, Working draft The current status of the study points is as follows: • SP1, Table of Contents Infineon (provisionally agreed at this meeting) • SP2, In band and out-band support of ISDN/POTS over xDSL Infineon (under study) • SP3, ATM based in-band support of voice services over xDSL (deleted; TM6 #24) • SP4, VoDSL Reference architecture configuration Infineon (agreed; TM6 #24) • SP5, Dynamic bandwidth Allocation for xDSL (under study) • SP6, Application requirements for DRR (under study) • SP7, Timeslot arrangement during DRR (under study) No new study points were created at this meeting. It was agreed to postpone WG Approval to November 2002. European Specific Splitter Requirements P. Golden (LEA) is the Rapporteur for TM-06028, European specific requirements for DSL splitters (Parts of TS 101 952). WD-13 contains the work plan for the splitter session. Work progressed on this work item: Part 1-2 (ADSL/POTS high pass) and Part 1-3 (ADSL/ISDN) were approved for forwarding to the TM AbC process. Parts 2-2, 2-3, and 2-4 (VDSL aspects) are currently scheduled for TM6 Approval in September 2002. TD-09 (B. Heise, Infineon) proposes a new work item to specify an optional extension of TS 102 080 (Transmission system for the ISDN-BA on metallic lines) by an integrated ISDN system including the low-pass component of a splitter for ADSL over ISDN or VDSL over ISDN. The spectral characteristics of ISDN are a burden for ADSL over ISDN and VDSL over ISDN systems. The standard configuration of xDSL over ISDN makes use of a passive splitter circuitry to connect the two systems sharing the same wire pair. The passive splitter is a straight-forward solution; however, problems have been reported. Currently, separate independent specifications exist or are in work for the ADSL or VDSL system, for the ISDN system, and for the splitter. There are upcoming cost effective solutions where the low pass of the splitter is integrated into the ISDN system. There are also highly integrated solutions with ADSL/VDSL and ISDN on the same board either on the CPE or on the CO side. No standard is available for these systems, since the requirements for an integrated solution cannot be derived from the standards named above. WD-30 contains the text of the approved new work item, Amendment to TS 102 080, created to define the inter-working between ISDN, ADSL and VDSL. Its scope is to define requirements for an ISDN system that includes the low pass of a splitter to work on the same pair with a VDSL or an ADSL system. Its objectives are to study PSD masks, pulse masks, performance requirements, input impedance, return loss, and/or the insertion loss of the ADSL signal path and longitudinal conversion loss. M. Löffelholz (T-Systems Nova GmbH) is the Rapporteur for this WI. WD-08r0 is the living list of current issues (SP1 only) connected with the revision of TS 102 080.

SP1, ADSL-friendly PSD Mask TD-19 (M. Löffelholz, T-Systems Nova GmbH; J. Binkofski, Vacuumschmelze GmbH & Co. KG) specifies requirements for ADSL splitters that allow transmission of ADSL over ISDN and ISDN 4B3T or ADSL over ISDN and POTS over the same copper pair. The current draft of TS

101 952 contains at least two different ADSL splitter definitions and specifications for ISDN (ADSL over ISDN) and POTS (ADSL over POTS), but no specific requirements for a splitter that supports POTS under ADSL over ISDN. With few restrictions, both specifications can be met with only one filter design. The basis for the specification of requirements for the low pass and high pass section of universal POTS/ISDN splitters proposed by TD-19 was proven to be reliable and feasible for ADSL over ISDN according to ETSI TS 102 080 v.1.3.1 (Integrated services digital network [ISDN] basic rate access; Digital transmission system on metallic local lines, November 1998). These splitters are intended to be installed at the local exchange side of the local loop and at the user side near the NTP. It was agreed that rather than send TD-19 as a liaison to ETSI TC AT, the authors will submit it directly as a contribution to the next TC AT meeting.

Splitter Testing TD-48 (J. Binkofski, J. Beichler, Vacuumschmelze GmbH & Co. KG) proposes a modified THD measurement for TM-06025, ADSL European specific requirements, and TS 101 952-3. To characterize the ADSL splitter harmonic distortion, any measurement technique must work at frequencies that are characteristic for the pass band of the ADSL high pass. The complex ADSL spectrum, with a wide frequency range and very different signal amplitudes (dependent on time), leads to an extremely wide range of magnetic flux densities for the cores of the inductors of the LPF. To ensure a low splitter harmonic distortion, a single THD measurement with only one amplitude is not enough because often a non-monotonous behavior of THD with the amplitude of the signal can be found. Therefore, conventional THD measurements are not suitable to ensure low ADSL-Splitter harmonic distortion. TD-48 proposes a measurement technique that covers a wide range of signal amplitudes and gives the ability to separate LPFs with low ADSL splitter harmonic distortion from those not suited for ADSL splitters: MA-THD (Multi Amplitude Total Harmonic Distortion). MA-THD ensures low ADSL splitter harmonic distortion. MA-THD, in contrast to a single THD-measurement, is directly related to the maximum bit rate for a given loop and to the maximum reach for a given bit rate. TD- 48 proposes to include a note in TS 101 388 and TS 101 952-3 about a measurement method that will ensure a low splitter harmonic distortion. The further development of such a method will be the subject of the new STF 215. TD-47r1 (J. Binkofski, Vacuumschmelze GmbH & Co. KG; M. Löffelholz, T-Systems Nova GmbH) proposes text for a new part for TS 101 952-1-3 to specify measurement directions for ADSL over ISDN-splitters. TS 101 388 specifies requirements for insertion loss, return loss, and isolation requirements. It is not clear at which ports of the splitter the return loss is specified or in which port direction the insertion loss and the isolation requirements are specified. TD-47r1 proposes to measure the insertion loss in the ISDN passband in both directions T -> L and L -> T. T, L and A represent the three ports of a splitter. T is the connection via the low pass to telephone or similar. A is the connection to the nearby DSL equipment and L is the connection to the line. There are two possibilities to measure the insertion loss of the splitter (A -> L and L -> A) in the ADSL band. Here in both cases the insertion loss is equal. TD-47r1 proposes to measure in the L -> A direction only. There are several possibilities to measure isolation requirement for the splitter (L -> T, T -> L, T -> A, A -> T). TD-47r1 proposes to measure in the T->A and in the A->T direction. There are two possible ports of the splitter to define a return loss (T and L). The return loss measured at the two ports is different. TD-47r1 proposes to measure return loss at port T only. These proposed changes had already been incorporated into the draft.

TD-62 (F. Flavio, Telecom Italia Lab) presents measurements results on the dynamic DC current behavior on ISDN lines, both as peak value and possible repetition rate found on the network. A note was added to the draft to address this issue.

STF 215 ETSI recently issued a call for experts on the specification and validation of splitter test methods. STF 215 is closely related with the work-item on splitter test methods. The preparatory meeting for STF 215 was held the week prior to this TM6 meeting at the ETSI premises, at which the STF candidates were selected. The STF will start its work on February 11; it consists of the following members: J. Binkofski (Vacuumschmelze GmbH & Co. KG), P. Jamelot (LEA), S. Gilchrist (KTL), and A. Ehre (CETECOM), who will lead the group. The deliverables that STF 215 will produce will be part of a multi-document technical report which is intended to be used as input for future drafts of TS 101 952. TM6 is responsible for the high-pass part of POTS splitters as well as ISDN splitters.

Draft TS 101 952-1-2 (High Pass ADSL/POTS Splitters) WD-22 is draft TS 101 952-1-2 (v.1.0.0), Technical specification of DSL splitters for European deployment: Transmission and multiplexing (TM); Specification of the high pass part of ADSL/POTS splitters. The Rapporteur presented the draft text resulting from the ad hoc editorial work during the meeting, outlined the changes that had been made, explained the origin of some of the clauses, and described the work remaining for further study in future revisions. To the question asked as to why this document does not cover all the topics dealt with in the previous document, it was responded that a separate part, TS 101 952-1-1 (produced by TC AT) deals with these topics. There were no objections from the meeting to these changes. Draft TS 101 952-1-2 was approved for forwarding to TM for the AbC procedure. WD-21 (P. Golden, LEA) proposes requirements for an Option C high pass filter for TS 101 952- 1-2. The current draft of TS 101 952-1-2 gives three options for the high pass part of an ADSL/POTS splitter. WD-21 assumes that the splitter unit is physically separate from the ADSL modem/terminal equipment, and thus the splitter high pass filter (which is specified by TS 101 952- 1-2) is considered to be only that part of the high pass filtering function that is physically within the splitter unit. Option A covers the case where the high pass function is fully implemented in the modem, and thus the splitter unit contains only a low pass function. Option B defines a first order high pass filter in the splitter unit which is to be implemented in the form of blocking capacitors. Option C is reserved for a higher order filter. A third order high pass filter in the splitter unit is sufficient from the perspective of POTS functionality. It is desirable to limit the order of this high pass filter due to possible adverse effects on the ADSL performance due to attenuation distortion, intermodulation distortion, and group delay distortion caused by the high pass filter in the splitter unit. WD-21 proposes a set of requirements for the option C high pass filter that will ensure minimal effect on the ADSL performance and enable accurate ADSL performance simulations to be carried out in the presence of the splitter function.

Draft TS 101 952-1-3 (ADSL/ISDN Splitters) WD-07 is draft TS 101 952-1-3 (v.0.0.3), Technical specification of DSL splitters for European deployment Sub-part 1-3: Transmission and multiplexing (TM); Specification of ADSL/ISDN splitters.

The Rapporteur presented the draft text resulting from the ad hoc editorial work during the meeting, and outlined the changes that had been made. There were no objections from the meeting to these changes. Draft TS 101 952-1-3 was forwarded to TM for AbC procedure.

DSL Splitter Living List The status of the living list study points were addressed at this meeting: • SP1, Implementation specific splitter requirements (keep for revision) • SP2, Effect of high pass filter on ADSL (keep for revision) • SP3, Test for non-linear distortion (keep for revision) • SP4, VDSL/POTS and VDSL/ISDN splitter requirements (valid for VDSL part)

Liaisons WD-16 is a liaison to ITU-T Q4/15 summarizing the scope and applicability of TS 101 952. It also recommends addition of the following reference in Section 2 of the main text: For Annex E: ETSI TS 101 952-1 (2002), Access and Terminals (AT) and Transmission and Multiplexing (TM), Technical specification of ADSL splitters for European deployment. It recommends adoption of the following text for the Annex on European splitter requirements: ADSL splitters shall comply with ETSI technical specification TS 101 952-1, Specification of ADSL splitters for European deployment. The relevant sub-parts are: Sub-part 1-1: Technical specification of the low pass part of ADSL/POTS splitters Sub-part 1-2: Technical specification of the high pass part of ADSL/POTS splitters Sub-part 1-3: Technical specification of ADSL/ISDN splitters

Work Plan It is hoped that by April all three parts of the ADSL splitter document will have been approved, and work will continue on the VDSL aspects between meetings. DSL Testing and Interoperability B. Mattsson (ETSI Technical Officer) presented a report (WD-09) from P. Cousin, the ETSI Interoperability Service Manager, concerning a proposed ETSI interoperability event on DSL to be co-organized with the DSL Forum. At the DSL Forum December 2001 meeting in Munich (see CSR 12.47), the idea and structure of PlugTests were presented to the Testing & Interoperability Working Group of the DSL Forum. Interest was expressed in a common PlugTests of ETSI and DSL-Forum. A suggested date is October 15-18, 2002. WD-09 offers the following rationale for TM6 discussion toward support of the ETSI interoperability event. Looking into the pending discussions and the related uncertainties (ADSL performance, splitter parameters, and splitter test methods), the ETSI PlugTests should be arranged in a way to gain from the results in these specific problems. Performance numbers in current papers are based on simulations that should be verified on a wide and vendor-independent basis. It is important that these values are feasible even when ATU-C and ATU-R are deployed by different vendors. Also the influence of the splitter behavior needs to be addressed with this.

The DSL Forum has expressed its interest in settled performance data that should then be fed into the interoperability test plans for Annex B systems. The DSL Forum is somewhat dependent on the help of the European standardization. The task of the newly created STF 215 is to describe and validate splitter test methods. The STF feels that a PlugTest would be a good opportunity to verify the parameters specified for splitters and the influence of standard-conformant splitters to real implementations. Even if the test methods will be validated separately, it should be determined whether the specification of splitters and the related test methods is sufficient to guarantee compatibility with ADSL and with the PSTN/ISDN. Finally, the DSL Forum has expressed interest in a splitter interoperability event in Europe. WD-09 proposes that the following topics be addressed during the ETSI PlugTests event: • ADSL, ETSI TS 101 388: Verification and cross-check of the performance data expressed in TS 101 388 on feasibility in mixed environments, where ATU-C and ATU-R from different vendors are used. • Verification of splitter parameters and the influence of standard-conformant splitters on the ADSL performance. • Interoperability of splitters with the PSTN/ISDN in complete configurations (ATU-C, ATU-R, splitters, PSTN/ISDN, reference terminal equipment for POTS/ISDN, etc.). The meeting agreed that this is of relevance to STF 215, which concerns itself with the specification and validation of splitter test methods, rather than TM6; nonetheless, the operators present in TM6 will consider the matter. Testing Methods for DSL Splitters J. Montenot (SCE) has to step down as Rapporteur for TM-06027, Testing methods for DSL Splitters. P. Golden (LEA) will take over as Rapporteur for this work item. Jacques A. Besseyre, Ph.D., Telecomsult

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February 21, 2002 Vol. 13.04 Copyright © CSR 2002 35 COMMUNICATIONS STANDARDS REVIEW TM6 #25 Meeting Roster, February 4 – 8, 2002, Torino, Italy Manfred Gindel (Telekom Austria) TM6 Chair Siegfried Schmoll (Alcatel) SDSL Rapporteur Marc Kimpe (Adtran) SDSL Acting Rapporteur Brian Waring (Infineon) VDSL Rapporteur Ragnar Jonsson (Conexant) ADSL Rapporteur Rob van den Brink (KPN) Spectral Management Rapporteur Neal King (Infineon) VoDSL Rapporteur Philip Golden (LEA) European-Specific Splitter Requirements Rapporteur Jean Montenot (SCE) Testing Methods for DSL Splitters Rapporteur (Outgoing) Philip Golden (LEA) Testing Methods for DSL Splitters Rapporteur (Incoming) Host: Telecom Italia Lab

Austria Telecommunications Research Centre Vienna Tomas Nordström (FTW) Austria Telekom Austria AG Manfred Gindel Belgium Alcatel Bell Peter Reusens Belgium Alcatel Bell Sigurd Schelstraete Belgium Siemens ATEA NV Victor Buyck Czech Republic Cesky Telecom a.s. Milan Meninger Finland Elisa Communications Corporation Tuomas Laine Finland Nokia Corporation Jari Lindholm Finland Tellabs Oy Janne Väänänen Finland VDSL Systems Oy Peter Kunnas France Conexant Systems SAS George Eisler France Conexant Systems SAS Ragnar Jonsson France ETSI Bernt Mattsson France France Telecom R&D Emmanuel Boulaire France LEA Laboratoire Européan ADSL Philip Golden France Motorola S.A Bernard Dugerdil France Paradyne International Bill Pechey France SAGEM Group Eric Dalle France SAGEM Group Roger Samy France Texas Instruments SA Krista Jacobsen France Texas Instruments SA Neil Quarmby Germany Alcatel Kommunikations Elektronik Ludger Dreier Germany Alcatel SEL AG Siegfried Schmoll Germany Analog Devices GMBH Josef Meser Germany Bundesministerium Fur Wirtschaft Thomas Schott Germany Deutsche Telekom AG Thomas Kessler Germany Deutsche Telekom AG Marko Löffelholz Germany Infineon Technologies Eyal Bick Germany Infineon Technologies Bernd Heise Germany Infineon Technologies Neal J. King Germany Infineon Technologies Brian Waring Germany Siemens AG Hagen Henniger Germany Siemens AG Josef Waldinger Germany Vacuumschmelze GmbH Johannes Binkofski Israel Metalink Ltd. IAEI Eyal Barnea

Israel Metalink Ltd. IAEI Amir Leshem Israel Orckit Almog Ariel Israel Orckit Octer Zeev Israel Tioga Technologies Reuven Franco Italy Aethra Telecommunicazioni Maurizio Giammarchi Italy Telecom Italia SPA Flavio Cucchietti Italy Telecom Italia SPA Lorenzo Magnone Italy Telecom Italia SPA Rosaria Persico Netherlands KPN Rob van den Brink Sweden Ericsson Telecom AB Per-Erik Eriksson Sweden Telia AB Marcus Jonsson Switzerland Adtran AG Marc Kimpe Switzerland Ascom AG Angus Carrick Switzerland BAKOM / OFCOM Kurt Bartschi Switzerland Pro Telecom Stefan Lüthi Switzerland Swisscom AG Andreas Thöny UK BT plc Rob Kirkby UK BT plc John MacDonald UK Fujitsu Europe Telecom R&D Centre Martin Pollakowski UK GlobeSpan Semiconductor Inc. Jim Frimmel USA Broadcom Corporation Vladimir Oksman USA Broadcom Corporation Olivier van de Wiel USA Communications Standards Review Jacques Besseyre USA WorldCom Paul Donaldson USA WorldCom Daryl C. Tannis

February 21, 2002 Vol. 13.04 Copyright © CSR 2002 37 COMMUNICATIONS STANDARDS REVIEW Acronym Definitions 2B1Q 2 Binary 1 Quaternary (US line coding for ISDN) 4B3T 4 binary 3 trinary (European line coding for ISDN) AbC Approval by Correspondence ADL All Digital Loop (without underlying POTS or ISDN) ADSL Asymmetric Digital Subscriber Line AFE Analog Front End AM Amplitude Modulation ANSI American National Standards Institute AT Access and Terminals (ETSI TC) ATM Asynchronous Transfer Mode ATMF ATM Forum ATU-C ADSL Transceiver Unit - Central Office End ATU-R ADSL Transceiver Unit - Remote Terminal End CENELEC Commission Europeenne de Normalisation Electrotechnique (European Electrotechnical Standards Committee) CO Central Office CPE Customer Premise Equipment DC Direct Current (steady state) DLC Digital Loop Carrier DRR Dynamic Rate Repartitioning DSL Digital Subscriber Line DTR Draft Technical Report (ETSI) DTS Draft Technical Standard (ETSI) EC Echo Canceler EMC ElectroMagnetic Compatibility EOC Embedded Operations Channel ERM ETSI committee on EMC and Radio spectrum Matters ES ETSI Standard ETSI European Telecommunications Standards Institute FDD Frequency Division Duplexing FEXT Far End Cross Talk FRF Frame Relay Forum FS VDSL Full Service VDSL (FSAN Committee) FSAN Full Service Access Networks Consortium FTTCab Fiber To The Cabinet FTTEx Fiber To The Exchange HDSL High-rate Digital Subscriber Line ICI Inter Carrier Interference IEEE Institute of Electrical and Electronic Engineers IETF Internet Engineering Task Force IMA Inverse Multiplexing for ATM (ATMF) IP Internet Protocol (IETF) IPR Intellectual Property Rights ISDN Integrated Services Digital Network ISDN-BA ISDN Basic Access ISI Inter Symbol Interference ITU-T ITU Telecommunications Sector LAN Local Area Network LAPV5 Link Access Protocol Version 5 LPF Low Pass Filter LT Line Termination

LTU Line Terminating Unit MA-THD Multi Amplitude Total Harmonic Distortion MCM Multi-Carrier Modulation NEXT Near End Cross Talk NT Network Termination NTP Network Termination Point NTU Network Terminating Unit ONU Optical Network Unit PACC Partition, Aggregation and Conditional Coding PBO Power Back Off POTS Plain Old Telephone Service PPP Point-to-Point Protocol (IETF) PSD Power Spectral Density PSE Power Source Element PSTN Public Switched Telephone Network QoS Quality of Service RF Radio Frequency RFC Designation for an IETF Standard RFI Radio Frequency Interference RT Remote Terminal RTR Revised Technical Report (ETSI) RTS Revised Technical Specification (ETSI) RX Receive SCM Single-Carrier Modulation SDSL Symmetrical high bit rate Digital Subscriber Line SHDSL Single-line High Speed DSL SM Spectrum Management SNR Signal to Noise Ratio SPAN Services and Protocols for Advanced Networks (ETSI TC) STQ Speech Transmission Quality (ETSI TC) TBD To be Determined TC Technical Committee TDM Time Division Multiplex THD Total Harmonic Distortion TM Transmission and Multiplexing (ETSI TC) TPS-TC Transport Protocol Specific-Transmission Convergence TR Technical Report TS Technical Specification TX Transmit UPBO Upstream Power Back-Off VDSL Very high speed DSL VOC VDSL Operations Channel VoDSL Voice over DSL WD Working Document WG Working Group WI Work Item xDSL all the different DSL technologies

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