CSR Volume 12 #44, November 28, 2001

COMMUNICATIONS STANDARDS REVIEW

Volume 12, Number 44 November 28, 2001

REPORT OF ETSI TM6 #24, ACCESS TRANSMISSION SYSTEMS ON METALLIC CABLES, NOVEMBER 12 – 16, 2001, SOPHIA ANTIPOLIS, FRANCE The following report represents the view of the reporter and is not the official, authorized minutes of the meeting. ETSI TM6 #24, Access Transmission Systems on Metallic Cables, November 12 – 16, 2001, Sophia Antipolis, France...... 2 SDSL...... 2 Deactivation/Warm Start...... 3 Inverse Multiplexing for ATM (IMA) Support...... 4 Test Noise...... 4 Multi-Pair...... 5 Loop/Noise Calibration Impedance...... 5 Additional Highlights...... 6 VDSL...... 6 Part 1. VDSL Functional Requirements, Revision of TS 101 270-1 (TM-06026-1)...... 6 Part 2. VDSL Transceiver Requirements, Revision of TS 101 270-2 (TM-06023)...... 8 ADSL...... 8 Noise Calibration Impedance...... 9 Noise Issues...... 9 Performance Issues...... 9 All Digital Loop...... 10 Splitter Issues...... 11 TM-06025 Living List...... 11 Spectrum Management...... 12 TM-06029 Part 1...... 12 TM-06029 Living List Part 2 Issues...... 14 TM-06029 Part 3...... 14 VoDSL...... 14 Dynamic Rate Repartitioning, SP 5...... 14 Timeslot Mapping...... 15 DSL Splitter Specification...... 16 High Pass of ADSL/POTS...... 16 ADSL/ISDN...... 16 DSL Splitter Living List...... 17 Testing Methods for DSL Splitters...... 17 TM6 Meeting Roster, November 12 – 16, 2001, Sophia Antipolis, France...... 18 Acronym Definitions...... 20 Communications Standards Review Copyright Policy...... 22

REPORT OF ETSI TM6 #24, ACCESS TRANSMISSION SYSTEMS ON METALLIC CABLES, NOVEMBER 12 – 16, 2001, SOPHIA ANTIPOLIS, FRANCE M. Gindel (Telekom Austria) is the TM6 chair. TD-00 contains the list of TDs and their abstracts. TD-01 is the meeting agenda. The next ETSI TM6 meeting will tentatively be held in Torino, Italy, hosted by Telecom Italia. M. Gindel is due for reelection at the next meeting of TM6; candidates should declare their candidacy well before the second meeting of TM6 meeting in 2002. G. Zedler (Deutsche Telekom), chairman of TM, is retiring so a new election for TM chair will also be needed. S. Schmoll (Alcatel) retired as the SDSL Rapporteur; M. Kimpe (Adtran) is the new SDSL Rapporteur. B. Waring (Infineon) announced that he will not be able to continue as rapporteur for VDSL after the second TM6 meeting of year 2002. TD-47 contains the work items assigned to TM6 at the beginning of this meeting.

ETSI numb. WI Title TS 101 524 RTS/TM-06018b TM; Access transm. Syst. on metallic access cables; SDSL DTS/TM-06021 TM; Access networks; Req.s 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 Req.s. ADSL/ISDN splitters TS 101 952-2-2 DTS/TM-06028-2-2 DSL Splitter Req.s; HP part VDSL/POTS splitters TS 101 952-2-3 DTS/TM-06028-2-3 DSL Splitter Req.s. VDSL/ISDN splitters. TS 101 952-2-4 DTS/TM-06028-2-4 DSL Splitter Req.s. VDSL/“Other services” splitters. TR 101 830-1 RTR/TM-06029-1 TM; Spectral management; part 1 SDSL The work plan for the SDSL session is given in WD-11. S. Schmoll (Alcatel), the SDSL Rapporteur, was unable to attend; M. Kimpe (Adtran) chaired the meeting in his absence. The

SDSL Working Group is revising TS 101 524 (TM-06022). The working draft is contained in permanent document TM6(00)18. The Living List of this SDSL revision is in TM6(00)17.

Deactivation/Warm Start WD-03, SDSL start-up instabilities (T. Nordström, FTW), discusses a potential instability problem during SDSL start-up. Through a “gedanken” experiment and simulations, they find that during start-up of SDSL modems they can get a ping-pong effect with multiple restarts. Furthermore, they see that for each restart they will be forced to reduce the bit-rates of earlier deployed modems. TD-10, Deactivation and Warmstart (B. Heise, Infineon Technologies), proposes a complete text for all power down mode, deactivation and warmstart.related items; it is the result of discussions among the interested parties. Some delegates did not agree with all of the proposals in TD-10. An ad hoc group met to improve the warm start work and provided direction in the form of answers (WD-28) to seven questions (below). The ad hoc was attended by representatives of Alcatel KE, Conexant, Tioga, GlobeSpan, and Infineon. 1. Shall the deactivation only be initiated by the LTU? Result: The ad hoc proposes to provide the possibility to initiate the deactivation from the LTU and/or the NTU. In different applications, the transceiver that controls the deactivation can differ. 2. Shall the options (wake-up signal, half-duplex segments) be used? Result: An important objective for defining the warm-start is to allow as few options as possible during the startup procedure to alleviate interoperability problems. 2.1: Result on wake-up signal: Conexant will evaluate whether G.hs tones are applicable. 2.2: Result on half duplex segments: All participants will evaluate the need of a half duplex segment for the NTU and for the LTU. The main aspect is the activation time in case of no or of small changes of the line characteristics, e.g., due to temperature variations. 3 What channel shall be used to communicate the options over the line? Available channels are: a new G.hs message, the activation framer, or the EOC channel. Result: It is recommended to use a G.hs message to communicate the capability of the warm- start. The implementation of the warm-start shall be optional. 4 Are timeouts required? Which? E.g.: “Maximum activation time,” the “Maximum time until the data is valid,” “minimum time for silence to communicate an exception state”? Results: –It is recommended that the value for the minimum time for silence to communicate the exception state shall be the same as for the cold-start –A value for the “Maximum time until the data is valid” will not be fixed as a timeout criterion to branch to the exceptions state. An appropriate nominal value remains under consideration –The use of “Maximum activation time” as a timeout and the nominal value is to be resolved following the investigations under 2.2. 5 Shall different m-sequences signals be used? Result: This issue will be discussed depending on the results on issue 2.1. 6 Shall the signal during synchronization be Tomlinson-precoded? Result: This issue will be solved on the tests according to 2.2. 7 What text shall be provided on non-stationary xtalk? Result: A note will be included in the text for the warm-start in the spirit of: “In warm-start, the transmission shall be active to at least a determined time to minimize effects of nonstationary xtalk to systems sharing the same binder.”

Inverse Multiplexing for ATM (IMA) Support TD-37, IMA support in SDSL (I. Volkeing, Infineon Technologies AG, Germany), proposes modification of subclause A.8.3 of SDSL along the lines of the text of E.9.2.3, of the Amendment to G.991.2. An ad hoc group met to create some text; the output text (below) which follows the text of G.991.2 E 9.2.3 (except where underlined) is contained in WD-14, and was agreed by the plenary. A.8.3.x IMA sub-layer functionality (informative) The ATM TPS-TC, as defined in §A.8, is intended to be compatible with Inverse Multiplexing for ATM (IMA) Specification, as defined in af-phy-0086.001 [1]. IMA is a protocol that provides for inverse multiplexing of an ATM cell stream over multiple physical layer transmission links. It operates by multiplexing the ATM cell stream between the links on a cell-by-cell basis and then inserting special IMA Control Protocol (ICP) cells into each of the individual ATM cell streams. Since the IMA cell stream for each link is structurally identical to a stream of normal ATM cells, IMA cell streams may be carried without modification using the SDSL ATM TPS-TC. Note that the IMA Specification assumes that the ATM TPS-TC will be compatible with the IMA exceptions to the Interface Specific Transmission Convergence Sublayer, as defined in the IMA Specification, §5.2.1 (specifically, items R-3 and R-4). The IMA Specification (§9.1) indicates that the differential delay from the IMA transmitter to the loop interface (U-R or U-C) is to be no greater than 2.5 cells. It is recommended that the maximum differential signal transfer delay between non-repeatered SDSL wire pairs be no more than 50 µs. With regard to repeaters, note that this Recommendation (Annex C) allows up to 8 repeaters in an access link; however, it does not define the delay though the repeater. Also note that the number of repeaters deployed in a loop is dependent on network specific conditions. Implementers are encouraged to take into account the various sources of differential delay, including differential latencies introduced by repeaters (if present), in the design of IMA systems.

Test Noise TD-39, Progress on SDSL Study Point 17 (A. Carrick, Ascom AG), presents the status of SDSL Study Point 17, Potential for simplification of the test noise specification. It proposes that the terms of the study point be changed to address merely a simplified description of the test noise in an informative annex.LAPV5. WD-02, Adtran Final Text Proposal for Annex A.10 (M. Kimpe, Adtran AG), proposes final text for Annex A.10, TPS-TC for LAPV5-controlled POTS or ISDN. The contribution was already presented in Ghent (as TD-51, CSR 12.21). This version incorporates editorial corrections and resolves the comments raised in TD-18 from Stockholm (CSR 12.35). The mapping and time slot allocation of STM-based, LAPV5 controlled, PSTN and ISDN-BRA transport is specified, which, for ISDN, is an alternative procedure to the simple use of D-channel messages as described in subclause A.6. It is not expected that the transport mode described in this annex will be used simultaneously with the ISDN transport described in Annex A.6 or the POTS transport described in Annex A.7. It also proposes additions to section A.9.4, the dual bearer mode text, Annex A.6 /Annex A.7 and the EOC Message ID definitions to completely described the operations of Annexes A.6, A.7 and A.10. There is a need to reserve the Message ID in G.shdsl as well through a liaison.

Multi-Pair TD-07, Considerations on Pair Selection (Belgacom), discusses the function of pair selection in the pair provisioning process. See Spectrum Management Part 1 (below) for details. TD-11, Adopting ITU-T SHDSL 4-Wire Mode and extending it to multiple pairs (B. Heise, Infineon Technologies), proposes to adopt the text from the optional 4-wire mode from the ITU G.shdsl recommendation and to extend this mode to transmission over multiple wire pairs. While the two-pair mode (4-wire) is already defined in ITU-T SHDSL, the generalization to the p-wire mode requires an additional protocol to determine the number of wire pairs and their ordering. The principle for the extension to the p-wire mode (activation frames) is adopted from the T1E1 HDSL2 Issue 2 Standard. The text proposed is from the ITU-T G.shdsl four wire mode. TD-16, Multichannel SDSL optional mode (A. Leshem, Metalink Broadband Access), proposes adopting the ITU G.shdsl two pair mode. Extension to multichannel will be considered in an accompanying contribution. The text is phrased such that extension to multi-rate can be easily incorporated. TD-21, Multi-pair SDSL with Multiple Symbol Rates (F. Reuven, Tioga), proposes requirements for multipair transmission, and suggests a functional model, which is based on separating the multipair multiplexing from the PMS layer. It proposes to use TDM multiplexing, which complies with all TPS-TC applications and allows using multiple bit rates with low latency. This multipair transmission mode is an extension of the ITU-T G.shdsl four-wire mode. Using multipair SDSL, the aggregate per pair bit rate may be higher than one single pair. Some discussion followed on what are the requirements from operator; What is the maximum number of pairs? What are the applications? How are the bytes spread? Improving the reach, reducing the latency, and bringing high bit rates to the subscriber seem to be the most interesting features; most operators would need up to three pairs, and some are ready to go up to 16 pairs. An ad hoc group met; its output is contained in WD-15. They agreed to use the ITU-T Recommendation text on 2 pair G.shdsl with some European changes. A new work item was created (supported by BT, Deutsche Telekom, Infineon, France Télécom, Paradyne International) for the study of more than two pairs. The text of that new work item is contained in WD-13. There was some controversy about the actual name of the new system since SDSL is actually a single pair system; and also on the actual output of the work item.

Loop/Noise Calibration Impedance This work was also discussed in the ADSL session, below. TD-06, Complex impedance for calibrating the injected noise level (R. F. M. van den Brink, KPN), proposes a complex impedance, to be used during the calibration mode of performance testing, for defining the ADSL reach requirements, and to solve the reach requirements for SDSL that appear to be too tight at lower bit rates. The proposed impedance is a compromise between simplicity (one impedance representing all test loops) and realism (much better than a frequency-independent value). The network has been taken from existing ETSI standards. TD-25, Calibration Impedance for ADSL tests (O. van der Viel, Broadcom), was intended for the ADSL session and was presented to the SDSL session for information. In the Stockholm meeting (CSR 12.35), it was proposed to use during the calibration phase of the noise, a frequency- dependent impedance that would better represent the loop frequency behavior than a flat Rv (= 100 Ohms) impedance. Such an approach has the advantage of avoiding the need to recalibrate the

November 28, 2001 Vol. 12.44 Copyright © CSR 2001 5 COMMUNICATIONS STANDARDS REVIEW noise source for each line –and hence each new test, a procedure that was initially proposed in the ADSL document. TD-25 investigates some of the proposals that have been made so far for the structure and the value of this impedance, as well as issues related to the process itself, and proposes a way forward to specify the value of this impedance. TD-44, Noise injection calibration for ADSL performance requirements (P. Reusens, K. Venken, Alcatel Belgium), notes that before a final version of performance requirements can be compiled, TM6 needs to define a complex valued line impedance for noise calibration. The proposal in TD- 06 (above) seems acceptable. TD-06 led to a long discussion: Do we need to change the test set up? Do we need to recalibrate the test equipment? See WD-20 (ADSL Noise Calibration Impedance, below) for a proposed way forward.

Additional Highlights The issue of coordination between the ITU-T SDSL recommendations and the work in ETSI TM6 was discussed at length. While it is important to create uniform standards for this work, it is also important that ETSI address European requirements specifically. The MoU between ITU-T and ETSI permits a free cooperation between Q4/15 and TM6. However, ETSI’s recognition by the European Commission and the European Free Trade Association may require ETSI to produce such documents which, upon publication by the EU, have a legal status in Europe. Thus TM6 must continue to produce DSL standards which address European requirements, while avoiding duplication of work in the ITU-T. Using pointers between the ITU G.shdsl /ETSI SDSL documents was recommended. No new Study Points were created at this meeting for SDSL, TS 101 524 (TM-06022). M. Kimpe (Adtran, editor and acting SDSL rapporteur) noted that it would be difficult to produce a stable draft of TM-06022 at the end of this meeting, as there are some issues in the Living List (see permanent document TM6(00)17) which require further study. He proposed postponing Working Group Approval from February 2002 to November 2002, with subsequent milestones adjusted according. This was approved. VDSL The work plan for the VDSL session is given in WD-05. The Living List is TM6(01)05a2. TD-04, Liaison to ETSI from FS-VDSL Committee presents TD-24 (see below) to this meeting which summarizes the results of a survey of a significant number of FSAN operators in which they comment on the VDSL PSD issue. This document had not been previously reviewed by equipment vendors.

Part 1. VDSL Functional Requirements, Revision of TS 101 270-1 (TM-06026-1) At the meeting in Stockholm (CSR 12.35), a study point was created to investigate the use of frequencies below 138 kHz (SP 1-9). TD-17, Use of the frequency band below 138 kHz (P. Reusens, Alcatel), contains a text proposal for the use of these frequencies. At the previous TM6 meeting a proposal was made (TD-24 [Stockholm], Merging of spectral allocation plans and PSD masks for VDSL, B.M. van den Heuvel, KPN; R. Persico, TILAB)

6 Vol. 12.44 Copyright © CSR 2001 November 28, 2001 COMMUNICATIONS STANDARDS REVIEW concerning the PSD masks for VDSL. That proposal addressed the merging of the VDSL band allocation plan (ETSI-TS 101 270-2 V1.1.1, February 2001) and the older requirements on the PSD in ETSI-TS 101 270-1 V1.2.1, (October 1999). This work is being progressed by FSAN operators as part of the FS-VDSL Committee. TD-24 from this meeting, PSD masks for VDSL: inclusions of comments (R. van den Brink, KPN; TILAB; with support from FSAN), contains the common viewpoint of a large number of operators. It proposes to use the interpolation on a logarithmic frequency scale, as proposed in TD-24 (Stockholm). It discusses a number of issues that were raised at the last ETSI meeting and during subsequent e-mail discussions. It prsents an improved literal text proposal that has taken these comments into account. An ad hoc group on TD-24 considered the issues, described as questions in the FS-VDSL liaison. A new SP1-14 (championed by Metalink) to consider proposals for a new “boosted” PSD mask was agreed and was also supported in the plenary. Based on the ad hoc discussions the reply to the issues raised in the TD-24 liaison is given in WD-21 (TM6 liaison to FS-VDSL Committee) as follows: TM6 also asked whether the optional low frequency band from 25-138 kHz can be used in FTTCab deployments, and if so, what are the proposals for the transmit PSD levels for upstream and downstream transmission? Issue 1: Shall the PSD masks be obtained joining the corner points with straight lines on a graph with a logarithmic or linear frequency scale (Hz)? Is there an added value in using one or the other approach? A flat PSD was supported (as proposed in TD-24) for the downstream PSD level to be used in the 25-138 khz band with a peak value of -36.5 dBm/Hz. This is the same value that is used in the ANSI trial use standard. Issue 2: Is it worthwhile to use appropriate constant in-band values for boosted PSDs in the upstream bands and the 2nd downstream band? In case positive, what values? The proposal to increase the PSD mask to -36.5 dBm/Hz in the band below 1.1 MHz for FTTEx deployments was not accepted. A preference was expressed to use values from the PSD masks in the VDSL Functional requirements specification. In addition a new SP1-14 was created to consider proposals for a new “boosted” PSD mask which takes account of the band plans adopted in TM6. 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 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: Is it needed to define a sort of “peak masks” to allow multi-carrier systems to exceed the “nominal masks” with their PSD ripples? What could be the risks in doing this? The proposal was not accepted and further justification of the performance benefits arising from the proposal is requested. With regard to the question of ripple in the real PSDs it was decided to open a new study point SP1-13 to study the need for a nominal PSD mask specification. Contributions to SP1-13 should concentrate on either the effects on egress of increasing the peak PSD levels or to provide justification for the existing peak PSD levels. Issue 5: Is it appropriate to relax the total power constraint (currently fixed at 11.5 dBm) up to 21 dBm (as proposed in TD-24) to actually allow the downstream PSD boosting in FTTEx configuration? The proposal was not accepted and contributions are invited to SP1-8 (implications of increasing the wide-band power for FTTEx) to quantify the performance benefits arising from an increase in wide-band, downstream, transmit power above +11.5 dBm.

Part 2. VDSL Transceiver Requirements, Revision of TS 101 270-2 (TM-06023) The Living List is TM6(00)15a3. TD-18, Comparison of Different Precoding Architectures for SCM VDSL (Tellabs Oy, Tioga Technologies), deals with the precoding for single carrier modulated (SCM) VDSL. There are two basic precoding schemes: Tomlinson-Harashima precoding (THP) and flexible precoding (FLP). These two precoder schemes are analyzed from the viewpoint of the SCM VDSL. As a result, the Tomlinson-Harashima precoding is proposed for SCM VDSL. TD-19, Constellations for QAM32 and QAM128 for SCM VDSL using Tomlinson-Harashima precoding (Tellabs Oy), proposes square constellations for QAM32 and QAM128 instead of the corresponding cross constellations in conjunction with a Tomlinson-Harashima precoder (THP). With a THP, the square constellations provide about 0.5 dB more noise margin than the cross constellations. With a DFE, the cross constellations are better than the square ones because of the shaping gain associated with the cross constellations. TD-20 (Tellabs Oy) handles the possibility of selecting between a DFE and a precoder mode independently for each QAM carrier (DS1, DS2, US1, US2). It turns out that significant savings in the hardware realization can be achieved if certain limitations are imposed on the mutual freedom to select the mode. It is proposed that in this respect the QAM carriers are grouped in pairs (DS1+US1) and (DS2+US2) and a pair can be set to the precoder or to the DFE mode independently. TD-33, Power consumption reduction by using Tomlinson precoding and Trellis code – initial estimation (Tioga Technologies), presents the assessments for saving in power consumption when a Tomlinson precoder is used together with a trellis code. Using conservative assumptions, it is shown that a trellis code offers 2 db of coding gain and the use of Tomlinson precoding improves the performance by an additional 1 db. The 3 db enhancement in performance can be translated to a 3 db reduction in the total transmit power. This reduction in the transmit power again translates to a net power saving of approximately 200 mw. It concludes that the use of a Tomlinson precoder does not only allow reliable operation, i.e., without long error bursts due to error propagation, but it also allows a power saving of up to 20% of the total power per line. WD-04, Working text on Packets Transport Mode (Broadcom Corporation, Infineon Technologies), proposes to introduce a Packets Transport Mode (PTM) into Part 2 of the VDSL specification TS 101 270-2 in the version as proposed in G.993.1 Annex H. A corresponding working text is attached. WD-17, Text proposal for UPBO specification (S. Schelstraete, Alcatel; BT, Texas Instruments), notes that there is currently an ambiguity in the way UPBO is specified. In particular, it is not specified how the estimate of the electrical length should be performed. WD-17 proposes to change the test in TS 101 270-2 to make the meaning more precise. This text was not approved and needs refinement. In particular, Broadcom does not support the new text. ADSL Revision of TS 101 388 (TM-06025) is the ADSL project. The work plan for the ADSL session is contained in WD-06.

Noise Calibration Impedance TD-06 was covered in the SDSL session (above). WD-16 reports on an ad hoc group (attended by Ascom, Spirent, Broadcom, KPN, Tioga, and later also Conexant and Adtran) to study the consequence of adopting the impedance proposed in TD-06. There was no consensus on any solution on how to proceed, so the original problems remain unsolved. In WD-20 the ADSL Rapporteur proposes a compromise on the issue of noise calibration impedance. A correction function is defined between performance and measurements when still done on an actual complex impedance compared to a pure resistive load of 100 Ohms. The text is based on clause 5.1.4 of the ETSI ADSL document, with the suggested changes to the text highlighted. but the text itself needs further refinement.

Noise Issues TD-13 (M. Leuffelholz, DTAG) gives a proposal for a same pair ISDN 4B3T noise template to be used to find performance numbers for FDD and EC ADSL over ISDN. TD-08, Proposal to Re-Name New ADSL Noises A and B (K. Jacobsen, Texas Instruments), proposes to re-name noises A and B in the revision of TS 101 388. The objective is to eliminate confusion between the older noise models A and B and the FSAN models A and B.

Performance Issues TD-43, Issues related to the performance requirements for ADSL (P. Reusens, Alcatel), notes that before a final version of performance requirements can be complied, TM6 needs to define the following, to calibrate the noise generators: 1) The more realistic line impedance for noise calibration. 2) The quantification of the difference between the injected noise power modeled in simulations and the actual current injection in the modems on a test bench. 3) The clarification of the required minimal operation in the opposite direction during the single ended performance measurements. 4) Some reference templates of the FSAN noise PSD types, on test loops, with representative lengths, to check the noise files. The noise profiles will be provided by each company participating in the performance evaluation (Alcatel, TI, Broadcom, Conexant). It was agreed to take the FSAN noise profile, calibrate with the new impedance, build the current source and check what gets into the impedance of the modem. Should the splitter be included in the performance? Problems with reproducibility? It was agreed to use only the low pass of the splitter, not the high pass which is part of the design of the receiver. WD-12 (K. Jacobsen, Texas Instruments) presents the results of TI’s latest time-domain FDD ADSL over ISDN simulation. Since the last meeting of ETSI TM6 in Stockholm, Texas Instruments’ time-domain simulations have been re-run. The major change was in the FEXT noise calculation, which was incorrect in previous versions of the simulator. The corrected noise PSDs were verified against noise PSDs generated by the Rapporteur. The projected reaches are generally in good agreement with those in WD 26 from Stockholm, which were derived using frequency- domain simulations. However, there are discrepancies in the reaches on loops 4 and 8 and in the case of noise D.

All Digital Loop TD-31, liaison response from ITU-T Study Group 15 (see TD-041[WP1/15] in CSR 12.42 for details) to ETSI TM6 conveys responses to the liaison from ETSI TM6 brought into the October 2001 meeting of ITU-T Study Group 15 in Geneva. TD-09, All Digital Loop Downstream PSD Mask for Overlapped Operation (Per-Erik Eriksson, LM Ericsson), notes that the “All Digital Loop” (ADL) has been under study since the Vienna 2000 meeting. TD-09 proposes a downstream PSD mask for the overlapped operation almost down to DC. The ADL enables operators to provide more capacity and extended reach. The lower tones from 1 to 6 (DC = tone 0) that are normally less attenuated on a cable can then be used for high bit constellations. The proposed mask is essentially a flat extension of the PSD mask used today for overlapped operation. The extension is almost down to DC, with a roll of below 3 kHz taking into account the second order effects from the presence of the line transformer. This proposed PSD mask was also brought to the previous SG15 Q4 meeting in Geneva (D.269, CSR 12.42) in October. The proposal was to use this PSD mask in Annex I and Annex J in G.dmt.bis (Annex I is for ADSL without underlying POTS, Annex J is for ADSL without underlying ISDN). Concerns about spectral compatibility of this new mask according to T1.417 (Spectrum Management for Loop Transmission Systems) were raised. The consensus in Q4/15 was to use the old overlapped mask defined in G.992.1 and let the new part of the PSD mask be for further study. TD-09 addresses the spectral compatibility issues with services used in Europe. TD-38, Tutorial on the All Digital Loop, i.e., ADSL without underlying service (P. Reusens, Alcatel), is a general tutorial on the All Digital Loop (ADL). It concludes that the all digital loop is primarily a product for the residential market, with “in band” POTS or ISDN. It can offer an alternative to the ADSL over POTS, with a gain of upstream bandwidth with 200 to 250 kbit/s. When used as an alternative to ADSL over ISDN, the upstream will increase 600 to 800 kbit/s and the range will be larger, because ADSL over ISDN is often limited by the upstream. TD-40, Tutorial on the Spectra of the ADSL-based All Digital Loop (P. Reusens, Alcatel), gives an overview on the proposed spectra of the different All Digital Loop variants, all intended to achieve improved spectral interworking with the existing ADSL variants with EC and FDD, over POTS and over ISDN. TD-41, Spectral compatibility of the ADL spectra with non-ADSL xDSL (P. Reusens, Alcatel), revisits the spectral compatibility of the All Digital Loop from TD-50 at Stockholm (CSR 12.35), including an ANSI-based proof already offered in TD-09 of the Ghent meeting (CSR 12.21). TD-42, Spectral compatibility of ADL with ADSL over POTS and over ISDN (P. Reusens, Alcatel), shows that there are spectral management techniques to allow ADSL over POTS and ADSL over ISDN to coexist. Similar methods can also allow ADL to use a wider upstream bandwidth than the simplest case of ADLU-32. Discussion on All Digital Loop followed the six presentations on ADL. One concern was raised: Why does the ANSI spectral management rules not apply to Europe? There are still no spectral management rules in Europe to deploy a new system. The intent of the Alcatel and Ericsson contributions is at minimum to input those ADL signal characteristics into Part 1 of Spectral Management. The question came up whether this ADL signal description is to be included in the standard signal description category or in the “proprietary” signal category. Telia and Belgacom support such an ADL system; others don’t support but don t object to it. The proposal is to have an informative Annex in the ADSL over ISDN European document.

WD-23, Informative Annex on ADL (ADSL Rapporteur, R. Jonsson, Conexant), proposes draft text for Annex G (Informative) Signal characteristics of all digital loop signals. This text captures the recommendations of the ad hoc session on an informative annex on ADL.

Splitter Issues See also DSL Splitter Specification (below). TD-03 is a liaison from AT Analogue (see CSR 12.38) regarding an advisory note on TBR 21 spectral limits (for V.92); it provides the final draft of TR 101 954 (A Study on POTS Requirements Applicable to ADSL Modems when Connected to an Analog PSTN Line) for review. TD-12, Alternative for lowpass of ADSL over ISDN-Splitter (B. Heidle, Infineon Technologies), presents an alternative to the passive splitter lowpass by implementing the filter into the ISDN system. TD-12 serves as the basis for an informal study point; if there are more contributions on the topic, a formal study may be initiated. TD-34, Proposal for a modified THD measurement of ADSL splitter harmonic distortion (MA- THD, Multi Amplitude Total Harmonic Distortion) (M. Bukofski, Vacuumschmelze), proposes a modified THD measurement for TM-06025 - Revision of TS 101 388 ADSL European Specific Requirements. MA-THD ensures low ADSL-Splitter harmonic distortion. MA-THD is, in contrast to a single THD measurement, directly connected with the maximum bit rate for a given loop or the maximum reach for a given bit rate. WD-01 is the ETSI call for experts on the splitter validation Specialist Task Force. WD-22, Proposed Liaison to ITU concerning splitters (DES/TM-06028 Rapporteur), Concerning the draft G.dmt-bis, provides the following input to ITU on the subject of European splitters: There are current work items in TM6 to produce parts of TS 101 952, which will be a technical specification for DSL splitters to be deployed in European networks. This document is to be a joint deliverable from both TM6 and TC-AT. For those parts of TS 101 952 that should be relevant to G.dmt-bis Annex E, i.e., those that specify ADSL/POTS and ADSL/ISDN splitters for Europe, some are TM6 deliverables and others are TC AT deliverables. The schedules of the TM6 deliverables target technical body approval in February 2002, with publication to follow in May 2002. This schedule is conducive to having the documents ready for reference by G.dmt-bis. With regard to the relevant parts of TS 101 952 that are deliverables of TC AT, this technical committee is aware of the proposed schedule for G.dmt-bis. The rapporteur for the relevant work items in both TM6 and TC AT is P. Golden (LEA, [email protected]).

TM-06025 Living List The Living List for TM-06025 is contained in permanent document TM6(01)08. No new Study Points were created at this meeting. The following Study Points will be either provisionally approved or provisionally deleted by the end of the year: 5 Out of band PSD limits for ISDN-BA and ADSL 7 RFI injection method including common mode 16 Co-existence problems between ISDN and ADSL-over-ISDN The following Study Points were kept for a potential revision:

10 Tone levels for RFI Ingress noise test 11 Test methods for RFI Ingress noise test 18 Mandatory capability for tones below 33 The following Study Points were considered relevant to potential future spectral management work: 8 Implementation methods to allow spectral co-existence of “ADSL over POTS” with “ADSL over ISDN” 9 General mechanism to support ditched PSD masks 14 Carrier Masking 15 Spectral Compatibility Carrier Masking Spectrum Management TM-06029 is the Spectrum Management project. TR 101 830-1 is Part 1: Definition of Signals. The session work plan for Spectrum Management is given in WD-07. R. van den Brink (KPN) is the Spectrum Management rapporteur.

TM-06029 Part 1 TD-05, On the Use of xDSL Technologies in the Same Quad (A. Thoeni, Swisscom AG), notes that experimental measurements show that the crosstalk within the same quad may be slightly stronger than the crosstalk with neighboring quads. According to Swisscom experience, the difference is typically 2 dB for NEXT and 7 dB for FEXT. The question is if there is a significant benefit to a disturbed xDSL system if only one xDSL system is allowed within a quad. TD-05 analyzes the impact of a limiting strategy on the number of systems per quad and concludes that the more disturbers in a bundle, the less benefit can be achieved with a “one system per quad” rule. TD-07, Considerations on Pair Selection (Belgacom), discusses the function of pair selection in the pair provisioning process. Belgacom pair selection is based on the fact that, although crosstalk shows a lot of variation, the following rules of the thumb (based on field measurements) for the use of quad wire groups in a cable bundle appear to be valid: • Crosstalk from an adjacent quad is some 4 dB lower than from within the same quad. • Crosstalk from a far quad is another 10 dB lower than from an adjacent quad. Two different simple pair selection rules are compared, both mutually as well as with the “no pair selection” reference case. Comparison is done in terms of complexity of the cable management system, the crosstalk and resulting service quality, and the possible restrictions on maximum cable fill. The advantage of pair selection in the case of sub-loop injection is also highlighted. TD-45, Including the All Digital Loop in Spectral Management Part 1 (P. Reusens, Alcatel), proposes addition of the FDD-ADSL signals for the revision of the ETSI TR 101-830-1, Spectral Management – Part 1. This catalog of DSL signals should also contain the All Digital Loop signals, which are part of the same ADSL DMT transmission standard. TD-14, The Construction of the UK Access Network Frequency Plan (ANFP) (J. MacDonald, BT), notes that BT has proposed that Spectrum Management Part 2 should concern design methods for spectrum management rule sets. A rule set for the UK has already been produced, and this paper presents the principles by which it was constructed. The UK ANFP defines four spectrum management (PSD) masks, one for the exchange end of a line and three for customer ends of lines at different distances from the exchange. The UK ANFP only limits where systems may be deployed and the PSD, it does not promise any particular performance.

TD-23, Spectral Management Approach in the Netherlands (R. van den Brink, KPN Research), notes that in order to make unbundling happen, specialists from competitive operators within the Netherlands, are working together in the Dutch forum “FIST.” One of the goals of this cooperation is to enable optimal broadband usage of the available copper resources in the Netherlands. For optimal broadband usage, “access rules” (based on ETSI Spectral Management Report, Part 1) have been set that are mandatory for all operators which share the same access network. By limiting the signal level that is allowed for injection into an access network, the total spectral pollution is bounded. This enables each involved operator to design its own deployment rules/guidelines. WD-09 (Siemens ATEA) provides a summary of the T1E1.4 /2001-002R2 of Nov. 5, 2001, Spectrum management for loop transmission systems (revision of T1.417). This document can be used as a source for topics to be covered in the ETSI Spectrum Management Part 2 document. It also recommends that ETSI consider the methodology defined by T1E1.4 for determining spectrum compatibility between xDSL technologies with adaptations required for the European requirements. It was agreed that V. Buyck (Siemens ATEA) would create a permanent document to collect and update the approaches to spectral management being implemented throughout Europe. WD-10, Siemens ATEA Overview of present regulation for the unbundled local loop (ULL) collected from Belgium, France, UK, Germany and Finland. Two methods are used to define allowed systems on the ULL: • Lists identifying the allowed technologies • Global PSD masks Unfortunately the technologies defined on the lists or derived from the PSD masks differ from country to country. WD-10 suggests that guidance from ETSI, on which technologies are spectrum-compatible, and what deployment rules are to be considered, could lead to more convergence and more motivated decisions. TD-15 (T. Kessler, DTAG) proposes a new work item on Spectral Management Part 2 construction methods for spectral management rules including scope and objectives. In the Stockholm meeting (CSR 12.35), a new work item on Spectral Management Part 2 was not agreed. This proposal suggests that concrete reach values for deployment rules are outside the scope of the work item. WD-08 (Siemens ATEA) attempts to identify the needs of the users of this Part 2. The users are the regulators, operators and designers. Only the needs for the technical aspects of spectrum management are covered. These needs provide the rational for an ETSI Spectrum Management Part 2 document, and also identify the possible topics to be covered in such a document. This contribution was input for the spectrum management ad hoc meeting. TD-22, Reference methods for performance calculations (R. van den Brink, KPN Research) notes that there is a common feeling within ETSI TM6 that a Spectral Management Part 2 is required, but a clear view on what its contents should be is currently lacking. Various wish lists have been contributed but it is still unclear what content is required for solving these topics. The lack of detail in TD-15 (above) hides the large amount of issues that are to be solved in a single document. TD- 22 proposes to reach this goal in smaller steps, to dedicate Part 2 solely to the calculation methods for evaluating performance, and work in parallel (Part 3) on additional issues, as suggested in TD- 15. This gives more progress because unsolved controversial issues will not block the publication of solved calculation methods (as happened in ANSI T1E1.4).

At the spectrum management ad hoc meeting, it was decided to create a new work item on spectral management tools; a number of issues/study points were then transferred to Part 2 and are given below.

TM-06029 Living List Part 2 Issues The following are the Study Points for Part 2. 2-1 Spectral management rules for non-stationary signals 2-2 Limits for noise that may leak into the local loop wiring 2-3 Scope, objective and table of contents of TR 101 830-2 2-4 Wetting current requirements 2-5 Interworking issues in case of line sharing 2-6 Methods for constructing spectral management plans

TM-06029 Part 3 A new work item on tools and methods to manage spectrum on a line was created and approved. WD-30 contains the work sheet for the new work item. This important step has the following scope and following objectives: The scope of this Spectral Management document is restricted to the methodology for defining scenarios and quantifying the performance of equipment within such a scenario. All judgment on what performance is acceptable or not, is beyond the scope of “Part 2.” The same applies for how realistic the example scenarios are. Objectives: The objective of this Spectral Management document is to provide the technical means for evaluating the performance from a chosen scenario, such as calculations and measurements. This includes: The definition of performance properties of equipment, e.g., being compliant to international product standards from ETSI, ITU, ANSI, or any other equipment of interest, such as in “Part 1.” Examples that help people to apply this methodology, such as examples on how to define the configuration and the conditions of a scenario in an unambiguous way. The distinction is that a configuration can be controlled by access rules (e.g., technology mix, cable fill) while the conditions cannot (e.g., cable properties). These objectives enable a consistent presentation of reproducible results, while studying the impact of changing various Spectral Management parameters. Another possible application is a clear methodology for demonstrating spectral compatibility between equipment (existing as well as newly defined). VoDSL N. King (Infineon) is the VoDSL Rapporteur. The work is being done under DTR/TM-06021. The work plan for the Voice over DSL session is in WD-25. The Living List for DTR/TM-06021 is in permanent document TM6(99)13. The newest version is in m00p13a4, rev. 3a

Dynamic Rate Repartitioning, SP 5 TD-02, Current status of DRR (M. Meninger, Czech Telecom;, GlobeSpan, Siemens), analyzes DRR methods proposed in TM6 (see WD-10, CSR 12.35), and proposes future steps.

TD-30, Voice Call Control Requirements To Be Considered For DRR (GlobeSpan), notes that TD- 53 from Stockholm presented a list of system-level requirements for Dynamic Rate Repartitioning (DRR) that would ensure DRR signaling and procedures will meet the voice call control requirements of any SDSL access network. TD-30 explains (requirement 2 in TD-53 [Stockholm]) the need to minimize the time to activate and deactivate a PCM voice timeslot by examining call control requirements for US-based access networks. TD-35, Converged DRR Procedure for DRR (Siemens AG; GlobeSpan Inc.), presents a DRR procedure which combines the advantages of fast signaling and fail-safe operation by converging two previous proposals (TD-15 from Ghent, Siemens, Infineon; and TD-54 from Stockholm, GlobeSpan) submitted to TM6. It proposes to standardize this solution in TS 101 524 rev. TD-32, G.shdsl.bis: Approaches to DRR Signaling (Rapporteur, VoDSL), was originally developed at a working session of ITU-T Q4/15 by Centillium. It describes three approaches for the signaling channel to control DRR within G.shdsl.bis. These are, in order of increasing complexity, (1) a bit mapped channel, (2) a simple non-HDLC protocol, and (3) a complete HDLC protocol. TD-32 reviews these approaches as well as the Siemens / GlobeSpan proposal (TD-35, above) and notes the need to consider multiple criteria in making the decision as to the most desirable DRR signaling method. While the target date of April 2002 remains the target, some delegates feel that there should be a well defined set of requirements like the one proposed in TD-32 and then proceed with solutions. N. Quarmby (TI), R. Jonsson (Conexant), M. Jonsson (Telia), J. MacDonald (BT), L. Dreier (Alcatel), L. Paley (GlobeSpan), N. King (Infineon), G. Eisler (Conexant), and A. Leshem (Metalink) met offline to try to define ways forward and requirements for VoDSL. WD-29 provides the output of this working group. It lists, but does not address, 33 questions that manufacturers have on the scope and options of VoDSL and DRR. WD-24, CCS processing delays for DRR (A. Carrick, Ascom AG), presents an extract from ETS 300 795 tabulating signaling transfer delays for information. ETS 300 795, V interfaces at the digital Local Exchange (LE); Access Network (AN) supporting V5; Transmission characteristics and performance design objectives for call handling and bearer channel connection management, provides the information regarding delay timing characteristics, defined in terms of “trigger events” which can be observed at “test points” specified for the AN configuration. These delays will have to be taken into account when defining a DRR mechanism.

Timeslot Mapping TD-36, Requirements on DRR related on CVoDSL (Infineon Technologies), describes the impact and general requirements to support Dynamic Rate Repartitioning in SDSL Dual Bearer Mode related on Channelized voice over DSL (CVoDSL) service. In the procedure proposed in TD-15 from Ghent, POTS and ISDN time slots of the SDSL frame are temporarily allocated by the ATM bearer part in the dual bearer mode. “Temporarily” means in the interval after disconnecting and before establishing a narrowband connection. A different procedure was presented in TD-19, TD- 53 and TD-54, all from Stockholm. POTS and ISDN time slots of the SDSL frame are re- arranged during active calls and re-allocated by using unused B-channels. In addition, after re- arrangement of the voice bearer, the ATM bearer is enhanced with the unused B-channels. TD-36 addresses only the mapping procedures of payload data and does not address any DRR protocol procedures or messages. However, the mapping of payload data is an important part of the DRR procedure and must be considered for the impact of the overall complexity.

November 28, 2001 Vol. 12.44 Copyright © CSR 2001 15 COMMUNICATIONS STANDARDS REVIEW DSL Splitter Specification The European Specific DSL Splitter Requirements (TS 101 952) Rapporteur is P. Golden (LEA). The work plan for the splitter session is given in WD-18. Permanent documents have been allocation as TM6(01)09, Living List for DSL Splitter Specification, and TM6(01)10, Working Draft of the DSL Splitter Specification. WD-22 contains a draft liaison to ITU-T summarizing the status of the splitter specification. It was approved. See ADSL splitter issues (above). TD-27, Proposal for Annex A of TS 101 952 (P. Golden, LEA), notes that ETSI splitter specifications (and the vast majority of European national specifications also) have to date used a fixed lumped RC impedance to terminate the line port at voice band frequencies. This is in contrast with the North American splitter specifications of ITU G.992.1 Annex E.2, which require splitter return loss and insertion loss to be measured for different loop configurations. Different three element compromise impedances are used to model line driving point impedances in different countries. These models are generally only applicable for the voice band (200 Hz - 4 kHz). The three main impedance models used are detailed in Annex C of TS 101 270 v1.2.1 (VDSL Transceiver Requirements). TD-27 proposes to include an informative Annex as part of TS 101 952, which presents the voiceband return loss of these three impedance models against some ETSI ADSL reference loops. TD-29 (P. Golden, LEA) proposes to open a study point in DES/TM-06028 on Active Splitter Requirements.

High Pass of ADSL/POTS

TD-28, Study of a third order filter with respect to POTS related functionality of the high pass part of an ADSL/POTS splitter (P. Golden, LEA; P. Reusens, Alcatel), examines the effect on POTS service of a third order high pass filter as the high pass part of an ADSL/POTS splitter. TD-28 shows that a third order filter can fulfill the POTS-related functionality of the high pass branch of an ADSL/POTS splitter. Adverse effects on telephony service performance due to dynamic impedance changes at the ADSL port are possible, and under study (TD-31 from Ghent, Influence from ADSL into ISDN in several rare states [M. Löffelholz, Deutsche Telekom]). The author is aware of no findings however, which suggest that raising the order of the high pass filter from 3 will result in any significant POTS performance increase in this respect. A study of the effect on ADSL performance of the high pass filter is necessary in order to more fully determine the effect of the high pass filter. TD-46, Study of the mismatch effects of the high pass of the ADSL splitter (P. Reusens, Alcatel), notes that there is a need to study the capacity loss for ADSL, caused by the extra third order high pass filter inserted in the ADSL line at the location of the low pass splitter filter.

ADSL/ISDN For the presentation of TD-34 and TD-12 see ADSL Splitter Issues (above). TD-26, Proposal to replace the ADSL insertion loss requirement in TS 101 952-1-3 with an input impedance requirement (P. Golden, LEA), gives a proposed requirement for the input impedance of the low pass part of an ADSL/ISDN splitter. It is felt that this requirement is sufficient to replace the current clause 5.10.1.

DSL Splitter Living List The first three Study Points were generated for the DSL Splitter work: 1 Implementation specific splitter requirements 2 Effect of high pass filter on ADSL 3 Test for non-linear distortion Testing Methods for DSL Splitters J. Montenot (SCE) is the Rapporteur for TM-06027, Testing methods for DSL Splitters. He introduced the project and showed the division of work items between TC AT and TC TM6. WD- 01 contains the budget for the STF to cover both ADSL splitters and VDSL splitters, through 2003. STF activity should being in mid-January 2002. Jacques A. Besseyre, Ph.D., Telecomsult

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November 28, 2001 Vol. 12.44 Copyright © CSR 2001 17 COMMUNICATIONS STANDARDS REVIEW TM6 Meeting Roster, November 12 – 16, 2001, Sophia Antipolis, France Manfred Gindel (Telekom Austria) TM6 Chair Marc Kimpe (Adtran) SDSL 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) DSL Splitter Specification Rapporteur Jean Montenot (SCE) Testing Methods for DSL Splitters Host: ETSI

Austria Telecommunications Research Center Vienna (FTW) Tomas Nordström Austria Telekom Austria Aktiengesellschaft Manfred Gindel Belgium Alcatel Bell Peter Reusens Belgium Alcatel Bell Sigurd Schelstraete Belgium Belgacom S.A. de droit public Guido Vanhoutte Belgium Siemens ATEA NV Victor Buyck Czech Republic Cesky Telecom a.s. Milan Meninger Finland Nokia Corporation Jari Lindholm Finland Tellabs OY Janne Vaananen Finland VDSL Systems Oy Peter Kunnas Finland VDSL Systems Oy Juri Sipilä France Cisco Systems Europe Justus Osude France Conexant Systems SAS George Eisler France Conexant Systems SAS Ragnar Jonsson France ETSI Secretariat Bernt Mattsson France ETSI Secretariat Gerry Mc Auley France France Telecom Emmanuel Boulaire France LEA (Laboratoire Europeen ADSL) Philip Golden France Paradyne International Bill Pechey France Paradyne International Doreen Pechey France Sagem Group Eric Dalle France Sagem Group Roger Samy France Secre Composants Electroniques Francis Coudiere France Secre Composants Electroniques Jean Montenot France Spirent Communications Michael Giroux France Texas Instruments France Krista Jacobsen France Texas Instruments France Neil Quarmby Germany Alcatel Kommunikations-Elektronik GmbH Ludger Dreier Germany Cetecom Andreas Ehre Germany Deutsche Telekom AG Ronald Hoffmann Germany Deutsche Telekom AG Thomas Kessler Germany Deutsche Telekom AG Marko Loeffelholz Germany Fraunhofer-Einrichtung für Systeme der Sven Keunecke Kommunikationstechnik Germany Infineon Technologies Bernd Heise Germany Infineon Technologies Neal King Germany Infineon Technologies Brian Waring

Germany Siemens AG Hagen Henniger Germany Siemens AG Wilfried Kubinger Germany Vacuumschmelze GmbH Johannes Binkofski Ireland PMC-Sierra Inc. Gerry Leavey Israel IAEI - Israel Association of Electronics Industries Amir Leshem Israel Tioga Technologies Ltd. Franco Reuven Italy Telecom Italia Lab S.p.A. Flavio Cucchietti Italy Telecom Italia Lab S.p.A. Lorenzo Magnone Netherlands KPN - Koninklijke PTT Nederland NV Rob van den Brink Norway Norwegian Post and Telecommunications Authority Rasmus Trevland Spain Ministerio De Ciencia Y Tecnologia-Secretaria De Jesus Labrado Estado De Telecomunicaciones Y Para La Soc. Info. Sweden Telefon AB LM Ericsson Per-Erik Eriksson Sweden Telia AB Marcus Jonsson Switzerland OFCOM Kurt Bartschi Switzerland OFCOM Daniel Voisard Switzerland Pro Telecom Stefan Luethi Switzerland Adtran AG Marc Kimpe Switzerland Ascom AG Angus Carrick Switzerland Swisscom SA Andreas Thoeny UK Samsung John Fenn UK Broadcom Corporation Olivier Van de Wiel UK BT Robert Kirkby UK BT John MacDonald UK Consultronics (Europe) Jim Eyres UK GlobeSpan Semiconductor Inc. Leon Paley USA Communication Standards Review Jacques Besseyre USA Worldcom Paul Donaldson USA Worldcom Daryl C. Tannis

November 28, 2001 Vol. 12.44 Copyright © CSR 2001 19 COMMUNICATIONS STANDARDS REVIEW Acronym Definitions ADLU All Digital Loop masks ADSL Asymmetric Digital Subscriber Line ANSI American National Standards Institute AT Access and Terminals (ETSI TC) ATM Asynchronous Transfer Mode CCS Common Channel Signaling DC Direct Current DES Draft European Standard DFE Decision Feedback Equalizer DRR Dynamic Rate Repartitioning DSL Digital Subscriber Line DTR Draft Technical Report (ETSI) DTS Draft Technical Standard (ETSI) EC Echo Canceled ETS European Telecommunications Standard (ETSI) ETSI European Telecommunications Standards Institute EU European Union FDD Frequency Division Duplexing FEXT Far End Cross Talk FSAN Full Service Access Networks FS-VDSL Full Service VDSL (FSAN Committee) FTTCab Fiber To The Cabinet FTTEx Fiber To The Exchange HDSL High-rate Digital Subscriber Line HP High-Pass ID Identification IMA Inverse Multiplexing for ATM ISDN Integrated Services Digital Network ISDN-BA ISDN Basic Access ISDN BRA ISDN Basic Rate Access ITU International Telecommunication Union LAPV5 Link Access Protocol Version 5 LTU Line Terminating Unit MoU Memorandum of Understanding NEXT Near End Cross Talk NTU Network Terminating Unit PCM Pulse Code Modulation PMS Physical Media Specific POTS Plain Old Telephone Service PSD Power Spectral Density PSTN Public Switched Telephone Network QAM Quadrature Amplitude Modulation RC Resistor/Capacitor RFI Radio Frequency Interference RTR Revised Technical Report (ETSI) RTS Revised Technical Specification (ETSI) SCM Single-Carrier Modulation SDSL Symmetrical high bit rate Digital Subscriber Line STF Specialist Task Force (ETSI) STM Synchronous Transmission Mode TBR Technical Basis for Regulation (ETSI)

TC Technical Committee (ETSI) THD Total Harmonic Distortion TM Transmission and Multiplexing (ETSI TC) TPS-TC Transport Protocol Specific-Transmission Convergence TR Technical Report TS Technical Specification UPBO Upstream Power Back-Off VDSL Very high speed DSL VoDSL Voice over DSL xDSL all the different DSL technologies

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