COMMUNICATIONS STANDARDS
REVIEW
Volume 12, Number 16
May 3, 2001
REPORT OF Q4/15 RAPPORTEUR’S MEETING ON xDSL NETWORK
ACCESS TRANSCIEVERS, APRIL 9 – 13, 2001, IRVINE, CA
The following report represents the view of the reporter
and is not the official, authorized minutes of the meeting.
Q4/15, xDSL Network Access Transceivers, Rapporteurs Meeting, April 9 – 13, 2001, Irvine, CA..2
G.gen, including G.lite.bis and G.dmt.bis...................................................................................2
Performance Improvement Methods.....................................................................................2
Conformance Testing............................................................................................................3
Coding..................................................................................................................................4
Modulation...........................................................................................................................7
Initialization..........................................................................................................................7
Framing................................................................................................................................9
OAM ................................................................................................................................10
Q-Mode (Quiescent Mode)................................................................................................10
POTS Splitter.....................................................................................................................12
Phone Line Compatibility...................................................................................................12
G.shdsl.bis................................................................................................................................13
Test Measurements.............................................................................................................13
G.vdsl.......................................................................................................................................13
G.pnt.........................................................................................................................................14
G.hs.ter.....................................................................................................................................14
G.ploam.bis..............................................................................................................................16
G.test.ter...................................................................................................................................16
G.ref.ter....................................................................................................................................16
G.voice......................................................................................................................................16
Q4/15 Partial Attendance Roster, April 9 – 13, 2001, Irvine, CA...............................................20
Acronym Definitions......................................................................................................................22
Communications Standards Review Copyright Policy....................................................................24
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REPORT OF Q4/15, XDSL NETWORK ACCESS TRANSCEIVERS,
RAPPORTEURS MEETING, APRIL 9 – 13, 2001, IRVINE, CA, USA
The scope of Q4/15 is the development of Recommendations related to digital subscriber line
(DSL). R. Stuart (3Com) is the Q4/15 Rapporteur. IC-000 is the document list. IC-001 is the
agenda. IC-002 is the report of the February 2001 Q4/15 Rapporteurs meeting at SG15 in Geneva,
Switzerland. IC-004 provides the Q4/15 Rapporteur meeting electronic document submission
guidelines. IC-005 is the Q4/15 attendance roster. Technical editor’s note: the issues addressed
in the papers below remain open unless otherwise indicated.
IC-068 is a notice that IBM has submitted a Patent Statement and Licensing Declaration (Annex 2
to TSB circular 245) to the TSB with Patent Policy Option 2 (paragraph 2.2) checked (nondiscriminatory basis and on reasonable terms and conditions). The database of statements is
available at: <http://www.itu.int/ITU-T/patent/>.
IC-089 (T. Starr, SBC; H. Sadjapour, AT&T; H. Taylor, BT) proposes to decide upon, specify, and
prepare for ITU Determination in October 2001 as many improvements as possible for ADSL
performance, robustness, diagnostics, power consumption, and backwards and forwards
interoperability. The following improvements are urgently needed and will greatly assist service
providers in making service available to a greater number of customers in a cost effective manner:
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Higher ADSL bit-rates for loops up to 15 kft, both downstream and upstream
Greater ADSL loop-reach for service rates of 384 kbit/s downstream and above
Improved robustness against bridged taps
Improved robustness against radio frequency ingress
Expanded and standardized ADSL loop diagnostics such as reporting loop conditions from the
far-end equipment
Reduced ADSL power consumption to permit higher equipment density, especially for
equipment at NGDLC-RTs
Improved clarity of standards to facilitate improved ADSL interoperability
G.gen, including G.lite.bis and G.dmt.bis
T. Cole (AMD) is the G.lite.bis Associate Rapporteur. IC-U18 is the G.lite.bis issues list, based
on contributions, discussion, and agreements as of the close of the February 2001 Geneva meeting.
IC-R18 is the G.lite.bis draft Recommendation. IC-A18 is the G.lite.bis work program.
F. Van der Putten (Alcatel) is the G.dmt.bis Associate Rapporteur. IC-U17r1 is the G.dmt.bis
issues list, based on contributions uploaded and discussed as of the close of the February 2001
SG15 meeting.
IC-R17 (F. Van der Putten, Alcatel, Editor) is the current draft of the G.dmt.bis Recommendation;
revision marks reflect the changes agreed at the Clearwater interim meeting in January. At the
August 2000 meeting, it was agreed that G.dmt.bis should reference other recommendations (e.g.,
G.lite.bis, existing, or to be created Recommendations) to avoid duplicating text in common with
G.lite.bis. In a few places, this G.dmt.bis draft indicates differences with G.lite.bis. Those
differences are only temporarily listed in this G.dmt.bis draft for clarification of the technical
developments within Q4/15; they will be moved to G.lite.bis when appropriate.
Performance Improvement Methods
IC-069 (E. Eleftheriou, S. Ölçer, IBM; M. Sorbara, M. Eyvazkhani, GlobeSpan) considers the
problem of bit-to-symbol mapping for LDPC coding in ADSL, and explores the merit of including
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uncoded information bits, along with code bits, for the selection of transmit symbols. It first shows
that, for bandwidth-efficient modulation, the inclusion of uncoded information bits allows higher net
coding gains to be achieved as compared to the case where symbol mapping is obtained via LDPC
code bits only. Second, it shows that for transmission over a channel with burst or impulse noise,
the uncoded bits are not more vulnerable to detection errors than the code bits. It concludes that
symbol mapping for large constellation sizes should employ code bits as well as uncoded bits.
IC-071 (E. Eleftheriou, S. Ölçer, IBM; M. Sorbara, M. Eyvazkhani, GlobeSpan) presents a new
reduced-complexity decoding algorithm for low-density parity-check codes that operates entirely in
the log-likelihood domain. The computationally expensive check-node updates of the sum-product
algorithm are simplified by using a difference-metric approach on a two-state trellis and by
employing the dual-max approximation. The dual-max approximation is further improved by using
a correction factor that allows the performance to approach that of full sum-product decoding.
IC-084 (A. Carlson, Broadcom) reports on the results of several simple simulations involving lowPAR signals. It considers the effects of interpolation, filtering, and inclusion of the cyclic prefix. It
was presented for information. It notes that when comparing absolute performance of various lowPAR signal proposals, results may vary by a few dB depending upon the detailed underlying
assumptions that are made in each case. At the same time, as a general rule it seems that a change
that decreases the PAR of a signal in a given case will decrease the PAR in most other cases as well.
IC-084 suggests that relative statements are more trustworthy than are absolute statements
concerning the PAR of a given class of signals.
IC-081 (D. Van Bruyssel, Alcatel) proposes, based on the ad hoc requirements, an architecture for
the advanced coding supporting a dual latency path configuration. It also proposes specific inner
and outer codes. This contribution focuses on the dual latency path case. A very important
supplementary requirement which is assumed, is that the first path is a low latency path (“Fast
path”) and the second path is a high latency path which needs improved protection against impulse
noise (“Slow path”). Possibly, the critical application supported on the fast path is interactive
gaming and on the slow path is video streaming.
It was agreed to open two questions: Shall the multi-level dual latency solution based on common
inner coding be mandatory in transmitters and, for the higher latency path, shall the use of
interleaving and Reed Solomon as in G.992 be mandatory as shown in Figure 3 of IC-081
(Proposed Architecture and Classes for Dual Latency Path Configuration)? Should the multi-level
dual latency solution with common inter code based on multi-level SCCC (2D or 4D) G.992.1
trellis as shown in Figure 3 and described in Section 4 (Proposed Coding Schemes for the Inner
Code) of IC-081 also be mandatory in transmitters?
IC-070 (E. Eleftheriou, X. Hu, S. Ölçer, IBM; M. Sorbara, M. Eyvazkhani, GlobeSpan) presents an
analytical study that allows comparison of the various schemes proposed for advanced coding in
G.dmt.bis and G.lite.bis on the basis of achievable performance. Results show that the channel
capacity of coded modulation schemes that employ Gray-labeling based signal mapping is higher
than that of coded modulation schemes using a set-partitioning based labeling. IC-070 determines
the impact of various Gray-labeling techniques on system performance, giving an indication of
appropriate code rates to be used with each approach. It describes the system model on which
computations of the performance limits are based, and provides numerical results allowing a
comparison of different labeling strategies adopted for coded modulation.
Conformance Testing
IC-029 (A. Ginesi, Catena) propose definition of a set of test cases where the maximum transmit
showtime PSD levels are specified as targets, given a desired data rate. This would allow testing of
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the fine gain-based power cut back for excess margin minimization. The objective is to enforce a
more consistent application of this power cut back method, which has the benefits of lowering the
unnecessary high level of interference into adjacent lines along with transmitter power consumption
reduction.
It was agreed that G.lite.bis shall specify a set of test cases where maximum transmit showtime
PSD levels are specified as targets, given desired data rates.
Coding
IC-033 (Q. Jin, Mitel Semiconductor) proposes a turbo trellis-coded modulation method for DMT
based xDSL system. The method uses turbo trellis coded modulation and Reed-Solomon
interleaver to achieve less than 3 dB away from Shannon capacity. The turbo structure is simple
and suitable for high data rate transmission such as VDSL.
IC-034 (Q. Jin, Mitel Semiconductor) compares the multi-level turbo coding method and the fullturbo coding method for G.vdsl and G.dmt.bis, and G.lite.bis. It concludes that the multi-level
coding scheme has performance advantages for high constellation and is less complex in general.
On the other hand, the full-coding method is suitable for low constellation and has much smaller
latency requirements, especially for low data rate transmission. IC-034 was presented for
information.
IC-024 (B. Li, A. Deczky, Catena) proposes the “multi-level” turbo TCM concatenated with RS
codes as the advanced coding method for the G.dmt.bis and G.lite.bis standards. In this proposed
advanced coding method, the RS encoder and “multi-level” turbo TCM encoder are separated by
an interleaver. This interleaver randomizes any burst errors and then the randomized errors can be
corrected by the RS decoder. See IC-025r1, below, for related agreements reached.
IC-027 (B. Li, A. Deczky, A. Ginesi, Catena) compares the data rates of “full” turbo TCM with
“multi-level” turbo TCM schemes in three real ADSL loops for both upstream and downstream.
It reports that both schemes provide close to the same performance throughout the three test cases.
But as the implementation of the “multi-level” turbo scheme is much less complex, it proposes that
the “multi-level” coding technique be adopted for advanced coding in both G.dmt.bis and
G.lite.bis. It also proposes that the number of bits coded be 2 for even constellations and 3 for odd
constellations, as per BI-090r1A, Turbo TCM scheme with low decoding complexity (B. Li, A.
Deczky, Catena, Q4/15 Bangalore, October 2000).
IC-026r1 (B. Li, A. Deczky, Catena) illustrates the existence of a parity bit mismatch problem for
the turbo TCM schemes using a fixed interleaver size. In the ADSL application, a DMT
modulation scheme is used. The receiver measures the signal-to-noise ratio (SNR), and does the bit
allocation for all the sub-carriers according to its SNR value. Therefore the bit loading is different
from sub-carrier to sub-carrier, and data rates are different for different loops. From the point of
view of the turbo code design, it is important and desirable to understand whether the interleaver
size should be fixed or flexible to be aligned with DMT symbols. IC-026 analyzes the parity bit
mismatch problem and shows that there will be some performance degradation for turbo TCM
using fixed interleaver size. It proposes that the interleaver size for turbo TCM not be fixed, and
that the interleaver size for turbo TCM be a multiple of DMT symbols.
IC-041 (A. Torres, V. Demjanenko, F. Hirzel, Vocal Technologies) proposes that the size of the
interleaver be fixed to an integer number of DMT symbols to take the maximum advantage of the
turbo code principle and to avoid degradation of the high order constellations.
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IC-042 (S. Abbas, Centillium; S. Heidari, Ikanos) proposes to independently enable trellis coding
in G.992.1 in each direction. Currently, the trellis coding option is always enabled in both
directions. Yet the benefit of trellis coding is not necessarily equal in upstream and downstream
directions. Thus a mechanism to enable this option in each direction independently is desirable.
IC-043© (S. Abbas, Centillium) proposes that trellis coding be mandatory for both G.dmt.bis and
G.lite.bis in the downstream and upstream direction. Advanced coding to gain an extra 2-3 dB
should consider the reuse of Reed Solomon and trellis coding as part of the complete scheme to
help reduce the overall complexity of the ADSL modems. Finally, trellis coding should be
improved to increase the net coding gain for long loops.
It was agreed that if section 0 (advanced coding gain) is not accepted into the main body of
G.lite.bis, Q4/15 shall mandate G.992.1 trellis coding up/down tx/rx, independently enabled by the
receiver during initialization in the upstream and downstream direction.
IC-061 (W. Farrell, iCODING Technology; D. Langston, SigmaTel) summarizes current options
and issues affecting the selection of a convolutional-based turbo coding scheme as the advanced
coding solution to G.dmt.bis and G.lite.bis. The most suitable coding scheme will depend on the
relative importance of factors such as hardware and software complexity, coding gain at short and
long loop channels, impulse noise protection, and simplicity of design. Given each of these
considerations, IC-061 details the most appropriate selection for each, and concludes that the multilevel scheme appears to be the most versatile, especially if a triple code is used, which results in a
very low complexity solution. The two main faults of the multi-level scheme are that it does not
perform as well for long loop channels and it does not provide the same impulse noise protection.
However its advantages of reduced complexity and coding gain performance over a large range of
loop lengths and latencies mean it is likely to be the preferred solution.
The most viable of full coding solutions is the triple code solution, which results in only 2.2 times
the complexity of the multi-level double scheme (not including the RS decoder, required for the
multi-level system). It also provides greater performance for long loops (approximately 1 dB,
depending on the latency) to extend the reach of the service, and at the same time provides greater
impulse noise protection.
IC-023 (A. Ginesi, A. Deczky, Catena) presents a proposal for testing improved coding gain
schemes with real loops. All the current tests required to assess and compare performance of new
coding schemes are quite abstract as they just specify a fictitious SNR profile and ask for coding
gain results. To quantitatively appreciate the real benefits of a new coding structure, it proposes to
add a set of real loop tests where achievable data rate is reported instead of net coding gain. Two of
the three loops proposed are part of agreed tests for performance targets: the 12 kft – 26 AWG and
the 18 kft –24 AWG loops. The third test is a lower data rate test and has been added to fully cover
the data rate range of interest, for high to low bit rates. It is a 17 kft – 26 AWG loop. All these
loops are supposed to have a noise source of –140 dBm/Hz AWGN and 24 DSL cross-talk
disturbers.
IC-040 (A. Torres, V. Demjanenko, F. Hirzel, Vocal Technologies) provides details on the
Euclidean distance, gain/loss, and PAR considerations of the non-square QAM constellations with
independent I and Q, proposed in CF-038 (F. Hirzel, J. Torres, V. Demjanenko, Vocal
Technologies, Q4/15 Clearwater, January 2001),
IC-025r1 (B. Li, A. Deczky, Catena) discusses the feasibility of using advanced coding without
Reed-Solomon codes for impulse noise protection. To achieve the same impulse noise protection
performance, advanced coding without RS code needs a frame size that is equivalent to the
interleaver size of advanced coding with RS code. This will lead to a huge RAM requirement that is
not feasible to implement. Using advanced coding concatenated with RS code is a good solution.
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IC-025 proposes that turbo codes replace the current TCM while the current RS codes are kept as
outer codes.
It was agreed that G.lite-bis advanced coding scheme shall consist of replacing the G.992.1 trellis
code while keeping the current RS code as outer code as shown in IC-025r1 Fig. 2.
IC-035 (Q. Jin, Mitel Semiconductor; H. Sadjadpour, AT&T) proposes a general turbo coding
structure for a DMT based xDSL system; it includes both the multi-level coding method and the
full-coding method. Using this structure, users can determine how many bits should be coded in
each frequency subcarrier.
IC-076 (K. Chu, Conexant) addresses programmable trellis codes for ADSL. There has been
extensive discussion about incorporating advanced coding schemes into G.dmt.bis and G.lite.bis;
much of the discussion has been focused on the technical details of the various Turbo codes. But
there has been less discussion about what is needed for ADSL and how best to address this need.
Easier and more reliable deployment are the main reasons why improved performance is desirable.
Improving performance can make deployment of ADSL more robust and can improve data rate and
reach relative to current ADSL systems. IC-076 proposes to use programmable trellis coding for
the advanced coding scheme in G.dmt.bis and G.lite.bis. This programmable trellis coding scheme
has many advantages including simple encoding structure, and allows trade-offs between
performance and decoder complexity. The programmable trellis code fits directly into the existing
ADSL coding scheme; the 16-state Wei code used in legacy ADSL becomes a special case.
Further, it allows a trade-off between latency and performance, and increased flexibility without
introducing interoperability problems. Programmable trellis codes have been used successfully for
ANSI HDSL2, ITU G.991.2, and ETSI SDSL.
IC-085 (B. Rezvani, S. Heidari, Ikanos) presents a new approach for turbo coding for G.gen.bis
applications. The new approach addresses two important system parameters: 1) availability of fast
and interleaved path, and 2) good coding gain with minimal complexity. Higher performance is
reached by utilizing a channel permuter, and lower complexity is achieved by using a binary
encoder. Furthermore, the latency issue associated with turbo codes is addressed by passing the
fast data buffer.
Due to inherent delay associated with the interleaver / deinterleaver of turbo coding schemes, in this
proposal Turbo Trellis Coded modulation is solely used in the interleaved path. This method has
the advantage of having similar structure to Trellis Coded modulation of ADSL and therefore from
complexity point of view it is a known quantity. In order to reduce the complexity of decoding, IC085 proposes a binary convolutional coding which allows constructing a simpler trellis decoder.
Furthermore, by using a simple channel permuter, an increase in the performance is reached. The
Turbo Encoder interleaver’s size is proposed to be a programmable value between 1 to 4 kbits,
where the user may trade-off the complexity and latency for performance.
IC-088r1 (A. Deczky, Catena; M. Sorbara, GlobeSpan; S. Ölçer, IBM; W. Ferrell, iCODING; J.
A. Torres, Vocal) proposes, to narrow down code features for advanced coding, that the features
listed below be agreed for inclusion as mandatory for advanced coding in G.dmt.bis and G.lite.bis:
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Symbol mapping is based on per-dimension Gray labeling
Symbol mapping includes uncoded information bits in addition to coded bits [for small QAMconstellation size (e.g., 16-QAM and smaller), symbol mapping may include code bits only]
RS coding according to G.992.1 and G.992.2 is supported
Advanced coding scheme represents an inner code when concatenated with outer RS code
The block size of the advanced code is variable
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Modulation
IC-028 (A. Ginesi, A. Deczky, Catena) presents a proposal for exchanging information on the
presence of the first transmit signal image above the Nyquist frequency. Some current G.992.1 and
G.992.2 modems implement the transmitter (either the U/S or the D/S) with an IFFT size greater
than the one specified by the standard. If the images of the transmit signal are correctly regenerated
with period equal to the clock frequency of the standard IFFTs (276 kHz for U/S and 2208 kHz for
D/S), there is no difference; the transmit signal is exactly the same as the signal generated by a
standard-size IFFT. But this does not occur in some of the G.992.x modems. Even though this
does not compromise interoperability, if the receiver is not made aware of the way the transmit
signal is generated, inter-performance may be affected, particularly on short loops.
IC-028 proposes to have some information exchanged between ATU-R and ATU-C in G.hs to let
the receivers know how the transmit signals are being generated. This way the receiver can adapt its
signal processing algorithms to adequately process the received signal. In particular, the transmitter
should tell the receiver whether or not the transmit signal images with periodicity equal to the clock
of the Standard–size IFFT are being generated (through a Standard-size IFFT or with bigger size
IFFT plus image restoration). It also proposes that the spectrum beyond the Nyquist frequency be
either zero filled or contain the complex conjugate image of the base-band signal. It further
proposes that this information be exchanged well before the receiver equalizer is trained, preferably
during G.hs. To this end, it suggests, new G.hs code-points need to be defined; it shows a way to
implement the required code-points in the standard information field at SPar(2) and NPar(3) levels.
It was agreed to exchange information about the presence or not of the first (complex conjugate)
image of the transmit signal above the Nyquist frequency between the ATU-R and ATU-C, prior to
training the receiver equalizer.
Initialization
IC-050 (M. T. Arvind, A. Verma, Sasken) proposes a simple procedure for deciding the U/S and
D/S transmit power levels during initialization. The procedure can be used to implement politeness
cutback, spectral shaping, and crosstalk control, as well as attenuation of particular carriers. It is in
line with the current set of agreements on initialization.
IC-049 (A. Ginesi, S. McClennon, Catena) proposes to apply the loop dependent power control
mechanism described in G.991.1 (G.shdsl) to G.lite.bis and G.dmt.bis modems. It is recognized
that a power/PSD limitation of the transmit signal in G.lite.bis and G.dmt.bis provides the benefit of
lower power consumption in the transmitters (both ATU-C and ATU-R) and lower cross-talk into
adjacent pairs. In a DLC environment, this can be beneficial for the downstream channel, as ADSL
from the cabinet may be running in parallel with ADSL from the CO. In a self-FEXT limited
environment, a loop length dependent power control for upstream does provide significant benefits
as it improves and stabilizes the performance across the subscriber base (See MA-073, Short loop
upstream power control in FEXT-limited ADSL Systems, Nortel Networks, Q4/15 Melbourne,
Australia, March-April 1999).
IC-051 (M. T. Arvind, A. Verma, Sasken) proposes modifications to the initialization proposal
(section 0.4.2 of IC-R17) to make the proposal consistent with the current set of agreements on
initialization. The modifications also address the editor’s notes.
IC-064 (M. T. Arvind, A. Verma, Sasken) presents a comparative study of the following current
proposals for G.dmt.bis and G.lite.bis initialization: Section 0.4.2 of draft G.dmt.bis (IC-051)
(Sasken), D.28 (Aware), BI-091 (Nortel) and BI-099 (Samsung). It takes the agreed set of
requirements in Section 0.4 as criteria for comparison. It compares power cutback, training, and
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exchange stages of initialization, and considers overall features, like flexibility, robustness, and
length of initialization. This comparison was presented for information.
IC-054 (K. Harris, M. Wingrove, Nortel) contrasts and analyzes a number of different initialization
proposals, and makes suggestions for each. Due to the complexity of initialization it is difficult to
analyze the sequence as a whole, but most of the innovations proposed can be analyzed individually.
IC-054 contrasts the positions found in:
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BI-091, New initialization sequence for G.lite.bis and G.gen.bis (K. Harris, Nortel)
FI-130R2, A shortened full initialization approach for fast retrain (A. Ginesi, Nortel)
CF-070, Initialization proposal for G.dmt.bis and G.lite.bis (M. Arvind, A. Verma, Sasken)
BI-099, Basic structure of adaptive length initialization sequence for G.dmt.bis and G.lite.bis
(M. Park, Samsung AIT)
D.28, Proposals for initialization (M. Tzannes, Aware, SG15, February 2001)
BI-096, A simplified initialization procedure for G.lite.bis and G.dmt.bis (B. Barazesh, R.
Banerjea, Lucent)
BI-111, Report of the Ad hoc on Initialization (T. Cole, AMD; F. Van der Putten, Alcatel)
CF-034, Interpretation of spectrum shaping parameters exchanged in handshake to support
operation with a notched transmit PSD (I. Sharfer, Tioga)
It focuses on the following areas:
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Timing recovery
Adaptive length equalization and capacity estimation
Determination of upstream and downstream cutback
Messaging of Bi and Gi Information
Rate adaptation
Fast retrain
Communication of reduction of REVERB tones
In the January 2001, Clearwater meeting, it was agreed to improve the randomness of MEDLEY.
This new PRBS (Pseudo Random Binary Sequence) generator proposed in IC-030 (A. Ginesi, A.
Deczky, Catena) re-uses the structure of the data path scrambler used in G.lite and G.dmt modems.
The 23-bit shift register would be used for both R-MEDLEY and C-MEDLEY, and would generate
a bit stream with period 223 -1=8388607, i.e., ~16384 DMT signal periods for C-MEDLEY and
~131072 DMT signal periods for R-MEDLEY.
IC-094 (Alcatel, Catena, Nortel, Sasken) presents a multi-company consensus proposal for
G.dmt.bis and G.lite.bis initialization. It was agreed to adopt IC-094 as working text (and remove
the proposed text from section 0).
IC-022 (A. Ginesi, A. Deczky, Catena) discusses bandwidth requirements of the REVERB signals
used for equalizer training. It is well known that the choice of bandwidth of the REVERB signals
(both for U/S and D/S) may have a great impact on the performance of DMT modems. In G.992.x
standards the set of tones to be used during REVERB is transmitter-discretionary, within the
recommendation that “…it should be sufficiently wide-band in order to probe the transmission
channel in such a way that the REVERB signal does not sufficiently lengthen the estimated channel
impulse response….” IC-022 proposes that:
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8
The set of transmitted tones to be used during REVERB shall be determined by the receiver, for
each direction.
The transmitter shall also be able to transmit the Nyquist bin. A TBD real number shall be used
to modulate the Nyquist bin.
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•
The cut back that can be applied to any tone during REVERB shall be less than TBD dB. The
max cut back shall be set to allow proper channel identification.
Framing
IC-038 (J. Carlo, B. Wiseman, K. Kratochwil, Texas Instruments) lists current agreements on
mandatory and optional framing parameters and proposes that the G.dmt.bis and G.lite.bis
standards agree to mandatory and optional framing parameters. Specifically, it proposes the
following:
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Mandatory FEC redundancy values on non-interleaved latency path shall be zero.
Mandatory FEC redundancy values on interleaved latency path shall be 0, 2, 4, 6, 8, 10, 12, 14,
16.
Mandatory Mp values shall be 1, 2, 4, 8, and 16.
Mandatory Bp,n values shall be integer and satisfy: 1 ≤ ∑ p,n Bp,n ≤ 255
Mandatory Tp values shall be all positive integers less than or equal to 68.
Mandatory support of two latency paths is TBD.
In multiple latency mode, the interleaved latency path shall have the highest latency path index
p = (N LP –1).
Do not restrict the interleaver length to be the same value as the length of the codeword; instead,
define the interleaving length according to G.992.1.
It was agreed that G.lite.bis framing requires support of R= 0, 2, 4, 6, 8, 10, 12, 14, 16 for the
mandatory latency path in each direction (tx/rx).
IC-044© (S. Abbas, Centillium) proposes that the mandatory interleaver memory requirements be
reduced in each direction for the second generation ADSL modems. Due to interactive gaming and
similar applications that customers are running on the ADSL modems, undesirable delay due to
interleaving is being experienced. Therefore, a number of service providers are not using the
required (mandatory) long interleaver depths. Current ADSL modems support up to D=64 in the
downstream and up to D=16 in the upstream directions. For a maximum interleaving block size of
256 bytes, this corresponds to a significant amount of memory, which requirement, in turn,
translates into a significant portion of the ADSL chipset die size (for one chip memory
implementations) and power consumption of the ADSL chip sets. This requirement appears to be
excessive and should be reduced to a reasonable number to bring down the power consumption and
complexity of the ADSL modems. Reduction in memory requirement may impact the impulse
noise immunity for short-loop high bit rate connections, where largest values of D and RS
codeword length are practically used, and consequently require largest memory. The exact number
for reduced memory should be studied further.
IC-052 (F. Van der Putten, K. Demuynck, Alcatel) proposes a mapping of overhead bytes into the
sync-byte of each MUX data-frame, defining two additional parameters. It also proposes a layout
for the indicator bits. Until now, it has been agreed that the CRC is sent in the same latency path it
relates to (BI-106, Framing and overhead ad hoc report, Q4/15 Bangalore, October 2000). The
other overhead information is carried in a bit-oriented structure or by messages. Some proposals
have already tried to define a mapping of the overhead into the framing structure. But as they all
still refer to “Fast” and “Interleaved” path (especially when defining the indicator bits), they
cannot be used for the second generation ADSL modem as these paths are no longer explicitly
defined. IC-051 proposes an approach that can be used when a maximum of four latency paths are
defined.
IC-037 (D. Mahesh, Sasken Communication Technologies) considers the issue of carrying packets
over ADSL service, based on the generic ADSL TC architecture. It proposes that the TPS-TC
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layers provide a method to carry packet-based traffic over the ADSL physical layer. IETF RFC1662 (PPP in HDLC-like Framing, July 1994) recommends specifications to carry packets over
bit-oriented and byte-oriented synchronous links. RFC-1662 recommends the usage of an HDLClike framing structure to transport PPP packets; this method can be extended to carry packets over
the ADSL link.
It was agreed that G.lite.bis should (as a goal) have shared text for packet TPS-TC with G.vdsl.
IC-039 (J. Carlo, B. Wiseman, F. Chow, K. Kratochwil, Texas Instruments) proposes a framing
scheme for the overhead channel, which combines the advantages of proposals BI-094, ADSL
overhead structure with a single and with multiple PMS-TC functions (F. Van der Putten, Alcatel),
and BI-048, Proposal for a multi-latency framing for support of simultaneous transport of data and
channelized voice over ADSL bis modems (ADC, Aware, Centillium, Cisco, Ikanos, Legerity,
Siemens, SigmaTel, Texas Instruments), from the Q4/15 October 2000 meeting.
The proposed framing scheme decouples the insertion of overhead bytes from the Mux Data Frame
and thus achieves that no frame overhead rate is wasted on latency paths that only carry CRC and
path-related Indicator Bits in the overhead channel. It proposes that if the ADSL modem operates
in multiple latency mode and one latency path is used to carry CVoDSL, then the HDLC-framed
overhead data is carried in the latency path that carries CVoDSL. It proposes that support of all
positive integers less than or equal to 68 for parameter Tp is mandatory. (See also companion
proposal IC-038, above.) This proposed framing of the overhead channel satisfies all the
requirements outlined in BI-106, the Framing and Overhead ad hoc report.
It was agreed to amend the Q4/15 framing structure to include the control parameter Tp on each
latency path as shown in Figure 1 of IC-039 (Proposed framing of the overhead channel for dual
latency mode and two frame bearers). Valid range of Tp is ≥1.
OAM
IC-053r1 (K. Harris, Nortel) proposes the addition of the physical layer protocol for ADSL and
ADSL.lite to retrieve from ATU-R during showtime the in-band downstream channel frequency
response H(f), the noise N(f) measured at initialization, and the signal to noise ratio SNR(f)
measured during showtime on a per bin basis. It also proposes to allow for retrieval of similar inband information in the upstream direction from ATU-C to enhance service maintenance and
diagnostics. The diagnostic parameters currently defined in G.992.1 and G.992.2 are not specific
enough for accurately determining line quality under certain circumstances.
Two agreements were reached: A mechanism shall be provided to transfer information from which
the channel transfer function per bin and noise PSD per bin can be derived into the ATU-C MIB.
A mechanism shall be provided to transfer information from which the ATU-C and ATU-R
showtime SNR per bin can be derived into the ATU-C MIB upon request.
Q-Mode (Quiescent Mode)
IC-036 (M. Tzannes, A. Friedmann, Aware) describes a receiver-transparent Q-mode that allows
the transmitter to enter and exit Q-mode as desired while the receiver is unaware of the Q-mode
state, and proposes that it be specified for G.dmt.bis and G.lite.bis. The benefit of this proposal is
that it provides all the power saving advantages of the current Q-mode proposals without requiring
the receiver to implement the complexities of detecting the entry and exit Q-mode symbols.
Furthermore, it is compatible with the current Q-mode proposals on several issues, including
allowing the transmitter to define the Q-mode signal and allowing a receiver to choose to operate as
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described in the current Q-mode proposal in G.dmt.bis (i.e., detecting the entry and exit Q-mode
symbols).
It was agreed that if G.lite-bis specifies Q-mode, the scrambler should be removed from the PMSTC layer and be replaced by an equivalent function in the PMD layer
IC-048 (P. Reusens, D. Van Bruyssel, M. Beck, Alcatel) describes a method to obtain a Q-mode
“filler” symbol resembling REVERB, with a reduced peak-to-average ratio (PAR). This method
optimizes the PAR of the Q-mode signal while conserving pure 4-QAM constellation points on all
carriers, thus allowing simple detection of the Q-mode and simple phase-locking at the receiver
side. Through the reduced PAR, the power dissipation at the transmitter side will be considerably
lower during Q-mode than during regular showtime.
It was agreed that the definition of a tolerance (TBD) on the amplitude only for the stationary and
non-stationary signals shall be added to the proposal as an additional proposal to that agreed in IC062r1.
IC-062r1 (I. Sharfer, Tioga) proposes a detector for the flexible semi-stationary Q-mode signal,
previously proposed as a means of reducing the non-stationary interference effects while allowing
significant power saving at the transmitter. IC-062r1 also shows several results of performance
analysis; these results indicate that the proposed detector can reliably distinguish between the Qmode signal and the normal showtime signal. It also makes some observations on the required
number of subcarriers and the distortion level.
It was agreed that the proposal be updated with the tolerance on the Q-mode signal to be a
specification on the maximum allowed signal-to-distortion ratio as defined in IC-062 section 2.2
(False alarm probabilities for a fixed miss probability).
IC-063 (R. Verbin, Tioga) presents a Q-mode signal example that combines the two approaches to
design a Q-mode signal: using a general 4QAM signal, and adding deviations to the 4QAM Reverb
constellation points. The resulting signal has an extremely low PAR of 4.5 dB and “distortion”
low enough to allow reliable detection (as presented in IC-062r1).
IC-080 (G. Long, Centillium) considers that the most suitable Q-mode filler symbol should be
receiver transparent, should have low par that is achievable at flexible complexity, and should keep
the same average TX PSD as showtime to ensure stationary characteristics of the crosstalk it
generates. A number of other contributions address these considerations but none of them achieve
all of the above features simultaneously. IC-080 proposes the definition of a Q-mode filler signal
definition that exhibits all of the above features simultaneously.
IC-065© (B. Wiseman, A. Redfern, Texas Instruments) collects a series of issues that, it suggests,
must be addressed by proposed Q-mode protocol mechanisms. It was agreed to include the items
listed in IC-065© as goals for information to provide on Q-mode proposals.
IC-092r1 (A. Carlson, Broadcom) outlines Q-mode issues to facilitate agreement to various parts
of the Q-mode proposal currently recorded in Section 0 of G.dmt.bis, and makes suggestions for
their resolution. It also proposes that:
•
•
False alarm and miss probabilities be specified for successful transitions into and out of Qmode.
While receiver is in Q-mode, each receive TPS-TC passes idle data appropriate to that TPS-TC
across its interface.
These proposals were added to the open issues list.
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IC-096r1 is the report of the Q-mode framing ad hoc group that met to discuss the TPS-TC and
PMS-TC changes needed to support the Q-mode proposal; it includes recommended text to be
added to Section 0 of G.lite.bis. The following companies attended: Texas Instruments, Broadcom,
Tioga, Lucent, Legerity, Alcatel, Aware, Intel, Centillium, and Analog Devices. The agreements
reached are:
1. TPS-TC requirements for Q-mode proposal
•
•
•
•
The transmit TPS-TC shall generate an all zero bearer channel if no user data are available
for transmission at the V reference point.
For a packet mode TPS-TC investigate “HDLC suspend/abort mode.”
For the general STM TPS-TC, it is not clear how to do Q-mode.
It is appears to be possible for the CVoDSL STM TPS-TC but the group did not
recommend a method.
2. PMS-TC requirements for Q-mode proposal
•
•
The PMS-TC shall pass all zero symbol data to the PMD when all zero data are received
from the TPS-TC (no user data at the V reference point) and no overhead information is
available for transmission.
Input is needed for transmission of NTR during Q-mode.
POTS Splitter
IC-021 (E. Eckert, Nortel) requests a change to the POTS splitter signature resistance defined in
G.992.1 to align it with the definition contained in T1.413; it represents a consensus view of
T1E1.4. It was agreed that G.992.1 shall be modified through a corrigendum to show the
resistance included in the signature test termination of the CO splitter with a value of 33 kohm
(instead of 110 kohm).
Phone Line Compatibility
IC-067 (M. Maranhao, M. Russel, Cisco) discusses the issue of sealing/wetting current, which has
received attention recently within a number of standards groups. The purported benefits of sealing
current are based on conventional wisdom from deployments of older technologies; they are not
based on real evidence of its impact on current xDSL technologies. Furthermore, the current
requirements are inconsistent across different sets of standards/draft standards.
IC-067 reports on the results found in the technical literature regarding cable splices, splice
deterioration due to exposure to contaminants, contact resistance, the impact of contact resistance
variation in data transmission, and sealing/wetting current. It presents evidence, based on
experimental results in a sample of phone companies’ loops, that only a relatively small percentage
of loops are actually affected by any form of sealing current. Also, 75% of junctions remain
unaffected when exposed to accelerated corrosive conditions. Results reported in the technical
literature show that sealing currents of the order of milliamperes still result in varying contact
resistances of a level that causes unreliable performance of analog modems, ISDN transceivers, and
DSL transceivers operating at 800 kbit/s. While no experiments have been done on the effects of
changes in contact resistance on other technologies like G.shdsl and ADSL, similar results can be
expected, based on:
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•
•
Evidence remained consistent across three different technologies: analog modems, ISDN, and
DSL operating at 800 kbit/s
The higher bandwidth and bandwidth efficiency of these newer technologies would make them
even more susceptible to changes in contact resistance
IC-067 concludes that that further study is needed before the appropriate requirements, if any, for
wetting current for current xDSL technologies under consideration can be quantified.
G.shdsl.bis
S. Blackwell (Centillium) is the G.shdsl Associate Rapporteur. IC-A15r1 is the G.shdsl agenda
and work plan. IC-R15© is the final draft text of Recommendation G.991.2 - Single-pair highspeed digital subscriber line (SHDSL) transceivers. IC-U15r2 is the updated issues list for
G.shdsl.bis; it reflects contributions to this meeting.
Test Measurements
IC-032 (R. Goodson, Adtran) proposes additions to G.991.2 §11.4.3 (Total Transmit Power
Requirement), allowing for measurement of transmit power in either data mode or activation mode.
It also includes text that clarifies the transmit power levels required during activation mode, and
proposes that this text be included in the G.shdsl Implementers Guide.
IC-057 (R. Goodson, Adtran) proposes additions to the test circuit calibration. The G.shdsl text
specifying the test circuit calibration specifies a very strict return loss, which is very difficult to
satisfy simultaneously at low and high frequencies. IC-057 proposes that a test circuit return loss
which obeys the specification of 11.4.2 (Test Circuit Calibration) in the 3 kHz to 3 MHz range be
acceptable.
IC-058 (R. Goodson, Adtran) discusses some typographical errors in G.991.2 paragraph B.3.5.6
(Measurement of Crosstalk Noise Margin), and proposes corrections required to reconcile G.shdsl
with ETSI SDSL.
IC-083 (S. Blackwell, Centillium) proposes to align Annex B (Regional Requirements - Region 2)
with Annex A (Regional Requirements - Region 1) by defining calibration in Annex B the same
way as it is defined in Annex A; Annex B currently does not define noise margin calibration.
IC-090 (S. Blackwell, Centillium) is the report of the ad hoc meeting held during this Q4/15
meeting to discuss plans for document publications related to G.shdsl (G.991.2) and G.shdsl.bis.
The ad hoc was attended by representatives of Adtran, Aware, Broadcom, Centillium, Conexant,
Intel, and Virata. Discussion centered on the mechanism for publishing corrections and changes to
the approved G.991.2 text. The ad hoc proposed development of a G.991.2 Implementers Guide ,
with papers proposing content delivered by August, and Q4/15 agreement on the Guide at the SG15
meeting in October 2001.
G.vdsl
S. Palm (Broadcom) is the G.vdsl Associate Rapporteur. IC-R11 is the draft G.vdsl
Recommendation. IC-U11 is the updated G.vdsl issues list, as of April 9, 2001. IC-A11 is the
G.vdsl agenda and work program.
IC-072 (T. Pollet, Alcatel) discusses the interpretation of the reference PSD for VDSL PBO. It
was previously agreed to express power back-off in VDSL in terms of a reference PSD, but the
current formulation in the standard contains an ambiguity that could lead to problems. In particular,
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there is no defense or robustness against overestimations of the electrical length. IC-072 proposes
to eliminate possible excessive crosstalk due to this by requiring that the receive PSD on any line
does not exceed the reference PSD.
G.pnt
J. Magill (Agere, formerly Lucent) is the G.pnt Associate Rapporteur. IC-U12 is the G.pnt
updated issues list; it includes the agreements from the February SG15 meeting. IC-R12 is the
draft Recommendation G.pnt.f, Phone line networking transceivers – Foundation.
IC-075 is a liaison from SG9 informing that they have initiated work under their Question 14 on
home networks in a broadband environment. The current draft of their developing requirements
Recommendation may be found at <http://ties.itu.int/u/tsg9/sg9/td/Geneva-06-032001/TD028r1.doc> (ITU password required). SG9 is aware that Q4/15 is also working on some
aspects of home networking. In the interest of harmonization of standardization efforts, SG9
invites Q4/15 to share the status of their work effort and to comment on the SG9 work. IC075attachment1© includes a copy of TD-028r1©, Draft Recommendation J.hnwr Home
Networking Requirements for Cable Based Services.
IC-091 is the proposed reply to the Q14/9 liaison in IC-075. Q4/15 informs that the SG15 work
on home networking was initiated in 1999 and is limited to home networks employing telephone
wiring. SG15 initiated this work partly in response to a concern over interference between home
networking equipment and DSL transceivers that may use the same wiring or pairs in the same
telephone cable. The result of SG15 work to date is Recommendation G.989.1, Home phone line
networking transceivers – Foundation. This Recommendation was approved by SG15 in February
2001, and is now available in pre-published form from the ITU: <http://www.itu.int/itudoc/itut/approved/g/g989-1.html>.
Q4/15 notes that in the SG9 draft Recommendation, Section 5.2, SG9 includes the use of telephone
wiring in the overall scope of their work. Q4/15 asks that SG9 make reference to G.989.1 when
they discuss the use of telephone wiring in their Recommendations, such that the specific
requirements of this application are understood.
Q4/15 notes they are continuing their work and currently have work items on full definition of
physical, MAC, and link layers, and requirements for isolation filters for use between the home
network and the access network.
G.hs.ter
L. Brown (Conexant) is the G.hs.ter Associate Rapporteur. IC-U16 is the G.hs.ter updated issues
list. IC-R16 is the draft revised Recommendation G.994.1, Handshake procedures for digital
subscriber line (DSL) transceivers.
IC-020 (Nortel, Adtran, Lucent, Mindspeed, ADC, SBC, Alcatel, GlobeSpan, 3Com) proposes
clarification of G.994.1 to specify that the vendor ID field contained in the identification field (I)
represents the equipment vendor, not the chip set provider. It also proposes to add additional code
points to identify the provider of the chip set or sub-system implementing the physical layer
functionality; both identifications are necessary. IC-020 also represents T1E1.4 consensus.
IC-082 (S. Palm, Broadcom) analyzes the situation described in IC-020 and proposes a technical
solution that does not require a revision of G.994.1. The physical layer chipset vendor ID
information would continue in Table 7. A new SPar(1) parameter would be added that supplements
the vendor ID information in Table 7/G.994.1. Table 9/G.994.1 contains the SPar(1) coding for
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the identification field; it would be the location of the high order bit for the supplemental
information. Table 9.12/G.994.1 would contain supplemental vendor ID information SPar(2)
coding. Table 9.12.1.X/G.994.1 would contain the eight octets of vendor ID information encoded
into eleven NPar(3) octets.
IC-031 is a liaison from the DSL Forum on the issue of the use of the vendor ID in G.994.1
(G.hs). The DSL Forum has identified a number of issues affecting interoperability raised by the
vendor ID; they ask that Q4/15 consider extending the vendor ID information that can be sent in
G.994.1 and work with the DSL Forum to regularize the use of vendor IDs in G.994.1. It is their
hope that once these issues are addressed by the ITU-T, the DSL Forum Testing and
Interoperability Group can develop appropriate tests and interoperability recommendations based
on the ITU-T’s recommendations for improvements in the definition and use of the vendor ID.
The next DSL Forum meeting will take place in Oslo, Norway, June 19 - 22, 2001.
IC-055 (K. Harris, Nortel) proposes expansion of the vendor ID. Both G.hs and the EOC register
of G.lite and G.dmt define a vendor ID field, but neither specifies the meaning of those fields. In
currently deployed modems, these fields have been inconsistently filled with either the chipset
vendor, the modem vendor, or left empty. Both the chipset vendor and the modem vendor are
desirable pieces of information, as is additional information on software and hardware versions.
IC-055 proposes a method of coding the complete set of desired parameters by the addition of
G.hs code points. This will allow a timely solution to the existing confusion and allow currently
deployed modems to continue to provide their level of performance and interoperability.
IC-056 (K. Harris, Nortel) proposes draft text for inclusion into G.hs to clarify and expand the use
of vendor ID information; it is based on the principles proposed in IC-055.
IC-059 (J. Mueller, 3Com) proposes codepoints for achieving the ITU clarification of the
interpretation of the vendor ID field for G.hs requested in IC-020r1. It requests that the vendor ID
information be signaled via the identification field and that the chipset vendor ID information be
signaled in the standard information field.
IC-093 (L. Brown, Conexant) is the report of the ad hoc group that met to discuss and resolve
issues associated with the G.994.1 vendor ID fields; it includes the reply to the communication
from the DSL Forum (IC-031). The ad hoc recognized that there are three aspects to the issue:
clarifications to the text of G.994.1, enhancing interoperability performance, and communication of
OA&M information. They came to the following conclusions:
Clarification of the G.994.1 text:
•
•
It was agreed to add the following text to § 9.3.3 of G.994.1:
– Note: This field should typically identify the vendor of the G.994.1 functionality, whether
implemented in hardware or software. It is not intended to indicate the system integrator.
– The only purpose of the country code is to identify the country of registry of the provider
code.
This text should be prepared as a corrigendum with the goal of application of the AAP
(Alternative Approval Procedures) at the October 2001 meeting of SG15.
Enhancing interoperability performance:
•
•
The ad hoc did not believe that expanding the vendor ID fields will help.
It was agreed that, where implementation flexibility exists that may affect interoperability
performance, a better course of action is to include code points within an xDSL branch of the
G.994.1 code tree (e.g., information relating to FFT length).
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•
Negotiation/selection of features that are beyond the scope of the xDSL Recommendations are
handled by the G.994.1 non-standard information field (§ 9.5).
OA&M information:
•
It was agreed that information such as equipment vendor name, model number, serial number,
and CLEI (Common Language Equipment Identification) code is important but falls within the
category of OA&M information, and is beyond the scope of G.994.1. This kind of information
should be handled within G.ploam and possibly exchanged over an embedded operations
channel.
G.ploam.bis
C. Storry (Alcatel Canada) is the G.ploam.bis Associate Rapporteur. IC-U19 is the updated issues
list for G.ploam.bis as of April 12, 2001.
G.test.ter
M. Tzannes (Aware) is the G.test.ter Associate Rapporteur. IC-R13 is the current draft of the
G.test Recommendation. G.test.bis (G.test 2001) was approved at the February 2001 ITU meeting.
IC-R13 contains the working text for the next version of G.test; at this point it only contains the
new working text that is to be added to G.test 2001. IC-U13 is the G.test issues list.
G.ref.ter
S. Abbas (Centillium) is the G.ref.ter Associate Rapporteur. IC-R14 is the draft G.ref.ter
Recommendation. IC-U14r1© is the G.ref.ter updated issues list, based on contributions and
agreements at the end of this meeting.
IC-097© is a draft liaison to the DSL Forum requesting permission to use material from approved
DSL Forum technical reports in the development of ITU-T Recommendations.
G.voice
C. Hansen (Intel) is the G.voice Associate Rapporteur. IC-U10© is the G.voice updated issues list.
IC-A10 is the G.voice agenda and work program. IC-R10 is the draft G.voice Recommendation.
IC-086 (C. Hansen, Intel) presents the minutes of the March 29, 2001, conference call on ATM and
G.voice. Attendees to this meeting were: Centillium, Intel, GlobeSpan, Nortel, Infineon, AMD,
Alcatel, Aware, Legerity, BT, Cisco, Qwest, Siemens, and Lucent. The focus of the meeting was to
consider how and what ATM functions to incorporate in G.voice.
The group discussed the general requirements for voice over ATM, which can be found in the DSL
Forum document TR-039, Requirements for VoDSL. It was noted that the ATM Forum document
AF-VMOA-0145.000, Voice and multimedia over ATM - Loop emulation service using AAL2, also
defines a mechanism to transport voice over ATM, but is not DSL-specific and does not employ
some of the new ADSL features Q4/15 is currently considering for G.adsl.bis. There are also
ETSI documents that relate to this topic (which a meeting attendee agreed to post to the reflector).
It was noted that the FS-VDSL group is interested in/considering such proposals.
Specifically, the group recognized that VoDSL in terms of ATM and PHY layer interaction may
support one of the following three architectures:
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1) “Big fat pipe”: The ADSL PHY layer is configured during initialization as one pipe. This could
be either as a fast or interleaved channel. This is a simple approach and can be easily supported
with current G.992.x. Q4/15 may need to describe this scenario better to ensure interoperability.
2) “N fat pipes”: In this mode the G.adsl.bis modem is configured during initialization to
simultaneously support both a fast and an interleaved channel. The concept is to use the fast
channel for the voice ATM traffic and the interleaved channel for data, video, and other.
3) “Dynamic allocation of bandwidth”: In this system architecture the DSL transceiver would
simultaneously support both fast and interleaved channels. But the bandwidth would be
dynamically allocated between the channels as required by the voice and other applications. This
may require the use of features considered for ADSL.bis, such as DRR and SRA.
It was agreed that the first action would be to accomplish baseline interoperability in architecture 1.
Once that is completed, work would follow on defining architectures 2 and 3. A concern was
voiced that any work beyond 1 would entail considerable effort, as interaction with other standards
would be necessary. The point was also raised that as DSL is increasingly being used for media
intensive applications, the potentially inefficient mode of architecture 1 will become wasteful. It was
also noted that schemes to optimize the PHY layer functions for voice should be considered for all
DSLs.
IC-045 (Centillium, Texas Instruments, ADC, Aware, Legerity) proposes updates to the text for a
common out-of-band mechanism to transport either CAS or CCS signaling messages across an
xDSL link for channelized voice, which was agreed for Section 0 of the G.voice in Geneva. An
HDLC-based frame structure is proposed to encapsulate both CAS and CCS signaling messages
associated with channelized voice. Use of an HDLC frame format provides CRC, multiplexing and
variable length framing benefits.
IC-095 (C. Hansen, Intel) is the report of the ad hoc on contribution IC-045. The ad hoc was
uncertain that the transport capacity with the IC-045 encapsulation is sufficient to support GR-303
and V.5 (remote terminal) requirements due to the HDLC overhead and transport capacity allocated
to STM signaling. Much discussion surrounded the applicability of mechanisms to support
various voice protocols already present in G.SHDSL to G.voice. It was noted by the group that
residential voice and business/SOHO voice applications may differ significantly in their
requirements and hence separate mechanisms may be required for G.voice and G.SHDSL.
The ad hoc recommended two agreements below and noted the one open issue:
Agreed: CCS signaling shall be carried over an octet oriented HDLC frame.
Agreed: Update section 0 in G.voice.
Open: Should CAS signaling be carried over an octet-oriented HDLC frame for ADSL?
IC-046 (S. Abbas, Centillium) proposes an update to the introductory working text for G.voice that
was agreed in the January 2001 Clearwater meeting (based on CF-044 [Texas Instruments, ADC,
Cisco, Centillium, Ikanos, Siemens]). The update delineates the three voice transport mechanisms
commonly known as Channelized Voice over DSL (CVoDSL), Voice over ATM (VoATM), and
Voice over IP (VoIP).
IC-047 (S. Abbas, Centillium) discusses the G.voice document structure and proposes updates to
the currently agreed table of contents. Currently, the main body is proposed to contain a general
introduction, classes of voice service functional interface, voice service elements definitions,
signaling mechanisms, supported TPS-TCs, and network interactions sections and annexes
containing TPS-TC specific descriptions. IC-047 proposes to reorganize the document structure
so that the main body contains the truly common information across all DSL Recommendations
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and VoDSL scenarios. Annexes for different flavors of VoDSL will describe the normative way to
support these across different DSL Recommendations.
IC-060r1 (P. Kelliher, Aware; I. Volkening, Infineon; V. Davar, Legerity; B. Wiseman, Texas
Instruments) defines a set of basic parameters (based on DSL Forum TR-039) that CVoDSL
G.voice must support in an xDSL modem to interoperate with a similarly defined xDSL modem.
IC-066© (S. Abbas, Centillium; B. Wiseman, Texas Instruments; R. Kroninger, ADC) proposes a
mechanism to transport channelized voice signaling and data across the ADSL STM-TC. The
ADSL STM-TC performs cross-layer communications by passing primitives with certain
parameters to the layers above and below. ADSL STM-TC configuration for channelized voice
should accommodate transport of both signaling and voice data. IC-066© proposes a fixed
bandwidth of 32 kbit/s for signaling transport. This capacity has been selected to minimize
complexity during rate adjustments and to provide sufficient throughput for both CAS and CCS
signaling messages.
IC-073 (L. Haster, Ericsson) addresses voice in the next generation network. It gives a brief
summary on the direction of future networks and how they will move from today’s TDM/circuitbased into more packet/cell-oriented networks. Such networks can be ATM or IP based.
The new packet-oriented network also needs new access types to work more efficiently. The
author’s impression of the G.voice terms of reference is to create a framework document that leads
to adoption of the exiting access types to the new network. The author notes this as fine, as long as
the transmission media is kept compatible.
IC-073 also notes that methods for existing PSTN/ISDN to interwork over packetized networks
already exist, e.g. VoDSL according to DSL Forum TR-039 (Version 1.1, March 2001):
Requirements for Voice over DSL and ATM Forum af-vmoa-0145.000 (July 2000): Voice and
Multimedia Over ATM-Loop Emulation Service Using AAL2.
IC-074 (submitted by Alcatel) is a copy of the publicly available TR-039 (DSL Forum); it was
provided to Q4/15 for information. TR-039 specifies an interoperable end-to-end architecture to
support broadband voice and data service over DSL systems operating in either packet-mode or
ATM-mode.
IC-077 (C. Hansen, Intel) presents the text from a selected number of ITU-T Recommendations
(G.114, G.174, G.176, and G.131) that consider the effect of delay introduced during voice
transmission that may bear upon the definition of G.voice; it was presented for information.
IC-078 (T. Cole, AMD; C. Hansen Intel) proposes a general system architecture as a basis for
further definition of the functionality contained in G.voice. The system model makes use of a
control and data interface into the TPS layer of DSL as well as new functions of the transceiver
layer that are under consideration for G.adsl.bis. IC-078 proposes this system model as a basis for
further discussion. It also presents three system modes of operation of increasing complexity
(similar to the three architectures offered under IC-086 above).
IC-079 (J. Carlo, B. Wiseman, G. Wunsch, Texas Instruments) proposes an updated mechanism
for dynamic rate repartitioning (DRR) for channelized voice over DSL (CVoDSL) systems; it was
proposed for information text to be added to the G.voice ADSL-specific section. VoDSL may
benefit from the re-allocation of bandwidth between voice and data streams at the ADSL physical
layer. Applications combining voice over DSL and data traffic benefit from the ability to share
bandwidth based on call demand. VoDSL solutions based on ATM or IP multiplexing perform
this bandwidth sharing at higher layers. CVoDSL solutions use the DSL physical layer to partition
voice and data traffic. To enable similar sharing of bandwidth between voice and data using
CVoDSL, DRR has been previously proposed (BI-071, B. Wiseman, Texas Instruments; Cisco,
18
Vol. 12.16 Copyright © CSR 2001
May 3, 2001
COMMUNICATIONS STANDARDS REVIEW
PairGain, Q4/15 Bangalore, October 2000), whereby the physical layer bandwidth is repartitioned
between voice and data streams based on call demand. The total physical layer bandwidth is not
changed.
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May 3, 2001
Vol. 12.16 Copyright © CSR 2001
19
COMMUNICATIONS STANDARDS REVIEW
Q4/15 Partial Attendance Roster, April 9 – 13, 2001, Irvine, CA
Dick Stuart, 3Com
Q4/15 Rapporteur
3Com
3Com
ADC Telecom
ADC Telecom
ADC Telecom
ADC Telecom
Adtran
Aethra Telecommunicaziom
Agere Systems
Alcatel
Alcatel
Alcatel
Alcatel
Alcatel
AMD
Analog Devices
AT&T
Aware
Aware
Aware
Broadcom
Broadcom
Broadcom Home Networking
BT
Catena Networks
Catena Networks
Centillium Communications
Centillium Communications
Cisco Systems
Cisco Systems
Conexant Systems
Conexant Systems
Conexant Systems
Conexant Systems
Copper Mountain Networks
Ericsson Telecom AB
Ericsson Telecom AB
Ericsson Telecom AB
ESS Technology Inc.
France Telecom R&D
GlobeSpan
Hitachi
IBM Zurich Res. Lab
ICoding Technology
Ikanos Communications
Infineon
Intel Corp.
Intel Corp.
Legerity Inc.
20
Joe Mueller
Richard Stuart
Chihchigng Tsai
Max Yang
Nelson Zagalsky
George Zimmerman
Richard Goodson
Roberto Flaiani
John Magill
Thierry Pollet
Chuck Storry
Danny Van Bruyssel
Frank Van der Putten
Ivo Van Gelder
Terry Cole
Vladimir Friedman
Hamid R. Sadjadpour
Arnon Friedman
Patrick Kellihor
Marcos Tzannes
Art Carlson
Miguel Peeters
Stephen Palm
Henry Taylor
Andrew Deczky
Alberto Ginesi
Syed Abbas
Steve Blackwell
Marcus Maranhao
Mark Russell
Rammy Bahalul
Les Brown
Keith Chu
George Eisler
Rick O’Connell
Stefan Allevad
Jan Bostrom
Mattias Hyll
Jordan Cookman
Hubert Mariotte
Massimo Sorbara
Yoichi Tsukioka
Sedat Ölçer
Wade Farrell
Behrooz Rezuani
Neal King
Chris Hansen
Kanna Krishnan
Vijay Davar
Vol. 12.16 Copyright © CSR 2001
May 3, 2001
COMMUNICATIONS STANDARDS REVIEW
Lucent Technologies
Lucent Technologies
Matsushita Graphic Communication Systems, Inc
Mitel Semiconductor
NEC
Next Level Communications
Nortel Networks (Canada)
NTT
PC-Tel
Sasken Communication Tech.
Sasken Communication Tech.
SBC
ST Microelectronics
Sumitomo Electric
Sumitumo Electric USA
Texas Instruments
Texas Instruments
Texas Instruments
Texas Instruments
Texas Instruments
Tioga Technologies Ltd.
Toshiba
Virata Corp.
Vocal Technologies Ltd.
Harry Mildonian
Carl Posthuma
Keiichi Tomita
Gary Jin
Hiroshi Okado
Todd Pett
Kate Harris
Koji Kikushima
Khashayar Mirfakhraei
M. T. Arvind
Amit Verma
Tom Starr
Stephania Boiocchi
Masami Ueda
Toshio Ooka
Steven Bieser
Jim Carlo
Konrad Kratochwil
Arthur Redfern
Grant Wunsch
Reuven Jlan
Yasumasa Kikunaga
Bijit Halder
Alberto Torres
Visit the CSR Web Pages: http://www.csrstds.com
The Web Pages include an on-line store (order subscriptions and reports), an updated
Telecom Acronym Definitions list, updated meeting schedules, background material on
telecom standards and CSR (the company), data sheets on both CSR technical journals, and
more.
May 3, 2001
Vol. 12.16 Copyright © CSR 2001
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COMMUNICATIONS STANDARDS REVIEW
ACRONYM DEFINITIONS
AAL
ADSL
ANSI
ATM
ATU-C
ATU-R
AWG
AWGN
CAS
CCS
CLEI
CO
CRC
CVoDSL
D/S
DLC
DMT
DRR
DSL
EOC
ETSI
FEC
FEXT
FFT
FS VDSL
HDLC
HDSL
ID
IETF
IFFT
IP
ISDN
ITU
ITU-T
LDPC
MAC
MIB
MUX
NGDLC
NTR
OA&M
OAM
PAR
PBO
PHY
PMD
PMS
PMS-TC
POTS
PPP
PSD
22
ATM Adaptation Layer
Asymmetric Digital Subscriber Line
American National Standards Institute
Asynchronous Transfer Mode
ADSL Transceiver Unit - Central Office End
ADSL Transceiver Unit - Remote Terminal End
American Wire Gauge
Additive White Gaussian Noise
Channel Associated Signaling
Common Channel Signaling
Common Language Equipment Identification
Central Office
Cyclic Redundancy Code
Channnelized VoDSL
Downstream
Digital Loop Carrier
Discrete MultiTone
Dynamic Rate Repartitioning
Digital Subscriber Line
Embedded Operations Channel
European Telecommunications Standards Institute
Frame Erasure Concealment
Far End Cross Talk
Fast Fourier Transform
Full Service VDSL (FSAN Committee)
High level Data Link Control
High-rate Digital Subscriber Line
Identification
Internet Engineering Task Force
Inverse Fast Fourier Transform
Internet Protocol
Integrated Services Digital Network
International Telecommunication Union
ITU Telecommunications Sector
Low Density Parity Check
Media Access Control
Management Information Base
Multiplexer
Next Generation Digital Loop Carrier
Network Timing Reference
Operations, Administration, and Maintenance
Operations, Administration, and Maintenance
Peak to Average Ratio
Power Back Off
Physical Layer
Physical Media Dependent layer
Physical Media Specific
Physical media Specific - Transmission Convergence
Plain Old Telephone Service
Point-to-Point Protocol
Power Spectral Density
Vol. 12.16 Copyright © CSR 2001
May 3, 2001
COMMUNICATIONS STANDARDS REVIEW
PSTN
QAM
RAM
RFC
RS
RT
RX
SDSL
SNR
SOHO
SRA
STM
TBD
TCM
TDM
TPS
TPS-TC
TSB
TX
U/S
VDSL
VoDSL
Public Switched Telephone Network
Quadrature Amplitude Modulation
Random Access Memory
Designation for an IETF Standard
Reed-Solomon (code)
Remote Terminal
Receive
Symmetrical high bit rate Digital Subscriber Line
Signal to Noise Ratio
Small Office Home Office
Seamless Rate Adaptation
Synchronous Transmission Mode
To be Determined
Trellis Coded Modulation
Time Division Multiplex
Transport Protocol Specific
Transport Protocol Specific-Transmission Convergence
Telecommunications Standardization Board (ITU)
Transmit
Upstream
Very high speed DSL
Voice over DSL
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Vol. 12.16 Copyright © CSR 2001
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COMMUNICATIONS STANDARDS REVIEW
COMMUNICATIONS STANDARDS REVIEW COPYRIGHT POLICY
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Year 2001 Standards Committee Meeting Schedules
Please see the updated calendar at http://www.csrstds.com/mtgs.html.
Communications Standards Review
regularly covers the following committee meetings:
TIA
TR-30
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Data Transmission Systems &
Equipment
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ITU-T
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xDSL, Access Technologies
Communications Standards Review (ISSN 1064-3907) reports are published within days after the related
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