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RE: [EFM-Copper] RE: [EFM] (forward) progress in EFM copper


In an attempt to provide some clarification I would like to point out to
members of the reflector, that digital duplexing and line coding are
entirely separate issues.

Digital duplexing is the concept of digitizing a region of spectrum and
employing digital filtering techniques to ensure that out of band signal and
noise is not applied to the receiving demodulator. Whether or not this
demodulator employs FFT or QAM demodulation is an entirely separate matter.

The main requirement for digital duplexing is that you have an A to D
converter that has enough dynamic range and low enough quantization noise to
enable digital techniques to be employed.  I am not aware of any advantage
that DMT has in its ability to be digitized more readily, or with any less
complexity than single carrier. If you are aware of these advantages I would
be very interested to learn more.

Best Regards,


-----Original Message-----
[]On Behalf Of
Behrooz Rezvani
Sent: Tuesday, July 02, 2002 10:36 PM
To: Wei, Dong; daun@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc:;; 'Zagalsky,
Subject: Re: [EFM-Copper] RE: [EFM] (forward) progress in EFM copper


I am not sure whether you wanted to propose both short and long reach on the
same baseline. My understanding was that in order to avoid any further
mixing of long and short it is better to choose the long reach on its own
merits and the short reach on its own merits. If one uses the selection
Criteria that you and Barry are developing for long and the one Baryy has
developed for short range criteria we should be able to converge

I guess if VDSL-dmt is selected then it is easy to show that using digital
duplexing methods as described in VDSL-dmt, one can choose any band
splitting one needs regardless of where it is located in frequency domain


----- Original Message -----
From: "Wei, Dong" <wei@xxxxxxxxxxx>
To: <daun@xxxxxxxxxxxxxxxxxxxxxxxxx>
Cc: <>; <>; "'Zagalsky,
Nelson'" <Nelson_Zagalsky@xxxxxxx>
Sent: Monday, July 01, 2002 9:26 PM
Subject: [EFM-Copper] RE: [EFM] (forward) progress in EFM copper

> Daun,
> I have been waiting for your solution of a single port type for both
> short-reach and long-reach objectives. You have promised the EFM people
> "a single port type is very simple to accomplish". For this reason, Nelson
> even suggested that we should study such a single-port solution before we
> consider a second PHY for long reaches.
> Unfortunately, I was not able to find any of your presentation addressing
> such a "very simple" solution at the EFM web site. However, I was
> to find that you are supporting a baseline presentation that proposes a
> second port type. I am confused.
> Could you help me on what I am missing? Thanks!
> Dong Wei, Ph.D.
> Senior Member of Technical Staff - Broadband Access
> SBC Technology Resources, Inc.
> 9505 Arboretum Blvd., Austin, TX 78759 U.S.A.
> Phone: (512) 372-5615    Fax: (512) 372-5691
> Pager: (888) 734-6520
> -----Original Message-----
> From: Daun Langston [mailto:daun@xxxxxxxxxxxxxxxxxxxxxxxxx]
> Sent: Wednesday, June 12, 2002 5:35 PM
> To: 'O'Mahony, Barry'; daun@xxxxxxxxxxxxxxxxxxxxxxxxx; 'Hugh Barrass';
> Cc: Wei, Dong;
> Subject: RE: [EFM] (forward) progress in EFM copper
> Barry,
> I agree on most of your points
> --I like objectives.  I like many objectives for a single port.  I don't
> like two ports for the same wire with the same connectors that cannot
> speak to each other.  It is the same wire being used for both short and
> long haul.  We get two port types because we have two lengths as
> objectives on the same wire?  I want two objectives for the same port.
> --I heard you say that market forces required all slower standards to be
> included.  Why mix a passband modulation technology with a baseband
> technology as you suggested?  The two technologies are unrelated in
> implementation.  Why not select just QAM or dmt for both long and short
> haul.  If you choose the same technology for both long and short haul
> they interoperate freely.
> --dmt and QAM could do long and short haul and always allow POTS.  dmt
> and QAM pack more bits per hertz when compared to shdsl.  I understand
> doing both long haul and short haul in QAM is challenging.  Some tell me
> that if we roll in interoperability between long and short haul as a
> requirement, we will be making the coding decision.  Is this true?
> The question is: does the length of the wire make such a difference that
> two distinct markets can be defined?
> But why go to all trouble when it is so easy to make Ethernet work
> everywhere?
> I would like to see
> --One coding technology for long and short haul
> --The faster Phy always talks to the slower Phy at the slower rate
> --I want my Ethernet to work when I plug it in.
> Why is there an objection to an interoperability requirement between
> long and short haul?  It is so easy with dmt it can be called a freebee.
> Does an interoperability requirement select the line coding technology?
> Daun
> Daun Langston
> -----Original Message-----
> From:
> [] On Behalf Of O'Mahony,
> Barry
> Sent: Wednesday, June 12, 2002 10:00 AM
> To: 'daun@xxxxxxxxxxxxxxxxxxxxxxxxx'; 'Hugh Barrass';
> Cc:;
> Subject: RE: [EFM] (forward) progress in EFM copper
> Daun,
> --The optics folks have 5 or 6 objectives, don't they?  Having two
> objective
> for copper is perhaps one for than some would like, but as a way to
> reach
> consensus and move things forward it doesn't seem unprecedented.
> --Ethernet does not ensure interoperability between different port
> types.
> 'never has.  Although in some cases, market forces drive putting more
> than
> one port type on a given device.  This is similar to the way the
> situation
> was for voiceband modems, e.g., one could build a compliant V.34 modem
> without including V.32bis, but for most applications, market forces
> required
> V.32bis and all slower standards to be included.
> --This concept is being talked about as a "long reach objective" and a
> "short reach objective", but I think the distinction is more than just
> that.
> If you look at the presentations from Dong and other carrier
> representatives, what we're really talking about are two disctinct
> market
> segments.  Technically, this comes down to an objective for loops that
> require POTS overlay, and an objective for loops that don't.  This
> satisfies
> the distinct identity requirement, I believe.  The objective for the
> loops
> not requiring POTS overlay has a longer reach than the other one, so
> referring to the two objectives as "short reach" and "long reach" is a
> handy
> shorthand, that's all.
> --Barry
> -----Original Message-----
> From: Daun Langston [mailto:daun@xxxxxxxxxxxxxxxxxxxxxxxxx]
> Sent: Wednesday, June 12, 2002 7:47 AM
> To: 'Hugh Barrass';
> Cc:;
> Subject: RE: [EFM] (forward) progress in EFM copper
> Hugh,
> I strongly support this objective because it is reaches the distance I
> have been pushing for at 2500 meters and the rate is 500 Kbit slower
> than I have been asking for.  This is not hard to accomplish with the
> same port type.
> I do not support the intent for a separate port type to the PHY.  A
> separate port type is not Ethernet.  By a separate port type you are
> suggesting they would not interoperate.  Should we be the first copper
> Phy in Ethernet that does not interoperate?  Let's try to make it the
> same port type which suggests interoperability as some common rate.
> Two identical connectors in the same marketplace called Ethernet that do
> not interoperate at some basic speed is not really what folks now call
> Ethernet.  Ethernet always works at some level.
> Should we not try first to stick to the 802 rules?  I not just want to
> see this pass 802.3ah but I also want to see this pass 802.3.
> A single port type is very simple to accomplish.  Why don't we try this
> first?
> Daun.
> Daun Langston
> Metanoia Technologies, Inc.
> 127 Mill Street
> Grass Valley, CA 95945
> POB 1843 Nevada City, CA 95959-1843
> daun@xxxxxxxxxxxxxxxxxxxxxxxxx
> daun@xxxxxxxxxxxxxx
> daun@xxxxxxxxxxxxxxx (SMS)
> +1 530 639-0311 office
> +1 512 698-0311 cell
> +1 530 671-0511 fax
> +1 530 273-4093 design center
> -----Original Message-----
> From:
> [] On Behalf Of Hugh
> Barrass
> Sent: Wednesday, June 12, 2002 1:19 AM
> To:
> Cc:;
> Subject: [EFM] (forward) progress in EFM copper
> All,
> I have been considering the possibilities for progress on the copper
> baseline
> following the pointers that we got from the straw polls at the end of
> the Edinburgh
> interim. In particular I have been discussing a compromise with Dong Wei
> of SBC
> which would combine the short reach objective and VDSL baseline (which
> nearly
> achieved consensus) with a longer reach objective (and associated
> baseline) to
> satisfy the needs of service providers that Dong has articulated. As a
> result of
> this discussion we have formulated some ideas which we have also
> discussed with
> some other copperheads and have reached what I like to call:
> "The Great Copper Compromise"
> In essence this can be summarized as: leave the short reach objective
> and VDSL
> baseline unchanged; add a new objective for longer reach along with a
> readymade
> baseline solution that meets the objective.
> Based on discussions that I've had with a number of copper track (and
> other EFM)
> members I think that this compromise could add the support for two
> different
> applications and get above the 75% threshold required for progress.
> Clearly this
> will only work if we can guarantee that everyone who has an interest in
> either
> solution votes positively for both. I cannot emphasize enough that we
> must
> aggregate all of the positive votes in Vancouver to keep the EFM effort
> moving.
> Many people believe that the copper component is vital to the whole of
> EFM and that
> no market will develop for the fiber (or OAM) components of EFM if there
> is no
> copper edge.
> The objective that we have been discussing is:
> PHY for single pair non-loaded voice grade copper distance >= 2.7km
> speed >= 2Mbps
> full duplex.
> The intent is that this would be a separate port type to the PHY which
> meets the
> existing objective.
> Dong Wei has agreed to lead the development of a presentation which
> could be
> adopted as a baseline meeting this objective. It is crucial that we get
> maximum
> support for this compromise, that means that we should attempt to
> maximize the
> number of people who review and support Dong's presentation. Please
> could you all
> consider working with Wei and adding your name as a supporter of his
> presentation.
> I will arrange a conference call (probably June 24th) before the
> submission
> deadline
> With thanks for your attention,
> Hugh.