Re: [10GBT] PAM12 performance
Dan,
I agree with you wholeheartedly.
To aid in reaching such a consensus, I look forward to answer any question,
address any issue or concern with the PAM8 proposal, either on the reflector
or in private, for anyone.
Best regards,
Sailesh Rao.
srao@phyten.com
>From: "Dove, Dan" <dan.dove@HP.COM>
>Reply-To: "IEEE P802.3an" <STDS-802-3-10GBT@LISTSERV.IEEE.ORG>
>To: STDS-802-3-10GBT@LISTSERV.IEEE.ORG
>Subject: Re: [10GBT] PAM12 performance
>Date: Wed, 25 Aug 2004 08:09:19 -0700
>
>Sailesh,
>
>Thanks for the clarification.
>
>I appreciate your concern for implementation issues. Ultimately the chips
>will land on PC boards with switching power supplies, clock distribution,
>high-frequency I/O busses, and imperfections that will make layout
>challenging. I too am concerned about some of the less tangible elements
>that are hard to quantify in a traditional signal analysis.
>
>All that said, I also have concerns about pragmatic need to make forward
>progress on the standard. I hope that the task force can fully digest these
>alternatives and make a good decision that allows progress to be made. I
>believe that lack of forward movement at the October meeting will
>effectively be a step backward as the glide slope for a UTP market
>opportunity is closing because fiber alternatives continue to drop in cost.
>
>Regards,
>
>Dan
>
> > -----Original Message-----
> > From: stds-802-3-10gbt@IEEE.ORG [mailto:stds-802-3-10gbt@IEEE.ORG]On
> > Behalf Of sailesh rao
> > Sent: Tuesday, August 24, 2004 6:20 PM
> > To: STDS-802-3-10GBT@listserv.ieee.org
> > Subject: Re: [10GBT] PAM12 performance
> >
> >
> > Dan,
> >
> > Scott is referring to theoretical comparisons of SNR margins based on
> > hypothetical PAM8 and PAM12 systems, operating under
> > worst-case conditions.
> > These SNR margins are computed relative to the separation of
> > levels at the
> > receiver output.
> >
> > I am referring to the EMI susceptibility margin that is computed with
> > respect to the amplitude of the noise at the input that can
> > be tolerated by
> > the receiver in an EMI range test.
> >
> > In any case, as was pointed out in a response to Hugh Barass
> > (and Scott
> > Powell), even this "slight" theoretical SNR margin advantage
> > that Scott
> > claims for PAM12 does not apply to the proposal on the table,
> > due to the
> > issues 3 through 5 that I listed in my summary e-mail.
> >
> > With respect to the implementation advantage for PAM12, it is
> > correct that
> > the 15% reduction in clock rate is helpful. However, on the
> > flip side, the
> > PAM12 receiver requires 3.9dB higher SNR at the output, which
> > implies that
> > the analog front end glitches and other AFE implementation
> > noises must be
> > kept 3.9dB lower for the PAM12 receiver. In my engineering
> > judgement based
> > on considerable lab experience with such AFE issues for a much simpler
> > problem, 1000BASE-T, the latter disadvantage strongly
> > outweighs the former
> > advantage, thus rendering PAM12 much more difficult to
> > implement than PAM8.
> >
> > Regards,
> > Sailesh.
> > srao@phyten.com
> >
> > >From: "Dove, Dan" <dan.dove@HP.COM>
> > >Reply-To: "IEEE P802.3an" <STDS-802-3-10GBT@listserv.ieee.org>
> > >To: STDS-802-3-10GBT@listserv.ieee.org
> > >Subject: Re: [10GBT] PAM12 performance
> > >Date: Mon, 23 Aug 2004 12:01:42 -0700
> > >
> > >Scott, Sailesh;
> > >
> > >Can I ask for a little help here? I am having a hard time with the
> > >following two phrases.
> > >
> > >Scott says;
> > > > At the risk of repeating myself, none of this changes the
> > > > fundamental fact
> > > > that it has been clearly shown that the PAM-8 and PAM-12
> > > > proposals have
> > > > similar performance (slight edge for PAM-12), but the PAM-12
> > > ^^^^^^^^^^^^^^^^^^^^^^^^
> > > > proposal offers
> > > > the advantage of a reduced operating frequency resulting in
> > > > reduced power
> > > > and reduced implementation difficulties.
> > >
> > >Sailesh says;
> > > > a). PAM8 has 3.9dB better susceptiibilty penalty than PAM12
> > > > over a 0m cable.
> > > > b). PAM8 has 3.2dB better susceptibility penalty than PAM12
> > > > over a 55m Cat-6
> > > > cable (existing Cat-6 cabling), c). PAM8 has 2.0dB better
> > > > susceptibility
> > > > penalty than PAM12 over a 100m Cat-6 cable (new Cat-6 cabling).
> > >
> > >Dan reads;
> > >
> > >PAM12 is slightly better than PAM8, but PAM8 is at least
> > 2.0dB better than
> > >PAM12!!!
> > >
> > >Even worse, that difference could be substantial if we are close to a
> > >regulatory or functional limit.
> > >
> > >Please... for those of us who really don't like conundrums, would you
> > >figure out a way to come to an agreement on the numbers?
> > Either one is
> > >better, or the other, but both can't be "better than the other".
> > >
> > >If it turns out that PAM8 has better theoretical
> > performance, but PAM12 is
> > >easier implemented and more likely to engender broad support... I can
> > >understand that. But both having better performance is too
> > puzzling for me.
> > >
> > >Thanks,
> > >
> > >Dan
> >
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