Re: [10GBT] Updated Tables
Vivek,
In that case, you need to penalize 0.5dB for the PAM12 proposal as well. I
don't consider the 1E13 bit simulation to be indicative of a 1E-12 BER. I've
seen how error events can occur in LDPC simulations - you have 1E13 bits
simulated with 0 errors and splat, you get a single frame with 60bits in
error, thus pushing the BER down to 6E-12. Therefore, until there are at
least 20 frame errors counted in a BER estimate, I'm skeptical of the
estimate.
Or, leave the PAM8 SNR requirement at 19.9dB.
Sailesh.
>From: Vivek Telang <vivek@VITESSE.COM>
>Reply-To: "IEEE P802.3an" <STDS-802-3-10GBT@listserv.ieee.org>
>To: STDS-802-3-10GBT@listserv.ieee.org
>Subject: Re: [10GBT] Updated Tables
>Date: Mon, 19 Jul 2004 21:07:31 -0500
>
>Sailesh,
>
>OK, for the sake of my simulations, I am going to assume your worst-case
>required SNR (from your earlier email) of 20.4dB, but ..., I'll hold the
>extra 0.5dB in "escrow", returnable in full to you, when either your sims
>or Amir Mezer's sims prove that the BER=1e-12 can in fact be achieved at
>19.9dB.
>Come on now, that's fair.
>
>Vivek
>
>-----Original Message-----
>From: stds-802-3-10gbt@ieee.org [mailto:stds-802-3-10gbt@ieee.org]On
>Behalf Of sailesh rao
>Sent: Monday, July 19, 2004 8:36 PM
>To: STDS-802-3-10GBT@listserv.ieee.org
>Subject: Re: [10GBT] Updated Tables
>
>
>Vivek,
>
>I disagree. The 1E-12 BER point for the PAM8 proposal is at 19.9dB and it
>should stay that way.
>
>The proposed PAM12 approach is fundamentally flawed in its use of SNR vs.
>BER. If you compute the formula,
>
>Fs = 10000/(4*log2(4N) -2)
>
>for N=3, you will find that PAM12 should be running at 810MHz instead of
>the
>supposedly "optimized" 825MHz. If you plug in N=2 in the above formula,
>you
>will find that Fs is 1000MHz, which is as it is proposed for the PAM8
>approach.
>
>Please don't compensate the SNR for our PAM8 proposal for the inadequacies
>of the supposedly "optimized" encoding schemes used in the PAM12 proposal.
>
>Please don't even think about it.
>
>Regards,
>Sailesh Rao.
>srao@phyten.com
>
> >From: Vivek Telang <vivek@VITESSE.COM>
> >Reply-To: "IEEE P802.3an" <STDS-802-3-10GBT@listserv.ieee.org>
> >To: STDS-802-3-10GBT@listserv.ieee.org
> >Subject: Re: [10GBT] Updated Tables
> >Date: Mon, 19 Jul 2004 19:58:44 -0500
> >
> >Sailesh,
> >
> >In that case, to simplify comparisons, I propose that we decouple the
>line
> >code variable from the analysis, and assume the same coding gain for both
> >line codes.
> >I believe the coding gain assumed in Scott's presentation was 10.0 dB
> >(33.8-23.8), so shall we say that the PAM-8 SNR required for BER=1e-12 is
> >30.3-10 = 20.3 dB?
> >
> >Vivek
> >
> >-----Original Message-----
> >From: stds-802-3-10gbt@ieee.org [mailto:stds-802-3-10gbt@ieee.org]On
> >Behalf Of sailesh rao
> >Sent: Monday, July 19, 2004 6:11 PM
> >To: STDS-802-3-10GBT@listserv.ieee.org
> >Subject: Re: [10GBT] Updated Tables
> >
> >
> >Vivek,
> >
> >Thanks for the opportunity.
> >
> >At the meeting, Jose pointed out that the extension of the SNR/BER curve
>I
> >made on the (2048,1723) code from 6E-11 BER down to 1E-12 BER (slide 10
>of
> >rao_1_0704.pdf) was not based on real simulations. I had assumed that the
> >1E-12 BER assertions on slide 4 of seki_1_0304.pdf was based on real
> >simulations, but it was apparently just a "hand extrapolation" of my
> >original SNR/BER curve. Unfortunately, this point was not clarified to
>me
> >during my e-mail correspondence with Dr. Seki.
> >
> >At the moment, I stand by the 6E-11 BER point in the BER vs. SNR curve of
> >the (2048,1723) LDPC code since I personally supervised the generation of
> >this simulation point. In the worst-case, assuming Murphy's law applies,
>we
> >can expect the BER/SNR curve for the (2048,1723) LDPC code to undertake a
> >slope change in parallel with the uncoded Gaussian curve and the
>intercept
> >for the 1E-12 BER will occur slightly higher than 19.9dB (my
>extrapolation
> >shows 20.4dB, not 20.9dB).
> >
> >However, this is a moot point. If Amir Mezer's LDPC simulations show that
> >the (2048,1723) LDPC code has a slope change at 6e-11 BER, I will
>instantly
> >recommend adding a row to the Djurdjevic construction for the (2048,1723)
> >code and pushing the slope change down below the 1E-12 BER point. Or, for
> >that matter, if Amir Mezer's simulations show that the (992,829) LDPC
>code
> >has no slope change until 1E-12 BER, I will recommend we switch to that
> >code. I am aware that Amir Mezer has close to infinite computing
>resources
> >since he is employed at Intel (Amir, I hope things haven't changed!!!),
>and
> >therefore, we can rely on him to validate the specific LDPC code the task
> >force is using down to 1E-12 BER and beyond.
> >
> >The bottom line is that the PAM8 modulation scheme is not wedded to a
> >specific Djurdjevic LDPC code and we should really dis-associate the
> >specific LDPC code choice from the choice of PAM levels. For instance,
>the
> >PAM8 proposal will work just fine with the (1024,833) code the PAM12
> >proponents are using, though I would personally hesitate to add such a
> >SONET-on-Steroids like framing complexity in an Ethernet standard. Heck,
>we
> >had interoperablilty problems with the scrambler definition on 1000BASE-T
>-
> >do we really want to deal with interoperability issues with such a
>complex
> >framing scheme in 10GBASE-T?
> >
> >Regards,
> >Sailesh Rao.
> >srao@phyten.com
> >
> > >From: Vivek Telang <vivek@VITESSE.COM>
> > >Reply-To: "IEEE P802.3an" <STDS-802-3-10GBT@listserv.ieee.org>
> > >To: STDS-802-3-10GBT@listserv.ieee.org
> > >Subject: Re: [10GBT] Updated Tables
> > >Date: Mon, 19 Jul 2004 16:17:39 -0500
> > >
> > >Hi Sailesh,
> > >
> > >At the meeting last week, there was a question raised (by Jose) about
>the
> > >PAM-8 SNR requirement of 19.9 dB for BER=1e-12 (column 3 of your
>table).
> >I
> > >think he said that it was actually ~1dB worse than that (~20.9dB), but
> >I'm
> > >not positive. There was a discussion, but I don't think the matter got
> > >resolved, so can you clarify?
> > >
> > >Thanks,
> > >
> > >Vivek
> > >
> > >-----Original Message-----
> > >From: stds-802-3-10gbt@ieee.org [mailto:stds-802-3-10gbt@ieee.org]On
> > >Behalf Of sailesh rao
> > >Sent: Monday, July 19, 2004 2:02 PM
> > >To: STDS-802-3-10GBT@listserv.ieee.org
> > >Subject: [10GBT] Updated Tables
> > >
> > >
> > >10GBT'ers:
> > >
> > >In the attached, I've updated the 3 tables in our July presentation
>based
> > >on
> > >the following:
> > >
> > >1. Change PAM12 symbol rate to 825Ms/s from 820Ms/s.
> > >2. Delete PAM10 entry.
> > >3. As Luc pointed out, add a 1.2dB emissions penalty for PAM12 due to
>its
> > >higher transmit PSD.
> > >4. As Jose pointed out, subtract 0.4dB from the PAM12 emissions penalty
> >due
> > >to the THP peak voltage adjustment.
> > >
> > >Next, I integrated the WGN for 1E-12 BER over the Nyquist frequency
>range
> > >to
> > >get a "wideband noise tolerance" measure for the two proposals.
>Finally,
> >I
> > >summed the noise immunity penalty and the emissions penalty for the
>PAM12
> > >proposal to form a "Total EMI Penalty" metric over the PAM8 approach.
> > >
> > >In Models 1 and 3, the penalty works out to be 2.6dB and 2.2dB
> >respectively
> > >for PAM12 over PAM8. However, in Model 2, which represents the existing
> > >cabling infrastructure, the penalty for PAM12 over PAM8 works out to a
> > >whopping 4.0dB!!
> > >
> > >Regards,
> > >Sailesh Rao.
> > >srao@phyten.com
> > >
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