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Re: [10GBT] Issues with solarsep_varlen7a.m



Samir,

This matlab code has many options and switches and I'm not sure that I
can verify the integrity of all my corrections and publish the modified code
prior to the plenary meeting, next week. In any case, I am more partial to
the straight-forward MMSE pulse analysis code that we used and
published in the IEEE 802.3ab task force since it results in a more
practical
comparison of the merits of one approach over another.

Regards,
Sailesh Rao.

>From: SAMIR THOSANI <samir@platolabs.com>
>Reply-To: SAMIR THOSANI <samir@platolabs.com>
>To: STDS-802-3-10GBT@listserv.ieee.org
>Subject: Re: [10GBT] Issues with solarsep_varlen7a.m
>Date: Wed, 7 Jul 2004 12:42:37 -0700
>
>Sailesh,
>
>Thanks for providing this information. We've had always some doubts abt
>this
>program. Can u please provide a modified code, so that we can have a look
>at
>that before the meeting?
>
>rgds,
>Samir.
>
>
>
>
>
>----- Original Message -----
>From: "sailesh rao" <sailesh_rao@HOTMAIL.COM>
>To: <STDS-802-3-10GBT@LISTSERV.IEEE.ORG>
>Sent: Wednesday, July 07, 2004 12:33 PM
>Subject: [10GBT] Issues with solarsep_varlen7a.m
>
>
> > George/Carlos,
> >
> > I would like to bring up some issues with the solarsep_varlen7a.m matlab
> > code that is found on
> >
> > http://grouper.ieee.org/groups/802/3/an/public/material/index.html
> >
> > I believe that these issues alter the conclusions that one could derive
>from
> > this code.
> >
> > 1. Frequency Base:
> > The frequency base for the DFE margin calculations is being inferred
>from
> > the first column in the Insertion Loss files found in this directory. As
>a
> > result, the frequency base ranges from 0 to 650MHz in all cases.
>However,
> > the average power P is being distributed evenly over (line 391)
> >
> > bwmhz=1250MHz for the 2-bit PAM system,
> >
> > bwmhz=1000MHz for the 2.5-bit PAM system,
> >
> > bwmhz=833MHz for the 3-bit PAM system
> >
> > This means that 48% of the input power is unused in the 2-bit system,
>35%
>is
> > unused in the 2.5-bit system and only 22% is unused in the 3-bit system.
> > This tips the scale in favor of the 3-bit PAM system.
> >
> > 2. Folded SNR calculation:
> >
> > The folded SNR calculations in lines 443, 453 and 463 are not right. If
>f1
> > and f2 are mirror frequencies about fs/2, the formula being used is
> >
> > S/N = ABS(S1/N1) + ABS(S2/N2) ;
> >
> > However, the actual SNR at the folded frequency would be
> >
> > S/N = ABS(S1+S2)/ABS(N1+N2)
> >
> > where S1, S2, N1, and N2 are complex phasors. Therefore, in the context
>of
> > folding, the actual PSD of the signal becomes relevant, whereas the
>original
> > Salz formula for the optimum DFE SNR is independent of the PSD.
> >
> > As done in the matlab code, this calculation also tips the scale in
>favor
>of
> > the 3-bit PAM system since signal power is assumed to be zero for
>f>650MHz
> > due to (1) above.
> >
> > 3. SNR Requirement for 1E-12 BER
> >
> > The SNR requirement for 2.5bit PAM is 3.01dB worse than the SNR
>requirement
> > for 2-bit PAM.
> > The SNR requirement for 3bit PAM is 6.23dB worse than the SNR
>requirement
> > for 2-bit PAM.
> >
> > The code is using 2.95dB and 5.94dB respectively in lines 446, 456 and
>466,
> > which also tips the scale in favor of the 3-bit PAM system.
> >
> > Regards,
> > Sailesh Rao.
> >
> > _________________________________________________________________
> > FREE pop-up blocking with the new MSN Toolbar - get it now!
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