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Re: [10GMMF] TP3 Meeting minutes, November 23rd


I completely agree with the statement that finite-length MMSE-DFE
calculations are indeed the way to go for an accurate analysis of the
problem. The infinite-length equalizer (PIE metric) has, however, the
strong benefit of very simple computation for fast estimation of the
challenge (penalty) of the problem.

I believe that there is no way around an analysis based on finite-length
equalizer in order to verify the link budget and Intel is working on
simulation results to share with IEEE. As a matter of fact, Intel
proposed back at the March meeting in Orlando (see to
focus on finite equalizers in order to establish a link to equalizers
with realistic filter complexity and thereby include up front the
penalty associated with finite vs infinite equalizers.


-----Original Message-----
From: owner-stds-802-3-10gmmf@IEEE.ORG
[mailto:owner-stds-802-3-10gmmf@IEEE.ORG] On Behalf Of Lars E. Thon
Sent: 30. november 2004 19:06
Subject: Re: [10GMMF] TP3 Meeting minutes, November 23rd

Dear Robert, and other contributors to this thread,

I believe that using finite-length MMSE-DFE calculations is indeed
a more accurate method for closing the the link budget.

For an exposition on the topic, please read

which I presented in Portland in July 2004. Other contributors,
including Intel and recently Georgia Tech, have also touched upon this
subject, either directly or indirectly.

I agree with Sudeep that MMSE-DFE (whether "ideal" or finite length) is
a better measure of the required penalty term of the link budget than is
a ZF-DFE. The latter ignores noise, while the former attempts to
balance noise and the pattern-specific ISI.

Neither MMSE-DFE nor ZFE-MMSE is the "optimal" DFE (Minimum BER or
MBER-DFE). However, I think an analytic method for calculating the
MBER-DFE in the general case is beyond the reach of current
communication theory, let alone a practical goal for an adaptation

Hence, I think it is a good choice to use MMSE-DFE for performance
evaluation and budget closure. The ideal/PIE-D/infinite version is good
because of its simplicity, whereas one should also contemplate using a
finite length version for more accurate analysis.


Lingle, Jr, Robert (Robert) wrote:
> I am less knowledgeable than many on this list, but I am trying to
> understand the difference between the ideal, infinite case and the
> finite case.  As a step in that direction, we tried in San Antonio
> presentation to take a step in that direction by looking at ideal,
> case.
> What we saw, but do not fully understand, is that it seemed that the
> the MSE PIE-D, the lareger the difference between PIE-D and any finite
> equalizer could be.  Some questioned my conclusions afterward, but
> refuted them conclusively.
> The implications are the following: suppose we set a limit that 99% of
> fibers must pass PIE-D < 5.5, and leave a 1 dB implementation penalty.
> what we really need to know is the following: do fibers with PIE-D
> 4.5 and 5.5, which nominally seem to pass, actually have
> penalties (hardware and equalizer design) that keep them below the 6.5
> limit?  If my logic is flawed, please help me correct it.
> do we have to calculate finite equalizer cases as well?
> Robert Lingle, Jr
> Fiber Design and Development
> OFS R&D, Atlanta, GA
> -----Original Message-----
> From: Bottacchi.external@INFINEON.COM
> [mailto:Bottacchi.external@INFINEON.COM]
> Sent: Tuesday, November 30, 2004 10:23 AM
> To:
> Subject: Re: [10GMMF] TP3 Meeting minutes, November 23rd
> Importance: High
> John,
> It is an interesting proposal, at least theoretically. Assuming
> length FFE, I guess zero forcing solution would be possible (in
> principle). This means no residual ISI at sampling instant (not just
> minimum error modulus like MMSE). As a consequence, noise enhancement
> strongly expected to be the limiting factor for EDC performances. I am
> quite curious to see how much would be the optical penalty since I
> calculated some month ago the PID-L for the zero forcing (linear)
> equalizer in term of noise bandwidth enhancement( I sent a ppt copy to
> Sudeep for comparison with PIE-D/L reported metrics). Does zero
> PIE-D expected to be different from noise bandwidth enhancement due to
> full frequency compensation for a given output ISI free spectrum
> (raised-cosine for example)?
> Thank you for posting this issue...
> Best regards
> Stefano
> -----Original Message-----
> From: owner-stds-802-3-10gmmf@IEEE.ORG
> [mailto:owner-stds-802-3-10gmmf@IEEE.ORG] On Behalf Of Abbott, John S
> Sent: Dienstag, 30. November 2004 15:48
> To:
> Subject: Re: [10GMMF] TP3 Meeting minutes, November 23rd
> In regard to Lew's and Sudeep's points, are there conditions where we
> should calculate the zero forcing PIE-D as well as the MSE PIE-D?  At
> the San Antonio meeting there seemed to be comments supporting both.
> Regards,
> John Abbott
> -----Original Message-----
> From: Sudeep Bhoja [mailto:sbhoja@BIGBEARNETWORKS.COM]
> Sent: Monday, November 29, 2004 5:39 PM
> To:
> Subject: Re: [10GMMF] TP3 Meeting minutes, November 23rd
> Lew,
> This in response to your Comment #1 below.
> The PIE-D equations from bhoja_1_0704 targets an infinite length DFE
> that minimizes mean square error (MMSE). MMSE Equalizers perform
> than Zero forcing Equalizers. Conventional adaptation algorithms such
> LMS, minimize mean squared error.
> If we agree on an MMSE based infinite length DFE, there are
> two variables that enter into the calculation:
> 1) The first variable is easy and follows directly from the link
> sigma^2 -> This is the Electrical noise floor at the input
> of the ideal EDC and is easily derived from the link budget.
> We had previously set sigma^2 = 10^(-17-2*6)/10 since we had allocated
> 6dB of total dispersion budget.
> However since the connector loss was updated to 1.5dB from 2dB Page 5
> lawton_1_1104 allocated 6.5dB to the total dispersion budget.
> Hence we need to update sigma^2 = 10^(-17-2*6.5)/10 = 10^(-30/10) in
> PIE-D calculations.
> 2) The rise time used in deriving the fiber pulse response in
> bhoja_1_0104 was set to 47.1ps (20-80% Gaussian). This number was
> from -LR.
> For the purpose of the TP3 stressed tests, we only need to represent
> rise time of the test setup of Fig 68.6 in D0.2. For this purpose
> is probably an adequate rise time.
> Best Regards,
> Sudeep
> -----Original Message-----
> From: owner-stds-802-3-10gmmf@IEEE.ORG
> [mailto:owner-stds-802-3-10gmmf@IEEE.ORG]On Behalf Of Lew Aronson
> Sent: Monday, November 29, 2004 12:47 AM
> To:
> Subject: Re: [10GMMF] TP3 Meeting minutes, November 23rd
> Some comments:
> 1) I think it is very important that all are aligned on the PIE-D
> calculation.  I would be interested in a discussion on the variables
> mentioned below, what differences exist now between different task
> members algorithms and the likely impact of changes of each of these
> parameters.
> Lew
> -----Original Message-----
> From: Michael Lawton [mailto:mike_lawton@AGILENT.COM]
> Sent: Wednesday, November 24, 2004 6:10 AM
> To:
> Subject: [10GMMF] TP3 Meeting minutes, November 23rd
> Dear TP3ers,
> Here are my notes from yesterdays call.
> Key issues which were raised:-
>         PIE-D has variables associated with it (rise time, sigma^2, ZF
> vs MMSE calculation) - how do we handle that?
> Any comments/corrections please get back with me.
> Best Regards
> Mike

Lars E. Thon <>
Aeluros Inc., 201 San Antonio Circle, Suite 172
Mountain View, CA 94040-1254
650-917-4113(w) 650-917-7394(f) 408-439-5914(c)