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

Robert, and all,

Your question and concerns are definitely valid. The PIE-D metric serves
as a good initial indicator of feasibility. But it does not address the
issue of complexity (specifically, filter lengths). To get a handle on
that, we need to compute the penalties for receivers based on
finite-length equalizers. I share your concern that
reasonable-complexity finite-length equalizers may not be able to meet
the 1dB budget for some of the more challenging fibers.

Fortunately, it is quite straightforward to determine the performance of
finite-length equalizer receivers, without having to run long BER
simulations. Closed form MATLAB analysis can be used to determine the
steady state performance of FFE/DFE based systems. This has a long
history in many of the DSP-based comm. systems, including 1000BASE-T and
now 10GBASE-T. Historically, the steps in determining feasibility have
been (1) Channel Capacity (ideal) (2) Salz Bound (PIE-D) (more
realistic) (3) Finite length MMSE analysis (much more realistic, except
for transient behavior) and (4) Finite length, finite precision
simulations (the real deal). We have been on step 2 so far, and it seems
like it's time to move to step 3.

So IMO, we should be using finite-length equalizer analysis to determine
the budget.



Vivek Telang
Broadcom Corp.

-----Original Message-----
[] On Behalf Of Lingle, Jr,
Robert (Robert)
Sent: Tuesday, November 30, 2004 9:00 AM
Subject: Re: [10GMMF] TP3 Meeting minutes, November 23rd

I am less knowledgeable than many on this list, but I am trying to
understand the difference between the ideal, infinite case and the real,
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,
finite case.

What we saw, but do not fully understand, is that it seemed that the
higher the MSE PIE-D, the lareger the difference between PIE-D and any
finite equalizer could be.  Some questioned my conclusions afterward,
but none 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.
Then what we really need to know is the following: do fibers with PIE-D
between 4.5 and 5.5, which nominally seem to pass, actually have
implementation penalties (hardware and equalizer design) that keep them
below the 6.5 dB limit?  If my logic is flawed, please help me correct

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
Sent: Tuesday, November 30, 2004 10:23 AM
Subject: Re: [10GMMF] TP3 Meeting minutes, November 23rd
Importance: High


It is an interesting proposal, at least theoretically. Assuming infinite
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 is
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 forcing
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


-----Original Message-----
From: owner-stds-802-3-10gmmf@IEEE.ORG
[mailto:owner-stds-802-3-10gmmf@IEEE.ORG] On Behalf Of Abbott, John S Dr
Sent: Dienstag, 30. November 2004 15:48
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.


John Abbott

-----Original Message-----
From: Sudeep Bhoja [mailto:sbhoja@BIGBEARNETWORKS.COM]
Sent: Monday, November 29, 2004 5:39 PM
Subject: Re: [10GMMF] TP3 Meeting minutes, November 23rd


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 better
than Zero forcing Equalizers. Conventional adaptation algorithms such as
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 budget.

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 in
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 our
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 chosen
from -LR.

For the purpose of the TP3 stressed tests, we only need to represent the
rise time of the test setup of Fig 68.6 in D0.2. For this purpose 47.1ps
is probably an adequate rise time.

Best Regards,


-----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
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 force
members algorithms and the likely impact of changes of each of these


-----Original Message-----
From: Michael Lawton [mailto:mike_lawton@AGILENT.COM]
Sent: Wednesday, November 24, 2004 6:10 AM
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