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Re: [10GBT] Proposed PAM8 vs. PAM12 resolution process

I think all you are saying is that
        i) $B!! (JBoth systems, PAM8 and PAM12 are showing roughly same noise margin with -150dBm/Hz BGN,
        ii) -150dBm/Hz BGN is defined as spectral density, and
        iii) PAM8 uses wider bandwidth than PAM12 by 17.5%,

therefore, PAM8 is suffereing bigger BGN at input by 0.8dB (not 2dB as you presented) than PAM12.


The tolerable external noise is identical for both systems. That is -150dBm/Hz! You can not convert this into rms value unless bandwidth is defined. The bandwidth is determined by the receiver itself. PAM8 needs more bandwidth than that of PAM12 which means that PAM8 is more sensitive to the higher frequency noise. What I am pointing out is that PAM12 rejects more noise than that can be rejected by PAM8.

Plus, as we discussed back room in Portland hotel, PAM8 pollute more than PAM12 does. I will show you more in detail soon.

I will take a look at default values in the matlab code and do more details. Do you prefer to have 0.75+0.25/Z in your PAM8 and compare with PAM12 without such filtering or just simple PAM8 and PAM12?

Hiroshi Takatori
KeyEye Communication

-----Original Message-----
From: stds-802-3-10gbt@IEEE.ORG [mailto:stds-802-3-10gbt@IEEE.ORG] On Behalf Of Sailesh Rao
Sent: Saturday, July 17, 2004 3:30 PM
Subject: Re: [10GBT] Proposed PAM8 vs. PAM12 resolution process


The default cancellation parameters are in the matlab source code on the
task force web site:

As far as the transmit PSD is concerned, please feel free to send me
what you think is optimum for the PAM12 system and I would be happy to
use that. Please note that the matlab code currently uses a flat
transmit PSD. However, I believe that the proposition before us, viz.,

"When two PAM systems have roughly the same SNR margin
(Margin(PAM8)=5.6dB,  Margin(PAM12)=5.9dB), the PAM system with the
smaller number of levels (PAM8) will be fundamentally more robust
towards external noise,"

holds regardless of the transmit PSD. For instance, whatever transmit
PSD is proposed for the PAM12 system, we can always scale that in
amplitude and frequency and reuse it for the PAM8 system.

Sailesh Rao

>From: hiroshi takatori <hiroshi.takatori@KEYEYE.NET>
>Reply-To: "IEEE P802.3an" <>
>Subject: Re: [10GBT] Proposed PAM8 vs. PAM12 resolution process
>Date: Fri, 16 Jul 2004 23:09:07 -0700
>Please, define default cancellation parameters and necessary parameters
>to create transmit PSDs for both PAM8 and 12.
>From: stds-802-3-10gbt@IEEE.ORG [mailto:stds-802-3-10gbt@IEEE.ORG] On
>Behalf Of Sailesh Rao
>Sent: Friday, July 16, 2004 9:01 PM
>Subject: [10GBT] Proposed PAM8 vs. PAM12 resolution process
>I would like to propose the following process for resolving the
>robustness of PAM8 vs. PAM12 towards external noise.
>1. Compute the Optimum DFE SNR Margin for PAM8 and PAM12 using
>solarsep_varlen7a.m for Models 1 and 3 using default cancellation
>parameters and -150dBm/Hz background noise.
>2. Compute the input-referred RMS noise power at the slicer by
>integrating the residual noise in the Optimum DFE solution. I volunteer
>to add this code to solarsep_varlen7a.m unless someone else wants to do
>3. Compute the input-referred external noise power that can be
>for a BER of 1E-12 for both systems using the results from (1) and (2)
>above. I volunteer to add this code to solarsep_varlen7a.m unless
>someone else wants to do so.
>Sailesh Rao.

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