Re: [10GBT] Proposed PAM8 vs. PAM12 resolution process
Scott,
Input-referred noise tolerance is a measure of robustness our customers see
and I feel it is very important. Otherwise, if the cable impairments
vanished below 170MHz, we would all be advocating 333Ms/s PAM-256 for
10GBASE-T...
The Crane test is another way of measuring the same robustness to input
noise and it has been a required parameter on the task force spreadsheet
since day one.
Regards,
Sailesh Rao.
srao@phyten.com
>From: Scott Powell <spowell@broadcom.com>
>Reply-To: spowell@broadcom.com
>To: STDS-802-3-10GBT@listserv.ieee.org
>Subject: Re: [10GBT] Proposed PAM8 vs. PAM12 resolution process
>Date: Sun, 18 Jul 2004 00:36:58 -0700
>
>Hi Sailesh,
> As was discussed last week, the bottom line performance goal is 1e-12
>BER
>which is determined most directly by the SNR at the decision device
>("slicer
>SNR") by the familiar BER vs SNR curves the task force has been using so
>far. I'd much rather see results presented in terms of slicer SNR than the
>more obscure "input-referred RMS noise power". The margin is then simply
>the dB difference between the "required SNR" and the slicer SNR. Perhaps
>others could voice their preference.
>
> As was also discussed, the "required SNR" for LDPC codes must be
>determined by simulation. Error floor and BER slope change issues
>inherent
>to many LDPC codes cannot be predicted and simulations must be performed to
>demonstrate that 1e-12 BER performance is possible from any given code.
>Extrapolations from 1e-9 or 1e-10 (or even 1e-11) are not always a reliable
>predictor of required SNR for 1e-12 BER. We have not yet seen results
>presented that establish the required SNR for the PAM8 case with the
>proposed LDPC (2048,1723) code as we have for the PAM12 case.
>
> Lastly, we didn't have time to discuss this in detail last week but
>there
>is some concern about the applicability of the so called "Crane" noise
>immunity test for these PHYs. Another bottom line performance goal is
>for
>the *PHY + connecting hardware* to pass legally required noise immunity
>tests. The noise immunity test consists of modulated sinusoidal fields
>applied to an actual operating PHY in a system. This PHY will still have
>all other noise sources and will have it's cancellers and equalizers in
>normal operating mode. As I understand it, the "Crane test" puts the PHY
>in
>the unrealistic condition of 1) no other external noise sources and 2)
>equalizers frozen, not adapting. The Crane test makes the further
>assumption that the same coding gain predicted for white Gaussian noise
>will
>be valid for sinusoidal noise - I don't believe I've seen presentations or
>literature which backs this assumption up. I don't think we have had
>enough
>discussion on the Crane test's advantages/disadvantages, options, and
>relationship to reality to simply adopt it and use the results to base our
>PHY architecture decision on.
>
>Regards,
> - Scott
>
>Dr. Scott Powell
>Senior Manager, Ethernet PHYs
>Broadcom Corp.
>(949)926-5105
>spowell@broadcom.com
>
>
>
>-----Original Message-----
>From: stds-802-3-10gbt@ieee.org [mailto:stds-802-3-10gbt@ieee.org] On
>Behalf
>Of hiroshi takatori
>Sent: Friday, July 16, 2004 11:09 PM
>To: STDS-802-3-10GBT@listserv.ieee.org
>Subject: Re: [10GBT] Proposed PAM8 vs. PAM12 resolution process
>
>
>
>Sailesh,
>
>Please, define default cancellation parameters and necessary parameters to
>create transmit PSDs for both PAM8 and 12.
>
>Hiroshi
>
>KeyEye
>
>
> _____
>
>
>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
>To: STDS-802-3-10GBT@listserv.ieee.org
>Subject: [10GBT] Proposed PAM8 vs. PAM12 resolution process
>
>
>
>All,
>
>
>
>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 so.
>
>
>
>3. Compute the input-referred external noise power that can be tolerated
>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.
>
>
>
>Regards,
>
>Sailesh Rao.
>
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