Re: [10GBT] PAM8 and PAM12 sys time domain analysis
Albert,
As you know, the PAM12 proposal (powell_1_0704.pdf, slide 6) used a 3rd
order Butterworth low-pass transmit filter with a 3dB point at 206.25MHz.
This filter has an attenuation of 18dB at fs/2=412.5MHz, which dwarfs the
attenuation due to the magnetics that you are showing. The SNR margin loss
due to this transmit filter is actually only around 1dB.
Therefore, I'm not sure of your calculations without having access to the
channel+magnetics attenuation curve that you are using. Can you please share
the equational form of this curve so that I can understand what you are
getting at?
In any case, please note that with the reduced symbol rate of 952.381Ms/s,
the PAM8 system will gain at least 1dB of additional SNR margin in Model 3,
which should improve the situation considerably in your simulations.
Regards,
Sailesh Rao.
srao@phyten.com
>From: Albert Vareljian <albertv@IEEE.ORG>
>Reply-To: "IEEE P802.3an" <STDS-802-3-10GBT@listserv.ieee.org>
>To: STDS-802-3-10GBT@listserv.ieee.org
>Subject: Re: [10GBT] PAM8 and PAM12 sys time domain analysis
>Date: Thu, 5 Aug 2004 10:44:34 -0700
>
>Sailesh,
>
>When the line transformers (specified roughly as per
>presentations the group has seen so far) are included in the
>analysis -- the channel shows additional ~5.6 dB of loss at
>500 MHz. See attached graph.
>
>This, combined with Tx 1 Vp launch constraint at the IC, but
>not at MDI, accounts for the bulk of SNR losses w.r.t. "ideal"
>Class E channel Salz SNR.
>
>The actual SNR loss in the time-domain bench vs. its frequency
>domain reference proves to be below 1 dB -- this would be a very
>hard target to achieve for any practical h/w implementation of
>10GBASE-T.
>
>Regards,
>
>Albert
>
>
>
>
>
>
>sailesh rao wrote:
>
>>Albert,
>>
>>I assumed that the reference to Model 3 in your report included ANEXT
>>with a
>>64.5dB intercept and other worst-case impairments, as agreed upon in the
>>task force.
>>
>>If there was no ANEXT or residual Echo/NEXT/FEXT in your simulations,
>>then I
>>calculate the implementation loss in your simulations to be at least
>>3.6dB
>>for PAM8 and at least 4.0dB for PAM12.
>>
>>I don't think we should be contemplating such implementations for
>>10GBASE-T.
>>
>>Regards,
>>Sailesh Rao.
>>srao@phyten.com
>>
>>>From: Albert Vareljian <albertv@IEEE.ORG>
>>>Reply-To: "IEEE P802.3an" <STDS-802-3-10GBT@listserv.ieee.org>
>>>To: STDS-802-3-10GBT@listserv.ieee.org
>>>Subject: Re: [10GBT] PAM8 and PAM12 sys time domain analysis
>>>Date: Fri, 30 Jul 2004 00:20:13 -0700
>>>
>>>Hi Jose,
>>>
>>>No ANEXT or other impairments except -140dBm/Hz were employed in sims
>>>covered in the report.
>>>
>>>Adding ANEXT would seem to be the next logical step. However, correctly
>>>modeling ANEXT may prove a bit tricky.
>>>
>>>As we already discussed on IEEE floor -- our agreed ANEXT models
>>>are specified only in terms of the frequency domain magnitude (no
>>>phase). So, the time-domain implementation has been left open up
>>>to the user...
>>>
>>>There could be many interpretations as to how one arrives at a
>>>reasonably behaved time-domain ANEXT TF and its excitation method.
>>>Our analysis indicates that end results in the system could vary
>>>significantly on the case by case basis, depending on the methodology
>>>used to model time-domain ANEXT behavior.
>>>
>>>Based on the above, it may be helpful if the group agrees on and adopts
>>>some "uniquely" defined causal, scalable time-domain capable model
>>>for ANEXT that could be used for system qualification. One possible
>>>example of ANEXT TF implementation in s-domain (usable in time- and
>>>frequency- sims) is illustrated in the attachment.
>>>
>>>
>>>Regards,
>>>
>>>Albert
>>>
>>>
>>>
>>>
>>>Jose Tellado wrote:
>>>
>>>>Hi Albert,
>>>>
>>>>Thank you for your detailed time-domain report, I have a couple of
>>>>simple questions on the simulation assumptions.
>>>>
>>>>Have you included the effects of ANEXT in these simulations? If so,
>>>>what
>>>>approved PHY channel model (1-4) would this approximate?
>>>>
>>>>Did you include other receiver impairments such as residual EC/NX/FX or
>>>>did you lump all these effect into the -140dBm/Hz noise?
>>>>
>>>>Regards,
>>>>Jose Tellado
>>>>
>>>>
>>>>
>>>>-----Original Message-----
>>>>From: stds-802-3-10gbt@IEEE.ORG [mailto:stds-802-3-10gbt@IEEE.ORG] On
>>>>Behalf Of Albert Vareljian
>>>>Sent: Monday, July 26, 2004 7:57 PM
>>>>To: STDS-802-3-10GBT@LISTSERV.IEEE.ORG
>>>>Subject: [10GBT] PAM8 and PAM12 sys time domain analysis
>>>>
>>>>Hi All,
>>>>
>>>>Pls find attached pdf report on PAM8 and PAM12 systems time domain
>>>>simulation and comparative analysis.
>>>>
>>>>Regards,
>>>>
>>>>Albert Vareljian
>>>>
>>>>
>>>>
>>><< ANEXT_Fig.doc >>
>>
>>
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><< channel_xf_tf.doc >>
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