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Re: [10GBT] Summary of issues with PAM12


With regard to issues 1 and 2, I don't believe that there are any disputes
about my calculations. I've already addressed these so-called disputes in my
summary e-mail and pointed out why my analysis stands.

With regard to issue 3, firstly, the main rationale advanced by the PAM12
proponents for their 3bits/baud scheme is that it has 0.7dB higher Salz SNR
margin over the 2.5bits/baud scheme used in PAM8, over a 100m cable.
However, once you put a hole in the constellation and throw away at least
1.1dB, would you now concede that this rationale is technically invalid, and
that the Salz SNR margin advantage also swings to PAM8 over PAM12 at ALL
cable lengths, from 0m to 100m?

Secondly, the hole in the constellation makes the PAM12 transmit PSD a
function of the THP coefficients. Therefore, every time a system vendor
finds that the system violates emissions limits, we can expect him/her to
demand to examine the THP coefficients of the PHY, if this task force
standardizes PAM12.

Thirdly, the  hole in the constellation makes the receiver SNR margin a
function of the THP coefficients of the alien neighbors.

With regard to issue 5, please check the details on the PAM8 proposal. You
will see that there are NO fixed patterns used anywhere to delineate data
frames or anything. Therefore, it is not "necessary" to use fixed patterns
for this purpose. These fixed patterns waste the precious Shannon capacity
which the cabling community is working hard to provide us, though not on the
same scale as the other issues with the PAM12 proposal, and which is why I
listed this issue last.

Sailesh Rao.

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