Re: [10GBT] Summary of issues with PAM12
In addition, the proponents of PAM-12 have not responded at all to three of
the issues that Sailesh raised.
----- Original Message -----
From: "Roberts, Hal" <Hal.Roberts@ADC.COM>
To: <STDS-802-3-10GBT@LISTSERV.IEEE.ORG>
Sent: Thursday, August 19, 2004 4:42 PM
Subject: Re: [10GBT] Summary of issues with PAM12
> Hugh,
>
> Ignoring the hilarious 'confidential' e-mails that this posting seemed to
have inspired, the 'hole in the constellation' just seems to me to be a
particularly obvious waste of margin in the PAM-12 proposal. What I am
really looking for is a PAM-12 proponent to summarize the issues with PAM-8
(like Sailesh did for PAM-12) so as to make a comparison. So far nobody has
attempted to create this summary.
>
> Your analogy of an 'issue with PAM-8' being 'only 12 bits/baud' is not a
good one since trading bits per baud for increased baud rate is a valid
engineering trade off. It is not an outright inefficiency like the
constellation problem.
>
> Like Sailesh said, "Did 10GBASE-T become a greatly simplified problem in
the intervening period
> that these margins are no longer important?"
>
> Hal
>
> -----Original Message-----
> From: stds-802-3-10gbt@IEEE.ORG [mailto:stds-802-3-10gbt@IEEE.ORG]On
> Behalf Of Hugh Barrass
> Sent: Wednesday, August 18, 2004 11:42 AM
> To: STDS-802-3-10GBT@listserv.ieee.org
> Subject: Re: [10GBT] Summary of issues with PAM12
>
>
> Hal,
>
> I don't understand why the "hole in the constellation" is seen as an
> issue. It causes the PAM-12 to be less "efficient" than it could be,
> just like the padding bits and encapsulation overhead. The net result is
> that the proposal using PAM-12 needs a symbol rate of 825Mbaud where a
> lower clock rate might be used if the efficiency was better. However, if
> the comparison is made using that proposal and PAM-12 still comes out
> better then perhaps the "inefficiency" is acceptable. If, on the other
> hand and as Sailesh maintains, the comparison comes out in favor of
> PAM-8 then the PAM-12 proponents might want to look at ways of "trimming
> the fat."
>
> It would be equally valid to raise the "issue with PAM-8" of "only 12
> bits/baud" and require the PAM-8 fans to address that...
>
> Personally, I think 10GBASE-T would be best addressed by 4 pair, bonded,
> 2BASE-TL on steroids :-)
>
> Hugh.
>
>
>
> Roberts, Hal wrote:
>
> >All,
> >
> >Sailesh provides a nice compact list of (his) issues with regard to
PAM12. I
> >have seen responses to some of these but nothing addressing or
summarizing
> >them all.
> >
> >In addition it would be useful (at least to me) to see a similar summary
of
> >"Issues with PAM8" from a PAM12 proponent. (Unless based on Sailesh's
> >criticisms there are no longer any PAM12 proponents? ;-)
> >
> >Finally, Sailesh has a good point that a number of his issues have been
> >completely unanswered. I am surprised no one has addressed the 'hole in
> >constellation' issue.
> >
> >
> >
> >
>