Re: [10GBT] Summary of issues with PAM12
Sailesh,
Sorry, you are right:
(825-780)/780*10000 Mb/s = 577Mb/s
Joseph
----- Original Message -----
From: "Joseph Babanezhad" <jobaba@PLATONETWORKS.COM>
To: <STDS-802-3-10GBT@LISTSERV.IEEE.ORG>
Sent: Wednesday, August 18, 2004 8:03 PM
Subject: Re: [10GBT] Summary of issues with PAM12
> Sailesh,
>
> (825-780)/780*10000 Mb/s = 57.7Mb/s (not 577Mb/s)
>
>
> Joseph
>
> ----- Original Message -----
> From: "sailesh rao" <sailesh_rao@HOTMAIL.COM>
> To: <STDS-802-3-10GBT@LISTSERV.IEEE.ORG>
> Sent: Wednesday, August 18, 2004 7:28 PM
> Subject: Re: [10GBT] Summary of issues with PAM12
>
>
> > Jose,
> >
> > The 780Ms/s symbol rate includes all the necessary overhead for the
> 64B/65B
> > etc. Therefore, the extra overhead in relation to the 64B/65B overhead
for
> > the hole in the constellation is
> >
> > 577/156.25 = 3.69 ~= 4
> >
> > When added to the pre-existing 64B/65B encoding, this becomes the
> equivalent
> > of 64B/69B encoding.
> >
> > Sailesh.
> > srao@phyten.com
> >
> > >From: Jose Tellado <JTellado@TERANETICS.COM>
> > >Reply-To: "IEEE P802.3an" <STDS-802-3-10GBT@listserv.ieee.org>
> > >To: STDS-802-3-10GBT@listserv.ieee.org
> > >Subject: Re: [10GBT] Summary of issues with PAM12
> > >Date: Wed, 18 Aug 2004 17:45:52 -0700
> > >
> > >Sailesh,
> > >
> > >Not sure what you had in mind, since this is not a mathematical
> > >coincidence ...
> > >
> > >If you check your math more carefully, at 825MHz the optimum PAM12
could
> > >carry at most 64B/67B. 64/69 would require 840MHz (actually higher if
> > >you include some LDPC framing and PHY control overhead such as THP
> > >updates, etc.)
> > >
> > >Cheers :)
> > >Jose
> > >
> > >
> > >-----Original Message-----
> > >From: stds-802-3-10gbt@IEEE.ORG [mailto:stds-802-3-10gbt@IEEE.ORG] On
> > >Behalf Of sailesh rao
> > >Sent: Wednesday, August 18, 2004 3:43 PM
> > >To: STDS-802-3-10GBT@listserv.ieee.org
> > >Subject: Re: [10GBT] Summary of issues with PAM12
> > >
> > >Hugh,
> > >
> > >Let's calculate the overhead due to the hole in the PAM12 constellation
> > >once again. As you know, I've variously stated that the "optimum" PAM12
> > >symbol rate should have been in the neighborhood of 780Ms/s. In
> > >comparison with the proposed symbol rate of 825Ms/s, the overhead is
> > >
> > >(825-780)/780*10000 Mb/s = 577Mb/s
> > >
> > >In contrast, the overhead due to the 64B/65B encoding is
> > >
> > >1/64*10000 Mb/s = 156.25Mb/s
> > >
> > >Therefore, the hole in the constellation is equivalent to doing a
> > >64B/69B encoding in PAM12. (No flames please, this is a mathematical
> > >coincidence and no double entendre intended)
> > >
> > >Regards,
> > >Sailesh Rao.
> > >srao@phyten.com
> > >
> > > >From: Hugh Barrass <hbarrass@CISCO.COM>
> > > >Reply-To: "IEEE P802.3an" <STDS-802-3-10GBT@LISTSERV.IEEE.ORG>
> > > >To: STDS-802-3-10GBT@LISTSERV.IEEE.ORG
> > > >Subject: Re: [10GBT] Summary of issues with PAM12
> > > >Date: Wed, 18 Aug 2004 09:42:26 -0700
> > > >
> > > >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.
> > > >>
> > > >>
> > > >>
> > > >>
> > >
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