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.
> > >>
> > >>
> > >>
> > >>
> >
> >_________________________________________________________________
> >On the road to retirement? Check out MSN Life Events for advice on how
> >to get there! http://lifeevents.msn.com/category.aspx?cid=Retirement
>
> _________________________________________________________________
> Express yourself instantly with MSN Messenger! Download today - it's FREE!
> http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/
>