Re: [10GBT] Summary of issues with PAM12
Joseph,
Thanks.
To get back to the real question, please note that the contrast between the
dire pessimism in the concluding slide of powell_1_0903.pdf and the sunny
optimism pervading powell_1_0704.pdf is stark. Therefore, what is the
technical basis for throwing away
1. 0.62dB to 1.05dB of emissions margin,
2. 2.0dB to 3.9dB of EMI susceptibility margin,
3. 1.1dB of SNR noise margin (by putting a hole in the constellation)?
Did 10GBASE-T become a greatly simplified problem in the intervening period
that these margins are no longer important?
Regards,
Sailesh Rao.
srao@phyten.com
>From: Joseph Babanezhad <jobaba@PLATONETWORKS.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 22:25:58 -0700
>
>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.
> > > > >>
> > > > >>
> > > > >>
> > > > >>
> > > >
> > > >_________________________________________________________________
> > > >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/
> > >
> >
_________________________________________________________________
Express yourself instantly with MSN Messenger! Download today - it's FREE!
http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/