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Samir,
At the March 2004 meeting there was a presentation
that proposed 4PAM for distances up to 55m and suggested 8PAM for
distances greater than 55m and up to 100m. The 4PAM proposal was a low complexity, low
power proposal suitable and probably very appropriate for short cable
lengths. The proposers themselves were not trying to claim it was
appropriate for 100m.
With 4PAM, with the additional constraint that you
limit the signaling rate to 1300Msym/sec to stay within the maximum specified
frequency for the channel model, the maximum bit rate possible is
1300M*4pairs*2bits/pair which comes out to 10.4Gb/s. This leaves insufficient
signaling for any significant FEC hence it will be hard to make this work for
100m cable lengths . For more details
on why, you will have to look at the prior presentations on minimum capacity
required - there was one on the subject by Scott Powell and another jointly
by Jose Tellado and Ofir Shalvi and probably several
others.
You can make different
assumptions and draw a different conclusion so feel free to make a
case for 4PAM if you like, but clearly lay out the performance you
expect and state the assumptions and we will have an opportunity to review it at
the upcoming meeting at Long Beach. I think we will see multiple
proposals that claim to meet the objectives and the discussion at Long Beach is likely to focus on which one
appeals to a majority of the task force participants.
Given that there are likely to be multiple proposals
that meet the distance objectives,
I am not greatly inclined to
expend time on proving that certain
schemes will not work if the proposers are not claiming that they will meet the
distance objectives.
Regards,
Sanjay
cell (650) 704-7686
office (408)
653-2235
From: stds-802-3-10gbt@IEEE.ORG [mailto:stds-802-3-10gbt@IEEE.ORG] On Behalf Of SAMIR THOSANI Sent: Saturday, May 15, 2004 9:36 PM To: STDS-802-3-10GBT@listserv.ieee.org Subject: Re: [10GBT] Symbol rate Dear Mr. Kasturia,
Can u please clarify based on what u r making the
following statement:
" As I
understand it, the PAM 4 type schemes that would use the much higher symbol rate
would NOT meet our distance objectives "
This might be just
YOUR understanding. so far, i dont think we have seen a single SOLID evidence to
the above in past 2 yrs.
i think we r all
still under the clouds, as they say. And as far as ur comment
regarding the 802.3 voters, i wud say that apart from
Mr. Sailesh Rao, i
dont think any of the major PHY vendors associated with development of
10GBASE-T ever designed a PHY before,
like 1GBASE-T. This
is a small world, btw, and we all know one another's track record. so, lets just
leave at that.
rgds,
Samir.
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