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Shannon capacity is based on the uncancellable noise profile used in the
calculation. The noise profile is based on the cancellation or
mitigation strategy. With no constraint on complexity such that large
levels of cancellation is possible, we get a capacity of 16.3Gbps using
Xiaopeng's Matlab code with a noise floor of -140. I would put forth that
this, or something close to it, is the theoretical
limit. Obviously, there are constraints on the implementation, but,
this is where innovation and engineering expertise takes over and,
generally, will only improve with time. I believe this is the essence
of George's remark.
Bill
While there may have
been innovations in DSP architectures since 1997, Shannon Capacity of CAT5/6
cables is a theoretical limit, and is unaffected by an individual’s time
horizon, or implementation sophistication.
Sreen
Raghavan
Vativ Technologies,
Inc.
-----Original
Message-----
From:
owner-stds-802-3-10gbt@majordomo.ieee.org
[mailto:owner-stds-802-3-10gbt@majordomo.ieee.org] On Behalf Of GEisler@aol.com
Sent: Friday, February 28, 2003 8:44
AM
To:
stds-802-3-10GBT-Modeling@ieee.org; stds-802-3-10gbt@ieee.org
Subject: [10GBASE-T]
Reflections
Guys,
Nice to hear from a
lot of the old crew that created the 1000BASE-T standard. I think that you can
all take a bow, judging from what is happening in the market and the
remarkable improvements in implementations achieved in three short years. But
no good deed goes unpunished, as they say, so you guys earned the job (and
created the need for) taking the next step up. Without a doubt, there are big
jumps in the performance demanded and we don't have the luxury that 1000BASE-T
enjoyed, namely the introduction of coding into the design. That has been done
already. This time around, we have to take advantage of the residual capacity
of the cabling, which we barely touched.
On the other hand, you
will agree that the levels of sophistication in analysis and implementation of
DSP based systems has also increased dramatically since 1997, when GigT
started in earnest.
While I enjoyed fond memories of your recollections
of what we knew (or suspected) then and what we added later when we got
smarter, it strikes me that that history is relatively immaterial today. That
was then and our current circumstances are quite different. We now need to
agree in the study group that it is feasible to do 10Gig on some form
of twisted pair cabling at the desired length and go on to form a Task Force
to do the hard work of coming to agreement on the precise details of the
signaling and channel specifications.
It is clear that the channel
specifications as written in 11801 will have to be modified and expanded for
our use and installation qualification test parameters will have to be
defined. This is more or less what happened for 1000BASE-T and seems to me to
be a normal and reasonable step. After all, why should the cabling industry be
expected to have already characterized cabling for the use of a standard for
which we are still in the Study Group phase? As for installed cabling, we will
see whether or how it may be qualified for 10G as part of our effort.
I
look forward to our meeting in Dallas and hope that we can get to work on a
PAR draft there.
George Eisler
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