RE: [10GBT-Modeling] RE: [10GBT-Cabling] [10GBASE-T] a channel capacity estim...
Boris -
I agree that as we go forward, more data will come out. The cabling
group was working this. I believe that we have now countered the
assertions made based on using limit lines that the problem was
substantially beyond capacity, not that it is easy, but hopefully you
can begin to see that it is possible. Make no mistake - this is a
high-performance system, not everyone will agree they can make it.
Fortunately technical feasibility means not everyone has to make it.
It is important that we begin to come to a common understanding of the
data required. This was part of the frustration I had with the
capacity-based calculation, in that I was pretty sure the next step
started to get to the time-domain simulations. It is fairly common
(e.g., in DSL systems) to build systems working close to performance
limits. We have presented time domain simulations in November which
address this. Bill's results that you reference use a higher noise
floor, but, you correctly point out that the cancellation ratios
required push most of the impairments significantly below the noise
floor. If you look at the November tutorial, you will see that this is
in fact where the design sits.
One thing to point out is that we realized that we left Xiaopeng's
cancellation parameters (and his RL estimate, hence the cancellation
will be his) in the simulation. Go ahead and replace them with the
numbers from the tutorial, you'll get substantially the same results.
I'm afraid that somewhere we're going to have to come to a common
ground. While we need to go further, the purpose of a technical
feasibility is not to do a complete design, it is also not to make it
look easier than it is, and it is not that everyone agrees they can do
it. It is only to show that multiple vendors think they can do the job.
As you undoubtedly know, this solution will have to minimize noise from
a number of areas. At the time, so did 1000 BASE-T, HDSL2, and early
ADSL systems. Yet, all exist as commercial, successful, multi-vendor
parts today.
George Zimmerman
gzimmerman@solarflare.com
tel: (949) 581-6830 ext. 2500
cell: (310) 920-3860
-----Original Message-----
From: Fakterman, Boris [mailto:boris.fakterman@intel.com]
Sent: Wednesday, February 26, 2003 3:48 AM
To: George Zimmerman; stds-802-3-10GBT@ieee.org;
stds-802-3-10GBT-Modeling@ieee.org
Subject: RE: [10GBT-Modeling] RE: [10GBT-Cabling] [10GBASE-T] a channel
capacity estim...
George, All
The primary purpose of the ongoing discussion was to decide if the PAM10
design could exist on 100m CAT5 cable. Following the discussion I don't
feel
on the solid ground as tens dBs in SNR grow and fall mostly in
cancellation
ratio parameters. The Alien NEXT level and possible cancellation are not
based with enough data.
The implications of the Echo, NEXT, FEXT cancellation ratio presented by
Solarflare also are not clear to me. The cancellation ratio will be
impacted
by coefficients resolution in digital domain, by jitter and other
impairments in analog domain. Does the proposed cancellation ratio
demand
reasonably achievable analog and digital parameters?
Meanwhile to promote the primary purpose I would like to refer to the
document distributed by William Jones few weeks ago (attached).
If I understand correctly it describes the SNR after the equalizer on
100m
CAT5 with ground noise only. The SNR for -140dBm/Hz ground noise (no
Echo,
NEXT, FEXT) is roughly 28dB. Assuming coded signal SNR for BER 10^-10 as
25dB, it remains only 3 dB margin for Echo,NEXT,FEXT, Alien NEXT and
implementation impairments.
Again if I understand correctly the graph, it seems that there will be
negative margin considering all noises exist.
Regards,
Boris Fakterman - Intel Communications Group, Israel
Tel: 972-4-865-6470, Fax: 972-4-865-5999
mailto:boris.fakterman@intel.com