Thread Links Date Links
Thread Prev Thread Next Thread Index Date Prev Date Next Date Index

RE: [10GBT-Modeling] RE: [10GBT-Cabling] [10GBASE-T] a channel capacity estim...

Sreen or Chris

Was the simulation activity for 1000BASE-T that you are referring to done during the study group or done during the task force?


-----Original Message-----
From: Booth, Bradley []
Sent: Wednesday, February 26, 2003 1:47 PM
Subject: RE: [10GBT-Modeling] RE: [10GBT-Cabling] [10GBASE-T] a channel
capacity estim...

These messages haven't been making it to the reflector due to a bad word
match.  The word has been deleted.


-----Original Message-----
From: "Sreen Raghavan" <>
To: <>, <>,
Subject: RE: [10GBT-Modeling] RE: [10GBT-Cabling] [10GBASE-T] a channel
capacity estim...
Date: Wed, 26 Feb 2003 13:33:09 -0800
Importance: Normal


I recall the 1000BT simulation efforts quite vividly, and measured cable
models were a huge part of it. In my opinion, there should be two
aspects to the study we all are involved in for 10GBaseT:

1. Does the effort make sense from channel capacity calculations with
(a) limit lines and (b) measured models of CAT5 and CAT6 cables?

2. If the answer to (1) is yes, then we should discuss the selection of
the appropriate line coding method for such cables. If the answer to (1)
is no even simply based on 1(a), we may be better off considering a
better cabling system (CAT7 comes to mind but I am in noway not wedded
to it) and then proceed to choose the appropriate line coding for the
selected media.

I do agree that we must confirm all our results with measured cable
models especially in step 2. I think by using calculations presented so
far regarding 1(a), we can easily eliminate some cabling choices for 100
meter transmission over twisted pairs, and focus our efforts on the
appropriate cabling systems.


-----Original Message-----
From: [] 
Sent: Wednesday, February 26, 2003 1:11 PM
Subject: Re: [10GBT-Modeling] RE: [10GBT-Cabling] [10GBASE-T] a channel
capacity estim...


The 1000BASE-T tutorial includes a presentation that Bob Cambell
(Lucent) and 
I made addressing
Category 5 cabling models for line code simulations. The presentation
the "measured data" used 
in the 1000BASE-T Matlab code to evaluate the 3 dB and 10 dB design

In 10BT, 100BT, and 1000BT we made many^10 (that's many to the 10th
to validate and test the design(s). The measurements are  the basis for
establishment of the
limits specified in those standards. 


Chris DiMinico

In a message dated 2/26/03 2:00:19 PM Eastern Standard Time, writes:

<< During 10BaseT, 100BaseTX, and 100BaseT standard developments, we
 assumed insertion loss limit lines for analysis and simulations. This
 would guarantee that every CAT5 or CAT5e cable will be able to achieve
 error free performance at a distance of 100 meters and beyond. We
 develop a standard based on "some measurements" of "some cables". 
 I would also add that in reality, every manufacturer of 1000BaseT PHYs
 satisfying the IEEE standard achieves well in excess of 100 meters of
 CAT5 performance (Most manufacturers of 1000BaseT PHYs guarantee
 error-free performance up to 140 meters). This extra distance is
 required by most system vendors as they believe it provides additional
 operating margin that they need. Based on my experience in LAN
 transceivers (My colleagues and I built DSP-based 10/100/1000 PHYs that
 are shipping in millions of quantities today), customers require
 error-free performance, i.e., an error-rate that is orders of magnitude
 below that specified in the standard. Hence, we must choose a solution
 to 10GBaseT that has substantial built-in SNR margin. 
 We at Vativ (formerly Myrica)have done substantial analysis work in
 MATLAB regarding the feasibility of the approach presented by
 at November 2002 meeting. The results we obtained are very similar to
 those presented by both Z. Roth and X.Chen. We plan to share our
 at the upcoming IEEE meeting in March 2003.
 In summary, based on almost any reasonable metric, the proposal by
 Solarflare is an unworkable approach.
 Sreen Raghavan
 Vativ Technologies, Inc. (Formerly Myrica Networks, Inc.)
 -----Original Message-----
 [] On Behalf Of William
 Sent: Wednesday, February 26, 2003 10:00 AM
 To: Fakterman, Boris; George Zimmerman;;
 Subject: RE: [10GBT-Modeling] RE: [10GBT-Cabling] [10GBASE-T] a channel
 capacity estim...
 Let me clarify two points.  First, the interpretation of the graph is
 that all residual noise sources combine to be below the noise level,
 example, -140 dbm/Hz.  This has a direct consequence with the
 implementation of the cancellers. Second, this particular data used the
 ISO insertion loss limit line.  Using measurement based models will
 yield additional SNR margin. 
 -----Original Message-----
 From: Fakterman, Boris []
 Sent: Wednesday, February 26, 2003 3:48 AM
 To: George Zimmerman;;
 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
 design could exist on 100m CAT5 cable. Following the discussion I don't
 on the solid ground as tens dBs in SNR grow and fall mostly in
 ratio parameters. The Alien NEXT level and possible cancellation are
 based with enough data. 
 The implications of the Echo, NEXT, FEXT cancellation ratio presented
 Solarflare also are not clear to me. The cancellation ratio will be
 by  coefficients resolution in digital domain, by jitter and other
 impairments in analog domain. Does the proposed cancellation ratio
 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
 CAT5 with ground noise only. The SNR for -140dBm/Hz ground noise (no
 NEXT, FEXT) is roughly 28dB. Assuming coded signal SNR for BER 10^-10
 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.
 Boris Fakterman - Intel Communications Group, Israel
 Tel: 972-4-865-6470, Fax: 972-4-865-5999
 -----Original Message-----
 From: George Zimmerman []
 Sent: Wednesday, February 26, 2003 3:24 AM
 Subject: RE: [10GBT-Modeling] RE: [10GBT-Cabling] [10GBASE-T] a channel
 capacity estim...
 Xiaopeng & Zeev -
 Respectfully, no matter how many times you say it, you continue to
 grossly distort the proposals put forward.  I have a plot generated by
 Zeev's version of your code to show the input noise levels, which can
 compared with the measurement-based models in the November tutorial. I
 tried to attach just the relevant graphs from the tutorial, but the
 reflector bounced it for size - you'll have to go to the web site.
 A few of the significant differences, some mentioned by Bill in an
 earlier email are:
 1) Use of smooth limit lines vs. a measurement-based model (such as was
 used for 1000BASE-T) scaled to worst-case.  This is NOT "a couple of
 dB", more like 4-6 dB, and, more importantly, changes the relationship
 for the required cancellation.
 2) Do NOT use the "required cancellation" numbers we gave for
 "achievable cancellation", and it is inappropriate to use them with
 different line models.  When there is more crosstalk, as has been said
 before, it is often the case that more cancellation is achievable.
 is often true because the root cause of the crosstalk has changed so
 that it involves a shorter time delay with stronger coupling.
 3) As more noise sources are accounted for the "background" must be
 reduced.  We used -143dBm/Hz in the November tutorial & support that
 less, based on measurements) when Alien crosstalk is accounted for
 separately, as was done in the capacity calculations in the tutorial.
 (worth 3 dB)
 4) the Alien NEXT model is overly pessimistic, this is a discussion in
 the modeling group. Not just the limit line, but data shows (see the
 November presentation, not from us, but from Sterling & Avaya) that
 actual Alien NEXT is significantly below (10 dB at least) the limit in
 the higher frequencies.
 5) Zeev has incorrectly used 0 dB alien NEXT reduction in his code
 "SolarFlare cancellation".  We clearly show 10 dB relative to our
 If the Alien NEXT model is different, more cancellation is likely
 possible.  I can't say without seeing a cable & the model.  You can't
 just adjust the model keep the cancellation fixed, they are related.
 dB improvement)
 So, we're seeing more than 20 dB pessimism here.  I'd scarcely say "a
 couple dB".  It's a pretty gross misrepresentation.  What we need to do
 is wait for code using proper models.
 George Zimmerman
 tel: (949) 581-6830 ext. 2500
 cell: (310) 920-3860
 -----Original Message-----
 From: [] 
 Sent: Tuesday, February 25, 2003 2:25 PM
 To: Ze'ev Roth
 Subject: RE: [10GBT-Modeling] RE: [10GBT-Cabling] [10GBASE-T] a channel
 ca pacity estim...
 Thank you for your message.  Your observation is right.  I thought that
 -140dBm/Hz background noise level is a double-sided PSD when I got it
 the document.  Either reducing the background noise by 3dB or
 the input signal PSD by 3dB should fix the problem.   You have also
 provided the capacity results after the modification.  They basically
 us the same story we have been facing.
 Of course the smooth limit line model used in the program will be
 by the scaled, selected, measured channel data when they are offically
 available.  Only couples of dB SNR improvement to performance based on
 channel limit model should be expected.   Once we obtain more accurate
 results on the channel capacity, we will be able to to assess our
 achievable targets for the 10GBT standard.
 "Ze'ev Roth" <> on 02/25/2003 05:50:48 AM
 To:    "''" <>,
 Subject:    RE: [10GBT-Modeling] RE: [10GBT-Cabling] [10GBASE-T] a
        ca   pacity  estim...
 Xiaopeng hi,
 Very good work.
 In order to probe into this deeper,  I  initially simplified your
 to having only a single simple impairment - background noise (i.e., I
 removed from your simulation all other impairment: NEXT, FEXT, ANEXT,
 The resulting capacity was 15.29Gbit/sec.
 This simplification allows me to  compare your results with my
 results. Running my routine on same parameters I got capacity of
 So clearly there was a discrepancy in the results.
 Previously I've cross checked my routine on simple problems and
 textbook results, as well as put it to scrutiny with a several
 so I am quite confident it yields correct results.
 Therefore, I dug a bit into your equations (in the Matlab file), I
 there is a slight problem with the definition of spectral density (it
 doesn't account for double sided) - there is a subtlety in capacity
 equations (the usual 3dB problem) and I think you may have fallen into
 pit. And indeed when I add 3 dB to the noise floor in my simulation I
 capacity of 15.327. The difference from 15.29 can probably be
 a different frequency grid and that I used an older version of the
 loss limit equation which is marginally different than the one you've
 I've taken the liberty to modify your code (I started out with the
 version you've sent) to account for the double sided density (one can
 switch between the original code and my correction) and attached it
 I've added comments showing were the single sided - double sided
 density switch occurred in my opinion. I've also  added a sanity check
 option for simple AWGN channel case.
 Running the modified program I got the following results:
 Cable=CAT-5E   Cancellation=Marvell             Capacity= 8.89 Gb/sec
 Cable=CAT-6     Cancellation=Marvell            Capacity=11.36 Gb/sec
 I've also added the option to use Solarflare's figures for
 DSP-improvement as presented in Kauai.
 Running the modified program under these assumptions yields:
 Cable=CAT-5E      Cancellation=SOLARFLARE        Capacity=5.57 Gb/sec
 Cable=CAT-6       Cancellation=SOLARFLARE        Capacity=7.26 Gb/sec
 Summarizing, although there was a small flaw in the original M file,
 basic conclusions seem to hold water and moreover using Solarflare's
 assumptions regarding DSP cancellation performance yield that neither
 nor CAT6 can support 10Gb/sec for 100m cable length.