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*To*: <stds-802-3-10GBT-Modeling@ieee.org>*Subject*: RE: [10GBT-Modeling] RE: [10GBT-Cabling] [10GBASE-T] a channel capacity estim...*From*: "Booth, Bradley" <bradley.booth@intel.com>*Date*: Wed, 26 Feb 2003 13:47:26 -0800*Cc*: <stds-802-3-10gbt@ieee.org>*Sender*: owner-stds-802-3-10gbt@majordomo.ieee.org*Thread-Index*: AcLd3saGBEpc70nREdembgACpYtLYQAAUeBw*Thread-Topic*: 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. Thanks, Brad -----Original Message----- From: "Sreen Raghavan" <sreen@myricanet.com> To: <CDimi80749@aol.com>, <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... Date: Wed, 26 Feb 2003 13:33:09 -0800 Importance: Normal Chris: 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. Regards, Sreen -----Original Message----- From: CDimi80749@aol.com [mailto:CDimi80749@aol.com] Sent: Wednesday, February 26, 2003 1:11 PM To: sreen@myricanet.com; 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... Sreen, 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 depicts the "measured data" used in the 1000BASE-T Matlab code to evaluate the 3 dB and 10 dB design points. In 10BT, 100BT, and 1000BT we made many^10 (that's many to the 10th power) measurements to validate and test the design(s). The measurements are the basis for the establishment of the limits specified in those standards. Regards, Chris DiMinico In a message dated 2/26/03 2:00:19 PM Eastern Standard Time, sreen@myricanet.com writes: << During 10BaseT, 100BaseTX, and 100BaseT standard developments, we always 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 cannot 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 Solarflare 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 results 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----- From: owner-stds-802-3-10gbt@majordomo.ieee.org [mailto:owner-stds-802-3-10gbt@majordomo.ieee.org] On Behalf Of William Jones Sent: Wednesday, February 26, 2003 10:00 AM To: Fakterman, Boris; 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... Boris Let me clarify two points. First, the interpretation of the graph is that all residual noise sources combine to be below the noise level, for 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. regards Bill -----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 -----Original Message----- From: George Zimmerman [mailto:gzimmerman@solarflare.com] Sent: Wednesday, February 26, 2003 3:24 AM To: 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... 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 be 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. This 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 (or 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 under "SolarFlare cancellation". We clearly show 10 dB relative to our model. 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. (10 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 gzimmerman@solarflare.com tel: (949) 581-6830 ext. 2500 cell: (310) 920-3860 -----Original Message----- From: xichen@marvell.com [mailto:xichen@marvell.com] Sent: Tuesday, February 25, 2003 2:25 PM To: Ze'ev Roth Cc: stds-802-3-10GBT-Cabling@ieee.org; stds-802-3-10GBT-Modeling@ieee.org; stds-802-3-10GBT@ieee.org Subject: RE: [10GBT-Modeling] RE: [10GBT-Cabling] [10GBASE-T] a channel ca pacity estim... Ze'ev, Thank you for your message. Your observation is right. I thought that the -140dBm/Hz background noise level is a double-sided PSD when I got it from the document. Either reducing the background noise by 3dB or increasing the input signal PSD by 3dB should fix the problem. You have also provided the capacity results after the modification. They basically tell us the same story we have been facing. Of course the smooth limit line model used in the program will be replaced by the scaled, selected, measured channel data when they are offically available. Only couples of dB SNR improvement to performance based on the 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. Regards, Xiaopeng "Ze'ev Roth" <zeevr@mysticom.com> on 02/25/2003 05:50:48 AM To: "'xichen@marvell.com'" <xichen@marvell.com>, CDimi80749@aol.com cc: stds-802-3-10GBT-Cabling@ieee.org, stds-802-3-10GBT-Modeling@ieee.org, stds-802-3-10GBT@ieee.org Subject: RE: [10GBT-Modeling] RE: [10GBT-Cabling] [10GBASE-T] a channel ca pacity estim... Xiaopeng hi, Very good work. In order to probe into this deeper, I initially simplified your simulation to having only a single simple impairment - background noise (i.e., I removed from your simulation all other impairment: NEXT, FEXT, ANEXT, ECHO). The resulting capacity was 15.29Gbit/sec. This simplification allows me to compare your results with my program's results. Running my routine on same parameters I got capacity of 17Gbit/sec. So clearly there was a discrepancy in the results. Previously I've cross checked my routine on simple problems and compared to textbook results, as well as put it to scrutiny with a several colleagues, so I am quite confident it yields correct results. Therefore, I dug a bit into your equations (in the Matlab file), I think 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 this pit. And indeed when I add 3 dB to the noise floor in my simulation I get capacity of 15.327. The difference from 15.29 can probably be attributed to a different frequency grid and that I used an older version of the insertion loss limit equation which is marginally different than the one you've used. I've taken the liberty to modify your code (I started out with the latest version you've sent) to account for the double sided density (one can easily switch between the original code and my correction) and attached it herein. I've added comments showing were the single sided - double sided spectral 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 impairements' 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, your basic conclusions seem to hold water and moreover using Solarflare's assumptions regarding DSP cancellation performance yield that neither CAT5E nor CAT6 can support 10Gb/sec for 100m cable length. Regards, Ze'ev Mysticom

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