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*To*: "George Zimmerman" <gzimmerman@solarflare.com>*Subject*: RE: [10GBT-Modeling] RE: [10GBT-Cabling] [10GBASE-T] a channel capacityestim...*From*: xichen@marvell.com*Date*: Wed, 26 Feb 2003 14:04:45 -0800*Cc*: <stds-802-3-10GBT-Modeling@ieee.org>, <stds-802-3-10GBT@ieee.org>*Sender*: owner-stds-802-3-10gbt@majordomo.ieee.org

George, I did not mention or emphasize any optimal DFE modeling in my message that you referred. I only agreed to work on a program that can help us to evaluate the situation. Before that I did not talk about anything of DFE modeling at all. The first thing I sent out for people's evaluation is the program that calculates the channel capacity. I have emphasized many times in some following emails that if the channel capacity calculation tells us that this is not feasible, then the optimal DFE modeling won't do anything better. The channel capacity metric can be somehow useless if most people in this group disagree with me. I believe that I have tried to put away my personal opinion in the discussion as much as possible. The channel capacity metric is not for use of implementation, but of feasibility only. In that sense, I think it is "flawless" if we use the group-accepted, scaled, selected, measured channel data and group-accepted achievable noise/interference cancellation levels with the program. Then the problem becomes that how much noise/interference cancellation can be achieved in implementation. If we can cancel all noise/interference completely, we can do anything we want. But the truth is that we cannot. We need to reach a consensus on how much we can achieve. I think this will be a topic in the Dallas meeting. Regards, Xiaopeng "George Zimmerman" <gzimmerman@solarflare.com> on 02/26/2003 12:01:35 PM To: <xichen@marvell.com>, <stds-802-3-10GBT-Modeling@ieee.org>, <stds-802-3-10GBT@ieee.org> cc: Subject: RE: [10GBT-Modeling] RE: [10GBT-Cabling] [10GBASE-T] a channel capacity estim... Xiaopeng - Perhaps you misunderstood me on using optimal DFE or time-domain simulations. As models of implementations, those are worse than capacity calculations. HOWEVER, capacity is sensitive to how much noise is left over after cancellation. A main issue was raised as to implementation losses & how much cancellation was feasible. DFE & time domain simulations are a proposal to address the concerns over implementation losses only. It is unfortunate that you have now taken a "flawless" model for your metric. I can only interpret that as a complete design for the system, including finite word length & circuit noise effects. This is WELL beyond what has been done in other standards. To refresh your memory: ---begin snip ---- -----Original Message----- From: xichen@marvell.com [mailto:xichen@marvell.com] Sent: Wednesday, January 15, 2003 9:18 AM To: William Jones Cc: stds-802-3-10gbt@ieee.org Subject: RE: [10GBASE-T] The channel model Bill, Sure. Once the common channel model (I only need the frequency domain model) is available, I can work on it. Regards Xiaopeng To refresh your memory: "William Jones" <wjones@solarflare.com> on 01/15/2003 08:56:07 AM To: <xichen@marvell.com>, <stds-802-3-10gbt@ieee.org> cc: Subject: RE: [10GBASE-T] The channel model Xiaopeng Would you be willing to sign up for technical feasibility based on an optimal DFE calculation? regards Bill -----Original Message----- From: xichen@marvell.com [mailto:xichen@marvell.com] Sent: Tuesday, January 14, 2003 3:01 PM To: stds-802-3-10gbt@ieee.org Cc: William Jones Subject: RE: [10GBASE-T] The channel model Bill, I has no problem to use TIA or ISO based channel and noise model once it is standardized. My point is that even using the frequency-domain model we can still give a quite good estimation of the practically achievable distance at a throughput of 10Gbps over CAT-5E or CAT-6 cables. Regards, Xiaopeng ------ end snip ----- 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: Wednesday, February 26, 2003 11:30 AM To: stds-802-3-10GBT-Modeling@ieee.org; stds-802-3-10GBT@ieee.org Subject: RE: [10GBT-Modeling] RE: [10GBT-Cabling] [10GBASE-T] a channel capacity estim... Hi, all, I may be short-memory, so I cannot remember where and when I have proposed to this group a so-called optimal DFE modeling. If somebody can recall that for me, your help will be highly appreciated. Any success in either 1000BASE-T, DSL, RF&wireless or any other standard does not guarantee our success. To my knowledge (I may be wrong since there are way too many things that I do not know and I am ready to learn), if you give a channel capacity estimation by the way I am using, you will find out that all the above systems have quite a lot SNR margin given what their specifications state. And I don't think that the channel capacity metric is unfortunately meaningless and "obstructive" in our case. If I am not wrong, the channel capacity estimation is relatively simple AND can give us a quite clear view of what the BEST thing we can do with the channel if the complexity is not a concern. If Shannon tells us that the channels that we are discussing cannot support the data/distance that we are targeting now, I don't think any time-domain simulation or optimal DFE receiver or any other remedy can help us at all. That is the only thing that I want to tell the group by using the channel capacity metric. Let's not forget that Shannon told us that there is something that we cannot do (given we well understand the conditions, e.g., noises, interferences, etc...) no matter how smart or whoever we are. If anyone can put forward a proposal that is flawless and can be accepted by most of the group, I have not problem to follow. If somebody tell me something that I may not agree, I will not simply call it "obstructive". I will first study what I heard, express my opinion, then discuss the problem constructively. I think that is the way I am trying to work here in this group. Regards, Xiaopeng "George Zimmerman" <gzimmerman@solarflare.com>@majordomo.ieee.org on 02/26/2003 10:09:05 AM Sent by: owner-stds-802-3-10gbt-modeling@majordomo.ieee.org To: <stds-802-3-10GBT-Modeling@ieee.org> cc: Subject: RE: [10GBT-Modeling] RE: [10GBT-Cabling] [10GBASE-T] a channel ca pacity estim... We have put forward more detailed models. It is very important that the group agree on a level of modeling necessary to go forward. Initially Xiaopeng proposed optimal DFE modeling, which has been used successfully in standards in the past. Then he put forward a simpler metric - capacity modeling. Now you are asking for more detail. We've only been going from what you have put forward. In November we provided detailed time-domain simulations, based on implementation-dependent architectures. That is fairly implementation specific and goes beyond what I believe is required. We must identify which items are near state of the art, and then work them individually. Today you will find 1000BASE-T systems routinely working at 140 meters, although lower bandwidth, and half the PAM levels, that is still 40% more dB loss, which translates directly to linearity & cancellation requirements. DSL systems operate with MUCH higher cancellation requirements today. RF & wireless systems, as well as read-channel devices also ship at higher bandwidth, and similar levels of noise performance. These problems are hard, but not impossible. All are technically feasible. Let us agree on a methodology for modeling to get to technical feasibility. Clearly following Xiaopeng's lead on the capacity calculation has lead to a dead end. It sounds like the second level, optimal DFE calculations, may be an appropriate point, and then enumerate the limited number of effects that are first-level models. Remember - technical feasibility is not a complete design in the committee. If you have an alternate proposal that you would consider acceptable to move forward it would be appreciated. Otherwise I can only conclude you are simply being obstructive. -george 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: Wednesday, February 26, 2003 9:51 AM To: Fakterman, Boris Cc: stds-802-3-10GBT@ieee.org; stds-802-3-10GBT-Modeling@ieee.org Subject: RE: [10GBT-Modeling] RE: [10GBT-Cabling] [10GBASE-T] a channel ca pacity estim... Boris, I completely agree with you. The undergoing discussion is to let everyone in this group understand what kind of problems we are facing in setting up the new standard. We are dealing with more than a academic problem, we are dealing with a standard that will be tested in the field. Therefore carefully counting all the factors in the real world is definitely necessary for our success. Before doing something, we must know what we can do and cannot. If we simply set up a goal and we actually don't know whether we can do it or not. Then a lot of the efforts in this group can be wasted without any return. So let's wait until the cable data accepted by everybody in this group are available. Then the discussion can restart on a solid ground. Regards, Xiaopeng "Fakterman, Boris" <boris.fakterman@intel.com>@majordomo.ieee.org on 02/26/2003 07:38:54 AM Sent by: owner-stds-802-3-10gbt-modeling@majordomo.ieee.org To: George Zimmerman <gzimmerman@solarflare.com>, stds-802-3-10GBT@ieee.org, stds-802-3-10GBT-Modeling@ieee.org cc: Subject: RE: [10GBT-Modeling] RE: [10GBT-Cabling] [10GBASE-T] a channel ca pacity estim... George, I agree that we need more data to collect. We should be based on the cables data accepted by everybody and the cables group does a great work to prepare it. I agree that it is a high performance system and the cancellation ratio you proposed is the state of the art. This is exactly the reason we should carefully consider the impact of the system definitions to the analog/digital blocks definitions, just not to cross the close border to impossible. For example the 1000BASE-T standard requires 10mV transmitter distortion on PAM5/125MHz system. Do you estimate the 10Gb standard will require much better performance on PAM10/833MHz system? Do I clearly understand you statement? Do you say that remaining after the DFE three dB margin will be enough for all cancellers? In any case it is required to remain at least 3 dB margin after all cancelled noises were counted. I can't see this from the discussed DFE analysis. Boris Fakterman -----Original Message----- From: George Zimmerman [mailto:gzimmerman@solarflare.com] Sent: Wednesday, February 26, 2003 5:08 PM To: Fakterman, Boris; 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 - 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

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