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*To*: STDS-802-3-10GMMF@xxxxxxxxxxxxxxxxx*Subject*: Re: [10GMMF] TP3 Meeting minutes, November 23rd*From*: Vivek Telang <vtelang@xxxxxxxxxxxx>*Date*: Tue, 30 Nov 2004 10:47:47 -0800*Reply-To*: "IEEE P802.3aq 10GBASE-LRM"<stds-802-3-10gmmf@xxxxxxxx>*Sender*: owner-stds-802-3-10gmmf@xxxxxxxx*Thread-Index*: AcTXAH4wZZ8UBh5fQfuxIJ/CSn84zwACds6w*Thread-Topic*: [10GMMF] TP3 Meeting minutes, November 23rd

Robert, and all, Your question and concerns are definitely valid. The PIE-D metric serves as a good initial indicator of feasibility. But it does not address the issue of complexity (specifically, filter lengths). To get a handle on that, we need to compute the penalties for receivers based on finite-length equalizers. I share your concern that reasonable-complexity finite-length equalizers may not be able to meet the 1dB budget for some of the more challenging fibers. Fortunately, it is quite straightforward to determine the performance of finite-length equalizer receivers, without having to run long BER simulations. Closed form MATLAB analysis can be used to determine the steady state performance of FFE/DFE based systems. This has a long history in many of the DSP-based comm. systems, including 1000BASE-T and now 10GBASE-T. Historically, the steps in determining feasibility have been (1) Channel Capacity (ideal) (2) Salz Bound (PIE-D) (more realistic) (3) Finite length MMSE analysis (much more realistic, except for transient behavior) and (4) Finite length, finite precision simulations (the real deal). We have been on step 2 so far, and it seems like it's time to move to step 3. So IMO, we should be using finite-length equalizer analysis to determine the budget. Regards, Vivek Vivek Telang Broadcom Corp. -----Original Message----- From: owner-stds-802-3-10gmmf@ieee.org [mailto:owner-stds-802-3-10gmmf@ieee.org] On Behalf Of Lingle, Jr, Robert (Robert) Sent: Tuesday, November 30, 2004 9:00 AM To: STDS-802-3-10GMMF@listserv.ieee.org Subject: Re: [10GMMF] TP3 Meeting minutes, November 23rd I am less knowledgeable than many on this list, but I am trying to understand the difference between the ideal, infinite case and the real, finite case. As a step in that direction, we tried in San Antonio presentation to take a step in that direction by looking at ideal, finite case. What we saw, but do not fully understand, is that it seemed that the higher the MSE PIE-D, the lareger the difference between PIE-D and any finite equalizer could be. Some questioned my conclusions afterward, but none refuted them conclusively. The implications are the following: suppose we set a limit that 99% of fibers must pass PIE-D < 5.5, and leave a 1 dB implementation penalty. Then what we really need to know is the following: do fibers with PIE-D between 4.5 and 5.5, which nominally seem to pass, actually have implementation penalties (hardware and equalizer design) that keep them below the 6.5 dB limit? If my logic is flawed, please help me correct it. do we have to calculate finite equalizer cases as well? Robert Lingle, Jr Fiber Design and Development OFS R&D, Atlanta, GA -----Original Message----- From: Bottacchi.external@INFINEON.COM [mailto:Bottacchi.external@INFINEON.COM] Sent: Tuesday, November 30, 2004 10:23 AM To: STDS-802-3-10GMMF@listserv.ieee.org Subject: Re: [10GMMF] TP3 Meeting minutes, November 23rd Importance: High John, It is an interesting proposal, at least theoretically. Assuming infinite length FFE, I guess zero forcing solution would be possible (in principle). This means no residual ISI at sampling instant (not just minimum error modulus like MMSE). As a consequence, noise enhancement is strongly expected to be the limiting factor for EDC performances. I am quite curious to see how much would be the optical penalty since I calculated some month ago the PID-L for the zero forcing (linear) equalizer in term of noise bandwidth enhancement( I sent a ppt copy to Sudeep for comparison with PIE-D/L reported metrics). Does zero forcing PIE-D expected to be different from noise bandwidth enhancement due to full frequency compensation for a given output ISI free spectrum (raised-cosine for example)? Thank you for posting this issue... Best regards Stefano -----Original Message----- From: owner-stds-802-3-10gmmf@IEEE.ORG [mailto:owner-stds-802-3-10gmmf@IEEE.ORG] On Behalf Of Abbott, John S Dr Sent: Dienstag, 30. November 2004 15:48 To: STDS-802-3-10GMMF@listserv.ieee.org Subject: Re: [10GMMF] TP3 Meeting minutes, November 23rd In regard to Lew's and Sudeep's points, are there conditions where we should calculate the zero forcing PIE-D as well as the MSE PIE-D? At the San Antonio meeting there seemed to be comments supporting both. Regards, John Abbott -----Original Message----- From: Sudeep Bhoja [mailto:sbhoja@BIGBEARNETWORKS.COM] Sent: Monday, November 29, 2004 5:39 PM To: STDS-802-3-10GMMF@listserv.ieee.org Subject: Re: [10GMMF] TP3 Meeting minutes, November 23rd Lew, This in response to your Comment #1 below. The PIE-D equations from bhoja_1_0704 targets an infinite length DFE that minimizes mean square error (MMSE). MMSE Equalizers perform better than Zero forcing Equalizers. Conventional adaptation algorithms such as LMS, minimize mean squared error. If we agree on an MMSE based infinite length DFE, there are two variables that enter into the calculation: 1) The first variable is easy and follows directly from the link budget. sigma^2 -> This is the Electrical noise floor at the input of the ideal EDC and is easily derived from the link budget. We had previously set sigma^2 = 10^(-17-2*6)/10 since we had allocated 6dB of total dispersion budget. However since the connector loss was updated to 1.5dB from 2dB Page 5 in lawton_1_1104 allocated 6.5dB to the total dispersion budget. Hence we need to update sigma^2 = 10^(-17-2*6.5)/10 = 10^(-30/10) in our PIE-D calculations. 2) The rise time used in deriving the fiber pulse response in bhoja_1_0104 was set to 47.1ps (20-80% Gaussian). This number was chosen from -LR. For the purpose of the TP3 stressed tests, we only need to represent the rise time of the test setup of Fig 68.6 in D0.2. For this purpose 47.1ps is probably an adequate rise time. Best Regards, Sudeep -----Original Message----- From: owner-stds-802-3-10gmmf@IEEE.ORG [mailto:owner-stds-802-3-10gmmf@IEEE.ORG]On Behalf Of Lew Aronson Sent: Monday, November 29, 2004 12:47 AM To: STDS-802-3-10GMMF@listserv.ieee.org Subject: Re: [10GMMF] TP3 Meeting minutes, November 23rd Some comments: 1) I think it is very important that all are aligned on the PIE-D calculation. I would be interested in a discussion on the variables mentioned below, what differences exist now between different task force members algorithms and the likely impact of changes of each of these parameters. Lew -----Original Message----- From: Michael Lawton [mailto:mike_lawton@AGILENT.COM] Sent: Wednesday, November 24, 2004 6:10 AM To: STDS-802-3-10GMMF@listserv.ieee.org Subject: [10GMMF] TP3 Meeting minutes, November 23rd Dear TP3ers, Here are my notes from yesterdays call. Key issues which were raised:- PIE-D has variables associated with it (rise time, sigma^2, ZF vs MMSE calculation) - how do we handle that? Any comments/corrections please get back with me. Best Regards Mike

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