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RE: [10GBT-Cabling] RE: [10GBASE-T] channel model




Chris,

Accounting for temperature dependencies by a simple extension of length may be reasonable for some frequency ranges as established in those forums.  But, we must be very careful to make sure that a similar extension is valid over the wider frequency ranges we are considering here. 

For the benefit of the study group, can you give us just the highlights of the "hot" debate?  Even a pointer to some of the key technical contributions in this debate would be helpful.  While we don't want to re-enter into a messy discussion, we do want to benefit from what has gone before.  

Bill

Chair Modeling Ad Hoc


Director of Systems Engineering
SolarFlare Communications, Inc.
949-581-6830, ext. 2550
mobile: 619-405-2445
fax: 949-581-4695
wjones@solarflare

-----Original Message-----
From: CDimi80749@aol.com [mailto:CDimi80749@aol.com]
Sent: Thursday, January 30, 2003 8:22 AM
To: CDimi80749@aol.com; William Jones;
stds-802-3-10GBT-Modeling@ieee.org
Cc: stds-802-3-10gbt@ieee.org; stds-802-3-10GBT-Cabling@ieee.org
Subject: Re: [10GBT-Cabling] RE: [10GBASE-T] channel model


Bill,
  
 Frequency range of channel characterization:
 Based on the modeling ad hoc input I'll recommend to the cabling ad hoc that 
they provide  
 channel characterization (measurement data) from DC to 500 MHz (min) and 
that we 
 consider measurements to 1 GHz.
 
 The use of temperature dependent transmission models:
 The ISO/IEC 11801 implementations (channel models) are based on component 
performance at 20 C. 
 For operating temperatures above 20 C a calculation is provided to adjust 
the horizontal link length.
 
 The use of temperature dependent channel models was "hotly" debated over a 
long period of time in both
  ISO and TIA. Let's avoid revisiting the fun and excitement and base our 
channel models on
 component performance consistent with ISO/IEC 11801. 
 
 
 Regards,
  
  Chris DiMinico
  Chair Cabling Ad Hoc
  MC Communications
  e-mail: cdiminico@ieee.org
  phone:978-441-1051
 
 
 In a message dated 1/29/03 6:43:18 PM Eastern Standard Time, 
wjones@solarflare.com writes:
 
 << Chris
  
  The issues that I see in determining the frequency range of the channel 
characterization are:
  
  1) The ability to make accurate high frequency measurements and to validate 
the results among multiple independent cable vendors.  This suggests a lower 
frequency range. 
  
  2) The frequency range must be the same for all types of measurements (line 
as well as crosstalk measurements).  So, although accurate higher frequency 
channel measurements may be possible, our experience has been that FEXT is 
the most challenging.  This can limit the frequency range more.
  
  3) Flexibility to perform system tradeoffs suggests a higher frequency 
range.
  
  Based on these considerations, I propose the characterization of all 
measurements (line and crosstalk) be 
  from DC to 500 MHz.
  
  Bill
  
  Chair Modeling Ad Hoc
  
  William W. Jones, Ph.D.
  Director of Systems Engineering
  SolarFlare Communications, Inc.
  949-581-6830, ext. 2550
  mobile: 619-405-2445
  fax: 949-581-4695
  wjones@solarflare.com
  
  
  -----Original Message-----
  From: CDimi80749@aol.com [mailto:CDimi80749@aol.com]
  Sent: Wednesday, January 29, 2003 9:32 AM
  To: Larry Cohen; William Jones; stds-802-3-10gbt@ieee.org;
  stds-802-3-10GBT-Cabling@ieee.org
  Subject: Re: [10GBASE-T] channel model
  
  
  Larry,
  
  Thanks for getting this started.
  
  Your contribution addresses (at least) three significant elements of the 
  channel model development: 
  
  1. frequency range of channel characterization
  2. the use of temperature dependent transmission models
  3.proposed model limits (with supporting measurement data)
  
  We should try to reach consensus on the elements.
  
  1. The modeling ad hoc should reach a consensus on the frequency range of 
  channel characterization.
  Note:We should limit the channel characterization to account for relevant 
  signal spectrum and 
  minimize excess bandwidth characterization. 
  
  2. The 10GBASE-T study group should reach consensus on temperature 
  dependencies (in the objectives?).
  
  3. I'm in the process of developing a straw proposal for the cabling ad hoc 
  to address 
  the generation of measurement  data.  Note: We need the resolution of the 
  frequency range of channel 
  charcterization (1).
  
  Regards,
  
  Chris DiMinico
  Chair Cabling Ad Hoc
  MC Communications
  e-mail: cdiminico@ieee.org
  phone:978-441-1051
  
  In a message dated 1/29/03 1:33:04 AM Eastern Standard Time, 
  lcohen@solarflare.com writes:
  
  << Attached is a proposed 100 meter Cat 5e channel model for 10GBaseT study 
  (CHANMOD.TXT).  This model is defined by complex-valued (X + jY format) 
  insertion gain in the at 500 kHz intervals from DC to 1 GHz.   
   
   The proposed model is derived from measurement (at 20 C) of a 100 meter 
  channel (with Cat 5e patch cords and 4 Cat 5e RJ45 connector interfaces).  
  The baseline 100 meter channel model was temperature corrected to 50 C. 
(122 
  F.) using the procedure defined in ASTM D4566 Section 26.4.  The above 
  mentioned temperature correction method modifies the magnitude but not the 
  phase of the insertion loss.  Experimental measurements confirm that 
  temperature effects on the phase are minimal so the approximation is 
  sufficiently accurate.  
   
   The most recent proposed model is an extrapolation of the ISO 11801 Class 
D 
  channel loss limit.  The ISO 11801 Class D limit is designed to accommodate 
  expected worst-case measurements below 100 MHz and consequently includes 
some 
  additional margin to meet this requirement.  Since this limit is only 
  specified below 100 MHz, extrapolation of the limit through smooth curve 
  fitting becomes less accurate as it is extended farther beyond its defined 
  boundaries.  The new proposed model is based upon measurements beyond 500 
MHz 
  and thus validated to at least 500 MHz (and somewhat beyond 500 MHz).  As 
  shown in the attached graphs (CHANMOD.DOC), the insertion loss for the 
  proposed model differs from the ISO 11801 Class D 2002 channel limit by 
less 
  than 0.2 dB from DC to 50 MHz and less than 0.5 dB from 50 to 100 MHz.  
While 
  it does not represent an absolute worst-case channel, it represents a 
  reasonable model for a feasibility study simulating a maximum length 
channel 
  under worst-case temperature conditions.