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


Frequency range of channel characterization should be such
that it would allow the fair evaluation of various line-
signalings. 1 GHz characterization, similar to that of Larry's, 
would help us to reach that goal.

Joseph N. Babanezhad
Plato Labs.

> 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:
> phone:978-441-1051
> In a message dated 1/29/03 1:33:04 AM Eastern Standard Time, 
> 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.
>  -Larry
>   >>

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