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[802.3_ISAAC] AW: Summary of this morning's channel and return loss ad hoc

Hello all,

 

I would like to address some of the items listed by George below.

 

  1. I am not sure what the reasoning is behind considering the same requirements for differential and single ended link segments. As differential and single ended varies significantly in physics, it would not be possible to define a link segment such that the receiver implementation can be optimum for both. I would therefore support defining different limit lines (and supported link lengths) for each cable type. I also second to focus on coaxial as the link segment that has to meet the 15m first.
  2. Concerning flexible and not flexible cable segments. From my experience, flexible cable segment would always be as short as possible and they would always be used only where flexibility is needed. This is in car doors or trunk lids. In my opinion, assuming three meters for the flexible segment is very generous, two meters or less are much more likely and would suffice from my perspective. But maybe other experts on this matter can comment, too.

 

Kind regards,

 

Kirsten

 

Von: George Zimmerman <george@xxxxxxxxxxxxxxxxxxxx>
Gesendet: Freitag, 2. August 2024 01:26
An: STDS-802-3-ISAAC@xxxxxxxxxxxxxxxxx
Betreff: [802.3_ISAAC] Summary of this morning's channel and return loss ad hoc

 

Sent from outside the BMW organization - be CAUTIOUS, particularly with links and attachments. 

Absender außerhalb der BMW Organisation - Bitte VORSICHT beim Öffnen von Links und Anhängen. 

All – for those who were unable to attend, we held the first channel and return loss ad hoc this morning.  Surprisingly, there seemed to be less consensus than the rather close presentations from July on insertion loss would suggest.  There was significant discussion on insertion loss and topologies, with consensus to focus initially on the coax link segment.  Beyond that, there was significant discussion about just what the ‘15m objective’ meant, what topologies to consider (e.g., how much flexible cable), and whether 15m was met only on new cable or whether that would included aging and temperature.  There was not significant discussion of return loss, noise, or other impairments.  The next ad hoc will be held on August 14, 7-9am pacific, chaired by Natalie Wienckowski.  I urge you to continue the discussions on the reflector in the meantime.  I have forwarded draft minutes, the agenda, and the presentation reviewed today to Jon for posting. 

 

Meanwhile, below, find the questions we generated for future presentations (thank you, Natalie):

 

From what point to what point do we need to define?  Link segment only, include MDI, include PCB limits?

 

Do we want to define separate differential and single ended requirements?  Focus on Coax first.

 

How much of the coax cable needs to be the flexible cable?  Percentage of total length, max number of meters regardless of total length, etc.

 

A better understanding of coax cable connector reflections and current limit lines in other organizations is needed.

 

More discussion is needed on noise models.

 

Is 15m with 4 in-lines the cable over the lifetime of the cable over the specified operating conditions, or are the limits based on the new cable only?

 

 

-george

 

 

George Zimmerman, Ph.D.

President & Principal

CME Consulting, Inc.

Experts in Advanced PHYsical Communications

george@xxxxxxxxxxxxxxxxxxxx

310-920-3860

 

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