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Re: [802.3_SPMD] Mixing segment definition - what is 'worst case'

Refreshing this conversation. 


Chris & any others – what do we need to get this to progress?




Peter Jones               Cisco Systems           

Distinguished Engineer    170 West Tasman Dr.

Enterprise Networks       San Jose, CA, 95134, USA.

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From: George Zimmerman <george@xxxxxxxxxxxxxxxxxxxx>
Sent: Wednesday, February 24, 2021 9:08 AM
To: STDS-802-3-SPMD@xxxxxxxxxxxxxxxxx
Subject: [802.3_SPMD] Mixing segment definition - what is 'worst case'


Chris – the issue I was trying to get to on your presentation was this – In what sense is the mixing segment worst case?


Specifically, please define the metric you are using to compare IL’s that differ in shape across frequency.


Once you define that as a metric, we can then determine whether we agree. (also, it would be good to provide some sort of sweep of network configurations)


For example, possible metrics are:

The absolute minimum on the insertion loss curve? (from what frequency to what frequency?)

The magnitude of the deviation from the 802.3cg insertion loss limit?

Is it some frequency-integrated metric (e.g., ISI-limited SNR with some presumed fixed receive filter, matched-filter SNR (if so, it what noise), or a Salz SNR?)


Since the deviation and notches in the insertion loss impact the equalization, they therefore are related to receiver assumptions – so we’d better discuss some more detail.


Additionally, I wouldn’t necessarily rule out something like a small number of nodes with bad loading being a problem – so this is linked to the issue of whether we have variable inductive loading as introduced by Michael Paul…


George Zimmerman, Ph.D.

President & Principal

CME Consulting, Inc.

Experts in Advanced PHYsical Communications




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