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● PUBLIC Hi, Ragnar! Regarding your email, please find my comments in
RED
below. 1 – Whether 100C IL should be used as a reference when selecting the IL limits. In addition to the temperature, I would suggest adding losses due to long term ageing as defined in the ISO document I brought up in my presentation.
2 - The second issue is whether there should be a single IL limit defined for both coax and balanced-pair, or separate IL limits for each. Here I would suggest two different IL levels as the cable types are performing completely differently. This is what we are currently doing at ASA. If
we assume a global IL level, then we might not need to check for the coax case as they will almost certainly have a superior performance in IL (provided the length are the comparable) and frequency range. Moreover, probably STP cables should also have “speed
grades” as the IL “suck-out” will determine the maximum operating frequencies of the differential pair. This is dependent on cable construction parameters.
3 - Collaboration on these and other issues. If I can support you anyhow, please let me know.
Best Regard, Jonathan From: Ragnar Jonsson <rjonsson@xxxxxxxxxxx>
Hello Everyone, I am working with others on presentation related to Insertion Loss (IL) limits for 802.3dm. I would greatly appreciate any feedback that the group may have on couple of the issues that I am discussing with my coauthors. The first issue I would like to hear peoples views on is related to reference insertion loss for coax cables. In Annapolis we had two presentations (one by Jonathan Silvano de Sousa and one by David Cliber and Bert Bergner)
that showed IL for cables that are compliant with CX31a and CX174d/e, as specified in ISO 19642-11: Road Vehicles – Automotive Cables – Part 11. David and Bert further suggested to “Use CX174d/e (flexible) and CX31a (low loss) cable grades for calculation of link segment insertion loss requirements”, which I think is a very good idea. In particular, I think that it would make sense to use the 100C IL as reference when selecting the IL limits. What do others
think about this? Related to this first issue, it would be good to understand if the limit lines for CX31a and CX174d/e are typical for cables that have already been validated by car manufacturers for similar applications. It would be
great if cabling experts could comment on this. The second issue that I would like to hear opinions on relates to defining single or separate IL limits for coax cables on one hand and balanced pairs on the other. The 802.3dm project is more focused on saving relative
cost, rather than pushing the technical limits on maximum reach. Therefore, the challenge of setting the IL limits becomes somewhat easier than in some earlier projects like 802.3ch and 802.3cy. More specifically, in my opinion, the setting of the IL limits
is mostly about finding the right balance in the relative cost of the cabling and the relative cost of the PHY, given our objective of 15m reach on some cables. If we put too strict limits on the IL, then we reduce the reach or drive up the relative cost of
the cables. If we define too relaxed limits on the IL, then we drive up the relative cost of the PHY. The right balance is somewhere in between. This brings be back to the question that I would like some feed back on: Should there be a single IL limit defined
that applies to both coax and balanced-pair, or should there be two separate IL limits, one for coax and one for balanced-pair? Related to the second issue, the only compelling reason I can think of for having separate IL for coax and balanced-pair, would be if there is fundamental difference in the Signal-to-Noise Ratio (SNR) at the receiver,
depending on if the medium is coax or balanced-pair cables. Is anyone aware of such fundamental difference that would justify having different IL limits for coax and differential-pairs? And if so, how much is this difference? As I highlighted in the Annapolis meeting, I would greatly appreciate collaboration on these and other issues. I will be sending more questions to this reflector, and if anyone is interested in collaboration on any of
these, please let me know. Ragnar To unsubscribe from the STDS-802-3-ISAAC list, click the following link:
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