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Re: [802.3_ISAAC] Some considerations for link length

It’s funny Kirsten as the conclusion to your email wasn’t where I saw it going. I thought you were saying that there is limited variability for placement of these things in the car and therefore, you could calculate estimates that would cover a majority of cases, independent of the manufacturer. I don’t know that the group is looking to influence link length, but instead determine the length that will satisfy the needs targeted by this proposed standard.

 

Do you disagree with where I thought you were going in your email? If so, could we get car manufacturers to submit a contribution making these estimates?

 

Regards,

 

Chad Jones

Principal Engineer, Cisco Systems

Chair, IEEE P802.3da Task Force

Principal, NFPA 70 CMP3

 

From: Kirsten Matheus <Kirsten.Matheus@xxxxxx>
Date: Thursday, October 26, 2023 at 11:27 PM
To: STDS-802-3-ISAAC@xxxxxxxxxxxxxxxxx <STDS-802-3-ISAAC@xxxxxxxxxxxxxxxxx>
Subject: [802.3_ISAAC] AW: Some considerations for link length

Hello George,

 

yes, it would be very interesting to have data about distribution of links and lengths in cars. I have not seen such data for the industry overall. In our case, we would need it specifically for sensor links. If any cable/harness manufacturer has respective data they could share, that would be very interesting.  

 

One thing I would like to point out though: Sensors (including cameras, and displays for that matter), have very limited variability in respect to their placement inside the car. Also large processing ECUs have limited options on where they can be. The dimensions of the car are typically not influenceable by the engineers concerned with electronics. This means that we have very little to no influence on the link length we need to support.

 

Kind regards,

 

Kirsten

 

Von: George Zimmerman <george@xxxxxxxxxxxxxxxxxxxx>
Gesendet: Mittwoch, 25. Oktober 2023 18:14
An: STDS-802-3-ISAAC@xxxxxxxxxxxxxxxxx
Betreff: Re: [802.3_ISAAC] Some considerations for link length

 

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. 

Yes, no tearing of your head, just a big thank you  for sharing this.  I was searching for the relevant presentations.  These appear to quote far more than 15m as the need, but highlight that we may very well need to choose what types of vehicles we are targeting.

I was hoping that given that we’ve had some deployment experience and some changes in architecture moving towards zonal cars, we might have some better defined data with a distribution of links & lengths.  There are many examples in LAN cabling – see, for example, slide 19 of https://www.ieee802.org/3/10GBT/public/nov03/10GBASE-T_tutorial.pdf

 To date, I haven’t seen that for automotive – but with experience, we should have some…

 

-george

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