Re: [Linuxptp-devel] Optimal P, I constants

[Keller, J. E <jac...@in...>]

> -----Original Message-----
> From: Miroslav Lichvar [mailto:mli...@re...]
> Sent: Tuesday, April 23, 2013 6:45 AM
> To: lin...@li...
> Subject: [Linuxptp-devel] Optimal P, I constants
> 
> I've been experimenting with phc2sys and the clknetsim simulator to
> find out how is the clock synchronization affected by changes in the
> P, I constants with different jitters and clock stabilities, and I
> thought others on this list might be interested in the results.

<snip>
> More data and the script which was used to generate it is available
> here:
> http://mlichvar.fedorapeople.org/clknetsim/ptp/pi_search/
> 
> I was wondering how useful it would be to have a new servo parameter
> for the Allan intercept and set the P, I constants automatically
> according the intercept and measured clock update interval. What do
> you think?
> 
> --
> Miroslav Lichvar
> 

Hey Miroslav -

First of all, thank you for the detail, this is an impressive in depth look at the P/I servos.

I think it might be better (at first) to create a new clock which is based on Allan intercept, since most people doing PTP are familiar enough with the P/I constants servo. I do think in the long term it definitely makes more sense to put the Allan intercept, as that appears to work better, and is easier to measure if I am not mistaken? (Jitter * wander in pbb, right?)


Wouldn't this also have to set the update frequency as well? It appears that some update frequencies cause the result to be unstable or too slow..

Thanks

- Jake