[ntp:hackers] A stop-gap authenticated time service
phk at phk.freebsd.dk
Sun Nov 15 09:35:51 UTC 2015
In message <56484F6A.1000807 at rubidium.dyndns.org>, Magnus Danielson writes:
>> The "Allan intercept" is a rule of thumb it has no formal mathematical basis.
>For NTP it relates back to an article by Judah Levine on the ACTS
>system, which got lifted into the NTP world without validating the noise
If I recall correctly, that article didn't leave any space for
the steering-mechnisms noise and time delay.
The PI steering used in typical PLLs introduce a very non-random
noise due to the (exponential-ish) tapering off of the P term
corrections and adds a significant time-delay, both of which must
be compensated for relative to the Allan Intercept.
I've found nobody who did the math to get from Allan Intercept to
optimal PI parameters.
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