[ntp:questions] IEEE 1588 (PTP) at the nanosecond level?

Brian Inglis Brian.Inglis at SystematicSw.ab.ca
Tue Mar 18 17:09:17 UTC 2014

On 2014-03-18 02:59, Martin Burnicki wrote:

> All depends on how accurate and precise you can get your timestamps, and this
> is probably easier with network packet timestampers at both sides of a cable
> than with a wireless time transfer method like GPS which usually suffers from
> delays which can't easily be measured, like ionospheric delays.
> And yes, I know that this can be improved if you receive 2 GPS frequencies
>instead of only the L1. ;-)

Problem with PTP accuracy is how do you set and discipline your GM?
With NTP probably.

NIST site has a paper on TWSTFT stating that some of the delays cancel and
others can be measured or estimated so that on commercial sat channels they
can get uncertainties between two stations down to 0.1-1ns, which is better
than they can get with common view even using L1+L2 freq and P code.

BIPM monthly national TAI/UTC comparisons show uncertainties up to 10-20ns.

Take care. Thanks, Brian Inglis

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