[time-nuts] [Announce] Simulation software for powerlaw noise and PTP clock synchronization

[Magnus Danielson]

Hi,

On 04/19/2016 07:46 AM, Wolfgang Wallner wrote:
> Hello Anders,
>
>> Do you get agreement between PLN time-series and calcluated ADEVs, as per
>> IEEE1139-2008 table B.2 ?
>
> Yes, I explicitly cite IEEE1139-2008 table B.2 in my thesis. I will
> write a more detailed reply with example data later when I get home.
>
> If you would like to try out the noise generations of libPLN: I also
> wrote a small command line utility for LibPLN, called PLN_Generator. You
> can find it in the Demo/ directoy [1].
>
>> I tried [3] using python libraries colorednoise [1] (also based on
>> Kasdin&Walter) and allantools [2], but it gives ADEVs that are
>> systematically higher than predicted by theory. OTOH the calculated MDEVs
>> seem to fall on the line that theory predicts. Image here:
>> http://www.anderswallin.net/wp-content/uploads/2016/04/colorednoise-1.png
>
> I have only used ADEV and AVAR so far, so I don't know about the
> MDEV-behavior of my simulated noise. I will try out your allan tools
> when I get home.
>
> But the conversion between AVAR and power spectral density has been
> quite confusing for me, see [2] for an example. I thought I had figured
> it out at the end, but maybe I'm still wrong :)

It depends. If you noises is true power-noises only and straight 
additions of them, then mapping works. But this is not generically true, 
so in generic there is no mapping guaranteed to work.

>> On your libPLN page the time-series graph is called 'time deviation'
>> which
>> could be a bit confusing as there is also an ADEV-like statistic called
>> time deviation. Perhaps time-series or 'phase observations' or similar is
>> better?
>
> Yes, I agree that the wording is very unfortunate. IEEE 1139 first calls
> x(t) time fluctuations and time derivative, but later refers to it as
> time deviation in the text.
>
> I only realized quite late that there is a name conflict with another
> statistic measure.
>
> I guess the easiest solution would be to replace all occurrences of
> 'time deviation' with e.g. 'time derivative'.

No. Keep Time deviation separate from TDEV and you are fine.

Cheers,
Magnus