Magnus, the paper http://tf.nist.gov/timefreq/general/tn1337/Tn121.pdf is thought-provoking. Not that I would simply say that you are right, but because I dont't understand some things.
> > N-2m > ___ > 2 1 \ 2 > sigma (tau) = ----------- > (x - 2x + x ) > y 2 /___ i+2m i+m i > 2(N-2m)tau i = 1 > > a non-interleaved variant would have to be written as > (assuming that m > divides N): > > N > - - 2 > m > ___ > m \ 2 > ------------ > (x - 2x + x ) > 2 /___ (i+2)m (i+1)m im > 2(N-2m)tau i = 1 No discussion about that, simply correct. However the note to figure 8 as well as the note to figure 9 cover the non-overlapping case. Indeed formulas (8) and (10) are overlapping and to me it is a bit kind of magic where they come from in regard to thise two notes. Do you agree to the fact that the ADEV for Tau = 2 s should be the same, regardless if computed from 1 s spaced phase data or from 2 s spaced phase data? Best regards Ulrich > -----Ursprungliche Nachricht----- > Von: [email protected] > [mailto:[email protected]] Im Auftrag von Magnus Danielson > Gesendet: Donnerstag, 22. Januar 2009 12:53 > An: Discussion of precise time and frequency measurement > Betreff: Re: [time-nuts] ADEV vs. OADEV > > > Ulrich, > > Ulrich Bangert skrev: > > Magnus, > > > >> Actually, what you describe is the estimator formulas rather than > >> definition. This is also targeting the fine point that I > am trying to > >> make. It's not about the basic definition, but accepted > convention to > >> denote the estimators. > > > > I still do not understand the fine point! A estimator might > have this > > property and that property and may perform this task good > and another > > task bad, but at the basics we have a formula and if the formula is > > new or different from prior art then the thing needs an name of its > > own. > > This part we agree on, however, you fail to see that what I > try to point > out is that you seems to have the wrong reference to start > with. What I > am trying to say is that it seems that ADEV is being used to > identify a > different estimator than I have in my old material, including the > articles collected in NIST TN1337, for instance "Time and Frequency > (Time-Domain) Characterization, Estimation, and Prediction of > Precision > Clocks and Oscillators" by David W. Allan. > http://tf.nist.gov/timefreq/general/tn1337/Tn121.pdf > See page 4 and formulas 8 and 9. These are overlapping. > > > In this sense the summation over square(y(i+1)-y(i)) is called the > > base of the "Allan variance/deviation" just for historical > reasons. So > > the name is "Allen deviation" and it is defined by its formula. > > A further reference would be the IEEE standard found in > > http://tf.nist.gov/timefreq/general/tn1337/Tn139.pdf > > This is also overlapping (from page 2): > > N-2m > ___ > 2 1 \ 2 > sigma (tau) = ----------- > (x - 2x + x ) > y 2 /___ i+2m i+m i > 2(N-2m)tau i = 1 > > a non-interleaved variant would have to be written as > (assuming that m > divides N): > > N > - - 2 > m > ___ > m \ 2 > ------------ > (x - 2x + x ) > 2 /___ (i+2)m (i+1)m im > 2(N-2m)tau i = 1 > > and these obviously isn't the same, the later form skips over samples > not being a multiple of m. > > Also, it is still overlapping in the sense that samples is > being re-used. > > >> Disagree. The estimator formulation that is classically > used includes > >> these "missed" tau0 steps that you claim that OAVAR/OADEV > >> includes. This is my point. Somewhere along the line the > established > > ADEV estimator > >> became the OADEV estimator and another estimator took the > ADEV place. > >> This is what I oppose without a more detailed look at things. > > > > The OAVAR/OADEV has this name of its own BECAUSE it includes the > > summands that are missed by the original AVAR/ADEV so its needs an > > name of its own. > > I deeply disagree, see my reference to early papers (I agree not > original). Also, the standardised form is overlapping. > > This is the reason for me to react. > > >> Somewhere along the line the established ADEV estimator became the > > OADEV estimator > > > > If you had said: "The currently established estimator for > oscillator > > stability is the OADEV estimator" I would have perfectly agreed. > > Well, that part was never what we disagreed on IMHO. > > > However, ADEV does already point to a different thing, so to say > > "Today we call ADEV what was formerly called OADEV and what was > > formerly called ADEV now is also called different" is not > excused with > > a certain sloppiness in language but simply wrong use of terms. > > Exactly this is the point why I said that the discussion is > dangerous. > > This is not a change in paradigm this is a case of > inaccurate use of > > scientifical terms. > > Well, if we were doing a shift in interpretation I fully > agree with you, > but what I reacted on was due to a shift in interpretation as I > experienced it and when looking at the old reference material > (altought > I have not had the time for an extensive search that I would feel > confident with). The issue was that I detected the dangerous > shift and I > wanted to bring it up to bring it back on tracks, or at least learn > something useful. > > I really kindly ask you or anyone else to bring forward articles > describing the non-overlapping ADEV and help plotting out the issues. > What has become standardised (and thus assumed accepted) as the ADEV > estimator is overlappping unless you can point out that I have made a > very deep misunderstanding of all those papers, in which case > I would be > happy to be corrected. > > Cheers, > Magnus > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-> bin/mailman/listinfo/time-nuts > and > follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
