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.
