Eric Blossom wrote:
Once you've got your individual streams of signals, for each one I
would compute an estimate of whether it is occupied.
Good suggestions.
Elaborating on this a little, you might consider taking
differences of successive magnitude or power spectra. If
you're actually looking for periodicities in the onsets and
releases, the resulting positive and negative pulses are
very easy to track. This is a standard technique for
first-order activity detection in spectral measurements.
Another productive technique is to take the wavelet
transform of the magnitude, power, or difference spectrum,
especially when the signals of interest are smeared over
several bins. In this case you are looking for large wavelet
coefficient magnitudes in the dilation region of the wavelet
transform that corresponds to the spreading bandwidth in the
original spectrum.
There is yet another arsenal of methods to throw at this
problem if you are in a position to keep a full tableau of
past spectra in three-dimensional form. For example, a
conventional histogram equalization on such a tableau of
past spectra is quite effective at bringing "activity
stripes" out of the noise, and there is a robust likelihood
score comparing before- and after-equalization densities.
But that's really getting ahead of the subject...
Frank
_______________________________________________
Discuss-gnuradio mailing list
Discuss-gnuradio@gnu.org
http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
