Hi, thaks again Martin, I will take a look at the block you suggested.
What I meant before, is that I was expecting that M&M block will tune it's internall coefficients ,or whatever, based on preamble that comes, since that should be the purpose of the preamble (like in hardware receivers). The structure of my receiver is more or less copied one from gfsk_loopback. But in that block, output of demodulator is connected to the M&M. In my case I provide M&M with pure digital signal, which should make things better in the meaning of finding correct edges. A the moment, M&M has 100% successful preamble detection, but then it starts to stuff some bits which make message incorrect. Best Nemanja On Thu, Feb 21, 2013 at 2:36 PM, Martin Braun (CEL) <[email protected]>wrote: > On Thu, Feb 21, 2013 at 02:10:24PM +0100, Nemanja Savic wrote: > > Preamble is indeed long. On the figure I attached in my first post it > can be > > seen the input and output od > > synchronization M&M block. I am expecting this block to do > synchronization > > based on preamble. > > Your packet sync, but not your clock sync (how would the M&M even know > about your preamble?). > > > Not quite sure that I understand, but I am sampling signal with ca. > 500k, and > > symbol rate is 19.2k, so if you were thinking about oversampling after > bit > > slicer, yes i have oversampling of ca. 25. > > Yeah, that's probably over the top. Filter and decimate, that saves > clock cycles and possibly improves your SNR. > > > In my receiver, after a bit filtered demodulated signal from quadrature > FM > > demodulator, I have a block, designed by myself, that does bit slicing. > It is > > basically simulation of a circuit that is used in > > > > some receivers with min and max diode detector circuits. Since I am > quite sure > > this is not the usual way of doing this, how am I supposed to get digital > > pulses from demodulated signal. > > I recommend parsing gr-digital/python/gmsk.py for an idea how this could > be done (though, granted, that doesn't work perfect either, but also > doesn't sync via preamble). > > MB > > -- > Karlsruhe Institute of Technology (KIT) > Communications Engineering Lab (CEL) > > Dipl.-Ing. Martin Braun > Research Associate > > Kaiserstraße 12 > Building 05.01 > 76131 Karlsruhe > > Phone: +49 721 608-43790 > Fax: +49 721 608-46071 > www.cel.kit.edu > > KIT -- University of the State of Baden-Württemberg and > National Laboratory of the Helmholtz Association > > _______________________________________________ > Discuss-gnuradio mailing list > [email protected] > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > -- Nemanja Savić
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