There's an excellent example using BPSK in
<gnuradio_root>/share/gnuradio/examples/digital/packet/example_corr_est.grc Also, you should be using a tagged stream and blocking tag propagation at the Channel Model. And since there are no taps in the Channel Model, you really don't need CMA Equalizer, and the Costas Loop - or even the Polyphase Clock Sync. Keep it simple until you understand how the above example works. The first thing I would do is loose the Constellation Modulator at the beginning. But don't confuse me with someone who knows what they're doing - I'm still wandering through the forest. -- Cinaed On 05/24/2017 10:32 AM, Mojtaba Mansour Abadi wrote: > Hi Everyone, > > > I am trying to benefit "Correlation Estimator" block to tag the preamble > of the transmit bit sequence in a QPSK-based system > > > The modulation is done as: > Data + Preamble -> Constellation Modulator > > > The way I am doing the demodulation is: > AGC -> FLL Band-Edge -> Correlation Estimator -> Correlation Estimator > -> Polyphase Clock Sync -> CMA Equaliser -> Costas Loop > > The hard decoding is done as: > Constellation Decoder -> Differential Decoder -> Map -> Unpacked to Packed > > After I execute the flowgraph, for a few seconds everything works fine > and I receive the correct sequences. However, after a while, the > received bits are not correct and their pattern changes periodically. > > When I bypass the "Correlation Estimator" block, everything works fine > and I receive the correct data. > > I am confused. Is the correlation block suppose to deteriorate the > demodulation performance? > > The flowgraph is attached to the email. > > > -- > Regards, > Mansour. > > https://www.linkedin.com/in/mojtaba-mansour-abadi-4311b451 > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
