m-psk for m=2, has 2 samples/symbol and log2(m)=1 - or 1 bit per symbol. Also, the polyphase clock has an input of 4 samples and output of 1 sps. It should have input of 2 sps and output of 1 sps.
Just change the sps everywhere to 2. Also, note there are only 2 symbols in the symbol map of the Constellation object so for sps equal to 2 the symmetry is 2 - or there will be 2 clusters on a horizontal straight line. Except when you use a tap in the Channel Model of 1+1j which will probably rotate the line by 45 degrees to the horizontal. In any case, this is known as bpsk - or your case dbpsk - differential bpsk. I would add the CMA Equalizer between the Polyphase clock and Costa Loop. -- Cinaed On 05/17/2017 08:59 AM, Mojtaba Mansour Abadi wrote: > Hi Everyone, > > The flowgraph I am implementing is simple and straight forward. I am > modulating a set of data plus preamble. The modulations I am looking at > are either PSK or QAM. After a block of "Channel Model" in the > flowgraph, I want to demodulate the signal and obviously, for fair SNR > values I should receive the same preamble and data values. > > Now the problem is that when I use the deprecated "PSK/QAM Mod" and > "PSK/QAM Demod", everything works fine. However, based on the examples > in "/digital/demod" and "/digital/packet" shiped with > gnuradio companion, when I try to use the "FLL Band-Edge" followed by > "Correlation Estimator", "Polyphase Clock Sync", and "Costas Loop" to > compensate the channel for PSK modulation, the results I am getting are > not correct (see the attached picture and file). > > It would be your kind if you could answer my questions please: > > 1- What is the correct way of demodulating the received signal? > 2- In the provided examples, no equalizer is used after "Polyphase Clock > Sync", whereas in a tutorial available at Gnuradio website a "CMA > Equaliser" is needed there. So which one is the correct one? > 3- If I move to QAM modulation, the only thing I need to do would be > replacing "Costas Loop" with a "Constellation Receiver", right? > > Cheers. > > 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
