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.
Test.grc
Pic.png