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.
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PSK_Mod_Demod.grc