[Discuss-gnuradio] A question on the order of the processing stages for the psk receiver

[Anh Duc Nguyen]

Dear all,

I have a question on the order of the processing stages for the psk receiver.

As I have seen from some source code (e.g., dqpsk.py in earlier version of GnuRadio 3.4.2 backwards), the sequence of blocks for a psk receiver is:

AGC -> RRC filter -> mpsk receiver (mpsk_receiver_cc) -> differential decoding -> symbol demapping (find closest constellation point) -> gray code decoding (optional) -> and so on.

My confusion here is why the differential decoding is placed before the symbol demapping block, while as my usual thought the demapping should goes ahead of  the differential decoding stage.

Can anyone explain that to me or just show me the related documents, i would be greatly grateful for it,

With best regards,