OFDM Receiver

Dear all,

I am using a slightly modified version of rx_ofdm.grc [https://github.com/gnuradio/gnuradio/blob/master/gr-digital/examples/ofdm/rx_ofdm.grc], where I am transmitting only BPSK symbols (header and payload) and bypassing the channel...

When watching the constellation post-FFT (either @ header or payload stream), we can see a phase shift such as this in the image below.

I don't understand why this happens. Since there's no channel and the Header/Payload Demux only copies the signals, I believe that the Schmidl & Cox OFDM synch. is introducing these phase shifts. Is this somehow expected? Am I missing something?

Thank you so much in advance.

Best regards,

Vinicius.