At the USRP2 receiver, after CFO compensation, I want to see the QPSK constellation.
Basically, the process is:
bit stream ---- ofdm mod ---- usrp2 sink
usrp2 source -- timing offset comp --- CFO comp ---- ofdm demod ----- constellation sink
Before ofdm_demod, the signal spectrum observed in USRP2_fft is good as far as I know.
But after OFDM demod block, I can not receive anything. No data output! :(But I am not sure about the number of tones, SNR.
Where can I find the definition of this block? What is the meaning of S and Time out?