Hi all, First time posting here, so hello everyone:)
I am trying to build this pair of GNUradio flow graph for QPSK signal transmitting and receiving over the air through USRP. Now the transmitter side is straight forward, only a random number generator and QPSK modulator plus a multiplier. The receiver side is as attached. The problem is, I can get well separated constellation points after synchronizations, however the they are not correct. For example, if I set the transmitter side to modulate and send symbol '333333...', the symbols after demodulation at receiver side is suppose to be '333333....'. instead, I get '01320132...' repeatedly. It seems that my constellation is constantly rotated with some frequency. I am not using differential modulation or demodulation, so it is some thing else rotating my constellation. My guess is that my synchronization is not good enough, there is a slight frequency offset which move the phase backward(forward?) from time to time. Any comments or suggestion are really appreciated. Howe Attachments: http://www.ruby-forum.com/attachment/11033/forum_question.png -- Posted via http://www.ruby-forum.com/. _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
