Looks like you're not resolving the pi/2 ambiguity. To do that, you either need something more sophisticated, or differential modulation.
-- M On 02/07/2017 11:42 AM, Minh Pham wrote: > Dear all, > > My name is Minh T. Pham, and I'm completely new to GNURadio. I want to learn > more about QPSK modulation and demodulation using GNURadio, so I started > reading through and follow the "GNURadio Guided Tutorials". In Tutorial 7: > PSK Symbol recovery, the model utilizes Constellation modulator for QPSK > modulation, and a QPSK demod block built in previous tutorials. In my > experiment, however, I want to use the blocks "PSK mod" and "PSK demod" > instead. (the block diagram is shown below) > > <http://gnuradio.4.n7.nabble.com/file/n62774/QPSK_mod_and_demod.qpsk_mod_and_demod> > > > Unfortunately, when I look at the result, it seems that the system fails to > recover the information I sent: > > <http://gnuradio.4.n7.nabble.com/file/n62774/Result.result> > > The constellation plot shown that the timing recovery works just fine, but > the bits I received in the end are just incorrect. > There are several possibilities for this issue: > 1. I had the wrong configuration for the PSK demod block > 2. The way I decode the information is incorrect > 3. The timing recovery process produced a false result > Please help me find the issue and a way to resolve it. > > Sincerely, > Minh. > > > > -- > View this message in context: > http://gnuradio.4.n7.nabble.com/QPSK-modulation-and-demodulation-using-PSK-mod-and-demod-blocks-tp62774.html > Sent from the GnuRadio mailing list archive at Nabble.com. > > _______________________________________________ > Discuss-gnuradio mailing list > [email protected] > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > _______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
