I can't open and look at your flow now, but it seems you have the necessary blocks in there. Here are some things that come to mind:
1) put a multiply const block in front of the usrp source at the tx. You don't want to feed values ranging from 1 to -1 but rather ~0.7 to -0.7. 2) keep usrp tx/rx analog gains below 20dB to avoid odd behavior. Keep the usrps close to each other for this debug. I use 15dB for initial testing. 3) Costas loop will only fix small frequency offsets. Try adding an FLL block before timing sync. 4) are you sure you used the right taps for the pfb clock sync block? How did you confirm this? 5) BPSK requires an equalizer if you have a bad channel. Are you using antennas or a coax cable? Rich Sent from my iPhone > On Oct 1, 2015, at 6:20 PM, Washbourne, Logan > <lwas...@ostatemail.okstate.edu> wrote: > > Rich, > > The test_corr_est block has the flow graph as follows: vector source-> > constellation modulator -> stream mux(with null source) -> throttle -> > channel model -> correlation estimator -> polyphase clock sync -> costas loop > -> constellation and time gui sinks. > > For my modified TX grc file I used the following flowgraph: vector source -> > constellation modulator -> stream mux(with null source) -> constellation and > time gui sinks as well as the UHD: USRP sink > > For the RX grc: UHD: USRP Source -> correlation estimator -> polyphase clock > sync -> costas loop-> constellation and time gui sinks. > > The grc files can be found at: https://github.com/loganwashbourne/Logan.git > > The files are called test_corr_est_TX and test_corr_est_RX. > > Thanks for your time, > > > Logan Washbourne > Electrical Engineering Graduate Student > (Electromagnetics) > > >> On Thu, Oct 1, 2015 at 3:44 AM, Richard Bell <richard.be...@gmail.com> wrote: >> Hi Logan, >> >> Can you give more detail on your synchronization choices for BPSK so we can >> tell you what more you may need to do? >> >> Rich >> >> Sent from my iPhone >> >> > On Sep 30, 2015, at 7:14 PM, Washbourne, Logan >> > <lwas...@ostatemail.okstate.edu> wrote: >> > >> > Hello, >> > >> > This is somewhat of an update to a previous post I made from last week. >> > After talking to Julian and Martin, it was made clear to me that I needed >> > to use a correlation system to insure my receiver would be synced up to my >> > transmitter when trying to communicate over the air. >> > >> > I am trying to utilize the Correlation Estimator block to help me achieve >> > those means. In order to ease myself into it, I am trying to turn the >> > test_corr_est.grc example into an over the air program. I am getting >> > communication between the transmitter and receiver(essentially I just >> > split the grc program in two and took out the throttle block and the >> > channel model and replaced them with UHD blocks). Now, I don't get any O's >> > or L's or an abundance of U's, and I can clearly see data coming in on the >> > RX side, but it seems to be a lot of noise, but noise generated by the TX >> > side, because it goes away when I stop transmitting. The center frequency >> > is 2.48GHz and the sample rate is 250k samples/sec. >> > >> > My testing method is plotting the constellation symbols right before they >> > get sent out on the TX side and then plotting them right after the UHD >> > block on the RX side. It is only bpsk and the symbols are covering all >> > four quadrants. >> > >> > I haven't changed any settings on the polyphase clock sync or the >> > modulation scheme. >> > >> > This is a little rambly but I appreciate your time, >> > >> > Logan Washbourne >> > Electrical Engineering Graduate Student >> > (Electromagnetics) >> > >> > _______________________________________________ >> > Discuss-gnuradio mailing list >> > Discuss-gnuradio@gnu.org >> > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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