Sent from my Cyanogen phone On Oct 2, 2015 3:12 AM, Richard Bell <richard.be...@gmail.com> wrote: > > 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. >
I will try that today. > 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. > I've kept it around 10dB normally, but I will double check. > 3) Costas loop will only fix small frequency offsets. Try adding an FLL block > before timing sync. > Will do. I don't think it's even getting to the costas loop to be honest, it seems to not be tripping the correlation estimator block. > 4) are you sure you used the right taps for the pfb clock sync block? How did > you confirm this? > I'm not sure if I used the right taps. I'm just using the ones that were included in the test_corr_est GRC file. Do you have a method of confirmation that you would recommend? > 5) BPSK requires an equalizer if you have a bad channel. Are you using > antennas or a coax cable? > I am using antennas. I'll look into the equalizer. Thank you for taking the time to help so far. > 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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