Hi All I am trying a modified example of the digital-bert routines, for communication between 2 USRP2s, and notice that I am getting a very large number of overflows (SSSS....) even with decimation rate at the receiver of 20, and 4 samples per symbol (sometimes even with 20 samples/symbol). If I don't get overflows (as has occurred when I used 20 for decimation as well as 20 for samples/symbol in one instance), I am able to capture the demodulated bits as 111111111111111111111111..., as expected for the example. However, with overruns, which seem to occur more for lower samples per symbol and/or lower decimation values, I get a large number of bit errors.
My receiver flowgraph is of the form: USRP2 Source --> RRC Filter --> Costas Loop --> Mueller and Muller Synch --> Complex to Real --> Binary Slicer --> Descrambler --> File Sink. The transmitter flowgraph uses the same blocks as per digital-bert/transmit_path.py, but with a USRP2 sink. I am transmitting over-the-air, and clocks are not synchronised between Tx and Rx. I have a gigabit Ethernet link, and 2 x 2 GHz CPUs in my PC, which is running Ubuntu 9.10. Can anyone suggest why I am getting so many over-runs, and how I could get around this problem? Thanks Ian. _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
