Hi Matt Myself and a colleague have created a C++ equivalent for the same flowgraph, with realtime scheduling enabled. We still have overruns for data rates above 2 Mbps, even on a Core i7 machine. We will try and make a multi-threaded version to hopefully resolve this, since our version is only single-threaded at this stage.
In regards to using GRC to create the flowgraph, how can I check if realtime scheduling is enabled, and/or enable realtime scheduling? Thanks Ian. -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Matt Ettus Sent: Thursday, 22 April 2010 4:15 PM To: Ian Holland Cc: [email protected] Subject: Re: [Discuss-gnuradio] Large number of overflows... On 04/11/2010 09:22 PM, Ian Holland wrote: > 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? These overflows indicate one of two things: - that your flowgraph is too slow to execute in real time on your computer - You haven't enabled realtime scheduling. Matt _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
