On 06/13/2012 05:15 PM, Phelps Williams wrote: > I have a simple bpsk transmitter setup with a custom udp source block > which outputs a fixed pattern if no data is available from the socket. > I have instrumented the block to indicate when data is read from the > socket inside of work(). > > My radio looks like this: > Custom UDP Source -> DPSK Mod (DBPSK, 10 samp/sym) -> Multiply Const > (0.3) -> UHD: USRP Sink > > My sample rate is 1e6. > > I can tell from my instrumented UDP Source that udp traffic is handled > by work and passed on almost immediately. However I can tell from > both monitoring the spectrum and the receiver output on the other side > that the data takes between 7 and 10 seconds before I see the expected > output from the N200. I thought this could be improved by reducing > the maximum socket buffer size (sudo sysctl -w > net.core.wmem_max=5000000) but that didn't seem to make a difference. > I went as low as wmem_max=10000 with no difference in delay. My goal > is to get the total delay to < 1sec. > > What else could be adding delay to my transmission path? Are there > other buffers I can tweak? Where else should I be looking? >
Well the usrp only has a megabyte of buffering, as does the socket. At that rate, you couldnt not be buffering more than half a second's worth in the post-gnuradio part of the chain. I bet you have produced a lot of data all at once, filled up all of the gnuradio buffering, and you are simply measuring the time it takes to drain these buffers at a rate of 1Msps. If thats the case, you might pace your inputs. Or not transmit when you have nothing to transmit, this lets things flush out and idle. -josh _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
