-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 > One interesting thing I noticed is that when I increased fusb_nblock > and fusb_block_size, it shows a lot of buffer overrun ('uO'). When I'm > using the default setting, these uO disappear. Why is this happening? > However, the packet loss ratio are high in both cases. And I also > tried enabling real time scheduling, but it doesn't have much > effects.
uO means "USRP Overrun". That is, the USRP is sending data to the computer faster than the computer can handle it. This probably means that you are sending at too high a data rate -- the online decoder is taking too much CPU. When you start logging with the file_source, then this CPU (and memory, etc) overhead disappears and all samples are logged. Then when the decoded samples are replayed, your receiver has ample CPU time to work. Fixes to decrease CPU load are: 1) Decrease the data rate (you tried this, and it worked!) 2) Insert a pwr_squelch_cc block with gating on to decode only packets and not all random noise. Note this requires some parameter tuning to get it to work properly. 3) Optimize the receiver. Once you've eliminated the uO's, if there are still packet losses, note that the default GNU radio receivers are not perfect or even necessarily that great... there might just be some problems recovering from the default channel distortions. Finally, you can also play with the gain on each end to attempt to improve the SNR. Which modulation scheme are you using with which boards at which frequency? Also, just to make sure, when you connect two USRPs directly make sure to use sufficient attenuation (~40dB I think, check the archives for emails from Matt Ettus for the actual number) with any of the RFX boards to avoid damage to the receiver! - -Dan -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFGp55My9GYuuMoUJ4RAthfAJ9/euUrNbUVop+8y0z7ExWmP+uz4QCggR+i EFcrFGwCGcdrIQKNCt6aGuU= =O/Dh -----END PGP SIGNATURE----- _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio