On Fri, 2015-07-17 at 16:54 -0400, Andy Walls wrote: > On Wed, 2015-07-15 at 16:30 -0700, Richard Bell wrote: > > Hi Andy, > > > > > > I've been pulling my hair out trying to figure out how I'm using this > > block wrong, or if it's bugs I'm seeing. I don't feel much closer to a > > decision. Let me explain what I've been seeing and hopefully you or > > someone else can shed some light on it. > > > > > > The Setup: > > > > A BPSK modulated single carrier radio using USRP N210's. The order of > > blocks in my receiver are as follows: > > > > > > USRP -> Power Squelch -> AGC -> FLL Band Edge -> Correlation Estimator > > -> Polyphase Clock Sync -> Costas Loop -> LMS DD Equalizer -> > > Header/Payload Demux -> Rest of Demodulation Chain > > No channel filtering or down sampling before the power squelch? > > Things outside of your desired channel can break your squelch. You > should be channelizing. > > USRP usually only support certain rates (e.g. 500 ksps) which are > usually a much higher rate than you need for a single narrowband > channel. Downsampling early will give you back CPU for everything else.
Also, why are you using squelch for a data channel? Normally you only need squelch for voice or audio. Modems don't care about garbage coming in, as they have to deal with it anyway. [snip] > The FF AGC block could stand some improvement. Just off the cuff: > > 1. It does a bubble-sort-ish search for the max on num_samples for every > new sample. That's O(n^2). A quicksort and then plucking the max value > would be better for largish values of "num_samples". Bah, forget the nonsense about sorts. I don't know what I was thinking. Still, improvements can be made to the block. > 2. It could also cache the envelope values it computes for samples > instead of continually recomputing them. > > I'm sure there's other things that can be done to that block's > internals. > Regards, Andy _______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
