Andy, Yes, I did mean the corr_est block. Thank you for the matlab code. I'll hopefully get to play with it today. The flowgraph I have write now is actually doing quite well with high AWGN just with switching to the enhanced symbol block and using the Mengali and d'Andrea timing recovery. For what it's worth, I'm stuck on GRC 3.7 so I had to check out from your git from before you removed the symbol sync block (assuming it was removed since it's been moved in-tree in 3.8)
Thanks, Alex. On Sun, Jun 28, 2020 at 7:32 AM Andy Walls <a...@silverblocksystems.net> wrote: > Hi Alex: > > On Sat, 2020-06-27 at 19:42 -0500, Alex Roberts wrote: > > Andy, > > > > I’m not sure how integrate the correlation sync block with gmsk. > > The correlate_and_sync block is an old block that was specific to RRC > filtered PSK. You must mean the corr_est block. > > > It expects modulated symbols and I’m not sure how to generate a > > modulated vector of gmsk symbols. There doesn’t seem to be a gmsk > > class that can be used by the modulate vector block. > > You can create a modulated GMSK preamble with the modulate vector block > in GNURadio. However, I do not recommend it. It provides little > insight or control over the exact correlation filter taps, so trimming > off start and end transients becomes a hassle. > > Instead, generate your correlation filter taps in MatLab or Octave. > Then you can also use Matlab or Octave to assess the performance of > your correlation filter taps against real or simulated data. > > See the attached script for an example of generating GMSK correlation > filter taps. Note that this script generates the conjugated and time > reversed filter taps. You'll have to check what the corr_est block is > expecting, as it may be performing a conjugation and time reversal for > you, under the assumption that you didn't do it. > > Regards, > Andy > > > > Thanks, > > Alex > > > > On Thursday, June 25, 2020, Andy Walls <a...@silverblocksystems.net> > > wrote: > > > Recommend reading > > > > > > > https://www.gnuradio.org/grcon/grcon17/presentations/symbol_clock_recovery_and_improved_symbol_synchronization_blocks/Andy-Walls-Samples-to-Digital-Symbols.pdf > > > > > > Yeah, the MSK TED selections for the symbol sync block expect the > > > constant envelope FSK waveform on the input. Demodulation from FSK > > > to baseband pulses should happen after the symbol sync block. > > > > >
