That fixed it!! Nick & Andy - thank you both so much for looking into it. Without your help, there is no way I would have fixed this… and without Nick’s code I couldn’t have built it in the first place.
- Luke > On Nov 4, 2014, at 8:28 PM, Nick Foster <[email protected]> wrote: > > Red face over here. > > There was a bug in correlate_access_code_tag -- which only gr-smartnet and > gr-ais use, so far as I know. The fix was pulled into master a couple of days > ago. This could explain the discrepancy you're seeing in the preamble mark. > > Pull latest GR master, build, and see if it fixes what you're seeing. > > --n > > On Tue, Nov 4, 2014 at 5:19 PM, Andy Walls <[email protected] > <mailto:[email protected]>> wrote: > On Mon, 2014-11-03 at 22:13 -0500, Luke Berndt wrote: > > Thanks Andy! Good catch - I made the changes you suggested. I was just > > doing a simple back of the envelope calculation to come up with > > channel size. It does look like cleans things up and adding the > > waterfall graphs does make it easier to see. Unfortunately, it does > > seem to change the decoding. I am still getting the same amount of CRC > > errors. > > > > Did the overall signal look right, like something that should be decodable? > > So I put the output of the FLL into a quad demod block and compared its > output to the PLL Freq det output. They are pretty much in line, except > the quadrature demod block output shows occasional burst of noise for a > few symbol times where the transmission must have stopped and restarted. > The PLL freq detect block just makes something up during these times. > So that seems generally OK. > > > > > Anything else I should try? > > Your PLL freq detector block output is swinging between -2 and 2. You > might want to reduce the max and min freq by a factor of 2, so that the > clock recovery block sees inputs limited to +/- 1.0. See Nick's > recommendation here: > http://lists.gnu.org/archive/html/discuss-gnuradio/2014-10/msg00473.html > <http://lists.gnu.org/archive/html/discuss-gnuradio/2014-10/msg00473.html> > > So after i did that, what I really noticed is that the correlator is > just not marking preambles properly. See the top plot of the attached > to window shots: Preamble_marked_late_twice.png and > Preamble_marked_early.png > > If the deinterleaver and/or crc block isn't searching around for where > the preamble really is, well that would explain it. > > Regards, > Andy > > > - Luke > > > > > > > > Hi Luke, > > > > > > I have not built the SmartNet blocks yet, but: > > > > > > Your low pass filter looks way too wide and you'll get aliases when you > > > decimate by 185. 2 Msps / 185 = 10.81 ksps, so the Nyquist frequency is > > > 5.405 kHz. I winged this is as a low pass filter and things looked > > > better: > > > > > > firdes.low_pass_2(1, samp_rate, 4500, 1000, 60, firdes.WIN_HANN, 6.76) > > > > > > The 60 dB down may be overkill, you can make it smaller for a filter > > > with less delay. > > > > > > I found an offset slider value of -15k made things look about centered > > > manually. > > > > > > You might want to put a waterfall sink before and after the FLL > > > Band-Edge filter to observe how it is making the spectrum wobble around > > > a little. If you change your offset slider, you can see the FLL > > > band-edge filter centering things back up; so that looks like it is > > > working. > > > > > > Regards, > > > Andy > > > > > > > > _______________________________________________ > Discuss-gnuradio mailing list > [email protected] <mailto:[email protected]> > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > <https://lists.gnu.org/mailman/listinfo/discuss-gnuradio>
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