Hi Glen, I defer to your expertise since my area is LTE infrastructure not radio access :) My modems are being designed for bands from 144 MHz up to 5-10 GHz, where spectrum is not an issue, and for linear sattelite transponders or airborne repeaters, where multipath is even less of an issue. I'm not a DSP expert, but I look at David's plotted BER for different modulation types and it seems 4FSK does better than 2FSK or BPSK, nevermind the fact that it does not require a very linear amplifier on the end of the stick, which can get very expensive as you go up in frequency. This is why I have some wideband modes like 4FSK 20 kbit/s. Also, to abuse the SDR architecture in the most meaningful way, one is almost forced to use Gnuradio, which enables very easy design of complicated stuff like multi-carrier systems, adjacent channel measurements, tight timing of bursts for TDMA systems, CDMA and other goodies.
73, Adrian YO8RZZ On 9/14/17, glen english <g...@cortexrf.com.au> wrote: > Hi Adrian > > Help me understand why the need to use 4FSK compared to say FSK OR BPSK > ? For voice at 700bps there are few bandwidth issues for amateurs... > > The multi level modulation (4FSK) will be inferior to others (without an > time delay equaliser) when the long delay multipath is severe.... > > The long delay multipath tolerance I think should be above all other > concerns. > > Or maybe I have "the wrong end of the stick " > > 73 > > -glen > > > On 14/09/2017 8:28 AM, Adrian Musceac wrote: >> Hi Glen, >> >> We don't need to use the same chain for digital demodulation, since we >> are not software constrained. Using Gnuradio, we can simply reuse a >> flowgraph and connect/disconnect blocks on a click of a button to >> switch from one mode to another. What > > > > ------------------------------------------------------------------------------ > Check out the vibrant tech community on one of the world's most > engaging tech sites, Slashdot.org! http://sdm.link/slashdot > _______________________________________________ > Freetel-codec2 mailing list > Freetel-codec2@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 > ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Freetel-codec2 mailing list Freetel-codec2@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freetel-codec2
