Hi Steve, Well an interesting area to be working in - even if it didn't work out this time. The 800XA waveform is interesting as it is a constant amplitude mode (FSK modem) - if we can make it work on multipath channels.
I do recall a paper re using FEC coding to help with PAPR as well. It's also worth trying tricks like offset qpsk or offsetting the carriers in time wrt to each other. Even hard or soft amplitude compression might help reduce PAPR, without impacting performance (ie BER on a fading channel) much. Cheers, David On 03/02/17 15:53, Steve wrote: > A long time ago I made a post about improving the crest factor by > changing to a bit-scrambled output (a la 9600 modems, etc). I was > playing with another idea today, and I'm pretty much convinced that > bit-scrambling doesn't improve anything. > > Just looking at the spectrum shows the similarity, but then actually > measuring the peak and rms of the WAV files shows that not much is > happening. > > Crest factor Clipping/Scrambled = 8.3491 dB (rms = 0.13624) (peak = > 0.35626) > Crest factor Clipping/Raw = 8.3931 dB (rms = 0.13654) > (peak = 0.35886) > > > .044 dB improvement - whoo-hoo... > > I seem to remember a technical article about bit-scrambling being highly > effective. Alas, maybe not with a PSK waveform. > > 73 > > > ------------------------------------------------------------------------------ > 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 > [email protected] > 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 [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
