[Feature request] 16-QAM 6400bps modem

[ggramaize]

Hi,

I'm currently planning field tests with the 4800bps modem, and while reviewing external documentation, I've seen 16-QAM signals seem have a similar noise to BER curve as 8-PSK waveforms. Thus, I think it would be interesting to have a 6400bps modem (16-QAM @ 1600bauds over a 1800Hz carrier, as does the V.27 modem) in direwolf to compare the performance of those two modulations.

Kind regards

[dranch]

This could be interesting and some QAM modems are available in the Linux Qsstv program for digital SSTV pictures. This code was ported from TRXAMADRM so I think there is a history of code sharing, etc. but I have no idea how appropriate this code would be.

[wb2osz]

It would be an interesting project and I've put some thought into it. The part I can't figure out is how to properly phase lock a local oscillator for the demodulating.

[guitarpicva]

Some experimental multi-carrier codecs use a pilot "tone" to orient the detector.

[wb2osz]

I don't understand how to do this.
Perhaps you could contribute some working code that could be adapted.