Hi David, Knowing the channel state at a particular time would be very useful. However it changes so quickly that a training sequence at the start wouldn't give us real time information. Some modems send continuous training sequences, and it is also possible to extract real time channel information from the BPSK pilot and data, such as SNR.
Cheers, David On Mon, 2013-03-18 at 11:40 -0700, David Ranch wrote: > Hello David, > > As always, a great read with real examples of how your working your way > through the optimization process for the freeDV suite. One thing did > peak my interest: > > "The fluttering at the start of the 1600 bit/s sample might be caused by > bit errors in the frame energy parameter causing the level to jump > around, or possibly bit errors in the voicing bit. If we know the > channel is bad (the modem can tell us), we could “lock down” a few bits > to enhance speech on poor channels." > > > Have you considered using a DVMDV training sequence say at the beginning > of the QSO much like what our old analog phone POTS modems used to do? I > think with an initial training and possibly mid-QSO re-training (the > FreeDV UI could also inform the user of the retraining vs. guessing why > the delay), the codec can get updated information on the link well as > non-FreeDV users might get informed what this "new mode" is. Methods > could be via a visual waterfall text (like how HamDRM based SSTV), a > PSK31, a new set of RSID codes, or even CW. > > Just a thought but I think there are benefits here to consider. > > --David > KI6ZHD > > ------------------------------------------------------------------------------ > Everyone hates slow websites. So do we. > Make your web apps faster with AppDynamics > Download AppDynamics Lite for free today: > http://p.sf.net/sfu/appdyn_d2d_mar > _______________________________________________ > Freetel-codec2 mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 ------------------------------------------------------------------------------ Everyone hates slow websites. So do we. Make your web apps faster with AppDynamics Download AppDynamics Lite for free today: http://p.sf.net/sfu/appdyn_d2d_mar _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
