Hi Glen, very interesting paper! Thanks for sharing the link. Yes, I agree that a realible 'simulator' providing the real world of a HF channel would be very helpful to compare communication modes. Man-made noise caused by PLC or SMPS etc. is another challenge especially on HF bands. Before I'll stop my laudation for the 'old' SSB another example what advanced DSP algorithms can effect in bad man-made noise enviroment:
https://www.dropbox.com/s/wt32pepaurnbvbq/W5WC_NB%2CSNB%2CNR2_OFF.mp3?dl=0 https://www.dropbox.com/s/tubqmidw4bor265/W5WC_NB%2CSNB%2CNR2_ON.mp3?dl=0 Hopefully nobody feels offended by my lanky posts, but after more than 50 years with activity on the commercial side of communications I think that I earned a ticket for my point of view. 73, Helmut, DC6NY -----Ursprüngliche Nachricht----- Von: glen english <g...@cortexrf.com.au> Gesendet: Montag, 7. Mai 2018 01:42 An: freetel-codec2@lists.sourceforge.net Betreff: Re: [Freetel-codec2] 700D vs SSB Comparison Hi David fair enough here is some good and reasonable recent work by one of your own..... http://search.ror.unisa.edu.au/record/UNISA_ALMA11140739050001831/media/digital/open/9916110811201831/12140739040001831/13140739030001831/pdf Maybe build into freeDV some sort of recording to disk and FTP upload to codec2 server.... On 7/05/2018 9:02 AM, David Rowe wrote: > The 700D waveform is designed for subset of those paths. As part of > the testing I'd like to crowd source some samples of where it works > and were it doesn't. > > Long term - if the average SNR is there, a waveform can be designed to > pass DV over it. Eventually. > > DV over HF is a tough problem, and every development consumes 1000's > of volunteer man-hours (mainly mine). So I'm taking a tractable path > through the problem. > > Currently the focus is on low SNR HF channels. I'll make incremental > improvements from there, e.g. rarer HF paths, higher speech quality at > higher SNRs etc. > > - David > > On 07/05/18 07:45, glen english wrote: >> SSB sometimes wins because the brain picks up the slack. like with a >> 0.5 second fade. >> >> In my opinion, for HF paths, to be broadly useful , voice DV modes >> need to pass an HF fading simulator, targeted at vertical incidence >> work, and bear in mind, that the channel profiles are quite different >> for Equatorial, Mid latitude and high latitude locations. And they >> must have minimal conversational delay, , < 0.25 seconds. >> >> take a look at >> >> https://www.itu.int/dms_pubrec/itu-r/rec/f/R-REC-F.1487-0-200005-I!!PDF-E.pdf >> >> >> >> several languages : >> >> https://www.itu.int/rec/R-REC-F.1487-0-200005-I/en >> >> >> >> This article, is useful for its 127 excellent references, >> https://link.springer.com/article/10.1007/s11235-017-0287-2#CR38 >> >> and has some excellent channel profile references . >> >> >> From the DRM spec, Annex B Definition of channel profiles >> Channel 6, path 4 >> delta delay : 6mS, path gain RMS = 0.0625, dopplershift : 3.6Hz, >> dopper spread 7.2Hz >> >> Some paths are worse than that .. especially vertical incidence paths >> what have values almost triple the above numbers.... >> >> >> ------------------------------------------------------------------------------ >> >> >> 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 ------------------------------------------------------------------------------ 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
