Thanks Joe! This has been a fun project, and I’m learning a lot from it.
I used your SimJT program to generate 1000 JT65A files at -24 dB SNR. Here’s what I get: kvasd (with Rx frequency set to 3000, so this should be the low-effort setting): 106 decodes out of 1000 (10.6%) sfrsd 5000 trials: 94 decodes (9.4%) sfrsd with 10000 trials: 112 decodes (11.2%) I expected higher percentages overall at this SNR but, in any case, the results seem to confirm that sfrsd is a viable decoder. I noticed that only a fraction of the files result in a vector being submitted to the decoder - maybe around 50% - I didn’t count carefully. Maybe this is another reason to take a look at the upstream processing. I think that your earlier results showed something closer to 40% at this SNR. Also, I am surprised at how little guidance the soft information is providing with the settings that we are using. Almost none, as it turns out. Note that if I change just the two probabilities that I use to set the erasure frequency of the “best” and “worst” symbols, such that all of the probabilities are the same, then we wouldn’t even need to sort the data according to probability (for the stochastic patterns), i.e. we would be using no soft information whatsoever! The results would change - but we’d be in the same ballpark. This makes me feel like one or both of the following might be true: 1. it may be possible to achieve the same results with fewer trials if the soft-symbol information was utilized in a smarter way and/or 2. the quality of the presently used soft-symbol information is so bad that it’s not worth using. In 2, I do not mean to say that there is something wrong with the signal processing. Instead, I’m wondering if information only on 2 of 63 symbols is just too watered down to be useful. Steve k9an > On Sep 19, 2015, at 2:11 PM, Joe Taylor <j...@princeton.edu> wrote: > > Hi Steve, > > I've looked again at the innards of sfrsd. I'm *much* impressed by what > you have done. > > Soon, it may be time to look again at the upstream decisions made in the > JT65 decoding chain -- decisions that determine what symbol vectors are > passed on to the actual decoder. Among other things to consider: > various parameters affecting those decisions were optimized (a long time > ago) for the EME situation with very weak signals, little if any QRM, > and only one or two signals in the Rx passband at a time. For HF use we > might want to change some of these parameters. > > -- Joe, K1JT > > ------------------------------------------------------------------------------ > _______________________________________________ > wsjt-devel mailing list > wsjt-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/wsjt-devel ------------------------------------------------------------------------------ _______________________________________________ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
