Hi Steve,
I finally found time for a quick look at "sfrsd", your drop-in
replacement for kvasd that uses the stochastic Chase algorith.
I compiled and ran it on a few test cases this morning, and (as will be
no surprise to you) found that it works, and it succeeds in some cases
where the hard-decision Berlekamp-Massey algorithm fails. Just like
kvasd... and no patents, non-disclosure agreements, or non-open source
code to worry about! Very impressive!!
I have not yet done any thorough tests of sensitivity relative to the
Koetter-Vardy algorithm. Have you? Are there any theoretical reasons
to expect that it should be (or not be) as good as K-V?
I will do further tests, as time permits.
On another matter, somewhat along the same lines:
Have you looked at all at the way I am presently decoding the MSK
signals in JTMSK? Especially since about r5848, I think the decoder is
pretty good; but since the demodulation process does not yet take full
advantage of signal coherency or the inherent symbol-to-symbol "memory"
in MSK modulation, I think a still better decoder is possible.
From reading Proakis I'm aware that (quite apart from the Viterbi
algorithm used to decode the K=13, r=1/2 convolutional code of JTMSK) a
Viterbi algorithm could also be used as an optimum receiver for these
continuous-phase signals. I also understand that using modulation index
h=0.715 (rather than the h=0.5 of MSK) might have advantages while still
requiring bandwith no more than 2 kHz.
Do you have any opinions here? Any interest in looking into these
questions further?
-- 73, Joe, K1JT
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