W dniu 2012-01-28 20:18, Andy Talbot pisze:
I've been thinking about the maths behind Wolf and it gets quite interesting.
One thing we can say, its definitely a spread spectrum system !!!!!!!!
SRI USA Hams :-(
A message of 15 characters taken from an alphabet of 40 (A-Z 0-9 and a
few punctuation) give 80 source bits of data after compression.
These are expanded to 480 data bits in six parallel tail-biting
convolutional encoders. In pure error correction terms this seems
like mega-overkill, so there's more than meets the eye going on...
Interleaving may or may not then be employed, but it doesn't affect
things.
The 480 bits are then merged with another 480 bits of a PN seqeunce
(in a not totally dissimilar way that I suspect Opera does) to allow
the decoder to lock to the sequence.
The whole lot is then transmitted at 10 Symbols/s BPSK so the whole
message takes 96 seconds
Dear Andy, LF Group,
In the general description of WOLF given by its Author, Stewart, KK7KA
http://www.scgroup.com/ham/wolf.html
there is a paragraph shortly describing the error control encoder.
There is also an interesting statement about the performance of turbo codes
used in the modern comm systems.
Unfortunately, the link to the 'comparison paper' is dead. However,
being in some way interested in the subject
i have managed to find that publication which possibly could be of some
interest to you and other fellows
it is available here:
http://www.toya.net.pl/~mlynarski/compare-codes.pdf
if you had an earlier access to this paper , pse disregard my mail.. :)
yours, Piotr, sq7mpj
qth: Lodz/jo91rs/
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