[op25-dev] hamming decoder

Matt D md123 at nycap.rr.com
Sat Sep 7 14:45:37 UTC 2013


Hey,

I am interested in writing the shortened hamming decoder and rs decoder
for the LC information.  Is there any sort of reference manuals that
describe how the shortened hamming code is implemented? From looking at
the op25 lib; op25_hamming.h in particular, it looks like its being done
bitwise in
hamming_15_decode function.    i just really don't know what that giant
encoding array & the small decoding array are and how those relate to
the generator matrices in the tia pdf?

i think i kind of have to know what those are about before i can proceed
to write a decoder of the LCWs. But thereafter i suspect it shouldn't be
to hard.

the matrix algebra approach is how i understand how to decode hamming
codes and that approach is not used in op25.  furthermore I am not sure
if implementing an algebraic approach would be appropriate (ie. fast
enough) for our use here?

so it would be a big help if I knew how exactly the hamming_15_decode
function works, and in particular what those to arrays (encoding &
decoding) are, and where they come from, and how the generator and
parity matrices (or functions) are utilized?

Thanks!


-- 
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Matt D
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