On Mon, 16 Aug 2010, Jonas M. Börner wrote:
Hi all,
I am trying to use the convolutional encoder and Viterbi provided by the
gr-trellis class within another environment. I have my own mapper and de-mapper
blocks which I want to use. So I tried to use the feed the viterbi_combined
with this arguments:
va_combined =
trellis.viterbi_combined_fb(fo,nsymbols,0,-1,1,[-1,1],trellis.TRELLIS_EUCLIDEAN)
My de-mapper outputs soft bits between -1 and +1. Here is an example output of
my test script:
data: [0, 1, 1, 0, 0]
encoded: (0, 3, 2, 2, 0)
unpacked: (0, 0, 1, 1, 1, 0, 1, 0, 0, 0)
modulated: ((1+0j), (1+0j), (-1+0j), (-1+0j), (-1+0j), (1+0j), (-1+0j),
(1+0j), (1+0j), (1+0j))
demodulated: (-1.0, -1.0, 1.0, 1.0, 1.0, -1.0, 1.0, -1.0, -1.0, -1.0)
decoded: (0, 0, 1, 0, 0, 1, 0, 1, 0, 1)
Another thing I don't understand is why the decoder outputs 10 values instead
of 5. I would be glad if someone told me what I am doing wrong.
Regards,
Jonas
If I remember correctly, when you start pushing symbols through the
trellis, it has some zero values before the input and some zero values
after your last symbol pushed into the trellis. I think this is typically the
length of your trellis. So at some point you will have to truncate the
trellis output.
Any one else care to comment?
--Colby Boyer
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