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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