Re: Turbo , Convolutional Codes

[oglop]

If I understand you correctly, you think that best for me would be to show
the Trellis decoding live on the board or so because the programming the
decoder is beyond the borders of small semester project. I found many
diploma thesis about decoding.
Yes I know the last two pairs are tail bits and they are flushed and are
not sent with message, I already told that in my first part of project.
The sad think is the only who would understand me would be my teacher
because they told us anything about trellis and state diagram etc. about
this. I had to learn everything myself..
Mainly from http://www.youtube.com/user/nptelhrd, their lectures are
awesome and In most cases much better then ours .. because what are we
tough in Czech Republic is not done with good approach in most courses :(

But thank you for your help.


2013/11/18 Mike Miller [via Octave] <
address@hidden>

> Cc'ing the help list. Please remember to include the mailing list on
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>
> On Mon, Nov 18, 2013 at 18:34:16 +0100, Jan 'oglop' Gazda wrote:
> > I have learned a lot about convolutional codes ... I started from
> scratch ..
> > The final output of my project should be simple example of coding and
> > decoding process for convolutional or turbocode .. primary in octave
> > If you know about better programming language or so, then tell me. I
> know
> > little of python and C
>
> Octave is certainly suitable. Whatever language you are most familiar
> with should be fine.
>
> > Let's say I have a
> > word which I want to code: W=[1 0 1 1]
> > with my convolutional coder which has Generator vectors: G1 = [1 0 1],
> G2 =
> > [1 1 1]
> > So code word can be done like this:
> > output1 = mod(conv(W,G1),2),
> > output2 = mod(conv(W,G2),2)
> >
> > output1 =  1   0   0   1   1   1
> >
> > output2 =   1   1   0   0   0   1
> >
> > CodeWord = [ 11 01 00 10 10 11] - I wrote simple function to merge the
> > outputs
>
> Looks ok so far. Note that by using the full convolution you are
> implicitly adding tail bits to flush the encoder. So technically this
> is the output for an input sequence of
>
>   w = [1 0 1 1 0 0]
>
> Adding tail bits gives you a known final state for the encoder trellis.
>
> > Now I have to decode the word, but I don't know how to demonstrate it
> like
> > this .. do I have to code full viterbi or hard decoder by myself or are
> > there any mathematical methods to decode it.
> > I did not get so far with viterbi decoding, I just know how it works and
> how
> > to use the trellis to decode.
>
> For a specific short example like this, you could start by manually
> recreating the steps that the Viterbi algorithm would do for each
> symbol in the coded sequence.
>
> HTH,
>
> --
> mike
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