I did some trellis decoding for 700B and used the following hacked together
extension of David's aforementioned script trellis.m
http://users.on.net/~esh/codec2/trellisextended.m
I've not had the chance to extend it to work with 700c or port it to C.
Generating the examples and experimenting with different distance measures
for my blog posts on it kept the uni of new england beowolf cluster cores
very busy for a few nights.
IIRC codewords over 6 or 7 bits in length bog down a bit with the
complexity of trellis decoding in octave.
Erich
VK5HSE
On 2 Nov 2017 22:38, <[email protected]> wrote:
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> 1. Re: developing a cognitive decoder (David Rowe)
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> ----------------------------------------------------------------------
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> Message: 1
> Date: Thu, 2 Nov 2017 07:03:35 +1030
> From: David Rowe <[email protected]>
> To: [email protected]
> Subject: Re: [Freetel-codec2] developing a cognitive decoder
> Message-ID: <[email protected]>
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> Feel free to experiment. We've done some similar work with trellis
> decoding that might be useful as a starting point:
>
> http://www.rowetel.com/?p=4147
>
> Many of the demodulators already output soft decision information.
>
> - David
>
>
> On 01/11/17 22:49, Matei Alexandru Coltoiu wrote:
> > Hello,
> >
> > I am trying to find a different approach regarding the poor error
> > handling issue.
> > My Idea is to write a demodulator from scratch. Instead of either having
> > an output consisting of approximated values (later to be fed into the
> > FEC decoder) or having none, we could write the demodulator so that it
> > adds a "tail" after each symbol so that we have
> > floating point values in the end. Take this example: The demodulator
> > would either aproximate a value between 00 and 01 or we would have an
> > error. With my example, it would output a value between 0000000001 and
> > 0011111111. We would than use a cognitive decoder to "guess" wich value
> > it should use. I am aware that a cognitive decoder is not a piece of
> > cake and that we ar fighting with highly compressed data. But, given the
> > overhead reduction from the FEC, we should bbe able to get a decent
> > gain. The result in low SNR should be a noisy output but inteligible,
> > similar to an analog radio (sort of).
> > --
> > Col?oiu Matei Alexandru, telefon: 0373741128 <tel:0373%20741%20128>
> > ?whatsapp 0748021325 <tel:0748%20021%20325>/0770663003
> > <tel:0770%20663%20003>. Skype: rav0rmat
> >
> >
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