Re: [Discuss-gnuradio] gr-trellis convolutional coder FSM

[Clemens Hopfer]

Hello Achilleas,

thanks for your reply,

On Tuesday 12 June 2012 19:53:10 Achilleas Anastasopoulos wrote:
> puncturing is not part of the FSM class.

ok, thanks for the clarification, that caused the biggest confusion.

> You can implement it as a simple memoryless device:
> eg, if i want to puncture every third bit, then the device
> accepts 3bits as inputs and outputs the first two.

Ok, I didn't really like to map each bit to a byte, but the data rate I want 
to use shouldn't be that high to get into performance problems.

> If you can give me more details on what exactly you want to
> implement i may be able to help you out.

I actually want to implement the inner coder used by DVB-S (ETSI EN 300 421, 
4.4.3).
But it's just a hobbyist project, so I'm not in a hurry implementing it.

> Similraly, if you let me know which part of the FSM/trellis documentation
> is hard to read, hopefully i will be able to help.

I'm currently working on my BSc and haven't really done a lot with state 
machines yet, so working with machine alphabets is pretty new for me, but I 
guess I figured it out by now.

Again, thanks for your reply.
I'm pretty busy right now, but in about 2 weeks I'll have enough time to work 
on it again.

Best regards,
Clemens


> --------------------
> Hi,
> 
> I'm working on a modulator using a punctured (non-recursive) convolutional
> coder based on a 1/2 rate mother code with length 7.
> 
> However I find the documentation of gr-trellis pretty hard to read, I don't
> really understand how punctuation should actually be implemented.
> 
> Are there any additional documents or papers on designing the FSM of a
> convolutional coder?
> 
> Thanks,
> Clemens

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