Re: gr-trellis convolutional coder FSM

GNU Radio
1

Clemens,

puncturing is not part of the FSM class.
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.

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

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

regards,
Achilleas

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

2

Hello Achilleas,

thanks for your reply,

On Tuesday 12 June 2012 19:53:10 Achilleas A. 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