Re: [Discuss-gnuradio] Receiving errors with Viterbi decoder block/Decoding AIM spacecraft

[Michael Sabino]

I'm going to post my flowgraph. I have added a CCSDS decoder block.
Please, if you can, provide input on how to improve the amount of
successfully decoded data with a short wave file and a doppler
shifting BPSK carrier.

My .wav file: http://1drv.ms/1bS3KxX

and here is my gnuradio flowgraph: http://1drv.ms/1m3o3N6

Using several different decoding methods, I have obtained strings
found in these two documents:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19880002723.pdf
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19800022222.pdf

(for the Aeronomy of Ice in the Mesosphere spacecraft). One is old
NASA teleoperator system reference, if that helps.

However, the gnuradio method (I was also using a seperate program
written for an SDR analysis/display utility called SDR#/SDRSharp), is
presently suboptimal.

I have some times where I see a BPSK constellation, but other times
(some in between the good constellations) I just see a ring where it
loses synchronization. Please provide help on how to improve my BPSK
demodulator.

Thanks

Michael Sabino

On 1/27/16, Achilleas Anastasopoulos <address@hidden> wrote:
> The problem is not the length 2048 but the way you use the fsm constructor
>
> trellis.fsm(2,7,[79,109])
>
> You are trying to create an FSM for a (7,2) CC.
>
> This means you need to provide a vector of 2x7 integers, each
>
> representing the generator polynomial between the i-th input (i=0,1)
>
> to the j-th output (j=0,1,...,6)
>
>
> However you only provide 2 of them.
>
>
> Are you sure this is what you want to do?
>
> ------------
>
> this is a snippet from fsm.cc
>
>
> //######################################################################
>     //# Automatically generate the FSM from the generator matrix
>     //# of a (n,k) binary convolutional code
>
> //######################################################################
>     fsm::fsm(int k, int n, const std::vector<int> &G)
>