Re: [Discuss-gnuradio] QAM demod Error in GRC

[Tom Rondeau]

On Mon, May 23, 2011 at 10:37 PM, Ben Reynwar <address@hidden> wrote:

On Mon, May 23, 2011 at 12:09 PM, Josh Blum <address@hidden> wrote:
>
>
> On 05/23/2011 03:29 AM, Vlad Stoianovici wrote:
>>
>> Dear Marcus and Bob,
>> I did understand that the block was hollow, but this thread is kindda old,
>> so I thought that in the mean time maybe someone implemented the code and
>> functionality you are referring to.
>> I'm using GRC, but I don't have time to start learning python with the sole
>> purpose of being able to write the QAM block.
>> It would probably be easier to use Simulink, which I'd rather not do.
>>
>
> This is a motivating example for a new gr-digital component that can
> make use of tags: the QAM deframer block. :-)
>
> -josh

In the psk8 branch of my github repo
(www.github.com/benreynwar/gnuradio/) there is QAM modulation and
demodulation within the "digital" category of GRC.  I haven't tested
it recently though.  Let me know if you try it and it doesn't work.

Cheers,
Ben

Ben's branch is based off of my 8psk branch in github, too. I still need to pull in his changes. I have a feeling we might be going back and forth a bit in the development of the gr-digital top-level directory. This will make it into the upcoming 'next' branch for the 3.5 release.

Currently, it includes a more robust version of the Costas loop (you specify the natural freq and damping factor instead of the gains; it sets the gains properly so that the system is more tolerant and locks better) as well as a reworking of the CMA equalizer. I have yet to use this equalizer on a real signal, only simulated multipath channels, so more experience would be good.

Note that if you are using this branch you should --disable-gr-trellis. I banged up the API that is used in gr-trellis and haven't got back to fix it, yet.

Tom