[Ground-station] challenges with correlation estimation block - flowgraphs, assumptions, next steps

[Brennan Ashton]

Michelle,
The PR I submitted reverts the functionality of the correlation estimator
back to exactly what it was prior to the addition of PFA if you put it in
absolute threshold mode, so if you are not having success in that mode I
suspect something else is up.

I'll try and take a look tonight or tomorrow now that I have the flow
graphs that you are using.

--Brennan

On Wed, Apr 11, 2018 at 10:17 AM Michelle Thompson via Ground-Station
<ground-station at lists.openresearch.institute> wrote:

> Here are the two flowgraphs that we believe aren't working due to the
> Correlation Estimation Issue here
> https://github.com/gnuradio/gnuradio/issues/1207
>
> We don't think it's operator error, but we're relatively new to GNU Radio,
> and would welcome any comment or critique that helps to solve this.
>
> FM_ARAP_to_downlink.grc is the flowgraph we are using for transmit side.
>
> What does it do?
>
> It collects up four analog FM channels, digitizes, and transmits a time
> division multiplexed signal out. This is, in general, a simple model of our
> uplink for a Groundsat or payload.
>
> We see the expected transmitted signal on a spectrum analyzer and on a
> HackRF portapack and on the receiving system across the lab.
>
> The receiving flowgraph is called TDM_downlink_rx.grc
>
> What does it do?
>
> It takes the time division multiplex signal and is supposed to break the
> channels back out.
>
> This demo has worked in the past, but not anymore, and definitely not over
> the air now.
>
> The problem seems to be the correlator, and it seems to be the same
> trouble reported in the issue.
>
> Here's a video of the lab session:
> https://youtu.be/T6TwN2FvfAo
>
> We want a DVB-S2/X correlator. I think we can also help fix this
> correlation estimation block. In all cases, we want to comply with the tag
> scheme produced, so that downstream blocks already in GNU Radio get what
> they're expecting, if they are expecting these types of tags.
>
> Thank you to all taking a look at this and helping get blocks together for
> the Block Party at GRCon2018.
>
> -Michelle W5NYV
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