Re: [Discuss-gnuradio] Simple Frame Detection

[Brian Padalino]

On Sun, Feb 8, 2015 at 11:01 AM, Aditya Dhananjay <address@hidden> wrote:
> Hello Daniel,
>
> Are you using OFDM? If so, read on, otherwise disregard the rest of the
> email.

This sounds much less like a problem with regards on how to figure out
the synchronization but more about how to do it inside the confines of
GNU Radio.

The original post wants to discard everything before a preamble they
detect.  Once preamble is detected, I assume a state machine down
stream will decode some information in the samples coming down which
says "The length of this transmission is 12345 symbols".  At this
time, the downstream block will send a message to the upstream block -
holding off the samples until it knows how many more to send down -
and finish up.

The feedback loop cannot be realized inside the flowgraph since
everything needs to be feed forward.

This is a great example of how someone may want to do RF burst
processing which may not necessarily be "real-time" but due to
dead-air or guard bands might be able to catch up on the processing if
you didn't have to keep processing every last incoming sample -
especially at a higher sample rate.  Moreover, it shows how blocks
could be used to message each other to create feedback loops and
convey downstream information to upstream processing elements which
may care - things like SNR estimation, timing information, etc.

I'm very interested to see how this all ends up.

Brian