Re: [Discuss-gnuradio] OOK reception

[Eric Blossom]

On Thu, Oct 09, 2008 at 11:39:29AM -0400, Dan wrote:
> Hi, I am working on an OOK receiver but am having some problems with the
> squelch.
> 
> I wrote a script with the following flow graph:
> 
> USRP.source_c -> complex_to_mag -> add_const_ff( -const ) ->
> binary_slicer_fb -> file_sink
> 
> This works fine, but I would like to have some sort of discrimination for
> when there is no signal.  I looked into adding a pwr_squelch_cc block after
> the source but this led to a lot of buffer overruns as the processing
> increased.  I am attempting to receive a bandwidth of 16 MHz using 8-bit
> samples so any more processing I add can make a difference.  The bandwidth
> is important as I am trying to maximize the data rates it can handle.
> 
> There is also the option of checking after the fact and counting the number
> of samples that are zero.  i.e. if there are x number of 0's then stop
> writing to file and wait for another 1 to come through.  Is there anything
> implemented for this or would I have to write my own block?
> 
> If you have any ideas or suggestions of what I should take into account
> (i.e. alpha and ramp for squelch) then please let me know.  My goal is to
> basically have a variable dwell time after a valid signal that will turn off
> after a certain delay.
> 
> Thanks,
> Dan

complex_to_mag_squared is many many times faster than complex_to_mag.
Using it would reduce your CPU consumption.

Eric