[Discuss-gnuradio] Regarding carrier- sensing in digital rx example

[Mattias Kjellsson]

Hi list,

I have looked at the digital rx example, and there is at least one thing
in particular that have caught my attention.

In the receive path, the channel- filters output is connected to two
blocks, first a carrier- sense (gr_probe_avg_mag_sqrd_c) and second a
"packet receiver".

In the packet receive block, the connection chain is: Demodulator ->
Access- code correlator -> gr_frame_sink_1

The frame sink does know if gr_access_correlator_bb has found an access
code through the flag- bit in the correlators output. But I can't find
any flag or similar for detecting the state of the carrier probe.
Shouldn't this be checked for since one might get a false trigger from
the Access code correlate block with the usrp receiving noise.

Can someone please clarify where/how/if the state of the probe is used?
Or is it the probability that noise generates the correlation bit-
sequence and a correct header, witch makes the frame_sink_1 put it in
its message_queue, that there is no need to check the probe status. In
that case, what is the probe doing there?

Best regards,
//Mattias Kjellsson