[Discuss-gnuradio] Dev call tomorrow? + digital mod/demod questions

[Nowlan, Sean]

It looks like there’s a dev call tomorrow. Is that 1700 or 1800 UTC? https://gnuradio.org/redmine/projects/gnuradio/wiki/Call20141120

 

As for input to the digital mod and packet structure discussion, I have a few questions, or at least food-for-thought for tomorrow:

-          It looks like the correlate_and_sync work is promising for allowing carrier and timing recovery loops to adjust more quickly when dealing with bursty, packetized traffic. However, most of the GR modem applications I’ve seen use the correlate_access_code block without the time and phase estimates being done on the preamble. I know the paradigm is slightly different, i.e. matched-filter preamble correlator vs. counting access code bit errors after MF and slicing, but is the intent to eventually merge the two approaches together?

-          What’s the best way to handle the sudden ramp in power at the start of a burst? Use squelch to detect power above a threshold? Use AGC? This may be a fundamental radio receiver design question but I think it makes sense to ask it in the context of how these blocks are implemented. In gr-air-modes it looks like the preamble detector scans for a rapid change in sample “voltage” before initiating a preamble search. This seems more efficient if packet traffic is expected to be low, otherwise all you’re doing is correlating against noise (correlate_and_sync) or junk bit decisions (correlate_access_code). If I’ve misunderstood anything here, please advise.

 

Thanks,

Sean