On Wed, 2016-08-24 at 13:55 -0400, Andy Walls wrote: > On Wed, 2016-08-24 at 12:00 -0400, [email protected] > wrote: > > Date: Tue, 23 Aug 2016 16:42:33 -0700 (MST) > > From: Paul Creaser > > To: [email protected] > > > In a real system the signal would be a preamble, which would normally be > > used > > for synchronization purposes at the receiver end (For example PLC system). > > > > "I'm not quite sure what you mean by "cyclic noise", but the example you > > give is 50 Hz (or 60 Hz) hum, so a narrowband interference." > > > > Cyclic noise, perhaps my understanding is incorrect. In a PLC system, the > > noise rejection system uses a Zero Cross detection to detect the beginning > > of a power cycle (50Hz/60Hz). During the cycle at the same phase point, > > noise repeatedly occurs. So on a scope you would see a nice sine wave for > > the power and noise which repeats at the same phase point in the power > > cycle. > > Ah, now I understand: a periodic noise impulse. So definitely not an > AWGN. > > > > This is different from the 50 Hz noise I suggested previously. However the > > idea/hope is that this noise is narrow band noise and because of its > > repetitive behaviour, > > Impulsive noise is usually broadband. Signals that are concentrated in > the time domain are spread out in the frequency domain, and vice versa > (this falls out from the Fourier transform). > > A periodic, broadband noise impulse is essentially going bump up the > noise floor for a short time every 50th (or 60th) of a second. > > > > > .i.e. occurring in the same point in the cycle, and > > relatively stable amplitude, it should be possible to remove it from a known > > signal. > > > > I will take on board all the useful advice and continue my studies. > >
This paper on impulsive noise mitigation in PLC systems seems apropos: https://arxiv.org/pdf/1303.1217.pdf -Andy _______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
