Re: [Discuss-gnuradio] Calculating additive noise power for known signal

[Andy Walls]

On Wed, 2016-08-24 at 13:55 -0400, Andy Walls wrote:
> On Wed, 2016-08-24 at 12:00 -0400, address@hidden
> wrote:
> > Date: Tue, 23 Aug 2016 16:42:33 -0700 (MST)
> > From: Paul Creaser
> > To: address@hidden
> 
> > 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