add noise to signal(alpha-stable)

[Mbqmbq]

hello all
I want to add noise to a simple digital signal in Matlab,
But the noise is not Gussian,it is Alpha-Stable
please help me!!!

 

[rahdirs]

Are you just trying to add Gaussian noise to a signal OR are you trying to transmit a signal through an AWGN channel---to show effect of noise ?????

If it is the first,as it appears from your question:

Adding Noise to a Signal:

• noisy signal = signal + noise
• y = x + randn(size(x)) % Gaussian noise

 

[Mbqmbq]

No it is not Gaussian,
as I writed in the second sentence,the noise is Alpha stable
so you can not use "randn"

 

[WimRFP]

Did you check mathworks.com for a STBL random generator?

If you don't have it, but you have the CDF or PDF for your combination of parameters, you may experiment with a non-linear transfer function to convert a uniform PDF into your Stable PDF.

 

[rahdirs]

No it is not Gaussian,as I writed in the second sentence,the noise is Alpha stable,so you can not use "randn"

In post 2,in that code,you add to signal x a random noise in size t & it should have been an N(0,1) white gaussian noise.But that doesn't seem to work.

• If your signal(x) is 1D,then
• y = x.*fspecial('gaussian', size(x),z);
• in place of z you can tune to any value(amplitude of the white Gaussian noise)you like.

• If you know snr,you can use 'awgn' command
• y = awgn(x,snr);

 

[Mbqmbq]

thank you sir/madam rahdirs
your suggestions are related to Gaussian noise,
but our noise is Alpha-Stable so we can not use these command:"awgn" & "randn"
and we have Characteristic function and pdf of the noise
now,how we can generate these noise?

 

[WimRFP]

You may know from statistics that you can map a uniform distribution into any other distribution. As you have the pdf (hence the cdf) of the target distribution, you can make your own transfer function. The method is described in many textbooks.

The basic principle to generate random numbers with any pdf out of a uniform random number generator is also given here:
https://www.av8n.com/physics/arbitrary-probability.htm

 

[Mbqmbq]

I saw that,it was good thank you
but there was no Matlab or any prevalent program code.
:-?