Hello, I strongly recommend take a look to the Matlab lybrary in order to find more information, but I let you this here:

Y = raylpdf(X,B)

% Copyright 2015 The MathWorks, Inc.

%%

% Compute the pdf of a Rayleigh distribution with parameter |B = 0.5|.

x = [0:0.01:2];

p = raylpdf(x,0.5);

%%

% Plot the pdf.

figure;

plot(x,p)

This is a easy way to calculate Rayleigh coefficients.

%Channel

H=(1/sqrt(2))*(randn(Nr,Nt)+randn(Nr,Nt)*1i)

thank you for your response