www.pudn.com > communication-systems-using-MATLAB-m-files.rar > gwnoise.m

function [m, d, s] = gwnoise(m, d, s) 
%GWNOISE generate valid mean value, standard deviation and seeds for GWNOISE block. 
%	[M, D, S] = GWNOISE(M, D, S) checks input mean M, standard deviation D, and 
%	seed S. When they are not valid, converts them to be valid for GWNOISE 
%	block, or gives out an error message. 
% 
 
%  Copyright 1996-2001 The MathWorks, Inc. 
%       $Revision: 1.17 $ 
 
if nargin ~= 3 
	error('Input variable must be 3 for GWNOISE.'); 
end; 
m = m(:)'; 
s = s(:)'; 
l_m = length(m); 
l_s = length(s); 
[n_d, m_d] = size(d); 
if n_d ~= m_d 
	if min(n_d, m_d) == 1 
		if any(d < 0) 
			error('Standard deviation cannot be negative number.'); 
		end 
		d = diag(d); 
	else 
		error('Standard deviation for Gaussian noise block is not valid.'); 
	end; 
else 
	[n_d, m_d] = chol(d); 
	if m_d ~= 0 
		error('Standard deviation for Gaussian noise must be positive definite.'); 
	end; 
end; 
l_d = length(d); 
if ((l_m < l_d) & (l_m ~= 1)) | ((l_m > l_d) & (l_d ~= 1)) 
	error('The dimensions of the mean and standard deviation for Gaussian noise block are not compatible.'); 
end; 
max_l = max(l_m, l_d); 
if l_s < max_l 
    new_seed = 1; 
    while l_s < max_l 
        seed_pos = find(s == new_seed); 
        if (length(seed_pos) == 0) 
            s = [s, new_seed]; 
            l_s = length(s); 
        end 
        new_seed = new_seed + 1; 
    end     
elseif l_s > max_l 
    if max_l ~= 1 
        s = s(1 : max_l); 
    else 
        d = eye(l_s) * d; 
    end; 
end; 
[d, tmp] = chol(d); 
if tmp > 0 
    error('Covariance matrix in AWGN noise generator is not a positively defined matrix.'); 
end; 
% end of gwnoise