multipath.m

无线仿真Matlab代码

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%   ***************************************************************************
%
%   UMTS-HSDPA channel generator 
%              
%   [omega] = omega(samples,rayleigh_fades,fD,spectrum)
%
%   Generate multipath fading.
%   This function is called for each ray.
%
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function [omega] = omega(samples,rayleigh_fades,fD,spectrum)

% Frequency vector. fD/rayleigh_fades is fundamental frequency
f = (-samples/2:samples/2-1)*fD/rayleigh_fades;
   
% Prevent divide by zero on doppler construction
neg_index=samples/2+1-rayleigh_fades; % index of negative doppler frequency
f(neg_index)=f(neg_index+1);

pos_index=samples/2+1+rayleigh_fades; % index of positive doppler frequency
f(pos_index)=f(pos_index-1);

% Generate Doppler spectrum
Doppler_filter = zeros(samples,1);
if strcmp(spectrum,'Jackes')    % Doppler Jakes filter 
    Doppler_filter(neg_index:pos_index) = sqrt(1./(sqrt(1-(f(neg_index:pos_index)./fD).^2)));
else                            % Doppler flat filter
    Doppler_filter(neg_index:pos_index) = sqrt(f(neg_index:pos_index));
end
Doppler_filter = fftshift(Doppler_filter);

% Filter random samples in frequency domain
xf = real(ifft(fft(randn(samples,1)).*Doppler_filter));
yf = real(ifft(fft(randn(samples,1)).*Doppler_filter));

% omega (not normalized); power of complex signal
omega = (abs(complex(xf,yf))).^2;

% Normalize
omega = omega./mean(omega);