signature.asv

Signature estimation using LMS algorith for CDMA systems

function [w1 w2] = signature(snr_in_dB,h)
E = 1; numoferr = 0;
SNR = 10^(snr_in_dB/10);         % signal to noise ratio
sgma = (E/sqrt(2*SNR));
w1 = [1 1 1 1]';N = 4;
w2 = [1 1 1 1]';w3 = w1;w4 = w1;
signat = 0.5*hadamard(4);            % using columns of hadamard matrix as spreading code
N=1000;mu = 0.1;
for i=1:N
    b1 = randsrc(1,1,[1 -1]);    % generation of the binary data source follows
    b2 = randsrc(1,1,[1 -1]);

    xsig1 = b1*signat(:,1);
    xsig2 = b2*signat(:,2);
    
    rec1 = conv(h,xsig1);
    rec2 = conv(h,xsig2);
   
    r = rec1(1:4)+rec2(1:4)+sgma*(randn(4,1)+j*randn(4,1)); 
    
    b1r = w1'*r;
    %b2r(i) = sign(real(b2r(i)));
    error1 = b1-real(b1r);
    w1 = w1 + 2*mu*error1*(r);
    w1 = real(w1);
    
    b2r = w2'*r;
    error2 = b2-real(b2r);
    w2 = w2 + 2*mu*error2*r;
    w2 = real(w2);
    
    b2r = w2'*r;
    error2 = b2-real(b2r);
    w3 = w3 + 2*mu*error2*r;
    w3 = real(w3);
    
    b4r = w4'*r;
    error4 = b4-real(b4r);
    w4 = w4 + 2*mu*error4*r;
    w4 = real(w4);
    E1(i) = error1;
    MSE1(i) = mean(E1(1:i).*E1(1:i));
    E2(i) = error2;
    MSE2(i) = mean(E2(1:i).*E2(1:i));
end
if (snr_in_dB == 30)
    figure;plot(MSE1);title('MSE');
    figure;plot(MSE2);title('MSE');
end