mmse_l2.m

是一个对mimo连续相位调制系统的均衡程序

function L_all = mmse_L2( noisy_sig, mtchd_fltr, D, Ns, H, L, sigma, L_a, M)
% This script used for demodulating CPM signals
% Input: 
%        noisy_sig: Received signals
%        mtchd_fltr: Matched filter
%        D: The duration of the pulse
%        Ns: Number of samples per symbol
%        M: samples rate  
%        H: Estimated channel coefficients
%        sigma : Deviation of  noise
% Output:
%        L_all: logarithm likelihood ratio per bit

mod_sym_num = length(noisy_sig)/Ns - L + 1;
noisy_sig = [noisy_sig.';zeros((D-L)*Ns,M)];
R = zeros(M, mod_sym_num);
r1 = zeros(M, mod_sym_num/2);
r2 = zeros(M, mod_sym_num/2);
dhat = zeros(1, mod_sym_num);
Mean = zeros(1, mod_sym_num);

for k = 1 : mod_sym_num/2
    for l = 1 : M
        R(l,2*k-1) = sum(noisy_sig((2*k-2)*Ns+1:(2*k-2+D)*Ns,l).*mtchd_fltr); % Info. after Matched filter 
        R(l,2*k)   = sum(noisy_sig((2*k-1)*Ns+1:(2*k-1+D)*Ns,l).*mtchd_fltr); % Info. after Matched filter
        r1(l,k) = R(l,2*k-1);
        r2(l,k) = R(l,2*k);
    end
end

rr1 = [zeros(M,1) r1 zeros(M,1)];
rr2 = [zeros(M,1) r2 zeros(M,1)];
RR1 = reshape(rr1,M*(mod_sym_num/2+2),1);
RR2 = reshape(rr2,M*(mod_sym_num/2+2),1);

L_a = [zeros(1,4) L_a zeros(1,4)]'; % priori info.
dd  = tanh(-L_a/2);                 % estimated info.

% With MMSE FIR
for l=1:D
    c(l) = sum(mtchd_fltr(1:(D-l+1)*Ns).*mtchd_fltr((l-1)*Ns+1:D*Ns)); % Matched coefficients
end

Sigma = sigma^2;

j = sqrt(-1);
for l = 1 : M
    h1(l,:) = [j*H(l,1)*c(3)+H(l,2)*c(2)  H(l,1)*c(2)-j*H(l,2)*c(3)   j*H(l,1)*c(1)+H(l,2)*c(2)  H(l,1)*c(2)-j*H(l,2)*c(1)  j*H(l,1)*c(3)  -j*H(l,2)*c(3)]/sqrt(2); % ISI coefficients
    h2(l,:) = [H(l,2)*c(3)  H(l,1)*c(3)   j*H(l,1)*c(2)+H(l,2)*c(1)   H(l,1)*c(1)-j*H(l,2)*c(2)  j*H(l,1)*c(2)+H(l,2)*c(3)  H(l,1)*c(3)-j*H(l,2)*c(2)]/sqrt(2); % ISI coefficients
end
HH1 = [h1 zeros(M,4);zeros(M,2) h1 zeros(M,2); zeros(M,4) h1];
HH2 = [h2 zeros(M,4);zeros(M,2) h2 zeros(M,2); zeros(M,4) h2];
HH = [HH2;HH1];

o_5 = [zeros(1,4) 1 zeros(1,5)]'; % the 5th element is one
o_6 = [zeros(1,5) 1 zeros(1,4)]'; % the 6th element is one
z_5 = [ones(1,4) 0 ones(1,5)]';   % the 5th element is zero
z_6 = [ones(1,5) 0 ones(1,4)]';   % the 6th element is zero

for n = 1 : mod_sym_num/2
    dhat(2*n-1) = (HH * o_5)' * pinv(HH * diag(1 - (dd(2*n-1:2*n+8).^2).*z_5) * HH' + eye(6*M,6*M)*Sigma) * ([RR2((n-1)*M+1 : (n+2)*M);RR1((n-1)*M+1 : (n+2)*M)] - HH * (dd(2*n-1:2*n+8) .* z_5));
    dhat(2*n)   = (HH * o_6)' * pinv(HH * diag(1 - (dd(2*n-1:2*n+8).^2).*z_6) * HH' + eye(6*M,6*M)*Sigma) * ([RR2((n-1)*M+1 : (n+2)*M);RR1((n-1)*M+1 : (n+2)*M)] - HH * (dd(2*n-1:2*n+8) .* z_6));
    Mean(2*n-1) = (HH * o_5)' * pinv(HH * diag(1 - (dd(2*n-1:2*n+8).^2).*z_5) * HH' + eye(6*M,6*M)*Sigma) * (HH * o_5);
    Mean(2*n)   = (HH * o_6)' * pinv(HH * diag(1 - (dd(2*n-1:2*n+8).^2).*z_6) * HH' + eye(6*M,6*M)*Sigma) * (HH * o_6);
end

L_all = -4*real(dhat/2)./(1-real(Mean/2));