% Alamouti_scheme.m
clear;
clc;
clf;
L_frame=130;
N_Packets=4000; % Number of frames/packet and Number of packets
NT=2;
NR=2;
b=2;
SNRdBs=[0:2:20];
sq_NT=sqrt(NT);
sq2=sqrt(2);
for i_SNR=1:length(SNRdBs)
SNRdB=SNRdBs(i_SNR);
sigma=sqrt(0.5/(10^(SNRdB/10)));
for i_packet=1:N_Packets
msg_symbol=randi([0,1],L_frame*b,NT);
tx_bits=msg_symbol.';
tmp=[];
tmp1=[];
for i=1:NT
[tmp1,sym_tab,P] = modulator(tx_bits(i,:),b);
tmp=[tmp; tmp1];
end
X=tmp.';
X1=X;
X2=[-conj(X(:,2)) conj(X(:,1))];
for n=1:NT
Hr(n,:,:)=(randn(L_frame,NT)+j*randn(L_frame,NT))/sq2;
end
H=reshape(Hr(n,:,:),L_frame,NT);
Habs(:,n)=sum(abs(H).^2,2);
R1 = sum(H.*X1,2)/sq_NT + sigma*(randn(L_frame,1)+j*randn(L_frame,1));
R2 = sum(H.*X2,2)/sq_NT + sigma*(randn(L_frame,1)+j*randn(L_frame,1));
Z1 = R1.*conj(H(:,1)) + conj(R2).*H(:,2);
Z2 = R1.*conj(H(:,2)) - conj(R2).*H(:,1);
for m=1:P
tmp = (-1+sum(Habs,2))*abs(sym_tab(m))^2;
d1(:,m) = abs(sum(Z1,2)-sym_tab(m)).^2 + tmp;
d2(:,m) = abs(sum(Z2,2)-sym_tab(m)).^2 + tmp;
end
[y1,i1]=min(d1,[],2);
S1d=sym_tab(i1).';
clear d1
[y2,i2]=min(d2,[],2);
S2d=sym_tab(i2).';
clear d2
Xd = [S1d S2d];
tmp1=X>0;
tmp2=Xd>0;
noeb_p(i_packet) = sum(sum(tmp1~=tmp2));
end % End of FOR loop for i_packet
BER(i_SNR) = sum(noeb_p)/(N_Packets*L_frame*b);
end % End of FOR loop for i_SNR
semilogy(SNRdBs,BER);
axis([SNRdBs([1 end]) 1e-6 1e0]);
grid on;
xlabel('SNR[dB]');
ylabel('BER');