dealamouti.m

some code in mimo ofdm

%Alamouti decoder for MIMO-OFDM System
%Author: Hoang Nguyen
%*************************************************



function Dec_data = DeAlamouti(R_data,h_data,dh,M,numcarr,Nr,Nt,Num_Path)

%Cac thong so cua ham *****************************
%Dec_data: data after decoding with Alamouti
%R_data: data for decoder
%h_data: tham so kenh truyen
%dh: nhom tin hieu dieu che QAM
%M: kieu dieu che M-ary QAM
%numcarr: so song mang mang du lieu trong 1 ky tu OFDM
%Nr: the number of receive antenna
%Nt: the number of transmit antenna
%Num_Path: so da duong
%**************************************************

%tao ma tran duong cheo kenh F(LNum_RxAnt)
for i=1:numcarr
    for l=1:Num_Path
        F(i,l)=exp(-j*2*pi*(l-1)*(i-1)/numcarr);
    end
end
I_matrix=eye(Nr,Nr);
Fl=kron(I_matrix,F);
%Fl_DeAlamouti=Fl

%Ma tran kenh truyen trong mien tan so 
H=Fl*h_data;

R_data=reshape(R_data,numcarr,Nr);
%Tinh gia tri xap xi cua R, X_est
for k=1:numcarr
    H_k_vector=[];
    for RxAnt=1:Nr
        H_k_row=[];
        for TxAnt=1:Nt
             H_k=H((RxAnt-1)*numcarr+k,TxAnt);
             H_k_row=[H_k_row,H_k];
             clear H_k;
        end
        H_k_vector=[H_k_vector;H_k_row];
        clear H_k_row;
    end
    X_est=H_k_vector'*R_data(k,:)';
    %tin_hieu_xap_xi_X_est=X_est
 
    %ML algorithm for detecting QAM Symbols
     X_dec_vector=[];
     for RxAnt=1:Nr
         temp=X_est(RxAnt);
         d_vector=[];
         for QAM_Sym=1:M
             d=abs(temp-dh(QAM_Sym))^2;
             d_vector=[d_vector,d];
             clear d;
         end
         [val pos]=min(d_vector);
         X_dec =dh(pos);
         X_dec_vector=[X_dec_vector;X_dec];
         clear val pos X_dec d_vector temp;
     end
     clear X_est H_k_vector;
end
Dec_data=X_dec_vector;
clear X_dec_vector;