%hold on
%該程序仿真STBC12編碼，QPSK調制的誤碼率
%SNR upto 20 dBs
EbNo=[0:2:20];
%initialize count
idx = 1;
%N, M: number of transmit and receive antennas
K=1000;
N=1;
M=2;Num=100;
%channel_model='AWGN ';%信道模型是高斯信道
model='Rayleigh';%信道模型是Rayleigh
for SNR=EbNo
   sigma=0.5/(10^(SNR/10));  
   % Num -> number of packets
       for packet_count=1:Num
         data=randint(K*2,N);
                BIT=2;
   tx_bits=data.';
   bits_in=tx_bits;
   full_len = length(bits_in);
    % Angle [pi/4 3*pi/4 -3*pi/4 -pi/4] corresponds to 
   % Gray code vector [00 10 11 01], respectively.
   table=exp(j*[-3/4*pi 3/4*pi 1/4*pi -1/4*pi]);  % generates QPSK symbols
   table=table([0 1 3 2]+1); % Gray code mapping pattern for QPSK symbols
   inp=reshape(bits_in,2,full_len/2);
   mod_symbols=table([2 1]*inp+1);  % maps transmitted bits into QPSK symbols
   P=4;% 4 constellation points
   temp=mod_symbols;
   s=table;
%ready to transmit symbols of length 'K'
X=temp.';
fr_length=length(X);
 
% MRC
x0=X;

% form the channel matrix
%if channel_model=='AWGN    '
    Hr=ones(fr_length,M);   %如果信道是高斯信道，則執行該語句
%else
 %   %如果信道是Rayleigh信道，則執行該語句
   Hr=(randn(fr_length,M)+j*randn(fr_length,M))/sqrt(2);

%end
        

%transmission matrix   
H=reshape(Hr,fr_length,M);
Habs=sum(abs(H).^2,2);

%received signal per receiver antenna   
r1=sum(H(:,1).*x0,2)/sqrt(N)+sqrt(sigma)*(randn(fr_length,1)+j*randn(fr_length,1));
r2=sum(H(:,2).*x0,2)/sqrt(N)+sqrt(sigma)*(randn(fr_length,1)+j*randn(fr_length,1));

 % demodulate the received signals
z1=r1.*conj(H(:,1))+r2.*conj(H(:,2));

%uncoded(1,1)
r01=H(:,1).*x0+sqrt(sigma)*(randn(fr_length,1)+j*randn(fr_length,1));

%form estimates
for m=1:P
   d01(:,m)=abs(r01-H(:,1)*s(m)).^2; %uncoded signal
   
   %coded signals
   d1(:,m)=abs(sum(z1,2)-s(m)).^2+(-1+sum(Habs,2))*abs(s(m))^2;
end
     
% determine the minimum of estimates      

%decision for detecting uncoded
[y0,i0]=min((d01),[],2);
s0d=s(i0).';
clear d01 
     
%decision for detecting s1     
[y1,i1]=min((d1),[],2);
s1d=s(i1).';
clear d1
    
% form received symbols    
Xd=[s1d];

%determine symbol errors   
error_un(packet_count)=sum(X(:,1)~=s0d);% for uncoded
temp1=X>0;
temp2=Xd>0;
error(packet_count)=sum(sum(temp1~=temp2));% for coded
end% end of FOR loop for "packet_count"
%calculate FER, SER and BER for current idx

%for uncoded signal
SER_uncoded(idx)=sum(error_un)/(Num*K);
BER_uncoded(idx)=SER_uncoded(idx)/BIT;
FER_uncoded(idx)=SER_uncoded(idx)*K;

%for coded signal
SER(idx)=sum(error)/(Num*K);
BER(idx)=SER(idx)/BIT;
FER(idx)=SER(idx)*K;

%increment idx  
idx=idx + 1;

%str_bar=[num2str(wb) '% Completed'];
%waitbar(wb/100,h,str_bar);
%wb=wb+9.09;

end    % end of FOR loop for SNR
%semilogy(EbNo,SER,'g')
%hold on

semilogy(EbNo,BER,'<')
%legend('SER','BER')
clc
clear