stbc22_est.m

信号与系统基础知识包括连续信号与模型、离散信号与模型；常用信号变换包括Z变换、

function [FER,FER_uncoded,SER,SER_uncoded, BER, BER_uncoded]=stbc22_est(channel_model,K,Num,no_tx_antennas,no_rx_antennas,modulation)

%SNR upto 20 dBs
EbNo=[0:2:20];

%N, M: number of transmit and receive antennas

N=no_tx_antennas;
M=no_rx_antennas;

%initialize count
idx = 1;

h=waitbar(0,'Percentage Completed');
set(h,'Position',[230 60 275.25 56.25]);
set(h,'name','Please wait...');
wb=9.09;

 
for SNR=EbNo

  sigma=0.5/(10^(SNR/10));  

  % Num -> number of packets
       for packet_count=1:Num
 
% we are interested in transmitting 'K' SYMBOLS not bits. Hence, K*2 for QPSK
% etc.
        switch (modulation)
            case 'BPSK '
                data=randint(K,N);
                BIT=1;
            case 'QPSK '
                data=randint(K*2,N);
                BIT=2;
            case '8PSK '
                data=randint(K*3,N);
                BIT=3;
            case '16QAM'
                data=randint(K*4,N);
                BIT=4;
            otherwise
                disp('No Modulation')
        end
tx_bits=data.';
temp=[];
temp1=[];
for i=1:N
    [temp1 s P]=tx_modulate(tx_bits(i,:),modulation);
    temp=[temp; temp1];
    temp1=0;
end

%ready to transmit symbols of length 'K'
X=temp.';

fr_length=length(X);
 
 % block coding-Alamouti
 x0=X(:,1);% required to verify a 1x1 system
 x1=X;
 x2(:,1)=-conj(X(:,2));
 x2(:,2)=conj(X(:,1));


      
for n=1:M
    R1=[];
R2=[];
R3=[];
y1=[];
%configure pilot 1 for one antenna
pilot1=[0 0 0 0 0 0 0 0 0 0 1 -1 -1  1 -1 -1  1 -1  1  1];

%extend the pilot symbols for full frame length
pilots1=(repmat(pilot1,fr_length,1));

%append the pilot1 symbols to the first antenna symbol
X1=[pilots1 x1(:,1)];
%configure pilot 2 for the second antenna. Pilot 2 is orthogonal to pilot 1
pilot2=[1 -1 -1 -1  1 -1 -1  1 -1  1 0 0 0 0 0 0 0 0 0 0];

%extend the pilot symbols for full frame length
pilots2=(repmat(pilot2,fr_length,1));

%append the pilot2 symbols to the second antenna symbol
X2=[pilots2 x1(:,2)];

%assign the symbols to be transmitted to variable y1 instead of x1. y1 is
%the signal transmitted in the first interval period from BOTH the antennas
y1=[X1 X2];

% transmit through channel
for i=1:fr_length
%channel coefficient for first antenna    
if channel_model=='AWGN    '
    H1(i)=ones(1,1);
else
    H1(i)=sqrt(0.5)*(randn(1,1)+j*randn(1,1));
end
    
%received signal per receiver antenna   
 R1(i,:)=H1(i)*y1(i,1:21)/sqrt(N)+sqrt(sigma)*(randn(1,1)+j*randn(1,1));% upto 21st column constitutes the transmission in the
                                                                         %first symbol interval from the FIRST antenna                                                                      %i
 R2(i,1)=H1(i)*x2(i,1)/sqrt(N)+sqrt(sigma)*(randn(1,1)+j*randn(1,1));%transmission in the second symbol interval from the FIRST
 %antenna.Note no pilot symbols are being transmitted as the assumption is that the channel does
 %not change through two symbol intervals
end
for i=1:fr_length
%channel coefficient for second antenna   
if channel_model=='AWGN    '
    H2(i)=ones(1,1);
else
    H2(i)=sqrt(0.5)*(randn(1,1)+j*randn(1,1));
end
 %received signal per receiver antenna   
 R3(i,:)=H2(i)*y1(i,22:end)/sqrt(N)+sqrt(sigma)*(randn(1,1)+j*randn(1,1));% column 22 till 42nd constitutes the transmission
                                                                            % in the first symbol interval from the SECOND antenna
 R2(i,2)=H2(i)*x2(i,2)/sqrt(N)+sqrt(sigma)*(randn(1,1)+j*randn(1,1));%transmission in the second symbol interval from the SECOND 
                                                                        %antenna.Note no pilot symbols are being transmitted as 
                                                                        %the assumption is that the channel does
                                                                         %not change through two symbol intervals
end
%gather the R1 matrix for transmission during the first symbol interval
R1=[R1 R3];

%extract the training symbols
tr_symbols1=R1(:,1:20); 
tr_symbols2=R1(:,22:41); 

%reconfigure the received signal matrix for first symbol interval from BOTH
%the antennas
temp1=[R1(:,21) R1(:,42)];

%assign to r1 and r2. The 'sum' function denotes summing at the outputs of
%BOTH antennas
r1(:,n)=sum(temp1,2);
r2(:,n)=sum(R2,2);

%estimate channel using MMSE
for i=1:fr_length
    H_est1(i,1)=mean(tr_symbols1(i,:).*conj(pilot1));
end

for i=1:fr_length
    H_est2(i,1)=mean(tr_symbols2(i,:).*conj(pilot2));
end

%final estimated channel coefficients to be used for reception
H_est=[H_est1 H_est2];

%original (perfect) channel coefficients used to transmit the signals
H=[H1.' H2.'];

%absolute ESTIMATED channel coefficients to be used later in this program
H_estabs(:,n)=sum(abs(H_est).^2,2);

% demodulate the received signals
 z1(:,n)=r1(:,n).*conj(H_est(:,1))+conj(r2(:,n)).*H_est(:,2);
 z2(:,n)=r1(:,n).*conj(H_est(:,2))-conj(r2(:,n)).*H_est(:,1);
end

%uncoded(1,1)TRANSMITTED signal. Note we use original channel coefficients, since this is the transmitted signal 
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_est(:,1)*s(m)).^2; % uncoded signal
%coded signals  
  d1(:,m)=abs(sum(z1,2)-s(m)).^2+(-1+sum(H_estabs,2))*abs(s(m))^2;
  d2(:,m)=abs(sum(z2,2)-s(m)).^2+(-1+sum(H_estabs,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
%decision for detecting s2
      [y2,i2]=min(d2,[],2);
      s2d=s(i2).';
      
      clear d2
% form received symbols    
    Xd=[s1d s2d];
     
%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
   
close(h);