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 dBsEbNo=[0:2:40];%N, M: number of transmit and receive antennasN=no_tx_antennas;M=no_rx_antennas;%initialize countidx = 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')        endtx_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 antennapilot1=[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 lengthpilots1=(repmat(pilot1,fr_length,1));%append the pilot1 symbols to the first antenna symbolX1=[pilots1 x1(:,1)];%configure pilot 2 for the second antenna. Pilot 2 is orthogonal to pilot 1pilot2=[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 lengthpilots2=(repmat(pilot2,fr_length,1));%append the pilot2 symbols to the second antenna symbolX2=[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 antennasy1=[X1 X2];% transmit through channelfor 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 intervalsendfor 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 intervalsend%gather the R1 matrix for transmission during the first symbol intervalR1=[R1 R3];%extract the training symbolstr_symbols1=R1(:,1:20); tr_symbols2=R1(:,22:41); %reconfigure the received signal matrix for first symbol interval from BOTH%the antennastemp1=[R1(:,21) R1(:,42)];%assign to r1 and r2. The 'sum' function denotes summing at the outputs of%BOTH antennasr1(:,n)=sum(temp1,2);r2(:,n)=sum(R2,2);%estimate channel using MMSEfor i=1:fr_length    H_est1(i,1)=mean(tr_symbols1(i,:).*conj(pilot1));endfor i=1:fr_length    H_est2(i,1)=mean(tr_symbols2(i,:).*conj(pilot2));end%final estimated channel coefficients to be used for receptionH_est=[H_est1 H_est2];%original (perfect) channel coefficients used to transmit the signalsH=[H1.' H2.'];%absolute ESTIMATED channel coefficients to be used later in this programH_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 estimatesfor 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 uncodedtemp1=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);