function [FER,FER_uncoded,SER,SER_uncoded, BER, BER_uncoded]=stbc21(channel_model,K,Num,no_tx_antennas,no_rx_antennas,modulation)%SNR upto 20 dBsEbNo=[0:2:20];%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));  % form the channel matrix for n=1:N     if channel_model=='AWGN    '         Hr(n,:,:)=ones(fr_length,N);     else         Hr(n,:,:)=(randn(fr_length,N)+j*randn(fr_length,N))/sqrt(2);     end end %transmission matrix   H=reshape(Hr(n,:,:),fr_length,N);Habs(:,n)=sum(abs(H).^2,2);%received signal per receiver antenna    r1=sum(H.*x1,2)/sqrt(N)+sqrt(sigma)*(randn(fr_length,1)+j*randn(fr_length,1)); r2=sum(H.*x2,2)/sqrt(N)+sqrt(sigma)*(randn(fr_length,1)+j*randn(fr_length,1));  % demodulate the received signals z1=r1.*conj(H(:,1))+conj(r2).*H(:,2); z2=r1.*conj(H(:,2))-conj(r2).*H(:,1);%uncoded(1,1) 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(:,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;   d2(:,m)=abs(sum(z2,2)-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%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 signals  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);