ofdm.m

This a matlab code that simulate the monte-carlo simulation of using 16-QAM with OFDM system under A

%Matlab Script for OFDM Simulation

N=32;
NS=10000;

SNRindB1=0:2:15;
SNRindB2=0:0.1:15;


for w=1:length(SNRindB1),
    snr_in_dB = SNRindB1(w);
    SNR=10^(snr_in_dB/10);
    N0=2.5/SNR;  %(Eav=10)
    error=0;
    for i=1:NS,
       b=2*randint(1,4*N)-1;
       b=reshape(b,N,4);

       %Generate the 16QAM points.
       XX=2*b(:,1)+b(:,2)+j*(2*b(:,3)+b(:,4));
       X=XX';
       sn=ifft(X,32);
  
       noise=sqrt(N0/2)*(crandn(1,N));
       r=sn*1+noise/N^.5; %Notice here, Matlab fft and ifft have scale problem.
       Y=fft(r,32);

       % Detect the nearest neighbor in the 16QAM constellation
       for k=1:N,
         if real(Y(1,k))>0,
              if real(Y(1,k))>2,
                Z(1,k)=3;
              else
               Z(1,k)=1;
              end;
          else
              if real(Y(1,k))<-2,
                Z(1,k)=-3;
              else
                Z(1,k)=-1;
              end;
          end;
          if imag(Y(1,k))>0,
              if imag(Y(1,k))>2,
                 Z(1,k)=Z(1,k)+3*j;
             else,
                 Z(1,k)=Z(1,k)+j;
             end;
          else
              if imag(Y(1,k))<-2,
                   Z(1,k)=Z(1,k)-3*j;
               else
                   Z(1,k)=Z(1,k)-j;
              end;
          end;
        end;
        error=error+sum(Z~=X);
    end;
error_rate(w)=error/(N*NS);
end

M=16;
k=4;
for i=1:length(SNRindB2),
  SNR=exp(SNRindB2(i)*log(10)/10);    	% signal to noise ratio
  % theoretical symbol error rate
  theo_err_prb(i)=4*qfunc(sqrt(3*k*SNR/(M-1)));  
end

% Plotting commands follow
semilogy(SNRindB1,error_rate,'*');
hold
semilogy(SNRindB2,theo_err_prb);
title('16-QAM Symbol Error rate with OFDM');
xlabel('{SNR in dB}');
ylabel('SER');
legend('simulation','16-QAM theoretical');