sir/mam....what's the problem?solve me & corrected the code...

% Computing the Symbol Error probability for a general M-QAM 
% using OFDM modulation

function compute_symbol_error_rate_qam_ofdm_awgn()

close all; figure
EsN0dB   = [0:33]; % symbol to noise ratio
M   = [16 64 256]; % 16QAM/64QAM and 256 QAM  
color_vec1 = {'b-','m-','g-'};    
color_vec2 = {'ks-','rx-','cd-'};    
for (jj= 1:length(M))
  k      = sqrt(1/((2/3)*(M(jj)-1))); 
  simSer(jj,:) = compute_symbol_error_rate(EsN0dB, M(jj));
  theorySer(jj,:) = 2*(1-1/sqrt(M(jj)))*erfc(k*sqrt((10.^(EsN0dB/10)))) ...
                - (1-2/sqrt(M(jj)) + 1/M(jj))*(erfc(k*sqrt((10.^(EsN0dB/10))))).^2;
  semilogy(EsN0dB,theorySer(jj,:),color_vec1(jj));
  hold on
  semilogy(EsN0dB,simSer(jj,:),   color_vec2(jj));
end
axis([0 33 10^-5 1])
grid on
legend('theory-16QAM', 'sim-16QAM', 'theory-64QAM', 'sim-64QAM', 'theory-256QAM', 'sim-256QAM');
xlabel('Es/No, dB')
ylabel('Symbol Error Rate')
title('Symbol error probability curve for 16QAM/64QAM/256QAM using OFDM');
return ;

function [simSer] = compute_symbol_error_rate(EsN0dB, M);

% ofdm specifications
nFFT = 64; % fft size
nDSC = 52; % number of data subcarriers
nConstperOFDMsym = 52; % number of bits per OFDM symbol (same as the number of subcarriers for BPSK)
nOFDMsym = 10^4; % number of ofdm symbols

% modulation 
k = sqrt(1/((2/3)*(M-1))); % normalizing factor
m = [1:sqrt(M)/2]; % alphabets
alphaMqam = [-(2*m-1) 2*m-1]; 

EsN0dB_eff = EsN0dB  + 10*log10(nDSC/nFFT) + 10*log10(64/80); % accounting for the used subcarriers and cyclic prefix

for ii = 1:length(EsN0dB)

     % Transmitter
     ipMod = randsrc(1,nConstperOFDMsym*nOFDMsym,alphaMqam) + j*randsrc(1,nConstperOFDMsym*nOFDMsym,alphaMqam);
     ipMod_norm = k*reshape(ipMod,nConstperOFDMsym,nOFDMsym).'; % grouping into multiple symbolsa

     % Assigning modulated symbols to subcarriers from [-26 to -1, +1 to +26]
     xF = [zeros(nOFDMsym,6) ipMod_norm(:,[1:nConstperOFDMsym/2]) zeros(nOFDMsym,1) ipMod_norm(:,[nConstperOFDMsym/2+1:nConstperOFDMsym]) zeros(nOFDMsym,5)] ;

     % Taking FFT, the term (nFFT/sqrt(nDSC)) is for normalizing the power of transmit symbol to 1 
     xt = (nFFT/sqrt(nDSC))*ifft(fftshift(xF.')).';

     % Appending cylic prefix
     xt = [xt(:,[49:64]) xt];

     % Concatenating multiple symbols to form a long vector
     xt = reshape(xt.',1,nOFDMsym*80);

     % Gaussian noise of unit variance, 0 mean
     nt = 1/sqrt(2)*[randn(1,nOFDMsym*80) + j*randn(1,nOFDMsym*80)];

     % Adding noise, the term sqrt(80/64) is to account for the wasted energy due to cyclic prefix
     yt = sqrt(80/64)*xt + 10^(-EsN0dB_eff(ii)/20)*nt;

     % Receiver
     yt = reshape(yt.',80,nOFDMsym).'; % formatting the received vector into symbols
     yt = yt(:,[17:80]); % removing cyclic prefix

     % converting to frequency domain
     yF = (sqrt(nDSC)/nFFT)*fftshift(fft(yt.')).'; 
     yMod = sqrt(64/80)*yF(:,[6+[1:nConstperOFDMsym/2] 7+[nConstperOFDMsym/2+1:nConstperOFDMsym] ]); 

     % demodulation
     y_re = real(yMod)/k;
     y_im = imag(yMod)/k;
     % rounding to the nearest alphabet
     % 0 to 2 --> 1
     % 2 to 4 --> 3
     % 4 to 6 --> 5 etc
     ipHat_re = 2*floor(y_re/2)+1;
     ipHat_re(find(ipHat_re>max(alphaMqam))) = max(alphaMqam);
     ipHat_re(find(ipHat_re<min(alphaMqam))) = min(alphaMqam);

     % rounding to the nearest alphabet
     % 0 to 2 --> 1
     % 2 to 4 --> 3
     % 4 to 6 --> 5 etc
     ipHat_im = 2*floor(y_im/2)+1;
     ipHat_im(find(ipHat_im>max(alphaMqam))) = max(alphaMqam);
     ipHat_im(find(ipHat_im<min(alphaMqam))) = min(alphaMqam);

     ipHat = ipHat_re + j*ipHat_im; 

     % converting to vector 
     ipHat_v = reshape(ipHat.',nConstperOFDMsym*nOFDMsym,1).';

     % counting the errors
     nErr(ii) = size(find(ipMod - ipHat_v ),2);

end
simSer = nErr/(nOFDMsym*nConstperOFDMsym);

return;

[Arthur Goldsipe]

You have not asked any actual question. You've just pasted MATLAB code. If you want help, please make a new post with a descriptive subject line and an actual question. More guidelines are available here: http://www.mathworks.com/matlabcentral/answers/6200-tutorial-how-to-ask-a-question-on-answers-and-get-a-fast-answer

[Walter Roberson]

Or better, edit this one to change the description. No need to start a new question.