main.m

LDPC码在TD-SCDMA系统中的应用仿真程序

clear all

% Write display messages to a text file
diary conv_link.txt

set_sim_consts
global sim_consts;

    rate = 1/3;   
    a = sim_consts.a;    
    niter = sim_consts.niter;
    ferrlim = sim_consts.ferrlim;
    EbN0db = sim_consts.EbN0;
    L_total = sim_consts.L_total;
    iter= sim_consts.niter;


fprintf('\n\n----------------------------------------------------\n'); 
    
fprintf('+ + + + Please be patient. Wait a while to get the result. + + + +\n');

for nEN = 1:length(EbN0db)
   snr = EbN0db(nEN);
   en = 10^(EbN0db(nEN)/10);      % convert Eb/N0 from unit db to normal numbers
   L_c = 4*a*en*rate; 	% reliability value of the channel
   sigma = 1/sqrt(2*rate*en); 	% standard deviation of AWGN noise

% Clear bit error counter and frame error counter
   errs(nEN,1:niter) = zeros(1,niter);
   nferr(nEN,1:niter) = zeros(1,niter);

   nframe = 0;    % clear counter of transmitted frames
   while ( 1)
      
      % block count
      nframe = nframe + 1;    
      
      % info source
      x = round(rand(1, L_total-sim_consts.m));    % info. bits
      xx = [x zeros(1,8)];
      
      % conv code      
      en_output = 2*convenc(xx,sim_consts.t)-1;  % encoder output (+1/-1)
      
      % rate match
      L_b = 88*sim_consts.cNumber*sim_consts.tsNumber*sim_consts.subFrames;
      en_output(size(en_output,2)+1:L_b) = en_output(size(en_output,2))*ones(1,L_b-size(en_output,2));
      clear L_b;      
      
      % modulater
      for kk=1:length(en_output)/2
          modulator_out(kk) = en_output((kk-1)*2+1) + j*en_output(kk*2) ;
      end  
      clear kk;
      
      % through the channel 
      % spread, frame, channel, estimate, JD, deframe and despread       
      s_all = modulator_out(:);
      L_f = 44*sim_consts.cNumber*sim_consts.tsNumber*sim_consts.subFrames;
      L_sf = 44*sim_consts.cNumber*sim_consts.tsNumber;
      r_all = zeros(L_f,1);      
      for fIdx = 1:sim_consts.subFrames
          s = zeros(L_sf, 1);
          s(:) = s_all((fIdx-1)*L_sf+1:fIdx*L_sf);
          r_middle= send(s,snr);       % child function, type 'help send' to see the detail 
          r_all((fIdx-1)*L_sf+1:fIdx*L_sf) = r_middle(:);
          clear s r_middle;
      end
      clear L_sf;
      
      % demodulation
      for i=1:L_f
          r_s((i-1)*2+1) = real(r_all(i)) ;
          r_s(i*2) = imag(r_all(i)) ;
      end
      clear L_f;
      
      % conv decode
      rec_s = zeros(1,sim_consts.L_total/rate);
      rec_s(:) = r_s(1:sim_consts.L_total/rate);
    

      
      [mmm,qcode] = quantiz(1-2*rec_s,[-.75 -.5 -2.5 0 .25 .5 .75],[7 6 5 4 3 2 1 0]);
    decoded2 = vitdec(qcode',sim_consts.t,sim_consts.tblen,'cont','soft',3);
    xhat = decoded2(sim_consts.tblen+1:end);
     
% Number of bit errors in current iteration
         err(iter) = length(find(xhat(1:L_total-sim_consts.m)~=x'));
% Count frame errors for the current iteration
         if err(iter)>0
            nferr(nEN,iter) = nferr(nEN,iter)+1;
         end   

      
% Total number of bit errors for all iterations
      errs(nEN,1:niter) = errs(nEN,1:niter) + err(1:niter);

      if rem(nframe,3)==0 | nferr(nEN, niter)==ferrlim | errs(nEN, sim_consts.niter) > sim_consts.errAll | nferr(nEN, niter)>sim_consts.ferrlim | nframe > sim_consts.nframeAll 
% Bit error rate
         ber(nEN,1:niter) = errs(nEN,1:niter)/nframe/(L_total-sim_consts.m);
% Frame error rate
         fer(nEN,1:niter) = nferr(nEN,1:niter)/nframe;

% Display intermediate results in process  
         fprintf('************** Eb/N0 = %5.2f db **************\n', EbN0db(nEN));
         fprintf('Frame size = %d, rate 1/%d. \n', L_total, 3);
         fprintf('%d frames transmitted, %d frames in error.\n', nframe, nferr(nEN, niter));
         fprintf('Bit Error Rate (from iteration 1 to iteration %d):\n', niter);
         for i=1:niter
            fprintf('%8.4e    ', ber(nEN,i));
         end
         fprintf('\n');
         fprintf('Frame Error Rate (from iteration 1 to iteration %d):\n', niter);
         for i=1:niter
            fprintf('%8.4e    ', fer(nEN,i));
         end
         fprintf('\n');
         fprintf('***********************************************\n\n');

% Save intermediate results 
         save conv_link EbN0db ber fer
      end
      if  nferr(nEN, niter)==ferrlim | errs(nEN, sim_consts.niter) > sim_consts.errAll | nferr(nEN, niter)>sim_consts.ferrlim | nframe > sim_consts.nframeAll  
          break;
      end    
   end		%while
end 		%nEN

diary off