turbo_sys_demo.m

20072010.rar:tubor,LDPC,convolution的部分代码

clc
clear all

   dec_alg = 0;


   L_total = 400;	 % infomation bits plus tail bits

   g = [ 1 1 1;
         1 0 1 ];
%g = [1 1 0 1; 1 1 1 1];
%g = [1 1 1 1 1; 1 0 0 0 1];

[n,K] = size(g); 
m = K - 1;
nstates = 2^m;

 puncture = 0;

% Code rate
rate = 1/(2+puncture);   

% Fading amplitude; a=1 in AWGN channel
a = 1; 
   niter = 10; 

   EbN0db = 0:0.5:2;
nn=0;
for nEN = 1:length(EbN0db)
    nn=nn+1;
   errall=0;
   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
  

   nframe = 0;    % clear counter of transmitted frames
   while nframe<100
      nframe = nframe + 1;    
      x = round(rand(1, L_total-m));    % info. bits
      [temp, alpha] = sort(rand(1,L_total));        % random interleaver mapping
      en_output = encoderm( x, g, alpha, puncture ) ; % encoder output (+1/-1)
          
      r = en_output+sigma*randn(1,L_total*(2+puncture)); % received bits
      yk = demultiplex(r,alpha,puncture); % demultiplex to get input for decoder 1 and 2
      
% Scale the received bits      
      rec_s = 0.5*L_c*yk;

% Initialize extrinsic information      
      L_e(1:L_total) = zeros(1,L_total);
      
      for iter = 1:niter
% Decoder one
         L_a(alpha) = L_e;  % a priori info. 
         if dec_alg == 0
            L_all = logmapo(rec_s(1,:), g, L_a, 1);  % complete info.
         else   
            L_all = sova0(rec_s(1,:), g, L_a, 1);  % complete info.
         end   
         L_e = L_all - 2*rec_s(1,1:2:2*L_total) - L_a;  % extrinsic info.

% Decoder two         
         L_a = L_e(alpha);  % a priori info.
         if dec_alg == 0
            L_all = logmapo(rec_s(2,:), g, L_a, 2);  % complete info.  
         else
            L_all = sova0(rec_s(2,:), g, L_a, 2);  % complete info. 
         end
         L_e = L_all - 2*rec_s(2,1:2:2*L_total) - L_a;  % extrinsic info.
         
% Estimate the info. bits        
         xhat(alpha) = (sign(L_all)+1)/2;

% Number of bit errors in current iteration
         err(iter) = length(find(xhat(1:L_total-m)~=x));
% Count frame errors for the current iteration
        end	%iter
        error(nframe)=length(find(xhat(1:L_total-m)~=x));
        errall=errall+error(nframe);
      end  %end while
      ber(nn)=errall./(nframe*(L_total-m));
      fprintf('ber=%g\n',ber(nn))   
    end		%end snr
   xx=[0:0.5:2];
   plot(xx,ber)
%diary off