trial.m

LDPC encoder and decoder design in MATLAB

% Bit error rate of BPSK modulated LDPC codes under AWGN channel
%
%
% Copyright priyabrata, 2009 

clc; 
clear all;

% LDPC matrix size, rate must be 1/2
% Warning: encoding - decoding can be very long for large LDPC matrix!
M =input('give the no. of rows:');
N =input('give the no. of cols:');

% Method for creating LDPC matrix (0 = Evencol; 1 = Evenboth)
method = 1;

% Eliminate length-4 cycle
noCycle = 1;

% Number of 1s per column for LDPC matrix
onePerCol =input('enter the no. of ones per column:');

% LDPC matrix reorder strategy (0 = First; 1 = Mincol; 2 = Minprod)
strategy = 2;

% EbN0 in dB
%EbN0=[-1 -0.5 0 0.5 1 1.5 2];
EbNo=[-1 -0.5 0 0.5 1 1.5 2];
% Number of iteration;
iter =input('Enter the number of iterations:');

% Number of frame (N bits per frame)
frame =input('Enter the frame number:');

% Make the LDPC matrix
H = makeLdpc(M, N, 1, 1, onePerCol);

for i = 1:length(EbNo)
   
   ber1(i) = 0;
  % ber2(i) = 0;
   
   % Make random data (0/1)
   dSource = round(rand(M, frame));
   
   for j = 1:frame
      fprintf('Frame : %d\n', j);
      
      % Encoding message
      [c, newH] = makeParityChk(dSource(:, j), H, strategy);
      u = [c; dSource(:, j)];

      % BPSK modulation
      bpskMod = 2*u - 1;
      % Additional white gaussian noise
      No = 1/(exp(EbNo(i)*log(10)/10));
      tx = bpskMod + sqrt(No)*randn(size(bpskMod));

      % Decoding (select decoding method)
      %vhat = decodeProbDomain(tx, H, newN0, iter);
      vhat1 = decodeLogDomain(tx, newH, No, iter);
      %vhat2 = decodeLogDomainSimple(tx, newH, iter);
      %vhat = decodeBitFlip(tx, newH, ter);
   
      % Get bit error rate (for brevity, BER calculation includes parity bits)
      [num1, rat1] = biterr(vhat1', u);
      ber1(i) = (ber1(i) + rat1);
      
      %[num2, rat2] = biterr(vhat2', u);
      %ber2(i) = (ber2(i) + rat2);
      
   end % for j
   
   % Get average of BER
   ber1(i) = ber1(i)/frame;
   %ber2(i) = ber2(i)/frame;
   
end % for i

% Plot the result
semilogy(EbNo, ber1, 'o-');
hold;
%semilogy(EbN0, ber2, 'o--');
grid on;
hold off;