RS_LDPC.m

%Copyright(c) 2011, USAtyuk Vasiliy 
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% Application generate QC-LDPC parity-check matrix based on RS-codewords
% 
clear all;



p=503; %
a=5; % primitive  element
k=0;
%etta=fldpow(k,a,p);
W(p-1,p-1)=zeros(); % full matrix have  qxq size
A(p-1)=zeros();
for i = 1:p-1
   if i ==1
      A(i)=0;
   else
   A(i)=mod(fldpow(i-1,a,p)-1,p);
   end
end
 W=circulant(A,1);
 
 powfld(p-1)=zeros();
for i = 1:p-1
    powfld(i)=fldpow(i-1,a,p);
end


%return power of primitive element  from array W

e(p-1)=zeros();
 e(1)=-1;
for i = 2:p-1
                
            for k= 1:p-1
            if powfld(k)== W(1,i)
                e(i)=k;
            end
            
            end
end
exp=circulant(e,1);