LDPC_MATLAB_工具箱_LDPC编解码程序

function [H]=gen_ldpc(rows,cols) %H=gen_ldpc(rows,cols) %For examples and more details, please refer to the LDPC toolkit tutorial at %http://arun-10.tripod.com/ldpc/ldpc.htm bits_per_col=3; for i=1:rows row_flag(i)=0; for j=1:cols parity_check(i,j)=0; end end %add bits_per_col 1's to each column with the only constraint being that the 1's should be %placed in distinct rows for i=1:cols a=randperm(rows); for j=1:bits_per_col parity_check(a(j),i)=1; row_flag(a(j))=row_flag(a(j))+1; end end row_flag; max_ones_per_row=ceil(cols*bits_per_col/rows); parity_check; %add 1's to rows having no 1(a redundant row) or only one 1(that bit in the codeword becomes %zero irrespective of the input) for i=1:rows if row_flag(i)==1 j=unidrnd(cols); while parity_check(i,j)==1 j=unidrnd(cols); end parity_check(i,j)=1; row_flag(i)=row_flag(i)+1; end if row_flag(i)==0 for k=1:2 j=unidrnd(cols); while parity_check(i,j)==1 j=unidrnd(cols); end parity_check(i,j)=1; row_flag(i)=row_flag(i)+1; end end end %try to distribute the ones so that the number of ones per row is as uniform as possible for i=1:rows j=1; a=randperm(cols); while row_flag(i)>max_ones_per_row; if parity_check(i,a(j))==1 parity_check(i,a(j))=0; row_flag(i)=row_flag(i)-1; newrow=unidrnd(rows); k=0; while row_flag(newrow)>=max_ones_per_row | parity_check(newrow,a(j))==1 newrow=unidrnd(rows); k=k+1; if k>=rows break; end end if parity_check(newrow,a(j))==0 parity_check(newrow,a(j))=1; row_flag(newrow)=row_flag(newrow)+1; else parity_check(i,a(j))=1; row_flag(i)=row_flag(i)+1; end end%if loop j=j+1; end%while loop end%for loop row_flag; parity_check; parity_check; %try to eliminate cycles of length 4 in the factor graph for loop=1:10 ones_position(1)=0; for r=1:rows ones_count=0; for c=1:cols if parity_check(r,c)==1 ones_count=ones_count+1; ones_position(ones_count)=c; end end for i=1:r-1 common=0; for j=1:ones_count if parity_check(i,ones_position(j))==1 common=common+1 ; if common==1 thecol=ones_position(j); end end if common==2 common=common-1; if(round(rand)==0) coltoberearranged=thecol; thecol=ones_position(j); else coltoberearranged=ones_position(j); end parity_check(i,coltoberearranged)=3; %make this entry 3 so that we dont use %of this entry again while getting rid %of other cylces newrow=unidrnd(rows); %while ((newrow==i)|(parity_check(newrow,ones_position(j))==1)) iteration=0; while parity_check(newrow,coltoberearranged)~=0 newrow=unidrnd(rows); iteration=iteration+1; if iteration==5 break; end end if iteration==5 while parity_check(newrow,coltoberearranged)==1 newrow=unidrnd(rows); end end parity_check(newrow,coltoberearranged)=1; end end end for i=r+1:rows common=0; for j=1:ones_count if parity_check(i,ones_position(j))==1 common=common+1 ; if common==1 thecol=ones_position(j); end end if common==2 common=common-1; if(round(rand)==0) coltoberearranged=thecol; thecol=ones_position(j); else coltoberearranged=ones_position(j); end parity_check(i,coltoberearranged)=3;%make this entry 3 so that we dont use %of this entry again while getting rid %of other cylces newrow=unidrnd(rows); %while ((newrow==i)|(parity_check(newrow,ones_position(j))==1)) iteration=0; while parity_check(newrow,coltoberearranged)~=0 newrow=unidrnd(rows); iteration=iteration+1; if iteration==5 break end end if iteration==5 while parity_check(newrow,coltoberearranged)==1 newrow=unidrnd(rows); end end parity_check(newrow,coltoberearranged)=1; end end end end end; parity_check; for i=1:rows row_flag(i)=0; for j=1:cols if parity_check(i,j)==1 row_flag(i)=row_flag(i)+1; end if eq(parity_check(i,j),3) %replace the 3's with 0's parity_check(i,j)=0; end end end variance=var(row_flag) H=parity_check; %Get the Parity Checks %A=0; %B=0; %for i=1:rows % for j=1:rows % A(i,j)=parity_check(i,j); % end %end %for i=1:rows % for j=rows+1:cols % B(i,j-rows)=parity_check(i,j); % end %end %ainvb=inv(sparse(A))*sparse(B); %ainvb=inv(A)*B; %toc