getgirth.m

LDPC codes .Using the matlab.

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function girth = GetGirth(checkMatrix_H)
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% @author   Andreas Waadt, 13. November 2005
% @param     checkMatrix_H : the parity check matrix of the code
% @return   girth : the girth of checkMatrix_H
% This function calculates the girth of a Parity-Check-Matrix H
% (checkMatrix_H). That's the length of the shortest cyclic way 
% through the tanner graph of checkMatrix_H;
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% checkMatrix_H = ParityCheckMatrixH()

sizeOfMatrix = size(checkMatrix_H);
% number of rows (check sums, check nodes)
j_rows = sizeOfMatrix(1);

girth = 10^16;
for start_node = 1:1:j_rows
    tmp_girth = CalcGirth(checkMatrix_H,start_node);
    if( tmp_girth < girth )
        girth = tmp_girth;
    end;
    if( girth <= 4 )
        break;
    end;
end;

%girth

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