Patent ID: 8078936

Claim:
An encoding method for encoding by use of a quasi-cyclic code having a code length of n=m n 0 and an information word length of k=m k 0 , said encoding method comprising: creating a systematic code with as many as (n 0 −k 0 ) parity bits inserted therein in units of an information word k 0 ; making all combinations of (n 0 −k 0 ) parity bit positions that may occur in units of n 0 bits out of said systematic code; describing a plurality of m×m cyclic matrices by rearranging the sequence of columns in a parity check matrix in all the combinations of the parity bit positions; subjecting said parity check matrix to elementary transformation in such a manner that (n−k)×(n−k) matrices made up of the columns corresponding to the parity bit positions are created as a unit matrix; regarding the matrix having undergone elementary transformation as a first matrix and said first matrix minus said unit matrix as a second matrix; and allocating (n−k) bit positions for the parity bits in such a manner that the number of non-zero elements included in said second matrix is minimized.