ENCODER AND ENCODING METHOD, DECODER AND DECODING METHOD

摘要

PROBLEM TO BE SOLVED: To improve code performance by extending the application of a calculation expression for determining a thresholdδ*of an error probability which is applicable to a regular LDPC (low density parity check) code so as to be applicable to an irregular LDPC code. SOLUTION: A degree sequence calculating section in an encoder expresses a degree sequence expressing the distribution of the number of "1" in a longitudinal direction in an inspection matrix by a polynominal consisting of the sum of two terms i.e. two different types of the numbers n1, n2of "1" and proportionsλ1,λ2, of the two types of the numbers n1, n2as parameters. The section also expresses a lateral degree sequence expressing the distribution of the number of "1" in a lateral direction in the inspection matrix by a polynominal consisting of the sum of two terms i.e. two different types of the numbers m1, m2of "1" and proportionsρ1,ρ2, of the two types of the numbers m1, m2as parameters. By doing this, a degree sequence in which the threshold of the error probability is the maximum is calculated. COPYRIGHT: (C)2004,JPO