7. The bit conversion method according to claim 6 , wherein the decision result indicates a log likelihood ratio of â€œ0â€ and â€œ1â€ for each bit of the bit string represented thereby.
6. A bit conversion method to be executed in a bit converter that is between an upstream decoder and a downstream decoder, the bit conversion method comprising: substituting a decision result from the upstream decoder representing a bit string of a predetermined pattern based on a substitution rule for converting the bit string of the predetermined pattern into a predetermined correct code word, the predetermined pattern being used for inspection and having a pattern that cannot be converted into the predetermined correct code word by the downstream decoder; and outputting the decision result from the upstream decoder as substituted according to said substituting, to the downstream decoder.