Information recording and reproduction apparatus, optical disk apparatus and data reproduction method

摘要

An information recording and reproduction apparatus has a turbo decoder (800) that decodes turbo encoded data. The turbo decoder has a number of likelihood ratio calculation units (614A, 614B, 625A, 625B), forward direction path probability calculation units (812, 816) the number of which is less than the number of the likelihood ratio calculation units, and backward direction path probability calculation units (813, 817) the number of which is less than the number of the likelihood ratio calculation units. The likelihood ratio calculation units calculate in parallel the likelihood ratio for each of a plurality of data blocks. The forward direction path probability calculation units time-divisionally calculate probabilities of the forward direction paths for the data blocks. The backward direction path probability calculation units time-divisionally calculate probabilities of the backward direction paths for the data blocks. <IMAGE>