| 摘要 |
A decoder apparatus capable of preventing its characteristic from degrading even when the decoding rate is high, while exhibiting reduced arithmetic amount and memory capacity. In the decoder apparatus, a migration probability calculating part (201) calculates a migration probability from a systematic bit (Y1), a parity bit (Y2) and a priori value (La1), and a forward probability calculating part (202) divides a data sequence into a plurality of windows and calculates a forward probability for each of the windows. A memory (204) has stored a backward probability of a predetermined time calculated in the previous repetitive decoding. A backward probability calculating part (203) divides the data sequence into a plurality of windows and calculates a backward probability for each of the windows by use of the backward probability stored in the memory (204) as an initial value in the current repetitive decoding. A likelihood calculating part (205) uses the calculated forward and backward probabilities to calculate likelihood information. |
