| 摘要 |
PROBLEM TO BE SOLVED: To provide a decoder which can be mounted while improving area efficiency and reducing complex and cost for various applications including the application of a wireless base station receiver or the like to utilize the code of a long restrict length. SOLUTION: This decoder has a branch metric calculator 88, add-compare- select(ACS) engine 90 and trace back unit 92. The branch metric calculator 88 calculates a branch metric corresponding to a transition inside a trellis expressing a convolution code used for generating a symbol. When the coincidence between a received symbol and a convolution code enable code word is satisfactory, the branch metric is reduced and when the coincidence between the received symbol and the convolution code enable code word is adverse, the branch metric is calculated from the offset binary expression of the symbol while using an inverse likelihood function to enlarge the branch metric. Therefore, the speed of increasing the correspondent path metric is decelerated.
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