| Co-Investigator(Kenkyū-buntansha) |
FUJIWARA Toru Osaka University, Professor, 大学院・基礎工学研究科, 教授 (70190098)
TOKUSHIGE Hitoshi Hiroshima City University, Information Sciences, Associate Researcher, 情報科学部, 助手 (50336921)
YOSHIDA Teruaki Hiroshima City University, Information Sciences, Professor, 情報科学部, 教授 (50316139)
KAJI Yuichi Nara Institute Science and Technology, Associate Professor, 情報科学研究科, 助教授 (70263431)
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| Research Abstract |
1. We introduced "adaptive maximum likelihood decoding" (abbreviated as AMLD). In AMLD, the most likely local (MLL) sub-codeword in a section is constructed by concatenating the MLL sub-codewords in its subsection which are found adaptively. We implemented a prototype program for AMLD, and evaluated decoding complexity of AMLD for several RM codes and BCH codes. The average complexity is considerably smaller than those of conventional maximum likelihood decoding algorithms. It turns out that for codes with relatively large parameter, there exist singular received sequences which occur at extremely rare intervals, however, winch require very long steps to guaarantee the optimality. To reduce the complexity furthermore, we have devised an effective method which makes good use of adjacency relation between the MLL sub-codewords in adjacent subsections [1, 3, 5]. In addition, we have studied early termination conditions with no or almost no loss of error performance.
2. We have devised an e
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ffective method of selecting successive search centers around which bounded distance decoding is carried out in a soft-decision iterative decoding algorithm. In conventional soft-decision iterative decoding algorithms by using bounded distance decoding, such as Chase II decoding algorithm, the duplication of search region and the decoding failure of bounded distance decoding degrade the error performance. For several BCH codes of lengths 128 and 256, simulation results [2, 4] show that this new selection method improves the error performance considerably by reducing the above negative effect.
3. For concatenated coding scheme whose outer code is an interleaved (225, 223) RS code a good choice of its inner code is proposed. The low weight structures of the binary images of shortened (8, 5) RS codes over GF(28) are analyzed extensively. Consequently, we have found several more promising shortened RS codes as the inner code than the conventional codes [6].
* [x] refers to the x-th paper in the references. Less
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