文化大學機構典藏 CCUR:Item 987654321/22226
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    題名: 線性區塊碼解碼之簡化複雜度Viterbi演算法
    作者: 孫振東
    貢獻者: 工學院
    關鍵詞: Viterbi演算法
    區塊碼
    trellis解碼
    Viterbi algorithm
    block codes
    trellis decoding
    日期: 2002-06-01
    上傳時間: 2012-05-09 15:03:31 (UTC+8)
    摘要: 傳統上線性區塊碼使用代數解碼演算法爲解碼演算法，而卷積碼使用Viterbi演算法(Viterbi algorithm; VA)，爲最大似然解碼演算法。理論上將線性區塊碼網格(trellis)型式表示，其亦可用VA解碼。線性區塊碼用VA解碼的主要優點是可以利用通道量測訊息做有效率的軟判決演算法解碼，但是VA的計算複雜度(Computational complexity)與碼的束縛長度(Constraint length)有關，這使得VA解碼器實現在許多應用上較不實際，本論文從計算複雜度觀點來研究VA用在線性區塊碼的硬判決與軟判決解碼，我們提出一種距離臨限(Distance threshold)觀念，其用以決定錯誤率性能與計算複雜度間之取捨，根據此觀念發展－簡化複雜度之Viterbi演算法(Reduced-Complexity Viterbi Algorithm; RCVA)，此RCVA顯示可大量減少網格(Trellis)及需要較少或無需度量比較。我們模擬白雜訊通道上用(23, 12) Golay code，以RCVA解碼結果顯示錯誤率性能與最大似然解碼器所得基本上是相近的。

    Traditionally, the algebraic decoding algorithm is used as the decoding algorithm for linear block codes, and the Viterbi algorithm (VA) is used as the maximum likelihood decoding algorithm for convolutional codes. Theoretically, by representing linear block codes in trellis form, the VA can also be used to decode linear block codes. A major advantage of the VA above traditional block decoders is the existence of efficient soft decision algorithms employing channel measurement information. However, the computational complexity of the VA exists a strong dependence on code constraint length. In most applications, this makes the decoder implementation practically unfeasible. In this paper, the VA for hard-decision and soft-decision decoding of linear block codes is studied from a computational complexity viewpoint. We introduce a concept of distance threshold which establishes a trade-off between error rate performance and decoding complexity. Using this concept, a reduced-complexity Viterbi algorithm (RCVA) is developed. The RCVA explores a drastically reduced trellis and requires either few or no metric comparisons at all. A computer simulation using the (23, 12) Golay code over an AWGN channel illustrates that the error rate performance achieved by the RCVA is essentially the same as that of a maximum likelihood decoder.
    關聯: 華岡工程學報 16期 p.85 -95
    顯示於類別:[工學院] 學報-華岡工程學報

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