在通訊領域中，脈衝雜訊(Impulse noise)一直是個嚴重的危害。瞬間的
強力干擾不僅破壞了傳送的訊號，還會使系統在資料的解讀上產生大
量的錯誤。為了解決這個問題，從以前到現在的研究莫不把心力投注
於編碼系統與訊號處理的發展上，甚至進一步結合兩者的長處以求互
補。但面對難以捉摸的脈衝雜訊，還是有不足之處需要改進。
面對這個問題，本論文首先以普遍應用於各標準中的渦輪碼(Turbo
Code)為對象，針對脈衝雜訊對於解碼器的干擾作出分析。接著參考
量度抹除維特比演算法(metric-erasure Viterbi algorithm)，發展出基於
量度上剪裁(clipping)，且只需部分雜訊參數的改進式渦輪碼來處理脈
衝雜訊。並考慮到渦輪碼驗證上的繁複，提出使用核密度估測(kernel
density estimation) 的外來資訊轉換區間曲線(extrinsic information
transfer band chart)來評估解碼器的效能，避免模擬上的時間浪費。
經由電腦的數值模擬與評估結果得知，我們所提出的量度剪裁渦輪碼
性能非常優秀。可以得到接近於直接針對雜訊模型最佳化的渦輪碼效
能，又能節省許多額外的運算，特別是只需要部分的參數就能有效運
作，在彈性上與泛用性得到很大的進步。

Impulse noise is a serious problem in communications. This intense noise
hinders transmitted signal and raises the error of exchanged data. Some previous
works on channel coding adopt traditional codes and signal processing to solve this
issue, but encountered many difficulties in handling the impulse.
Regarding impulse noise, first we analyzed the impact of impulse noise to turbo
code, which is a robust and popular code in white Gaussian channel. Referring to
metric-erasure Viterbi algorithm, we developed a metric clipping turbo code based on
partial information of impulse model. To evaluate this code in non-Gaussian channel
exactly, we introduced kernel density estimation into extrinsic information transfer
band chart for operating evaluation.
The result of computer simulation and evaluation shows the performance is close
to model-modified turbo code and the complexity is almost the same as primary turbo
code.

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