低密度同位元檢查碼是一種線性方塊碼。其在大部分的資料傳輸環境上或儲存器通道上都可以貼近省農限制。近幾年來，許多低密度同位元檢查碼的研究專注於設計一個具有較大周長的同位檢查矩陣以得到更低的錯誤機率，或是探討如何在編解碼上更有效率。本篇論文基於結構性建構的半循環式低密度同位元檢查碼，提出一種隨機區塊排列建構的同位檢查矩陣編碼方式。對於較長的碼，由於同位檢查矩陣的隨機性使然，隨機建構的同位檢查矩陣會優於半循環式低密度同位元檢查碼。本篇論文以半循環式低密度同位元檢查碼為基礎，提出一種以隨機區塊排列的同位元檢查矩陣。我們發現我們提出的方法尤其在高訊號雜訊比時會優於傳統的半循環式低密度同位元檢查碼。但由於隨機性的不足使然，在純高斯雜訊環境下其效能仍比隨機性建構式來的差。在衰落通道環境下，隨機區塊排列之效能甚至很接近隨機建構的方法。很幸運地，隨機區塊排列的方法並不會將原本半循環式的結構破壞殆盡。

　Low-density parity-check (LDPC) codes are a class of linear block codes. It provides near Shannon limit performance on a large collection of data transmission and storage channels. Recent these years, a lot of researches focus on the performance improvement by design a good code which has large girth, or focus on efficient encoding/decoding schemes. For long code length, because of the ensemble of the parity-check matrix, random construction outperforms quasi-cyclic (QC) LDPC. In this thesis, base on QCLDPC, we propose another code construction by using random block permutation. We observed that the proposed scheme outperforms QCLDPC, especially in high SNR. But it is worse than random construction in AWGN channel due to the less randomness. It is also superior to QCLDPC under the fading channel, and even approaches random constructed LDPC codes. Fortunately, the random block permutation shouldn’t break the structure of the QCLDPC code largely.

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