針對非均勻訊源之固定長度整合訊源與通道編碼系統之設計

Abstract

固定長度整合訊源與通道編碼(FLEC)為一個將訊源編碼與通道編碼結合的系統。在這篇碩士論文中，我們提出了兩個可用於非均勻訊源(non-uniform source)的FLEC的設計方法。第一個方法基於所推導的FLEC的聯集錯誤率上界(union bound)，設計使此上界相對較小的FLEC。由於第一個方法僅能適用於碼長較短的FLEC設計，我們因此再提出第二個方法。第二個方法基於渦輪碼(turbo code)的架構，重新設計可適用於非均勻訊源的渦輪碼的解碼量度。模擬結果顯示我們所提出的第一個方法，系統錯誤率會比傳統結合赫夫曼(Huffman)來源編碼與BCH碼的分離式設計低。而第二個方法的效能比結合赫夫曼(Huffman)來源編碼與渦輪碼的分離式設計好。

In this thesis, the design of fixed-length joint source-channel error-correcting codes (FLEC) for generally non-uniform source statistics is considered as contrary to the usual variable-length joint source-channel error-correcting coding system. Such a system has the advantage that the receiver can identify easily the codeword margin via a length counter. Two different approaches are attempted. We first derive the union bounds of decoding errors of the FLECs for generally non-uniform sources, and then find the FLECs that have acceptably good union bound values. Since the first approach is only suitable for FLECs of short block length, the second approach assumes the turbo code structure and modifies the turbo decoding metrics to adapt to the tranceiving of non-uniform information. Simulations show that the first pro-posed approach outperforms the traditional tandem scheme that concatenates the Huffman source code with a BCH code, while the second proposed approach beats the concatenation of the Huffman source code with a turbo code of similar rate.