整合可變長度碼及迴旋碼的合併訊源通道解碼機制

Abstract

本論文主要探討基於可變長度碼之索引層級合併訊源通道解碼機制，以及雙向性可變長度碼的雙向解碼方法。針對具有特定機率分佈的訊源，可建構其霍夫曼碼，並以此發展具有錯誤更正能力的雙向性可變長度碼。傳統的通道解碼演算法受限於其位元層級處理模式，與基於索引層級而推導的訊源解碼演算法存在著相容性問題。因此，我們利用可變長度碼在索引層級上的分段籬柵結構，結合通道編碼器之狀態轉移以建立三維狀態的籬柵圖，再依據此籬柵圖推導合併訊源通道解碼演算法。實驗模擬証實，引用一階相關性的索引層級合併解碼機制能有效提升系統的強健性能。

Reliable transmission of convolutionally encoded source codec parameters over noisy channels can benefit from the use of joint source‐channel decoding (JSCD). This thesis focuses on the design of a symbol-based JSCD for convolutionally encoded variable‐length codes (VLC). We also investigate bidirectional decoding schemes by using reversible variable length code (RVLC). Our work starts with a sectionalized code trellis whose two-dimensional states are created by combing the symbol-based VLC trellis and the state transition of a channel encoder. Then, we derive the recursive implementation of JSCD algorithm according to the three-dimensional sectionalized code trellis. Simulation results on both Gauss-Markov sources and ECG signals demonstrate the error-resilience capabilities of symbol-based joint decoding by using the first-order source correlation.