ターボ原理に基づく繰り返し検出のEXIT解析: An Instruction Manualof EXIT Chart

摘要

This paper introduces EXIT chart analysis which visualizes behavior of iterative detection based on the turbo principle. At the beginning, a relationship between log likelihood ratio (LLR) and mutual information, for the sake of revealing requirements involved in the EXIT chart analysis. Then, a simple turbo code structure is proposed, in order to provide better understanding about a methodology of the analysis. After demonstrating examples of the analysis, validity and problems are discussed.%本稿では，ターボ原理に基づく繰り返し検出の振る舞いの正当性を評価するEXIT（EX trinsic Information Transfer）解析手法を紹介する．まず，EXIT解析に要求される前提条件を明確にするために，対数尤度比（LLR：Log Likelihood Ratio）と相互情報量の関係を詳しく述べる．さらに，EXIT解析の手法を説明するため，簡易なターボ符 号を提案した上で，解析例を示す．その解析例に基づき，EXIT解析の有効性と問題点を言及する．