資料儲存系統之渦輪碼與訊號處理研究; Study of Turbo Coding and Signal Processing for Data Storage Systems

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题名:	資料儲存系統之渦輪碼與訊號處理研究;Study of Turbo Coding and Signal Processing for Data Storage Systems
作者:	蔡蕙逢;Hui-Feng Tsai
贡献者:	電機工程研究所
关键词:	資料儲存系統;渦輪碼;部份反應;data storage systems;turbo coding;partial response
日期:	2006-04-20
上传时间:	2009-09-22 11:37:45 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	在論文中，我們提出一種符合通道特性的碼，稱為TMTR調變碼，此碼在數位記錄通道中具有優異的編碼增益。文中建議新的TMTR調變碼，運用在光記錄通道系統中，用以取代傳統EFMPlus碼，除了碼率為高於EFMPlus碼外，在低頻部份，也同樣具有更低功率頻譜密度。另外，在編解碼方面，我們使用列舉式(Enumerating)編解碼，將符合限制條件的碼字與整數做一對一的映射。在高傳輸速度的要求下，對一個有限頻寬的數位資料，同時考慮有雜訊及ISI (Intersymbol Interference)的通道，常需要更有效率的訊號偵測技術，以提供解決ISI的最佳方法。在論文中，引進渦輪碼(Turbo Code)作為數位資料儲存系統的錯誤更正碼，利用其優良的錯誤更正能力使得讀回資料的錯誤率降低，其次結合具有編碼增益之TMTR調變碼(碼率為 )成為一個串接碼(Serially Concatenated Code)系統，此外，為了顯示渦輪碼在解碼方面的特點，我們定義兩個名詞首先為外圈迴圈(Outer Iteration):意指串接碼的內層碼(MAP偵測器)跟外層碼(渦輪碼)之間消息的更新，其次為內圈迴圈(Inner Iteration):意指渦輪碼兩個RSC解碼器之間消息的更新。研究發現，結合了渦輪碼、TMTR碼以及光學記錄通道，形成一串接碼，藉由內圈迴圈以及外圈迴圈之間消息的更新，使得通道解碼偵測器在偵測時也能獲得更新後的先驗消息，因而渦輪碼的解碼效能也更加顯著。另外，在系統時序恢復研究、設計方面，論文中探討Raised Cosine(升餘弦)與其他常用全數位插值時序恢復（Interpolator Timing Recovery）方法之MMSE、Sinc及Cubic的比較，包括電腦時間模擬的估算、硬體複雜度的計算、位元錯誤率效能分析等。在相似的計算複雜度上，升餘弦插值器的位元錯誤效能優於其他插值器；另外，表現優異的升餘弦插值器應用在數位記錄密度的儲存系統之時間恢復研究及設計，也獲得相同的效果。這一套全數位化的插值時序恢復運作機制不只適用於一般通訊系統的接收端，它也適用於數位記錄通道系統。 This article proposes several approaches to enhance the data storage system performance by coding and interpolated timing recovery. In this dissertation, a new method for the magnetic recording channel construction employing TMTR codes and the optical recording channel using TMTR codes is proposed. This code can achieve better timing recovery performance compared to the previously proposed method. The modulation code used in a digital versatile disc (DVD) recording system is referred to as the EFMPlus code with a rate of . In this work, we present a new time-varying maximum transition run code (TMTR) to replace the conventional EFMPlus code for DVD recording systems, with a rate higher than the EFMPlus code and a lower power spectral density (PSD) at low frequencies. Computer simulations indicate that the proposed TMTR code outperforms the EFMPlus code when applied to a partial response optical recording channel. The turbo (iterative) decoding for the TMTR-coded partial response optical recording channel is also investigated, in which the TMTR-coded partial response channel is viewed as the inner code and two parallel concatenated convolutional codes (PCCC’s) as the outer code. The error performance of the proposed coding scheme is investigated and compared with the conventional coding scheme, in which both the TMTR code and partial response channel are independently decoded or detected. In this dissertation we also propose using interpolated timing recovery (ITR) was substituted for the conventional voltage controlled oscillator (VCO) timing recovery method in the magnetic recording channel. In this work an interpolator that uses the raised cosine pulse is applied to digital timing recovery. This study indicates that the raised cosine interpolator outperforms other commonly used interpolators in digital timing recovery such as sinc, polynomial and MMSE interpolators with a similar computational complexity. Simulation results show that the raised cosine interpolator is superior in error performance to other interpolators with a similar computational complexity. The superiority of the raised cosine interpolator is demonstrated on a digital recording channels. The main advantages of the raised cosine interpolator are that it is simpler and leads to fully digital implementation.
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