低密度同位元檢查碼在DVD數位資料儲存系統之研究與應用; Study of Low Density Parity Check Codes on DVD Storage Systems

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题名:	低密度同位元檢查碼在DVD數位資料儲存系統之研究與應用;Study of Low Density Parity Check Codes on DVD Storage Systems
作者:	林銀議
贡献者:	通訊工程系
关键词:	電信工程
日期:	2006-07-01
上传时间:	2010-12-06 16:31:03 (UTC+8)
出版者:	行政院國家科學委員會
摘要:	為提高數位資料儲存系統之記錄密度和資料傳輸速率，現在之數位資料儲存系統如DVD 系統常用比較先進之訊號處理技術，利用等化器將讀回信號等化成部份反應信號以降低雜訊接著再利用最佳估算偵測法則即維特比法則(Viterbi Algorithm) 將信號還原為數位資料，此種訊號處理技術稱為部份反應/最佳估算(Partial Response and Maximum Likelihood Detection, PRML)通道技術。前期計畫我們分析及探討兩種反覆偵測法則(BCJR 演算法則及視窗-事後機率演算法則)以取代傳統維特比偵測法則，並加入了視窗(window)的概念，稱之為視窗-事後機率演算法 (window-APP algorithm)。利用視窗-事後機率演算法，在進行通道偵測時可以做到平行處理，這大大的降低了因為使用BCJR 演算法所造成的時間延遲。並在此DVD 通道偵測外部加入效能優異的錯誤更正碼-渦輪碼（Turbo Code），利用渦輪碼/MAP 偵測的訊號流通演算法而形成渦輪等化器（Turbo Equalizer），但該類系統需要用到三個串連式（Serial）的最大事後機率演算法模組（外部渦輪碼解碼器，由兩個平行系統迴旋碼組成，需要利用兩個MAP 模組，內部PRML 讀回訊號偵測利用一個MAP 模組），雖然有很好的錯誤更正效能，但解碼延遲過長，在即時（Real Time） DVD 系統上無法應用。本期計畫將延續前期計畫針對這個缺失改進系統，在DVD 通道之訊號偵測器利用視窗-事後機率演算法，進行通道偵測時以做到平行處理，使偵測演算法由原先耗時的串連MAP 演算法改變為快速的平行（Parallel）架構，並加入調變碼（Modulated Code），使訊號更適合在DVD 媒體上記錄。除此之外，外部錯誤更正碼(渦輪碼)部分利用擁有平行解碼結構的低密度同位元檢查碼（LDPC Codes）以取代由兩個平行系統迴旋碼組成之渦輪碼，探討由上述兩平行內外解碼(分別為 LDPC 碼及視窗-事後機率通道之訊號偵測器)組成的訊息流通（Message-Passing）渦輪等化器，除找尋適用於DVD 系統通道的LDPC 碼外，亦將模擬並分析此新系統之性能，並與其他舊系統相比較。 The advanced signal processing technique referred to as the partial response and maximal likelihood (PRML) channel is usually employed in the digital recording systems to increase the recording density and/or data transmission rate. In the PRML channel, the recording channel is equalized as a partial response channel and the Viterbi algorithm (VA) is used for the detection of equalized signals. In the previous proposal instead of the Viterbi detection based upon the message-passing algorithm we have been investigating two iterative detection algorithms (BCJR algorithm and Window APP algorithm respectively) for the detection of the PRML recording channel. The performance of these two iterative detections have been analyzed and simulated based upon the factor graph of the PRML channel. In addition, the performance of a turbo equalization scheme was investigated in which a turbo code consisted of two parallel systematic convolutional codes was employed as an outer code and the window APP detection of the TMTR-coded partial response channel was employed as an inner code. Although in the proposed turbo equalization scheme the window APP detection for the TMTR-coded partial response channel can be processed in a parallel way and the decoding delay could be ignored, the decoding of the outer code however could result in a very significant decoding delay due to that two serial APPs are required in the two parallel systematic convolutional codes. And this turbo decoding scheme is not suitable for the DVD data storage system that requires a real-time operation. The recent research for the turbo decoding has been focused on the low-density parity-check (LDPC) codes due to that a parallel processing architecture for decoding of the LDPC codes is possible, and this leads to a short decoding delay. In this project, instead of using two parallel convolutional codes the low density parity check (LDPC) codes are employed as the outer code in the turbo equalization scheme. The turbo decoding for the TMTR-coded partial response channel with the LDPC codes will be investigated. The performance of the turbo decoding for the TMTR-coded DVD partial response channel will be studied and compared with other DVD systems that use the parallel convolutional codes as the outer code. 研究期間：9408 ~ 9507
關聯:	財團法人國家實驗研究院科技政策研究與資訊中心
显示于类别:	[通訊工程學系] 研究計畫

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