渦輪解碼器終止疊代演算法

Iteration Stopping Algorithms for Turbo Decoding

余思翰(Si-Han Yu)

指導教授 ： 李穎

元智大學/工程學院/電機工程學系/碩士(2002年)

摘要

渦輪碼於1993年提出後，由於其性能可接近沈農極限(Shannon limit)，受到廣泛的重視。在第三代行動通訊系統標準提案之一的cdma2000規格中，即採用了渦輪碼的技術。由於渦輪解碼需經兩個元件解碼器數次疊代才能完成，而每次疊代均需耗費相當大量的運算量與時間，有效率且簡單的終止疊代法將可減低整體運算量與節省時間。過去在探討終止疊代演算法時，並沒有將計算指標與停止策略分開來討論。本研究中提出了將終止疊代演算法分為計算指標與終止策略兩部分來分析。同時也探討在低訊雜比時，不同終止疊代演算法在平均次數的性能表現上所呈現兩種截然不同特性的原因，並建議在低訊雜比區域時，應積極地提早將疊代解碼終止。基於上述概念提出了HDR(Hard Decision Ratio)演算法。

關鍵字

渦輪解碼器 ； 終止疊代演算法 ； 疊代解碼

並列摘要

Since Turbo code was proposed in 1993, it has attracted a great deal of interest in the field of communications. Turbo codes can achieve near Shannon-limit error-correction performance, and have been adopted by the 3G cdma2000 standard. Each of iteration in Turbo decoding requires lots of processing and results in additional time delay. Efficient and simple iteration stopping algorithms could reduce decoding complexity and save time. Past research in iteration stopping algorithms did not separately discuss the index to be computed and the stopping strategy. In this research, We analyze the index to be compute and the stopping strategy separately. We also discuss a wide discrepancy between iteration stopping algorithms at low SNR, and propose to stop more aggressively at low SNR region. We present the HDR algorithm and analyze its performance.

並列關鍵字

Turbo Decoder ； Iteration Stopping Algorithms ； cdma2000 ； Iterative Decoding

參考文獻

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