臺灣博碩士論文加值系統

渦輪碼(Turbo code)提供在較低的雜訊比(SNR)下有低的位元錯誤率
(BER)，我們提供兩種渦輪等化器在多載波分碼多工多使用者存取
(MC-CDMA) 在最小均方演算法(LMS) 下沒有使用訓練序列(train
sequence)。期望訊號(desired signal)使用在更新方程式(update equation)產生下靠直接決策(decision-directed )演算法在展頻端的輸出，這是一種直觀的方法。然而，更新方程式跟渦輪解碼是個別獨立，在一般性中，渦輪解碼器可以得到更可靠的結果，所以我們提出第二個架構。結合等化器跟渦輪解碼，將額外的資訊迴授到渦輪的解碼器中當作期望訊號。

Turbo code offer very low BER under lower SNR. We propose two turbo equalization scheme for MC-CDMA based on LMS algrithm without training sequence. The desired signal used in the updated equation is produced by decision-directed algorlthm in despreader output ,this is a intuitive method. However, its updated equation is independent with turbo decoding. In general , the turbo decoder can obtain more reliable result, so we propose the secondscheme to combine the equalization and turbo decoding the extrinsic
information of turbo decoder is feed back to use for the desired signal。

CHINESE ABSTRACT i
ENGLISH ABSTRACT ii
LIST OF TABLES v
LIST OF FIGURES vi
1 INTRODUCTION 1
2 OFDM SYMBOL DESCRIPTION 5
3 SYSTEMMODEL 9
3.1 Turbo Coding. . . . . . . . . . . . . . . . . . . . . 9
3.2 Interleaving . . . . . . . . . . . . . . . . . . . . . . 14
3.2.1 Block Interleaver . . . . . . . . . . . . . . . . . . . . . . 14
3.3 Multicarrier-CDMATransmission System. . . . . . . . 16
4 THETURBODECODING 20
4.1 The Soft-Output Viterbi Algorithm(SOVA) . . . . . . . 27
4.2 IterativeDecoding . . . . . . . . . . . . . . . . . . . . 31
5 TURBO EQUALIZATION ALGORITHM FOR MC-CDMA 32
6 SIMULATION RESULTS 37
7 CONCLUSION 47
8 BIBLIOGRAPHY 48

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