馮世邁臺灣大學：電信工程學研究所陳鼎堯Chen, Ting-yaoTing-yaoChen2007-11-272018-07-052007-11-272018-07-052004http://ntur.lib.ntu.edu.tw//handle/246246/58897對於操作於頻率選擇性頻道中之上鏈非同步直序多碼分工(DS-CDMA)系統，可利用其特殊性質採用較有效率之接收機架構來降低系統複雜度。而前白化削樹(PWTP)演算法也可套用。我們提出了一種PWTP之降態修改，稱之為代表點(RP)演算法，其可進一步降低大信號星群(signal constellation)系統之複雜度。模擬結果顯示，在相同複雜度下，代表點演算法之表現優於傳統演算法。 互補分碼鍵控(CCK)是一種非線性編碼調變。在多路徑環境中，傳統等化器可能輸出無效的CCK序列。我們提出了加入限制路徑的序列估測演算法，其利用了碎碼間的特殊關係，並保證輸出有效的序列。最後，我們使用電腦模擬以比較並評估各演算法之表現。For uplink asynchronous direct sequence code division multiple access (DS-CDMA) systems in frequency-selective channels, efficient receiver structures utilizing the special properties of the systems can be applied to lower complexity. The pre-whitening tree pruning (PWTP) algorithm can be used with the structures. We propose the representative point (RP) algorithm, which is a reduced-state modification to PWTP algorithm, to further lower the complexity when large constellations are used. Simulation shows that RP outperforms the traditional algorithm with complexity being equal. Complementary code keying (CCK) is a nonlinear coded modulation. In multipath environment, traditional equalizers regard each chip as an independent symbol and may output invalid CCK sequences. We propose sequence estimation with restricted path (SERP) algorithm, which utilizes certain relationships between chips of CCK sequences and guarantees outputting valid sequences. Simulation is used to compare and evaluate the algorithms.摘要 i 誌謝 iii Abstract v Contents vii List of Figures ix List of Tables xi Chapter 1 Introduction 1 Chapter 2 Signal Models of Spread Spectrum Communications Systems 5 2.1 General Signal Model for Linearly Modulated System 6 2.2 Signal Model for DS-CDMA Systems 9 2.2.1 Downlink Synchronous DS-CDMA in Flat Channels 9 2.2.2 Uplink Asynchronous DS-CDMA in Multipath Channels 12 2.2.3 A Note on the Spreading Sequences for DS-CDMA 15 2.3 Other non-CDMA Spread Spectrum Systems 17 2.3.1 Signal Model for Direct Sequence Spread Spectrum Systems 17 2.3.2 Signal Model for Complementary Code Keying Systems 19 Chapter 3 Conventional Multiuser Detection 23 3.1 Detection in CDMA Systems 24 3.2 Conventional Single-User Matched Filter Receiver 24 3.3 Optimal Multiuser Detection 26 3.4 Suboptimal MUDs 27 3.4.1 Linear Detectors 28 3.4.2 Nonlinear Detectors 30 3.4.3 Near-Optimal Pre-Whitening Tree Pruning (PWTP) Detector 34 Chapter 4 Low Complexity Structures and Proposed Algorithm 39 4.1 System Parameters 40 4.2 Efficient Receiver Structure 41 4.2.1 Iterative Block-wise Detector (IBD) 42 4.2.2 Efficient Cholesky Factorization 43 4.3 Proposed Algorithm for PWTP 44 4.3.1 Representative Point Algorithm Description 45 4.3.2 Complexity Comparison 49 Chapter 5 Receiver Algorithms for WLAN Systems 51 5.1 Detection for CCK Systems 52 5.2 Iterative Interference Cancellation (IIC) 54 5.3 Chip Level Detector 56 5.3.1 Chip Level Decision Feedback Equalizer for CCK 57 5.3.2 Sequence Estimation with Restricted Path for CCK 60 Chapter 6 Simulation Results 65 6.1 Simulation Results for DS/CDMA 65 6.1.1 Simulation Parameters 65 6.1.2 Simulation Results for DS/CDMA 66 6.2 Simulation Results for CCK 73 6.2.1 Simulation Parameters 73 6.2.2 Simulation Results 73 Chapter 7 Conclusion 77 Bibliography 79763325 bytesapplication/pdfen-US展頻演算法通訊系統Spread SpectrumCommunication SystemCDMACCKthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/58897/1/ntu-93-R91942021-1.pdf