李學智臺灣大學：電信工程學研究所楊天泓Yang, Tien-HungTien-HungYang2007-11-272018-07-052007-11-272018-07-052004http://ntur.lib.ntu.edu.tw//handle/246246/58559在無線通信中，信號在時域上的互相干擾 (ISI；ICI) 會妨礙信號的有效傳送。本篇論文描述一種應用於直序展頻分碼多工之超寬頻系統的等化性耙式接收器；在架構上，此接收器使用數種不同形式的等化器；在此系統中，ICI 會明顯地降低系統性能。我們把時間分集的概念應用到所提出的接收器架構上，此接收器有能力收集足夠之經由多路徑抵達接收器的能量，並且藉由耙式接收器結構把這些收到的能量結合起來，如此可以有效地提高訊雜比值。 我們模擬此系統而且說明這種接收器在數種通道模型(環境)中的性能，這些環境包括“有直接波的”，“沒有直接波的”，以及“不同發射器與接收器的間隔距離”等各種環境。我們說明了等化性耙式接收器能夠有效地減輕 ICI，所以此接收器的性能優於匹配濾波器型式的耙式接收器以及慣用的等化器，慣用等化器的性能與有兩個分支的等化性耙式接收器的性能相近。此外，在模擬結果中，藉由耙式接收器架構結合能量的能力，我們所提出的接收器都能獲得分集增益。Inter-symbol interference (ISI) is one of the main impediments to efficient transmission in wireless communication. This thesis proposes an equalized-RAKE receiver with different types of equalizers for the DS-CDMA based UWB system in which the inter-chip interference (ICI) degrades the system performance significantly. We apply the concepts of time diversity to the proposed receiver which can gather enough multipath energy and effectively increase SNR by RAKE combining. We simulate the system and demonstrate the performance of the proposed receiver in several kinds of channel models (or environments), including LOS, NLOS, and different distances between transmitter and receiver. We show that the equalized-RAKE receiver can effectively mitigate ICI and has a performance better than the matched-filter-type RAKE receiver and the conventional equalizer which has the performance close to that of a 2-finger equalized-RAKE receiver. Besides, the diversity gain is always obtained by RAKE combining in our simulation.Abstract Ⅰ Contents Ⅲ List of Figures Ⅶ List of Tables XI Chapter 1 Introduction 1 1.1 Motivation 2 1.2 Outline of this thesis 3 Chapter 2 Fundamentals of UWB and DS-CDMA Techniques 5 2.1 What is UWB 5 2.1.1 Monocycle Shape 6 2.2 Characteristics of UWB 9 2.3 Spread Spectrum Techniques 10 2.3.1 Kasami Sequences 12 2.3.2 A Notion of Direct Sequence Spread Spectrum 13 Chapter 3 System Architecture 17 3.1 Transmitter Structure 18 3.2 Channel Type and Noise Calibration 20 3.2.1 AWGN Channel 21 3.2.2 Calibration of Noise 22 3.3 Receiver Structure 24 3.3.1 RAKE Receiver 26 3.3.2 Matched Filter 27 3.3.3 Linear Equalizer 28 3.3.4 Linear Feedback Equalizer 32 3.3.5 Adaptive Filter 34 Chapter 4 Channel Model 37 4.1 Channel Model by Measurement 37 4.1.1 Measurement Methods 37 4.2 Modified Saleh-Valenzuela Model 40 4.2.1 Channel Model 1 43 4.2.2 Channel Model 2 47 4.2.3 Channel Model 3 51 4.2.4 Channel Model 4 55 4.2.5 Summary 59 Chapter 5 Simulation Procedure and Results 61 5.1 Simulation Procedure 61 5.2 Simulation Results 64 5.2.1 An Experiment in Sparse Multipath Channel 67 5.2.2 Performance in Measured Channel 69 5.2.2.1 Single-user Performance 69 5.2.2.2 Multiple-user Performance 70 5.2.3 Performance in Statistical Channel 71 5.2.3.1 Performance in CM 1 71 5.2.3.2 Performance in CM 2 73 5.2.3.3 Performance in CM 3 75 5.2.3.4 Performance in CM 4 77 5.2.3.5 Performance Comparison between Different CMs 79 5.2.3.6 Performance of Adaptive Filter in Different CMs 82 Chapter 6 Conclusion 85 References 89en-US時間分集最大比例結合等化性耙式接收器線性回授等化器線性等化器耙式接收器後第三代行動通信直接序列分碼多工超寬頻路徑分集最小均方誤差time diversityMaximum Ratio Combiningequalized-RAKE receiverLinear Feedback EqualizerLinear EqualizerRAKE receiverBeyond 3rd GenerationDirect-Sequence Code-Division Multiple AccessUltra-Widebandpath diversityMinimum Mean-Square Errorthesis