本篇論文提供一種多波束天線陣列的波束調準方法，包括下列步驟：基地台依序採用多組多峰波束樣式來傳送數個同步訊號；用戶設備掃描同步訊號，並判斷接收功率最強的同步訊號，判斷接收該最強同步訊號所對應的接收波束方向，接著，用戶設備藉由隨機接取通道傳送初始接取訊息，該初始接取訊息包括(明示或是暗示)該最強同步訊號之索引；基地台在隨機接取通道上採用多組單峰波束樣式接收初始接取訊息，並判斷對初始接取訊息之接收功率最強的單峰波束樣式，最後，基地台將所判斷的最強接收單峰波束樣式與初始接取訊息中的該最強同步訊號索引所對應的多峰波束樣式的主波束進行比對，以確定傳送給用戶設備的最佳波束方向。

In this thesis, a beam alignment method for multi-beam antenna array is provided. The steps are summarized below: A base station (BS) sequentially uses one of a plurality of multi-modal beam patterns to transmit synchronization signals (SS). A user equipment (UE) scans the synchronization signals, and determines the synchronization signal with strongest received power and a receive beam direction corresponding to the strongest synchronization signal. Further, the user equipment transmits an initial access message including an (explicitly or implicitly) index of the strongest synchronization signal through a random access channel. The base station uses a plurality of single-modal beam patterns to receive the initial access message on the random access channel, and determines the single-modal beam pattern with a strongest access power for the initial access message. Finally, the base station determines an optimal beam direction for the transmission to the user equipment by comparing the strongest receive single-modal beam pattern and the multi-modal beam pattern corresponding to the index included in the initial access message.

ABSTRACT II
誌謝 IV
CONTENTS V
LIST OF FIGURES VI
LIST OF TABLES VIII
Chapter 1 Introduction 1
1.1 General Background Information 1
1.2 Related Works 3
Chapter 2 System Model and Channel Model 5
2.1 Hybrid Precoding for Massive MIMO System 5
2.2 Channel Model 6
2.3 Problem Formulation 8
Chapter 3 Beam Alignment Algorithm 9
3.1 Conventional Beam Search Scheme 9
3.2 Multi-Modal Beam Search Scheme 11
3.2.1 Synchronization Signals Transmission 11
3.2.2 Random Access Response 15
3.2.3 Decision of Optimal Beam 17
Chapter 4 Multi-Modal Beam Pattern Design 20
4.1 Phase Extraction of Multi-Beam Vector (PEMBV) Approach 20
4.2 Special Case of PEMBV 24
4.3 Multi-Beam by Spacing of Active Antennas (MBSAA) Approach 26
Chapter 5 Simulation Results 29
5.1 Evaluation of CDF of Link SNR Performance 30
5.2 Evaluation of Mean Angle Estimation Error (MAEE) Performance 38
5.3 Evaluation of Beam Alignment with Quantized Phase Shifter 48
Chapter 6 Conclusion 53
References 54
APPENDIX A 57

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