可重構智慧表面（RIS）的突出特點激發了RIS 輔助通道的許多研究興
趣。本論文的目標是通過設計發射器的波束成型向量和RIS 元素的相位位
移，使RIS 輔助的多用戶多輸入單輸出（MISO）系統的傳輸速率總和最大
化。由於發射器和RIS 之間的通道是由多個用戶共享的，不同用戶經歷的
通道衰減時常是相關的，這嚴重惡化了總速率的性能。為了解決這個問題，
發射器採用了兩階段波束成型（TSB），其中包含一個內部預編器和一個外
部預編器，用於處理相關衰減引起的多用戶干擾。接著，固定發射波束成
型向量，RIS 元素的相位位移使用黎曼共軛梯度（RCG）演算法進行優化。
最後，發射波束成型向量和RIS 相位位移在交替式最佳化（AO）的基礎上
被聯合優化。通過模擬結果評估了所提出的聯合式發射波束成型和RIS 相
位位移設計演算法的傳輸速率總和性能。

The salient features of reconfigurable intelligent surface (RIS) stimulate much
research interests in RIS-aided communications. Our goal in this thesis is to maximize
the sum rate of the RIS-aided multiuser multi-input single-output (MISO)
system by designing the beamforming vector at the transmitter and the phase shift
of RIS elements. Since the channel between the transmitter and the RIS is shared
by multiple users, the channel fading experienced by different users tends to be
correlated that severely deteriorates the sum rate performance. To tackle this issue,
the transmitter applies the two-stage beamforming (TSB) containing an inner and
an outer precoders for handling the multi-user interference due to correlated fading.
Then phase shifts of RIS elements, for a fixed transmit beamforming vector are optimized
using the Riemannian Conjugate Gradient (RCG) algorithm. Finally, the
transmit beamforming vector and the RIS phase shifts are jointly optimized based
on the alternating algorithm (AO). The sum rate performance of the proposed joint
transmit beamforming and RIS phase shift design algorithm is evaluated through
simulations.

摘要i
Abstract ii
誌謝iii
1 Introduction 1
1.1 Motivations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 Related Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Thesis Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 System Model and Problem Formulation 4
2.1 System Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1.1 Uncorrelated Channel . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1.2 Correlated Channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1.3 Grouping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.2 Signal Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.3 Problem Formulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3 Proposed Method 14
3.1 Two-stage Beamforming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.1.1 Outer Precoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.1.2 Inner Precoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.2 Phase Optimization for RIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.3 Alternating Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4 Simulations Results and Discussion 23
4.1 Simulation Scenario . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.2 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
5 Conclusion 32
References 33

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