為求增加系統吞吐量以及穩健性，多重解析度服務的概念已廣泛應用於廣播系統中，能使那些位於遠處並且處於不好的通道狀態下的接收者至少能夠擁有一個基本的通訊服務品質；擁有較佳通道狀態下的接收者能擁有更高的通訊服務品質。階層式調變是一種用來實現多重解析度服務的方法，它是由多種資訊串流所組成，那些資訊串流會根據其重要性的不同給予相對應的保護能力;其中，最重要的資訊(基礎位元)能被所有接收者解碼出來，然而，次要的資訊(精細位元)只能被那些擁有較佳通道狀態的接收者解碼出來。
在無線通訊系統中，為了減輕通道造成的訊號衰褪以及增大服務涵蓋範圍，合作式通訊是一個具有前景的技術，藉由中繼節點協助傳輸方式提供合作分集。為因應多媒體通訊需求的日益增長，可預期多重解析度服務與合作式通訊的結合應用將逐漸增加並成為下世代無線通訊系統中主要的傳輸模式。因此在這篇博士論文中，我們藉由中繼節點協助傳輸至具有較差傳輸通道的使用者來改善其多重解析度服務的整體性能表現，特別是精細位元的接收性能。在這篇博士論文的第一部分，基於現有方法的缺點，我們提出一個保護性對調的概念來提高中繼節點端之精細位元的保護能力，並且分別設計其最佳星座圖與最佳星座參數給訊源節點與中繼節點使用。此方法我們稱為保護性對調暨星座點重組。
此外，訊號空間分集也是一般會用來對抗無線通訊系統中通道衰落的技術。因此，在這篇博士論文的第二部分，我們結合訊號空間分集與階層式調變在合作式網路下，提升整體傳輸品質。相較於傳統訊號空間分集設計方法是直接把旋轉矩陣執行在疊加後星座圖上，其限制了搜尋旋轉角度時的選擇性，對此，我們提出多階層旋轉的概念:在進行星座圖疊加之前，各階層旋轉各自對應的角度，藉此增加在設計旋轉角度時的自由度。
根據模擬結果，如預期般，我們所提出保護性對調暨星座點重組及多階層旋轉的方法，對於精細位元而言能夠得到大幅度的改善增益。

To enhance system throughput and robustness, the concept of multi-resolution services, widely used in broadcast systems, allows the receivers that are located farther away from the source and experience bad channel conditions to receive at least a basic quality of service; the receivers with good channel quality receive a higher quality of service. Hierarchical modulation (HM) is one practical way to achieve multi-resolution services, which consists of multiple transmitted data streams with different degrees of protection based on their importance; that is, the most important information (known as the base bits) can be recovered by all receivers, while the less important information (known as the refinement bits) can be recovered only by receivers with better reception conditions.
In wireless communications, to mitigate fading effect and to extend service coverage, cooperative communication is a promising technology that provides cooperative diversity via the assistance of relay transmission. To meet the growing demand for multimedia communications, it is expected that the incorporation of multi-resolution services and cooperative communication will gradually become the major transmission mechanism in next-generation wireless communication systems. Therefore, in this dissertation, we focus on improving the overall performance of multi-resolution services, especially the reception performance of the refinement bits, for users with poor channel conditions by using relay-assisted transmission. In the first part of the dissertation, motivated by the drawbacks of the existing schemes, we propose the concept of protection level exchanging for the relay node to greatly enhance the protection of the refinement bits, and design the optimal constellation mappings and assign the optimal constellation parameters for the source node and the relay node, respectively. This scheme is referred to as the protection level exchanging with re-mapping (PERM).
Furthermore, signal space diversity (SSD) is also a technique commonly used to combat the fading effect by the additional modulation diversity in wireless communications. Therefore, in the second part of the dissertation, to further enhance overall transmission quality, we incorporate the SSD technique in cooperative networks with HM. Unlike a conventional SSD approach that directly performs the rotation matrix on the superimposed constellation, which leads to a limitation of the selectivity in search of the rotation angle, we propose the concept of multiple-layer rotation (MLR) that each layer, respectively, rotates its own angle on the corresponding constellation before performing constellation superposition to increase the degree of freedom of the rotation angle in the design.
As expected, based on the simulation results, the proposed PERM scheme and MLR scheme can lead to significant improvement gains on the refinement layer.

CHAPTER 1
Introduction.....................................................1
CHAPTER 2
Protection-Level-Exchanging Based Hierarchical Modulation........7
2.1 Preliminaries...............................................8
2.1.1 Hierarchical Modulation...................................8
2.1.2 System Model..............................................9
2.2 The Proposed PERM Based HM Scheme..........................11
2.2.1 Basic Concept............................................11
2.2.2 Optimal 4/16-QAM HM Constellation for the Relay Node.....12
2.2.3 Overall BER Performance Analysis.........................16
A. Exact SER on Source-Relay Link............................17
B. Exact BER for the Non-Cooperative Case....................18
C. Upper Bound of the BER for the Cooperative Case...........19
2.2.4 Constellation Priority Parameters Optimization...........21
2.3 Performance Evaluation.....................................24
2.4 Summary....................................................31
CHAPTER 3
Multiple-Layer Rotation Based Hierarchical Modulation for Signal Space Diversity.................................................32
3.1 Preliminaries..............................................33
3.1.1 Signal Space Diversity...................................33
3.1.2 System Model with Conventional SSD.......................34
3.2 The Proposed MLR Based HM Scheme...........................36
3.2.1 Basic Concept............................................38
3.2.2 SER Performance Analysis at the Relay Node...............40
A. Union Bound (UB) Approach.................................40
B. Nearest Neighbor (NN) Approximation.......................42
3.2.3 Rotation Angle Optimization..............................46
3.3 Performance Evaluation.....................................47
3.4 Summary....................................................55
CHAPTER 4
Rotation Angle Optimization with MLR Scheme for Signal Space Cooperative Communication.......................................57
4.1 System Model...............................................58
4.1.1 Signal Space Cooperative (SSC) Communication.............58
4.1.2 Problem Description......................................61
4.2 Performance Analysis.......................................61
4.2.1 Investigation of Relationship Between the Expanded Constellation and the Rotation Angles...........................62
4.2.2 Exact Symbol Error Rate at the Relay Node................63
4.2.3 Rotation Angle Optimization..............................66
4.3 Performance Evaluation.....................................67
4.4 Summary....................................................74
CHAPTER 5
Conclusion......................................................76
Appendix A......................................................78
Appendix B......................................................81
References......................................................84

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