近年來，隨著平均每人持有的行動裝置的數量越來越高，各種應用越來越多，對於頻譜的需求也呈現爆炸性地成長。但頻譜資源是珍貴且有限的，為了應付這樣爆炸性成長的data traffic，在5G行動通訊系統中，提高整體的sum capacity成為了大家所關注的議題。NOMA和D2D則是其中兩個目前被高度討論的議題，研究顯示傳統OFDMA的system total throughput會比NOMA來的高，這是由於傳統OFDMA服務只一個有最佳通道狀況的CUE使用一個完整的RB，但NOMA服務兩個以上，仍需要克服兩個CUE間彼此干擾的問題，儘管如此，為提高頻譜使用效益，使頻譜被更有效率地應用，我們仍然採用NOMA的技術來分配資源。而本篇主要針對在NOMA的環境下，分配資源給D2D。
在傳統無線網路下，當兩個裝置間的距離夠小，就能夠直接互相溝通(Device-to-device communication)，不需要額外透過基地台(Base station)的幫忙，如此一來可降低基地台的負擔，並能夠提升整體的傳輸量。然而，當越來越多裝置共享同一頻段，彼此間的干擾也會越大，在進行資源分配時，我們須保證CUE得QoS仍被滿足。
我們的環境設定允許多個D2D pair共享同一RB，也允許每一D2D pair 使用多個RB。而為了要在被允許的D2D pair數量和被滿足的D2D pair數量間取得平衡，我們提出了一系列heuristic的方法來分配資源。每對D2D pair會根據和CUE的距離來決定是否可以共用RB，而為了使後面的資源分配更有效率，我們會先針對每對D2D pair可使用的RBs進行排序。在決定每回合要被分配的RB後，會依據各對D2D pair之間的距離建立conflict graph，以決定哪些D2D pairs能夠共用同一RB。最後在進行D2D pair的傳輸功率分配時，我們仍必須保證所有共用同一RB的CUE能滿足他們的服務品質需求。
最後，實驗結果顯示出我們的資源分配演算法能有效提升頻譜使用效率和整體的傳輸率。

In this thesis, we propose a Non-orthogonal Multiple Access (NOMA) based Device-to-device (D2D) communication system underlying cellular networks to achieve higher spectral efficiency and system sum rate. We consider a many-to-many scenario for D2D communication. There are multiple D2D pairs allowed to reuse the same RB and each D2D pair is allowed to reuse more than one RB. However, there are mutual interference between D2D pairs and CUE but also inter D2D pairs. We should determine the permitted D2D pairs and control the transmission power of D2D pairs in order to guarantee the minimum rate requirement of CUEs and maximize the system sum rate in every RB simultaneously. We propose a method to sort the reusable RBs of each D2D pairs in order to let the allocation more efficiency. And we also propose a heuristic method to determine the permitted D2D pairs and consider both total throughput and the number of satisfied D2D pairs. In the step of the power control for D2D pairs, we formulate some constraints in order to guarantee the minimum rate requirement of CUEs. Simulation results show that the proposed NOMA-based D2D communication system can improve both of the spectrum efficiency and the system sum rate.

Table of contents
Abstract iii
中文摘要 iv
Table of contents v
List of figures vii
Chapter 1 1
Introduction 1
1.1 Concept of NOMA 1
1.2 Concept of Coordinate Multi-Point (CoMP) 2
1.3 Concept of NOMA + CoMP 3
1.4 Concept of NOMA + borrowedCoMP 4
1.5 Concept of D2D 4
Chapter 2 Related work 6
Chapter 3 9
System model 9
3.1 System model 9
3.2 Problem formulation 13
Chapter 4 15
Resource allocation algorithm 15
4.1 SINR Limited Area (SLA) 15
4.2 Determining the priority of reusable RBs for each D2D pair 17
4.3 Determining the reused RB and selected D2D pairs 19
4.4 Power control of D2D pairs 20
Chapter 5 21
Simulation 21
5.1 Simulation settings 21
5.2 Simulation results 22
Chapter 6 30
Conclusion 30
Reference 31

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