臺灣博碩士論文加值系統

本文提出了在多細胞下行鏈路非正交多重接取（non-orthogonal multiple access，NOMA）系統中的協調波束成形設計和功率分配機制。在此系統中，基站採用波束成形來減少細胞間干擾和細胞內干擾，並採用功率域多工疊加傳送來同時服務一組內的兩個用戶(以下稱為用戶對)。當給定波束成形向量時，我們可以求得最差干擾狀態假設下的最大化總加權速率的用戶對內功率分配機制。彌後，則可在傳送功率固定時，依據所提出的機制更新波束成形向量。本文提出了考慮功率域多工效應的兩種協調波束成形方案，即與迫零波束成形結合的協調排程（coordinated scheduling with pair-wise zero-forcing，CSPZF）和與最大化信號與洩漏加噪聲比值結合的協調排程（pair-wise signal-to-leakage-plus-noise ratio，PSLNR）機制。 CSPZF波束成形技術利用每個基站的可用空間自由度來同時分離細胞內服務的用戶對的信號以及消除強大的細胞外干擾。另一方面，PSLNR波束成形技術則在增強自我用戶信號的同時，去抑制對其他用戶（包含其他細胞中的用戶）的干擾。針對每個機制，本文都提出了多細胞的用戶協調排程來最大化總加權速率。CSPZF波束成形技術在效能受到干擾限制的高SNR區域表現優於PSLNR波束成形技術，反之亦然。我們提出的機制的效能可以通過模擬得到證明。

In this work, coordinated beamforming and power allocation schemes are proposed for multicell downlink non-orthogonal multiple access (NOMA) systems. Beamforming is adopted at the base-station to mitigate both intercell and intracell interference whereas power-domain multiplexing between a pair of users is considered in each spatial dimension. Given the beamforming, intra-pair power allocation is first determined by maximizing the weighted sum rate under worst-case interference. Then, two coordinated beamforming schemes that take into consideration the effect of power-domain multiplexing are proposed, namely, the coordinated scheduling with pair-wise zero-forcing (CSPZF) and the maximum pair-wise signal-to-leakage-plus-noise ratio (PSLNR) beamforming schemes. CSPZF beamforming utilizes the available spatial degrees of freedom at each base-station to separate signals intended for intracell user pairs as well as to eliminate strong out-of-cell interference. PSLNR beamforming, on the other hand, enhances the signal intended for each user pair while suppressing its leakage towards other users (including those in other cells). For each scheme, the coordinated user schedule of multicell is proposed to maximize the weighted sum rate. CSPZF is shown to outperform PSLNR beamforming in the high SNR region where the performance is interference-limited and, vice versa. The effectiveness of our proposed schemes are demonstrated via simulations.

Abstract i
Contents ii
1 Introduction 1
2 System Model and Problem Formulation 6
3 Intra-Pair Power Allocation with Fixed Beamforming for Multicell NOMA
Systems 10
3.1 Weak User Limited Case 14
3.2 Strong User Limited Case 15
3.3 Equal Case 16
4 Coordinated Beamforming Schemes for Multicell NOMA System 17
4.1 Coordinated Scheduling with Pair-wise ZF Beamforming 17
4.2 Maximum Pair-Wise SLNR Beamforming 20
5 Simulation 23
6 Conclusion 33

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