目前非正交多重接取技術已經被視為極具潛力的無線通訊技術之一，與傳統的正交多重接取技術相比，此種接取技術在許多參考文獻中已被證明在下行廣播通道可以更有效率的使用頻譜資源並達到較佳的通道容量。此技術的基本原理為在接收端將多個使用者的訊號在功率上做疊加，並在接收端採用連續干擾消除取得目標的訊號。由於非正交多重接取技術允許將一個資源分配給多個用戶，功率域不再由單一用戶獨享，並能有效的消除用戶彼此間的干擾，因此能有效的提升通道容量。
在本篇論文之中，研究了基於下行多輸出單輸入非正交多重接取技術下的通訊系統，傳送端為有多根天線的基地台，接收端則為多個單一天線的使用者，利用強制歸零預先編碼消除部分使用者彼此間的干擾，此篇論文主要的探討主題為分析不同分組方法對於系統效能的影響，並提供出了一個基於使用者通道功率差異以及通道相關性的分組方法，另外，在分組的過程中，如果使用者的正交性、通道功率差異或通道相關性不夠大時，強迫分組反而會降低系統效能，針對這個問題，也提出分組組數最佳化方法來達到系統的最佳輸出容量。

Non-orthogonal multiple access (NOMA) has been recognized as a promising technology in future wireless communication systems, which can greatly improve spectral efficiency and system capacity by employing the superposition coding (SC) at the transmitter and successive interference cancellation (SIC) at the receiver. Different from conventional multiple access, multiple users can share the same radio resources and multiplex in power domain under NOMA systems.
In this thesis, we investigate a downlink single-cell MISO-NOMA system with uniformly deployed user. We focus on the influence of different user clustering algorithms and propose a user clustering algorithm on the basis of channel power difference and channel correlation. Moreover, we also develop cluster size decision methods to identify the optimal number of clusters for maximizing the total throughput. Simulation results demonstrate that our proposed user clustering algorithm and our proposed cluster size decision methods are able to enhance the system performance under small user space as well as large user space.

中文摘要 ..........................................................................................................................I
ABSTRACT II
誌謝....................................................................................................................................III
CONTENTS IV
LIST OF FIGURES VI
LIST OF TABLES IX
Chapter 1 Introduction 1
1.1 Background 1
1.2 Superposition Coding with SIC 3
1.3 Contributions 5
Chapter 2 System Model 6
2.1 NOMA with Zero-Forcing BF and SIC 8
2.2 NOMA with User Clustering Algorithm and Power Allocation 12
2.3 Problem Formulation 18
2.3.1 Problem I 18
2.3.2 Problem II 20
Chapter 3 Performance Analysis 23
3.1 Performance Analysis of User Clustering Algorithms 23
3.2 Proposed Cluster Size Decision Method 27
3.2.1 Proposed Cluster Size Decision Method I 27
3.2.2 Proposed Cluster Size Decision Method II 30
Chapter 4 Simulation Results 32
4.1 Statistical Results under User Clustering Algorithms 32
4.1.1 Case I: PMF and Total Throughput under Small User Space 32
4.1.2 Case II: PMF and Total Throughput under Large User Space 39
4.1.3 Case III: PMF and Total Throughput under Large 45
4.2 Simulation with Two Proposed Cluster Size Decision Methods 50
Chapter 5 Conclusion 59
References ........................................................................................................................60

[1] Y. Saito et al., “Non-Orthogonal Multiple Access (NOMA) for Future Radio Access,” in Proc. IEEE VTC Spring, June 2013, pp. 1–5.
[2] A. Benjebbour, Y. Saito, Y. Kishiyama, A. Li, A. Harada, and T. Nakamura, “Concept and practical considerations of non-orthogonal multiple access (NOMA) for future radio access,” in Proc. IEEE ISPACS, pp. 770–774, Nov. 2013.
[3] A. Benjebbovu et al., “System-level performance of downlink NOMA for future LTE enhancements,” in Proc. IEEE GLOBLECOM Workshop, pp. 66–70, Dec. 2013.
[4] Z. Ding, Z. Yang, P. Fan, and H. V. Poor, "On the performance of non-orthogonal multiple access in 5G systems with randomly deployed users," IEEE Signal Processing Lett., vol. 21, no. 12, pp. 1501–1505, Dec. 2014.
[5] H. Zhang, D-K. Zhang, W-X. Meng, and C. Li, “User pairing algorithm with SIC in non-orthogonal multiple access system,” in Proc. IEEE Intern. Conf. Commun. (ICC), May 2016, pp. 1-6.
[6] Y. Liu, Z. Ding, M. Elkashlan, and H. V. Poor, “Cooperative non-orthogonal multiple access with simultaneous wireless information and power transfer,” IEEE J. Sel. Areas Commun., vol. 34, no. 4, Apr. 2016.
[7] Z. Ding, P. Fan, and H. V. Poor, "Impact of user pairing on 5G Non-orthogonal multiple-access Downlink transmissions," IEEE Transactions on Vehicular Technology, vol. 65, no. 8, pp. 6010–6023, Aug. 2016.
[8] M. S. Ali, H. Tabassum, and E. Hossain, ‘‘Dynamic user clustering and power allocation for uplink and downlink non-orthogonal multiple access (NOMA) systems,’’ IEEE Access, vol. 4, pp. 6325–6343, Aug. 2016.
[9] N. Otao, Y. Kishiyama, and K. Higuchi, “Performance of non-orthogonal access with SIC in cellular downlink using proportional fair-based resource allocation,” in Proc ISWCS, pp. 476-480, Aug. 2012.
[10] F. Liu, P. Mahonen, and M. Petrova, “Proportional fairness-based user pairing and power allocation for non-orthogonal multiple access,” in Proc. IEEE PIMRC, pp. 1306-1310, Sep. 2015.
[11] E. Okamoto, “An Improved Proportional Fair Scheduling in Downlink Non-Orthogonal Multiple Access System,” in Proc IEEE Vehicular Technology Conference, Sept 2015, pp. 1–5.
[12] F. Liu, Petri Mayh´ ynen and M. Petrova, “Proportional fairness-based power allocation and user set selection for downlink NOMA systems,” in Proc IEEE ICC, May 2016.
[13] B. Kim et al., “Non-orthogonal multiple access in a downlink multiuser beamforming system,” in Proc. IEEE MILCOM, Nov. 2013, pp. 1278–1283.
[14] J. Kim, J. Koh, J. Kang, K. Lee, and J. Kang,, “Design of user clustering and precoding for downlink non-orthogonal multiple access (NOMA),” in Proc. IEEE MILCOM, Oct. 2015, pp. 1170-1175.
[15] X. Sun, D. Duran-Herrmann, Z. Zhong, and Y. Yang, “Non-orthogonal multiple access with weighted sum-rate optimization for downlink broadcast channel,” in Proc. IEEE MILCOM, Oct. 2015, pp. 1176–1181.
[16] S. Liu, C. Zhang, and G. Lyu, “User selection and power schedule for downlink non-orthogonal multiple access (NOMA) system,” in Proc. IEEE Intern. Commun. Conf., June 2015, pp. 2561–2565.
[17] M. A. Khalighi, K. Raoof, and G. Jourdain, “Capacity of wireless communication systems employing antenna arrays, a tutorial study,” Wireless Personal Commun., vol. 23, no. 3, pp. 321–352, Dec. 2002.