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

[1] Qualcomm , ''The 1000x Mobile Data Challenge," White Paper, Nov. 2013.
[2] Q. Li, H. Niu, A. Papathanassiou, and G. Wu, ''5G network capacity: Key elements and
technologies," IEEE Veh. Technol. Mag., vol. 9, no. 1, pp. 7178, Mar. 2014.
[3] J. G. Andrews, S. Buzzi, W. Choi, et al. ''What will 5G be?" IEEE J. Sel. Areas
Commun., vol. 32, no. 6, pp. 1065-1082, Jun. 2014.
[4] Y. Saito, Y. Kishiyama, A. Benjebbour, T. Nakamura, A. Li and K. Higuchi, ''Non-
Orthogonal multiple access (NOMA) for cellular future radio access," in Proc. IEEE
VTC Spring, 2013, pp. 1 - 5.
[5] Y. Saito, A. Benjebbour, Y. Kishiyama and T. Nakamura, ''System-level performance
evaluation of downlink non-orthogonal multiple access (NOMA)," in Proc. IEEE PIMRC,
2013, pp. 611 - 615.
[6] 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,
2012, pp. 476 - 480.
[7] 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 Process.
Lett., vol. 21, no. 12, pp. 1501-1505, Dec. 2014.
[8] H. Weingarten, Y. Steinberg, S. Shamai. ''The capacity region of the Gaussian multipleinput
multiple-output broadcast channel." IEEE Trans. Inf. Theory, vol. 52, no. 9, pp.
3936-3964, 2006.
[9] S. Venkatesan and H. Huang, System capacity evaluation of multiple antenna systems
using beamforming and dirty paper coding, Bell Labs.
[10] G. Caire and S. Shamai, ''On the achievable throughput of a multi-antenna Gaussian
broadcast channel," IEEE Trans. Inf. Theory, vol. 49, pp. 16911706, Jul. 2003.
[11] B. Kim, S. Lim, H. Kim, S. Suh, J. Kwun, S. Choi, C. Lee, S. Lee, and D. Hong,
''Non-orthogonal multiple access in a downlink multiuser beamforming system," in Proc.
IEEE MILCOM, 2013, pp. 1278 - 1283.
[12] K. Higuchi and Y. Kishiyama, ''Non-orthogonal access with random beamforming and
intra-beam SIC for cellular MIMO downlink," in Proc. IEEE VTC Fall, 2013, pp. 1 - 5.
[13] Z. Ding, F. Adachi and H. V. Poor, ''The application of MIMO to non-Orthogonal
multiple access," IEEE Trans. Wireless Commun., vol. 15, no. 1, pp. 537 - 552, 2016.
[14] D. Gesbert, S. Hanly, H. Huang, S. Shamai Shitz, O. Simeone and W. Yu, ''Multi-
Cell MIMO Cooperative Networks: A New Look at Interference," IEEE J. Sel. Areas
Commun., vol. 28, no. 9, pp. 1380-1408, Dec. 2010.
[15] A. Zarrebini-Esfahani, T. A. Le, M. R. Nakhai, ''Robust cognitive beamforming for
cell-edge coverage in multicell networks with probabilistic constraints," Global Commu-
nications Conference (GLOBECOM) 2013 IEEE, pp. 1253-1258, 2013.
[16] M. K. Karakayali, G. J. Foschini and R. A. Valenzuela, ''Network coordination for
spectrally ecient communications in cellular systems," IEEE Wireless Communications,
vol. 13, no. 4, pp. 56-61, Aug. 2006.
[17] S. Jing, D. N. C. Tse, J. B. Soriaga, et al. ''Multicell downlink capacity with coordinated
processing," EURASIP Journal on Wireless Communications and Networking, Vol. 2008,
No. 18, Apr. 2008.
[18] H. Dahrouj and W. Yu, ''Coordinated beamforming for the multicell multi-antenna
wireless system," IEEE Trans. Wireless Commun., vol. 9, no. 5, pp. 1748-1759, May
2010.
[19] M. Li, I. B. Collings, S. V. Hanly, C. Liu and P. Whiting, ''Multicell coordinated
scheduling with multiuser zero-forcing beamforming," IEEE Trans. Wireless Commun.,
vol. 15, no. 2, pp. 827 - 842, 2016.
[20] M. Sadek, A. Tarighat and A. H. Sayed, ''A leakage-based precoding scheme for downlink
multi-user MIMO channels," IEEE Trans. Wireless Commun., vol. 6, no. 5, pp. 1711 -
1721, 2007.
[21] J. Choi, ''Non-orthogonal multiple access in downlink coordinated two-point systems,"
IEEE Communications Letters, vol. 18, no. 2, pp. 313-316, Jan, 2014.
[22] Y. Tian, S. Lu, A. Nix and M. Beach, ''A novel opportunistic NOMA in downlink
coordinated multi-point networks,"in Proc. IEEE VTC Fall, 2015, pp. 1 - 5.
[23] A. Beylerian and T. Ohtsuki, ''Coordinated non-orthogonal multiple access (CONOMA),"
in Proc. IEEE GLOBECOM, 2016, pp. 1-5.
[24] W. Shin, M. Vaezi, B. Lee, D. J. Love, J. Lee and H. V. Poor, ''Coordinated beamforming
for multi-cell MIMO-NOMA," IEEE Commun. Lett., vol. 21, no. 1, pp. 84-87, 2017.
[25] H. Kim and Y. Han, \A proportional fair scheduling for multicarrier transmission systems,"
IEEE Commun. Lett., vol. 9, no. 3, pp. 210 - 212, 2005.