為了因應次世代大量行動裝置而造成的傳輸量需求，下行鏈路的非正交多頻分址技術 (NOMA) 被視為是一個重要的解決方案，有別於傳統只能將資源按照時間或頻率切割成資源區塊後，分配給單一用戶的正交多頻分址技術，非正交多頻分址技術藉由疊加編碼及連續干擾消除法的技術，可使用單一的資源區塊來服務多個用戶以增加頻譜效益。為了非常貼近實際行動網路的情況，本篇論文的系統模型中，我們考慮了用戶端非零的中斷概率及異質的資源區塊。在本篇論文中，我們提出了一個結合用戶配對與功率分配的演算法，主要目的為最大化滿足服務品質的使用者數量，次要目的是最大化系統整體傳輸速率。在模擬結果中，可以顯示出我們在滿足服務品質的使用者數量上，明顯優於其他與我們比較的演算法。

In order to meet the explosive demand incurred by mobile applications, the downlink non-orthogonal multiple access (NOMA) has been regarded as a promising solution. Different from conventional orthogonal multiple access (OMA) technologies that different users are allocated to distinct orthogonal resources in either time or frequency domain, NOMA, which multiplexes multiple users in the same frequency resource, can enhance spectrum efficiency with the help of the use of superposition coding (SC) and successive interference cancellation (SIC). To be very practical, our system model takes non-zero outage probability at UEs and heterogeneity of resource blocks into account. We propose a joint user pairing and power allocation algorithm whose primary objective is to maximize the number of satisfied users and whose secondary objective is to maximize sum rate. Simulation results indicate that the proposed algorithm outperforms the compared algorithms significantly in terms of the number of satisfied users.

[1] Doppler, K., Rinne, M., Wijting, C., Ribeiro, C. and Hugl, K., “Device-to-device communication as an underlay to LTE-advanced networks,” IEEE Communications Magazine, vol.47, no.12, pp.42-49, Dec. 2009.
[2] Larsson, E., Edfors, O., Tufvesson, F. and Marzetta, T., “Massive MIMO for next generation wireless systems,” IEEE Communications Magazine, vol.52, no.2, pp.186-195, Feb. 2014.
[3] Damnjanovic, A., Montojo, J., Wei, Y., Ji, T., Luo, T., Vajapeyam, M., Yoo, T., Song, O. and Malladi, D., “A survey on 3GPP heterogeneous networks,” IEEE Wireless Communications, vol.18, no.3, pp.10-21, Jun. 2016.
[4] Dai, L., Wang, B., Yuan, Y., Han, S., I, C. and Wang, Z., “Non-orthogonal multiple access for 5G: solutions, challenges, opportunities, and future research trends,” IEEE Communications Magazine, vol.53, no.9, pp.74-81, Sep. 2015.
[5] Y.-C. Peng and J.-C. Kao, “Efficient Resource Allocation for Non-Orthogonal Multiple Access in Downlink Coordinated Multi-point Systems,” master thesis, National Tsing Hua University, Taiwan, Jul. 2015.
[6] Z.-X. Huang and J.-C. Kao, “Resource Allocation for Non-Orthogonal Multiple Access in Mobile Networks with Coordinated Multi-point Support,” master thesis, National Tsing Hua University, Taiwan, Jul. 2016.
[7] Y. Saito, Y. Kishiyama, A. Benjebbour, T. Nakamura, A. Li, and K. Higuchi, “Non-orthogonal multiple access (NOMA) for future radio access,” IEEE Vehicular Technology Conference (VTC Spring), pp. 1-5, Jun. 2013.
[8] B. Di, S. Bayat, L. Song, and Y. Li, “Radio Resource Allocation for Downlink Non-Orthogonal Multiple Access (NOMA) Networks using Matching Theory,” IEEE Global Communication Conference (GLOBECOM), San Diego, CA, Dec. 2015.
[9] S. Zhang, B. Di, L. Song, and Y. Li, “Radio resource allocation for non-orthogonal multiple access (NOMA) relay network using matching game,” in Proc. IEEE International Communication Conference (ICC), Kuala Lumpur, Malaysia, pp. 1-6, May. 2016.
[10] Xunan Li, Chong Li and Ye Jin, “Dynamic Resource Allocation for Transmit Power Minimization in OFDM-based NOMA Systems,” IEEE Communications Letters, vol.20, no.12, pp. 2558-2561, Dec. 2016.
[11] Yao, L., Mei, J., Long, H., Zhao, L., and Zheng, K., “A novel multi-user grouping scheme for downlink non-orthogonal multiple access systems,” IEEE Wireless Communications and Networking Conference (WCNC), pp. 1-6, Sep. 2016.
[12] M. Grant and S.Boyd, “CVX: Matlab software for disciplined convex programming, version 2.0,” available: http://cvxr.com/cvx, Apr. 2011.
[13] H. Haci, “Non-orthogonal multiple access (NOMA) with asynchronous interference Cancellation,” Ph.D dissertation, School Eng. Digit. Arts, Univ. Kent, Canrerbury, Canterbury, U.K., Mar. 2015.
[14] B. Kim, W. Chung, S. Lim, S. Suh, J. Kwun, S.Choi, and D. Hong, “Uplink NOMA with multi-antenna,” IEEE Vehicular Technology Conference (VTC Spring), Jul. 2015.
[15] Zhao, J., Liu, Y., Chai, K. K., Chen, Y., Elkashlan, M., and Alonso-Zarate, J., “NOMA-Based D2D Communications: Towards 5G.” IEEE Global Communications Conference (GLOBECOM), pp 1-6, Dec. 2016.
[16] H. Sun, Y. Xu and R. Q. Hu, “A NOMA and MU-MIMO Supported Cellular Network with Underlaid D2D Communications” IEEE Vehicular Technology Conference (VTC Spring), May 2016.
[17] J. Choi, “Non-orthogonal multiple access in downlink coordinated two-point systems,” IEEE Communication Letter, vol.18, no.2, pp.313-316, Feb. 2014.
[18] K. Higuchi and Y.Kishiyama, “A novel opportunistic NOMA in downlink coordinated multi-point networks,” IEEE Vehicular Technology Conference (VTC Fall), Sep. 2015.
[19] Y. Xu, H.Sun, R. Q. Hu and Y. Qian, “Cooperative Non-orthogonal Multiple Access in Heterogeneous Networks,” IEEE Global Communications Conference (GLOBECOM), Dec. 2015.
[20] Zeng, M., Tsiropoulos, G. I., Dobre, O. A., & Ahmed, M. H., “Power allocation for cognitive radio networks employing non-orthogonal multiple access,” IEEE Global Communications Conference (GLOBECOM), pp.1-5, Dec. 2016.
[21] N. Otao, Y. Kishiyama, K. Higuchi, "Performance of non-orthogonal access with SIC in cellular downlink using proportional fair-based resource allocation," International Symposium on Wireless Communication Systems (ISWCS), pp.476-480, pp.28-31, Aug. 2012.
[22] Blair, J. R., Peyton, B. “An introduction to chordal graphs and clique trees,” In Graph theory and sparse matrix computation, pp.1-29, 1993.
[23] A. Brandstadt, P.Ficur, A. Leitert, and M. Milanic, “Polynomial-time algorithms for weighted efficient domination problems in AT-free graphs and dually chordal graphs,” Information Processing Letter, pp.256-262, Nov. 2014.
[24] D.R. Fulkerson, O.A. Gross, “Incidence matrices and interval graphs,” Pacific J. Math., vol.15, no.3, pp.835-855, 1965.
[25] R. Tarjan and M. Yannakakis, “Simple linear-time algorithms to test chordality of graphs, test acyclicity of hypergraphs, and selectively reduce acyclic hypergraphs,” SIAM J. Comput, vol.13, pp.556, 1984.
[26] Z. Galil, “Efficient algorithms for finding maximum matching in graphs,” ACM Computing Surveys (CSUR), vol.18, no.1, pp.23-38, Mar. 1986
[27] H. Zhang, D.-K. Zhang, W.X. Meng, and C. Li, “User pairing algorithm with SIC in non-orthogonal multiple access system,” IEEE International Conference on Communications (ICC), pp.1-6, May. 2016.
[28] Munkres, James. “Algorithms for the assignment and transportation problems,” Journal of the society for industrial and applied mathematics, vol.5, no.1, pp.32-38, Mar. 1957.
[29] Yang, M. J., & Hsieh, H. Y., “Moving towards non-orthogonal multiple access in next-generation wireless access networks,” IEEE International Conference on Communications (ICC), pp.5633-5638, Sep. 2015.