在本篇論文中，我們提出基於通道統計資訊之下行多載波非正交多重接取系統的資源分配演算法，這個系統有K個使用者及N個子載波。提出的演算法是想解決一個包括使用者選擇、子載波分配以及功率分配的最佳化問題而發展的，這個最佳化問題設法讓系統的通訊容量期望值最大化，並使每個使用者獲分配之通訊容量的期望值滿足預設的比例公平限制條件。每個演算法都是以疊代的方式運作，並包括了：1)使用者配對以及2)同時考慮子載波和功率的分配兩個部份。在使用者配對的部分，我們每次選出目前通訊容量的期望值除以目標比例因子最小的兩個使用者，並將他們配對在一個可用的子載波上進行非正交傳輸。在考慮子載波和功率分配的部分，我們根據適當機制決定將哪一個可用的子載波分配給剛剛選出的兩個非正交使用者，並適當地在兩個使用者間分配功率來達到最大的通道容量總和期望值。為了加入使用者中斷機率限制條件到最佳化問題中，我們同時發展了一個曲線契合函數來簡化演算法中使用者配對部分之每個使用者中斷機率的計算。我們所提出的演算法可以提供一個次佳解，並具有O(N^2+K^2)的時間複雜度，而且電腦模擬結果亦顯示其可同時滿足比例公平限制條件及使用者中斷機率限制條件。與傳統的正交多重接取系統在相同的比例公平限制條件下比較，我們所提出的多載波非正交多重接取系統可達到更好的通訊容量期望值，並且具有相同的時間複雜度。加入使用者中斷機率限制條件後，我們所提出的系統亦可以達到與未加入此限制條件時差不多的系統效能。

In this thesis, we propose a resource allocation algorithm for a downlink multicarrier non-orthogonal multiple access (NOMA) system with K users and N subcarriers based on statistical channel state information. The proposed algorithm is developed by solving an optimization problem of user selection, subcarrier assignment, and power allocation for maximizing the expected system capacity under a proportional user fairness constraint. The algorithm operates in an iterative manner and includes two parts at each iteration: 1) user selection; 2) joint subcarrier assignment and power allocation. In the user selection part, two users with the smallest and second smallest achieved expected-capacity-to-fairness-factor ratios at present are paired for NOMA transmission on a subcarrier. In the joint subcarrier assignment and power allocation part, one of available subcarriers is assigned to the pair of NOMA users with appropriate power allocation for maximizing the expected sum capacity of both users. To include a user outage constraint in the resource allocation optimization problem, we also develop a closed-form fitting function to simplify the calculation of each user’s outage probability for use in the corresponding user selection part. The proposed algorithm can provide a suboptimal solution with low time complexity of O(N^2+K^2). Computer simulation results also demonstrate that the resource allocation performance well satisfies the proportional user fairness constraint and the user outage constraint. As compared with the conventional orthogonal frequency division multiple access system, the proposed multicarrier-NOMA scheme offers higher expected system capacity with the same order of time complexity under the same proportional user fairness constraint. When the user outage constraint is considered, similar performance is also achieved for the proposed scheme.

[1] 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. Int. Symp. Intell. Signal Process. Commun. Syst. (ISPACS), Okinawa, Japan, Nov. 2013, pp. 770–774.
[2] Z. Ding, Y. Liu, J. Choi, Q. Sun, M. Elkashlan, C.-L. I, and H. V. Poor, “Application of non-orthogonal multiple access in LTE and 5G networks,” IEEE Commun. Mag., vol. 55, no. 2, pp. 185–191, Feb. 2017.
[3] S. M. R. Islam, N. Avazov, O. A. Dobre, and K.-S. Kwak, “Power-domain non-orthogonal multiple access (NOMA) in 5G systems: Potentials and challenges,” IEEE Commun. Surveys Tuts., vol. 19, no. 2, pp. 721–742, 2nd Quart., 2017.
[4] Y. Liu, Z. Qiu, M. Elkashlan, Z. Ding, A. Nallanathan, and L. Hanzo, “Nonorthogonal multiple access for 5G and beyond,” Proc. IEEE, vol. 105, no. 12, pp. 2347–2381, Dec. 2017.
[5] L. Lei, D. Yuan, C. K. Ho, and S. Sun, “Power and channel allocation for non-orthogonal multiple access in 5G systems: Tractability and computation,” IEEE Trans. Wireless Commun., vol. 15, no. 12, pp. 8580–8594, Dec. 2016.
[6] F. Fang, H. Zhang, J. Cheng, and V. C. M. Leung, “Energy-efficient resource allocation for downlink non-orthogonal multiple access network,” IEEE Trans. Commun., vol. 64, no. 9, pp. 3722–3732, Sep. 2016.
[7] B. Di, L. Song, Y. Huang, and Y. Li, “Sub-channel assignment, power allocation, and user scheduling for non-orthogonal multiple access networks,” IEEE Trans. Wireless Commun., vol. 15, no. 11, pp. 7686–7698, Nov. 2016.
[8] J. Zhu, J. Wang, Y. Huang, S. He, X. You, and L. Yang, “On optimal power allocation for downlink non-orthogonal multiple access systems,” IEEE J. Sel. Areas Commun., vol. 35, no. 12, pp. 2744–2757, Dec. 2017.
[9] C.-L. Wang, T.-Y. Chen, Y.-F. Chen, and D.-S. Wu, “Low-complexity resource allocation for downlink multicarrier NOMA systems,'” in Proc. IEEE 29th Int. Symp. Pers., Indoor Mobile Radio Commun. (PIMRC), Bologna, Italy, Sep. 2018, pp. 1–6.
[10] C.-W, Hung, “Proportional-fairness resource allocation for a downlink multicarrier NOMA system,” M.S. thesis, Inst. Commun. Eng., National Tsing Hua Univ., Hsinchu, Taiwan, Aug. 2019.
[11] C.-L. Wang and C.-W. Hung, “Proportional-fairness resource allocation for a downlink multicarrier NOMA system,” in Proc. 14th Int. Conf. Signal Process. Commun. Syst. (ICSPCS), Adelaide, Australia, Dec. 2020, pp. 1–6.
[12] W. Cai, C. Chen, L. Bai, Y. Jin, and J. Choi, “User selection and power allocation schemes for downlink NOMA systems with imperfect CSI,” in Proc. IEEE 84th Veh. Technol. Conf. (VTC-Fall), Montreal, Canada, Sep. 2016, pp. 1–5.
[13] K. Senel and S. Tekinay, “Optimal power allocation in NOMA systems with imperfect channel estimation,” in Proc. IEEE Global Commun. Conf. (GLOBECOM), Singapore, Dec. 2017, pp. 1–5.
[14] F. Fang, H. Zhang, J. Cheng, S. Roy, and V. C. M. Leung, “Joint scheduling and power allocation optimization for energy-efficient NOMA systems with imperfect CSI,” IEEE J. Sel. Areas Commun., vol. 35, no. 12, pp. 2874–2885, Dec. 2017.
[15] X. Wang, J. Wang, L. He, and J. Song, “Outage analysis for downlink NOMA with statistical channel state information,” IEEE Wireless Commun. Lett., vol. 7, no. 2, pp. 142–145, Apr. 2018.
[16] Q. Cheng, D. Wang, X. Li, Z. Wang, and Y. Wang, “Low-complexity user scheduling and power allocation for downlink multicarrier NOMA with imperfect CSI,” in Proc. IEEE Symp. Comput. Commun. (ISCC), Natal, Brazil, Nov. 2018, pp. 1–5.
[17] M. R. Zamani, M. Eslami, M. Khorramizadeh, and Z. Ding, “Energy-efficient power allocation for NOMA with imperfect CSI,” IEEE Trans. Veh. Technol., vol. 68, no. 1, pp. 1009–1013, Jan. 2019.
[18] C.-L. Wang, Y.-C. Wang, and P. Xiao, “Power allocation based on SINR balancing for NOMA systems with imperfect channel estimation,” in Proc. 14th Int. Conf. Signal Process. Commun. Syst. (ICSPCS), Gold Coast, Australia, Dec. 2019, pp. 1–6.
[19] C.-L. Wang, C.-C. Hsieh, Y.-C. Ding, and S.-H. Huang, “Power allocation for downlink NOMA systems with imperfect channel estimation,” in Proc. IEEE Wireless Commun. Netw. Conf. (WCNC), Nanjing, China, Mar./Apr. 2021, pp. 1–7.
[20] S. Li, M. Derakhshani, S. Lambotharan, and L. Hanzo, “Outage probability analysis for the multi-carrier NOMA downlink relying on statistical CSI,” IEEE Trans. Commun., vol. 68, no. 6, pp. 3572–3587, Jun. 2020.
[21] C.-L. Wang, J.-Y. Chen, and Y.-J. Chen, “Power allocation for a downlink non-orthogonal multiple access system,” IEEE Wireless Commun. Lett., vol. 5, no. 5, pp. 532–535, Oct. 2016.
[22] S. Li, M. Derakhshani, and S. Lambotharan, “Outage-constrained robust power allocation for downlink MC-NOMA with imperfect SIC,” IEEE Int. Conf. Commun. (ICC), Kansas City, MO, USA, May 2018, pp. 1–7.
[23] Z. Shen, J. G. Andrews, and B. L. Evans, “Adaptive resource allocation in multiuser OFDM systems with proportional rate constraints,” IEEE Trans. Wireless Commun., vol. 4, no. 6, pp. 2726–2737, Nov. 2005.
[24] C. Mohanram and S. Bhashyam, “A sub-optimal joint subcarrier and power allocation algorithm for multiuser OFDM,” IEEE Commun. Lett., vol. 9, no. 8, pp. 685–687, Aug. 2005.