此篇提供一個，在有幹擾信號的非正交多址系統中，使用波束成型的傳輸方式，基於多個用戶在系統中所處位置的角度資訊，設計了一種用戶選擇與配對的方式以達到更佳的通道容量表現。由於NOMA系統中，對多使用者使用波束成型的傳輸方式時，如果隨機將用戶分組去傳輸毫米波的信號，往往因為使用者所在位置的隨機性，從而導致波束權重與通道的結合不能產生較好的增益效果，因此與一般隨機配對的方式不同，本篇以兩兩用戶為一組，將系統中角度相近的用戶作分組配對傳輸訊號，從而使得對應的波束權重與用戶通道間相比於隨機分配而言，會有更好的增益效果，從而可達到更好的通道容量。此外，在系統中存在多個用戶時，根據天線服務的信號區域篩選角度最為相近的用戶配對並傳輸相比於隨機配對傳輸時，也會有明顯的通道容量增益。同時，本篇在對用戶兩兩分組後，根據通道與波束權重的結合資訊，區分了強弱使用者的身份，從而對二者的傳輸能量也作了一定的設定以達到更佳的系統通道容量。但是由於該系統是多天線傳輸並且多個組中的使用者共用子載波傳輸訊息，因此各組也會受到來自其他天線的幹擾以及多個使用者之間也會受到同頻帶的幹擾。所以本篇採用了Zero-Forcing Beamforming的方式消除其他天線對對應使用者組的幹擾，同時也採用了連續幹擾消除技術(SIC)以去除來自組中高傳輸功率用戶的幹擾。最後經過電腦模擬模擬分析，證實所提出的方法是有效果的。;In this paper, we proposed an algorithm about user selection and grouping in downlink non-orthogonal multiple access system (NOMA) with beamforming (BF) transmission. First, we simulate the situation where the users are randomly separated in the system. Then, we develop a scheme of user selection under the similarities of angle among all users. Based on the former result, the users are divided into groups-each group contains 2 users. Besides, in order to eliminate the interference among different groups, we obtain zero-forcing to produce beamforming weight. Within the selection and grouping scheme, the aim is to enhance the system performance. Finally, we compared system throughput between the proposed scheme and the random selection algorithm. Simulation results show that the proposed user grouping design provides better sum capacity than the random grouping scheme. However, because the system is multi-antenna transmission and users in multiple groups share sub-carriers to transmit messages-each group will also receive interference from other antennas and multiple users will also experience interference in the same frequency band. Therefore, this article uses Zero-Forcing Beamforming (ZFBF) to eliminate interference from other antennas to the corresponding user group, and also uses successive interference cancellation technology (SIC) to remove interference from users with high transmission power in the group.
