In this study, joint users selection and beamforming based on users positioning are proposed for enabling non-orthogonal multiple access (NOMA) in the millimetre-wave (mmWave) transmissions. In the proposed scheme, the mmWave users are arranged in descending order based on their estimated distances from the mmWave base station (BS), which guarantees the users ordering based on their line-of-sight availability, as well. Out of the ordered users, the two users having the minimum pairing angle and expected to lie within the specified mmWave beamwidth are selected as the two NOMA users. In this study, the users' pairing angle is defined as the maximum expected difference angle between two users considering their location-uncertainty areas. Consequently, the BS antenna beam is formed towards the two selected NOMA users by adjusting its boresight angle to lie in between their estimated location angles. Then, the fixed power allocation scheme is used to adjust the power allocation coefficients of the selected NOMA users. Mathematical analysis is performed to bound the performance of the proposed mmWave NOMA scheme. Also, numerical simulations are conducted to prove the mathematical findings and to show the superior performance of the proposed scheme over the well-known technique of using random beamforming.

中文翻译：

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基于用户定位的下行毫米波NOMA联合用户选择和波束成形

在这项研究中，提出了基于用户定位的联合用户选择和波束成形技术，以实现毫米波（mmWave）传输中的非正交多路访问（NOMA）。在提出的方案中，mmWave用户根据他们与mmWave基站（BS）的估计距离以降序排列，这也保证了用户根据其视线可用性进行排序。在有序用户中，将具有最小配对角度且预期位于指定毫米波波束宽度内的两个用户选为两个NOMA用户。在这项研究中，用户的配对角定义为考虑到他们的位置不确定性区域的两个用户之间的最大预期差异角。所以，BS天线波束通过调整其视轴角使其位于两个估计的定位角之间而朝向两个选定的NOMA用户形成。然后，使用固定功率分配方案来调整所选NOMA用户的功率分配系数。进行数学分析以限制所提出的mmWave NOMA方案的性能。此外，进行了数值模拟，以证明数学上的发现并显示出所提出的方案优于使用随机波束成形的公知技术的优越性能。