In this paper, we investigate the multiple input multiple output (MIMO)-non-orthogonal multiple access (NOMA) transmission with the aid of location information. We first consider two users separated in both the distance and angle domains. With different access distances, NOMA could be used to serve the near-user and the far-user simultaneously, whereas spatial division multiple access (SDMA) would be applied if the two users have largely-separated angles of departure (AOD) that guarantees spatial orthogonality. Comparing the ergodic sum rates of these two multiple access (MA) schemes, we first characterize the preferable MA regions in the angle-distance plane. Analytical expression of the region boundary between NOMA and SDMA is derived. Moreover, NOMA-preferable regions are expressed in terms of the maximum distance difference and the minimum angle difference between the two users, respectively. On basis of these results, we further propose a location-based low-complexity user pairing algorithm for the general multiuser scenario. Numerical results confirm the accuracy of the derived region boundaries, and the simulations show that the proposed user pairing algorithm can effectively improve the resource utilization rate, compared to the conventional MA and user pairing schemes.

中文翻译：

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基于位置的 MIMO-NOMA：多接入区域和低复杂度用户配对

在本文中，我们借助位置信息研究了多输入多输出 (MIMO)-非正交多址 (NOMA) 传输。我们首先考虑在距离域和角度域中分开的两个用户。对于不同的接入距离，NOMA 可用于同时为近端用户和远端用户提供服务，而如果两个用户具有较大分离的离开角 (AOD)，则可应用空分多址 (SDMA)，以保证空间正交性。比较这两种多路访问 (MA) 方案的遍历求和率，我们首先在角距离平面中表征优选的 MA 区域。导出了 NOMA 和 SDMA 之间区域边界的解析表达式。而且，NOMA-preferable region 分别用两个用户之间的最大距离差和最小角度差来表示。在这些结果的基础上，我们进一步提出了一种用于一般多用户场景的基于位置的低复杂度用户配对算法。数值结果证实了导出区域边界的准确性，仿真表明，与传统的 MA 和用户配对方案相比，所提出的用户配对算法可以有效提高资源利用率。