Non-cooperative cellular massive MIMO, combined with power control, is known to lead to significant improvements in per-user throughput compared with conventional LTE technology. In this paper, we investigate further refinements to massive MIMO, first, in the form of three-fold sectorization, and second, coordinated multi-point operation (with and without sectorization), in which the three base stations cooperate in the joint service of their users. For these scenarios, we analyze the downlink performance for both maximum-ratio and zero-forcing precoding and derive closed-form lower-bound expressions on the achievable rate of the users. These expressions are then used to formulate power optimization problems with two throughput fairness criteria: i{i} ) network-wide max-min fairness, and ii) per-cell max-min fairness. Furthermore, we provide centralized and decentralized power control strategies to optimize the transmit powers in the network. We demonstrate that employing sectorized antenna elements mitigates the detrimental effects of pilot contamination by rejecting a portion of interfering pilots in the spatial domain during channel estimation phase. Simulation results with practical sectorized antennas reveal that sectorization and multi-point coordination combined with sectorization lead to more than 1.7×1.7\times and 2.6×2.6\times improvements in the 95%-likely per-user throughput, respectively.

中文翻译：

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具有扇形天线的大规模 MIMO 系统中的多点协调


众所周知，与传统 LTE 技术相比，非协作蜂窝大规模 MIMO 与功率控制相结合可显着提高每用户吞吐量。在本文中，我们研究了大规模 MIMO 的进一步改进，首先是三倍扇区化的形式，其次是协调多点操作（有扇区化和无扇区化），其中三个基站在联合服务中进行合作他们的用户。对于这些场景，我们分析了最大比率和迫零预编码的下行链路性能，并得出用户可实现速率的封闭式下界表达式。然后使用这些表达式来制定具有两个吞吐量公平性标准的功率优化问题：i{i} )网络范围的最大-最小公平性，以及ii)每小区最大-最小公平性。此外，我们提供集中式和分散式功率控制策略来优化网络中的发射功率。我们证明，采用扇区天线元件可以通过在信道估计阶段拒绝空间域中的部分干扰导频来减轻导频污染的有害影响。实际扇区化天线的仿真结果表明，扇区化和多点协调与扇区化相结合，分别使每用户吞吐量提高了 1.7×1.7 倍和 2.6×2.6 倍（95% 可能）。