Large-Scale Antenna Systems with Hybrid Analog and Digital Beamforming for Millimeter Wave 5G
Large-Scale Antenna Systems with Hybrid Analog and Digital Beamforming for Millimeter Wave 5G
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DOI：
10.1109/mcom.2015.7010533
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发表时间：
2015-01-01
影响因子：
11.2
通讯作者：
Rowell, Corbett
中科院分区：
文献类型：
--
作者：
Han, Shuangfeng;Chih-Lin, I;Rowell, Corbett
由于传统蜂窝频段频谱严重短缺，毫米波频段的大型天线系统可能有助于满足 5G 时代移动流量的预期需求。然而，在大规模天线系统中实施数字波束成形存在许多具有挑战性的问题：复杂性、能耗和成本。在实际的大规模天线部署中，混合模拟和数字波束形成结构可能是重要的替代选择。在本文中，研究了混合波束成形结构的优化设计，重点是 N（收发器数量）× M（每个收发器有源天线数量）混合波束成形结构。讨论了多用户波束成形场景中的最佳模拟和数字波束成形设计。同时还分析了N x M波束赋形结构的能效和频谱效率，包括能效-频谱效率曲线上绿点（即能效最高点）处的关系、给定频谱效率值下N对能效性能的影响以及N对绿点能效的影响。这些结果可以方便地用于指导实际的 LSAS 设计，以实现最佳的能量/频谱效率权衡。最后，提出了混合波束成形结构的参考信号设计，与仅基于模拟波束成形的方法相比，该设计获得了更好的信道估计性能。预计毫米波频段内具有混合波束成形结构的大型天线系统可以在5G中发挥重要作用。
With the severe spectrum shortage in conventional cellular bands, large-scale antenna systems in the mmWave bands can potentially help to meet the anticipated demands of mobile traffic in the 5G era. There are many challenging issues, however, regarding the implementation of digital beamforming in large-scale antenna systems: complexity, energy consumption, and cost. In a practical large-scale antenna deployment, hybrid analog and digital beamforming structures can be important alternative choices. In this article, optimal designs of hybrid beamforming structures are investigated, with the focus on an N (the number of transceivers) by M (the number of active antennas per transceiver) hybrid beamforming structure. Optimal analog and digital beamforming designs in a multi-user beamforming scenario are discussed. Also, the energy efficiency and spectrum efficiency of the N x M beamforming structure are analyzed, including their relationship at the green point (i.e., the point with the highest energy efficiency) on the energy efficiency-spectrum efficiency curve, the impact of N on the energy efficiency performance at a given spectrum efficiency value, and the impact of N on the green point energy efficiency. These results can be conveniently utilized to guide practical LSAS design for optimal energy/spectrum efficiency trade-off. Finally, a reference signal design for the hybrid beamform structure is presented, which achieves better channel estimation performance than the method solely based on analog beamforming. It is expected that large-scale antenna systems with hybrid beamforming structures in the mmWave band can play an important role in 5G.