[论文解读] Fully-/Partially-Connected Hybrid Beamforming Architectures for mmWave MU-MIMO

Xiaoshen Song, Thomas Kühne+1 more|arXiv (Cornell University)|Apr 23, 2019

Millimeter-Wave Propagation and Modeling参考文献 39被引用 13

一句话总结

本文研究了毫米波多用户MIMO系统中全连接（FC）与每子阵列单流（OSPS）混合波束成形架构，联合优化波束对准与预编码。结果表明，两种架构在频谱效率方面表现相近，但OSPS在硬件复杂度和能耗效率方面更优，代价是由于角分辨率降低，波束获取时间略有延长。

ABSTRACT

Hybrid digital analog (HDA) beamforming has attracted considerable attention in practical implementation of millimeter wave (mmWave) multiuser multiple-input multiple-output (MU-MIMO) systems due to the low power consumption with respect to its fully digital baseband counterpart. The implementation cost, performance, and power efficiency of HDA beamforming depends on the level of connectivity and reconfigurability of the analog beamforming network. In this paper, we investigate the performance of two typical architectures that can be regarded as extreme cases, namely, the fully-connected (FC) and the one-stream-per-subarray (OSPS) architectures. In the FC architecture each RF antenna port is connected to all antenna elements of the array, while in the OSPS architecture the RF antenna ports are connected to disjoint subarrays. We jointly consider the initial beam acquisition and data communication phases, such that the latter takes place by using the beam direction information obtained by the former. We use the state-of-the-art beam alignment (BA) scheme previously proposed by the authors and consider a family of MU-MIMO precoding schemes well adapted to the beam information extracted from the BA phase. We also evaluate the power efficiency of the two HDA architectures taking into account the power dissipation at different hardware components as well as the power backoff under typical power amplifier constraints. Numerical results show that the two architectures achieve similar sum spectral efficiency, while the OSPS architecture is advantageous with respect to the FC case in terms of hardware complexity and power efficiency, at the sole cost of a slightly longer BA time-to-acquisition due to its reduced beam angle resolution.

研究动机与目标

• 评估全连接（FC）与每子阵列单流（OSPS）混合波束成形架构在毫米波MU-MIMO系统中的性能权衡。
• 利用初始波束对准阶段获得的波束方向信息，联合优化波束对准与数据预编码。
• 通过建模硬件功耗与功率放大器回退，评估两种架构的能耗效率。
• 在实际毫米波系统中，识别在频谱效率、硬件复杂度与能耗之间实现最优平衡的架构。

提出的方法

• 提出一种联合波束对准（BA）与预编码框架，利用初始BA阶段获得的波束方向信息，实现高效数据通信。
• 采用作者先前开发的先进波束对准方案，高精度估计波束方向。
• 应用针对BA阶段提取的波束信息定制的MU-MIMO预编码方案，以最大化频谱效率。
• 对射频链路、移相器与功率放大器的功耗进行建模，包括典型功率放大器约束下的回退效应。
• 在真实硬件约束下，通过评估频谱效率、波束获取时间与总能耗效率，对比FC与OSPS架构。
• 采用数值仿真量化关键指标的性能表现，包括总频谱效率与能耗效率。

实验结果

研究问题

• RQ1 在毫米波MU-MIMO系统中，全连接与每子阵列单流混合波束成形架构在总频谱效率方面如何比较？
• RQ2 波束对准时间对系统性能有何影响，特别是对不同角分辨率架构而言？
• RQ3 FC与OSPS架构之间的硬件复杂度有何差异，其对能耗效率的影响如何？
• RQ4 功率放大器回退在多大程度上影响混合波束成形架构的整体能效？
• RQ5 OSPS架构能否在显著降低硬件复杂度与功耗的同时，实现与FC架构相当的频谱效率？

主要发现

• 全连接与每子阵列单流架构在毫米波MU-MIMO系统中实现了相近的总频谱效率。
• OSPS架构在能耗效率方面表现更优，且硬件复杂度更低，优于FC架构。
• FC架构需要更多的射频链路与移相器，导致功耗与硬件成本上升。
• OSPS架构由于角分辨率降低，波束获取时间略有延长。
• 功率放大器回退显著影响整体能耗效率，尤其在高数据速率场景下。
• 尽管波束获取时间更长，OSPS架构在频谱效率、硬件成本与能耗效率之间实现了有利的权衡。