Channel-Reconstruction-Based Hybrid Precoding for Millimeter-Wave Multi-User MIMO Systems
Channel-Reconstruction-Based Hybrid Precoding for Millimeter-Wave Multi-User MIMO Systems
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DOI：
10.1109/jstsp.2018.2819135
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发表时间：
2018-05-01
影响因子：
7.5
通讯作者：
Peleato, Borja
中科院分区：
文献类型：
--
作者：
Castellanos, Miguel R.;Raghavan, Vasanthan;Peleato, Borja
本文的重点是毫米波系统的多用户多输入多输出传输与混合预编码结构在基站。为了实现多用户传输，基站在初始波束对准阶段使用波束成形向量的小区特定码本。每个用户使用波束成形向量的用户特定码本来在单用户设置中根据观察到的信噪比（SNR）来学习前P个（其中P >= 1）波束对。从每个用户反馈前P个波束索引沿着以及它们的SNR，并且基站利用该信息来生成用于同时传输的波束权重。生成波束权重的典型方法是仅使用每个用户的最佳波束，并且沿着该波束操纵能量沿着，或者利用该信息来减少多用户干扰。其他波束用作解决阻塞或移动性的回退选项。这样的方法完全丢弃了所学习的关于信道条件的信息，即使每个用户反馈该信息。在此背景下，本文提出了一种先进的定向预编码结构，同时传输的成本额外的边际反馈开销。该构造依赖于三个主要创新：第一，附加反馈，以允许基站重构其与每个用户之间的信道矩阵的秩P近似;第二，迫零结构，其通过在预编码器设计中保持接收器波束知识的不可知性来利用该信息来对抗多用户干扰;以及第三，混合预编码架构，其允许以低复杂度和成本进行幅度和相位控制，以允许实现迫零结构。数值研究表明，该方案的结果在一个显着的和速率性能的改善，甚至与天真的计划，粗糙的初始波束对准码本。
The focus of this paper is on multi-user multi-input multi-output transmissions for millimeter-wave systems with a hybrid precoding architecture at the base station. To enable multi-user transmissions, the base station uses a cell-specific codebook of beamforming vectors over an initial beam alignment phase. Each user uses a user-specific codebook of beamforming vectors to learn the top-P (where P >= 1) beam pairs in terms of the observed signal-to-noise ratio (SNR) in a single-user setting. The top-P beam indices along with their SNRs are fed back from each user and the base station leverages this information to generate beam weights for simultaneous transmissions. A typical method to generate the beam weights is to use only the best beam for each user and either steer energy along this beam, or to utilize this information to reduce multi-user interference. The other beams are used as fall-back options to address blockage or mobility. Such an approach completely discards information learned about the channel condition(s) even though each user feeds back this information. With this background, this paper develops an advanced directional precoding structure for simultaneous transmissions at the cost of an additional marginal feedback overhead. This construction relies on three main innovations: first, additional feedback to allow the base station to reconstruct a rank-P approximation of the channel matrix between it and each user; second, a zero-forcing structure that leverages this information to combat multi-user interference by remaining agnostic of the receiver beam knowledge in the precoder design; and third, a hybrid precoding architecture that allows both amplitude and phase control at low complexity and cost to allow the implementation of the zero-forcing structure. Numerical studies show that the proposed scheme results in a significant sum rate performance improvement over naive schemes even with a coarse initial beam alignment codebook.