Hybrid analog-digital beamforming stands out as a key enabler for future communication systems with a massive number of antennas. In this paper, we investigate the hybrid precoder design problem for angle-of-departure (AoD) estimation, where we take into account the practical constraint on the limited resolution of phase shifters. Our goal is to design a radio-frequency (RF) precoder and a base-band (BB) precoder to estimate AoD of the user with a high accuracy. To this end, we propose a two-step strategy where we first obtain the fully digital precoder that minimizes the angle error bound, and then the resulting digital precoder is decomposed into an RF precoder and a BB precoder, based on the alternating optimization and the alternating direction method of multipliers. Besides, we derive the quantization error upper bound and analyse the convergence behavior of the proposed algorithm. Numerical results demonstrate the superior performance of the proposed method over state-of-the-art baselines.

翻译：混合模拟-数字波束成形作为未来大规模天线通信系统的关键技术而备受关注。本文研究针对角度离开（AoD）估计的混合预编码器设计问题，特别考虑了移相器有限分辨率的实际约束。我们的目标是设计射频（RF）预编码器和基带（BB）预编码器，以实现对用户AoD的高精度估计。为此，我们提出了一种两步策略：首先获得能够最小化角度误差界的最优全数字预编码器，然后基于交替优化和乘子交替方向法，将所得全数字预编码器分解为RF预编码器与BB预编码器。此外，我们推导了量化误差上界并分析了所提算法的收敛特性。数值结果表明，所提方法相较于现有主流基准方法具有显著性能优势。