Millimeter‐wave bands (mmWave) are considered as a strong candidate for achieving high‐quality communication links for the future outdoor cellular systems to overcome the spectrum congestion problem. Due to the extremely high path loss in mmWave band, large antenna arrays at both the transmitter and receiver are necessary. Hybrid beamforming architectures are used to exploit the potential array gain with several RF chains, which poses a problem of complexity when estimating the mmWave channel. To address the challenge of this hardware complexity, we propose in this paper an approach to design a multiresolution hierarchical codebook to meet parallel multistream data based on the physical design via hybrid analog/digital architecture with low complexity, i.e., 2‐bit phase state and few numbers of RF chains. The simulation results verify that our proposed method to design the codebook has better design performance of beams and can achieve higher average spectral efficiency gains of channel estimation compared to the one based on high hardware complexity.

中文翻译：

---

基于低复杂度分层码本设计的毫米波MIMO系统信道估计

毫米波频段（mmWave）被认为是实现未来室外蜂窝系统克服频谱拥塞问题的高质量通信链路的强大候选者。由于毫米波波段的路径损耗极高，因此在发射器和接收器处都需要大型天线阵列。混合波束成形架构用于利用多个RF链利用潜在的阵列增益，这在估算mmWave通道时会带来复杂性问题。为了解决这种硬件复杂性的挑战，我们在本文中提出了一种方法，可通过物理设计，通过低复杂度（即2位相位状态和少量的RF链。