Angle Domain Channel Estimation in Hybrid Millimeter Wave Massive MIMO Systems

This paper proposes a novel direction-of-arrival (DOA)-aided channel estimation for a hybrid millimeter-wave (mm-wave) massive multiple-input multiple-output system with a uniform planar array at the base station. To explore the physical characteristics of the antenna array in mm-wave systems, the parameters of each channel path are decomposed into the DOA information and the channel gain information. We first estimate the initial DOAs of each uplink path through the 2-D discrete Fourier transform and enhance the estimation accuracy via the angle rotation technique. We then estimate the channel gain information using a small amount of training resources, which significantly reduces the training overhead and the feedback cost. More importantly, to examine the estimation performance, we derive the theoretical bounds of the mean squared errors (MSEs) and the Cramer-Rao lower bounds (CRLBs) of the joint DOA and channel gain estimation. The simulation results show that the performances of the proposed methods are close to the theoretical MSEs' analysis. Furthermore, the theoretical MSEs are also close to the corresponding CRLBs.

本文针对基站采用均匀平面阵列的混合毫米波（mm - wave）大规模多输入多输出系统，提出了一种新颖的波达方向（DOA）辅助信道估计方法。为了探究毫米波系统中天线阵列的物理特性，将每个信道路径的参数分解为波达方向信息和信道增益信息。我们首先通过二维离散傅里叶变换估计每条上行链路的初始波达方向，并通过角度旋转技术提高估计精度。然后，我们使用少量训练资源估计信道增益信息，这显著降低了训练开销和反馈成本。更重要的是，为了检验估计性能，我们推导了联合波达方向和信道增益估计的均方误差（MSE）理论界和克拉美 - 罗下界（CRLB）。仿真结果表明，所提方法的性能接近理论均方误差分析结果。此外，理论均方误差也接近相应的克拉美 - 罗下界。