论文标题
非常大规模的MIMO系统的混合LOS/NLOS环境中的近场通道估计
Near-Field Channel Estimation in Mixed LoS/NLoS Environments for Extremely Large-Scale MIMO Systems
论文作者
论文摘要
准确的通道模型和通道估计对于在具有超高光谱效率的6G网络中赋予极大的大规模MIMO（XL-MIMO）至关重要。随着XL-MIMO场景的天线阵列孔的急剧增加，电磁传播场将从远场变为近场变化。不幸的是，由于近场效应，大多数现有的XL-MIMO通道模型无法同时描述混合视线（LOS）和非线视线（NLOS）路径组件。在本文中，提出了混合LOS/NLOS近场XL-MIMO通道模型与实用的近场XL-MIMO场景匹配，在该场景中，LOS路径组件是通过几何自由空间传播假设对NLOS路径组件进行建模的，而NLOS路径组件是由近场响应响应向量建模的。然后，为了定义XL-MIMO的近场范围，得出了Mimo Rayleigh距离（MIMO-RD）和MIMO Advanced Rd（Mimo-ARD）。接下来，提出了两个阶段通道估计算法，其中分别估算了LOS路径组件和NLOS路径成分。此外，本文得出了所提出的算法的CRAMER-RAO下限（CRLB）。数值模拟结果表明，提出的两个阶段方案能够在理论通道模型和Quadriga通道仿真平台中胜过现有方法。
Accurate channel model and channel estimation are essential to empower extremely large-scale MIMO (XL-MIMO) in 6G networks with ultra-high spectral efficiency. With the sharp increase in the antenna array aperture of the XL-MIMO scenario, the electromagnetic propagation field will change from far-field to near-field. Unfortunately, due to the near-field effect, most of the existing XL-MIMO channel models fail to describe mixed line-of-sight (LoS) and non-line-of-sight (NLoS) path components simultaneously. In this paper, a mixed LoS/NLoS near-field XL-MIMO channel model is proposed to match the practical near-field XL-MIMO scenario, where the LoS path component is modeled by the geometric free space propagation assumption while NLoS path components are modeled by the near-field array response vectors. Then, to define the range of near-field for XL-MIMO, the MIMO Rayleigh distance (MIMO-RD) and MIMO advanced RD (MIMO-ARD) is derived. Next, a two stage channel estimation algorithm is proposed, where the LoS path component and NLoS path components are estimated separately. Moreover, the Cramer-Rao lower bound (CRLB) of the proposed algorithm is derived in this paper. Numerical simulation results demonstrate that, the proposed two stage scheme is able to outperform the existing methods in both the theoretical channel model and the QuaDRiGa channel emulation platform.
