论文标题
RIS AID的近场定位和子terahertz系统的渠道估计
RIS-Aided Near-Field Localization and Channel Estimation for the Sub-Terahertz System
论文作者
论文摘要
低硬件成本使得超大（XL）可重构智能表面（RIS）成为可以增强本地化和通信系统的性能的有吸引力的解决方案，但它导致了近场传播渠道，尤其是对于高频通信系统，例如。 mmwave和sub-terahertz（Subthz）系统。 这使得在RIS辅助SubthS系统的近场中进行了本地化和渠道估计更具挑战性。 在本文中，我们考虑了在RIS的帮助下，在SubthS系统近场中的球形波前传播。 基于近场通道模型的二阶菲涅耳近似，提出了近场通道估计和定位（NF-JCEL）算法。 具体来说，我们首先通过下采样的Toeplitz协方差矩阵将用户设备（UE）距离（AOA）的角度解脱，以便可以单独估计阵列转向矢量中的垂直和方位角AOA具有较低的复杂性。 然后，可以通过简单的一维搜索来估计UE距离，并且通道衰减系数是通过正交匹配追踪（OMP）方法获得的。 仿真结果验证了所提出的NF-JCEL算法与常规远场算法的优越性，并表明该算法可以获得更高的分辨率精度。
The low hardware cost makes ultra-large (XL) reconfigurable intelligent surface (RIS) an attractive solution for the performance enhancement of localization and communication systems, but it results in near-field propagation channels, especially for the high-frequency communication systems, e.g. mmWave and sub-terahertz (subTHz) systems. This makes localization and channel estimation in the near field of the RIS-aided subTHz system more challenging. In this paper, we consider the spherical wavefront propagation in the near field of the subTHz system with the assistance of a RIS. A near-field channel estimation and localization (NF-JCEL) algorithm is proposed based on the derived second-order Fresnel approximation of the near-field channel model. To be specific, we first decouple the user equipment (UE) distances and angles of arrival (AoAs) through a down-sampled Toeplitz covariance matrix, so that the vertical and azimuth AoAs in the array steering vectors can be estimated separately with low complexities. Then, the UE distance can be estimated by the simple one-dimensional search, and the channel attenuation coefficients are obtained through the orthogonal matching pursuit (OMP) method. Simulation results validate the superiority of the proposed NF-JCEL algorithm to the conventional far-field algorithm, and show that higher resolution accuracy can be obtained by the proposed algorithm.
