RIS-Aided Localization Under Position and Orientation Offsets in the Near and Far Field
RIS-Aided Localization Under Position and Orientation Offsets in the Near and Far Field
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DOI：
10.1109/twc.2023.3270029
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发表时间：
2022-10
影响因子：
10.4
通讯作者：
Student Member Ieee Don-Roberts Emenonye;S. M. I. Harpreet S. Dhillon-S.-M.-I.-Harpreet-S.-Dhillon-2226656304;F. I. R. Michael Buehrer
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文献类型：
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作者：
Student Member Ieee Don-Roberts Emenonye;S. M. I. Harpreet S. Dhillon-S.-M.-I.-Harpreet-S.-Dhillon-2226656304;F. I. R. Michael Buehrer
本文对源自单个基站 (BS) 并由用户设备 (UE) 接收的信号信息（包括视距 (LOS) 路径和多个可重构智能表面 (RIS) 的反射）进行了严格的贝叶斯分析。对于全面的贝叶斯分析，需要考虑近场和远场两种情况。贝叶斯分析将 RIS 的位置和有关 UE 的先前信息视为 UE 定位的先验信息。由于过时的先验信息，RIS的位置和方向偏移成为需要估计并反馈给BS进行校正的参数。我们首先表明，当 RIS 元件具有半波长间距时，该 RIS 方向偏移是 RIS 路径路径损耗的一个因素。随后，我们通过通道参数的贝叶斯等效费希尔信息矩阵（EFIM）表明，当远场区域中接收信号存在未知相位偏移时，RIS 方向偏移无法校正。然而，在近场中观察到的接收信号中的信道参数的相应EFIM表明，当UE具有多于一根接收天线时，这种未知的相位偏移不会妨碍RIS方向偏移的估计。此外，我们使用 EFIM 作为 UE 位置参数，以在存在 RIS 不确定性的情况下呈现 UE 定位的界限。我们严格证明，无论大小和传播方式如何，只有当存在有关 RIS 位置的先验信息时，RIS 才有助于定位。最后，通过对 EFIM 及其最小特征值的数值分析，我们证明了当远场模型错误地应用于经历近场传播的 UE 接收的信号时，信息会丢失。
This paper presents a rigorous Bayesian analysis of the information in the signal (consisting of both the line-of-sight (LOS) path and reflections from multiple reconfigurable intelligent surfaces (RISs)) that originate from a single base station (BS) and is received by a user equipment (UE). For a comprehensive Bayesian analysis, both near and far field regimes are considered. The Bayesian analysis views both the location of the RISs and previous information about the UE as a priori information for UE localization. With outdated a priori information, the position and orientation offsets of the RISs become parameters that need to be estimated and fed back to the BS for correction. We first show that when the RIS elements have a half wavelength spacing, this RIS orientation offset is a factor in the pathloss of the RIS paths. Subsequently, we show through the Bayesian equivalent Fisher information matrix (EFIM) for the channel parameters that the RIS orientation offset cannot be corrected when there is an unknown phase offset in the received signal in the far-field regime. However, the corresponding EFIM for the channel parameters in the received signal observed in the near-field shows that this unknown phase offset does not hinder the estimation of the RIS orientation offset when the UE has more than one receive antenna. Furthermore, we use the EFIM for the UE location parameters to present bounds for UE localization in the presence of RIS uncertainty. We rigorously show that regardless of size and propagation regime, the RISs are only helpful for localization when there is a priori information about the location of the RISs. Finally, through numerical analysis of the EFIM and its smallest eigenvalue, we demonstrate the loss in information when the far-field model is incorrectly applied to the signals received at a UE experiencing near-field propagation.