AI 中文总结
针对RIS辅助定位中实际波束与模型存在差异致定位误差下限升高的问题，提出现场波束校准框架，利用延迟域稀疏恢复和基于梯度的估计器估计波束模型参数，经模拟验证可有效降低定位误差下限。
AI 中文摘要
高精度定位是智能交通和增强现实等下一代通信应用的关键推动因素。可重构智能表面（RIS）技术能通过提供额外角度信息和改善受阻传播条件下的覆盖范围来增强定位。但实际RIS波束与RIS辅助定位中常用的简化或理想波束响应模型有显著差异，导致波束模型失配和定位误差下限升高。本文提出一种现场RIS波束校准框架，通过从现场测量中估计实际的3D RIS波束响应模型来降低误差下限。校准算法首先利用延迟域稀疏恢复从校准代理采样感兴趣角度范围接收到的信号中提取RIS反射信道响应，然后用基于梯度的估计器估计波束模型参数。为验证该框架，测量了66种相位调制下的3D波束方向图并纳入模拟。角度采样步长为1度时，校准模型与地面真值的平均波束响应相似度达88.5%，理想模型为43.7%。定位误差绝对下限低于0.5米的概率从未校准时的0.52增至校准时的0.74，表明现场RIS波束校准有效降低了由实际波束模型失配导致的定位误差下限。
英文摘要
High precision positioning is a key enabler for next-generation communication applications such as smart transportation and augmented reality. Reconfigurable intelligent surface (RIS) technology can enhance positioning by providing additional angular information and improving coverage under obstructed propagation conditions. However, true RIS beams can differ significantly from the simplified or ideal beam response models commonly used in RIS-aided positioning, leading to beam model mismatch and an elevated positioning error floor. This paper proposes an on-site RIS beam calibration framework that reduces this error floor by estimating a realistic 3D RIS beam response model from on-site measurements. The proposed calibration algorithm first extracts the RIS-reflected channel response from signals received by a calibration agent sampling the angular range of interest, using delay-domain sparse recovery, and then estimates the beam model parameters with a gradient-based estimator. To validate the proposed framework, 3D beam patterns under 66 phase modulations were measured and incorporated into simulations. With an angular sampling step of 1 deg, the calibrated model achieves an average beam response similarity of 88.5% with respect to the ground truth, compared with 43.7% for the ideal model. The probability that the absolute lower bound of the positioning error is below 0.5m increases from 0.52 without calibration to 0.74 after calibration, showing that on-site RIS beam calibration effectively reduces the positioning error floor caused by true beam model mismatch.
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