Wideband channel estimation (CE) in high-mobility scenarios remains challenging because channel responses vary rapidly, while practical systems can allocate only sparse pilots to accommodate dense users. Fortunately, many high-mobility environments, such as high-speed railways, exhibit scheduled trajectories, predictable velocities, and a limited number of dominant propagation paths. These properties induce a delay--beam power spectrum that is more stable than the instantaneous complex channel frequency response (CFR), less sensitive to the random phase coherence, and rich in geometric information. To exploit such environmental properties, we propose GeoGS-CE, a two-stage channel estimation framework for sparse-pilot high-mobility scenarios. In the offline stage, GeoGS-CE jointly models: 1) a scene-level 3D Gaussian representation that captures the non-line-of-sight (NLoS) geometric scattering support, and 2) a leakage-aware differentiable wireless rendering process that maps the NLoS Gaussians, together with an explicit virtual line-of-sight (LoS) component, to the measured delay--beam power spectrum, while accounting for practical OFDM delay and array leakage effects. In the online stage, the delay--beam power spectrum is predicted for each user location and used as a strong covariance prior, enabling accurate full-band and full-array CFR reconstruction and tracking through a linear MMSE estimator. Simulations based on channels generated from a segment of the Guangshen high-speed railway show that the proposed geometric prior substantially improves CFR reconstruction over pilot-only and non-geometric baselines.

翻译：高移动性场景中的宽带信道估计仍具挑战性，因为信道响应快速变化，而实际系统只能分配稀疏导频以容纳密集用户。幸运的是，许多高移动性环境（如高速铁路）具有规律轨迹、可预测速度及有限数量的主传播路径，这些特性使得时延-波束功率谱比瞬时复数信道频率响应更稳定，对随机相位相干性更不敏感，且富含几何信息。为利用此类环境特性，我们提出GeoGS-CE——一种适用于稀疏导频高移动性场景的两阶段信道估计框架。离线阶段中，GeoGS-CE联合建模：1）捕获非视距几何散射支持的场景级三维高斯表示，以及2）考虑泄漏的可微分无线渲染过程，该过程将非视距高斯分量与显式虚拟视距分量映射至实测时延-波束功率谱，同时计及实际OFDM时延和阵列泄漏效应。在线阶段中，对每个用户位置预测时延-波束功率谱，并将其作为强协方差先验，通过线性最小均方误差估计器实现全频段全阵列CFR重建与跟踪。基于广深高速铁路某区段信道生成的仿真结果表明，所提几何先验相比纯导频基线及非几何基线显著提升了CFR重建性能。