AI 中文总结
针对AFDM-ISAC中连续值延迟-多普勒参数估计的能量泄漏等问题，提出CC-NOMP估计器，其性能优于基线方法且角度估计精度相当。
AI 中文摘要
仿射频分复用（AFDM）是一种极具潜力的基于线性调频的多载波波形，适用于高移动性集成感知与通信（ISAC）场景。准确的角度、延迟和多普勒估计对AFDM感知至关重要。由于目标延迟和多普勒频移通常为连续值，将其表示在离散延迟-多普勒网格上会导致离散仿射傅里叶变换（DAFT）域出现能量泄漏和峰值位移。AFDM线性调频还会在DAFT域响应中引入延迟-多普勒耦合，使得生成的DAFT域匹配得分曲面呈现出与归一化延迟和归一化多普勒轴不对齐的局部脊线。为解决这些问题，本文针对共址AFDM-ISAC感知架构研究角度与连续值延迟-多普勒参数的联合估计，从分数阶DAFT域响应构建变换域稀疏感知模型，基于该模型提出耦合坐标牛顿化正交匹配追踪（CC-NOMP）估计器。CC-NOMP利用AFDM引入的耦合坐标参数化主导局部脊线，结合耦合坐标牛顿细化、受保护更新、耦合对齐延迟细化及循环多目标细化，以估计角度、连续归一化延迟和归一化多普勒。本文还推导了确定性克拉美罗界和主导阶复杂度分析。采用连续值离网目标参数的仿真结果表明，与所考虑的基线方法相比，CC-NOMP在保持相当的角度估计精度的同时，实现了更低的延迟和多普勒误差底噪。
英文摘要
Affine frequency division multiplexing (AFDM) is a promising chirp-based multicarrier waveform for high-mobility integrated sensing and communication (ISAC). Accurate angle, delay, and Doppler estimation is essential for AFDM sensing. Since target delays and Doppler shifts are generally continuous-valued, representing them on a discrete delay--Doppler grid causes energy leakage and peak displacement in the discrete affine Fourier transform (DAFT) domain. The AFDM chirp also induces delay--Doppler coupling in the DAFT-domain response. The resulting DAFT-domain matching-score surface exhibits a local ridge that is not aligned with the normalized-delay and normalized-Doppler axes. To address these issues, this paper investigates joint estimation of angle and continuous-valued delay--Doppler parameters for a colocated AFDM-ISAC sensing architecture. A transform-domain sparse sensing model is formulated from the fractional DAFT-domain response. Based on this model, a coupled-coordinate Newtonized orthogonal matching pursuit (CC-NOMP) estimator is developed. CC-NOMP uses the AFDM-induced coupling coordinate to parameterize the dominant local ridge. It combines coupled-coordinate Newton refinement with safeguarded updates, coupling-aligned delay refinement, and cyclic multi-target refinement to estimate angle, continuous normalized delay, and normalized Doppler. A deterministic Cramér--Rao bound and a dominant-order complexity analysis are also derived. Simulation results with continuous-valued off-grid target parameters show that CC-NOMP achieves lower delay and Doppler error floors than the considered baselines while maintaining comparable angle-estimation accuracy.
