Leveraging channel state information from multiple Wi-Fi bands can improve delay resolution for ranging and sensing when a wide contiguous spectrum is unavailable. However, frequency gaps shape the delay response, introducing sidelobes and secondary peaks that can obscure closely spaced multipath components. This paper examines multipath delay estimation for Wi-Fi-compliant multiband configurations using channel state information (CSI). For a two-path model with unknown complex gains and delays, the Cramér-Rao lower bound (CRLB) for delay separation is derived and analyzed, confirming the benefit of larger frequency aperture, while revealing pronounced, separation-dependent oscillations driven by gap geometry and inter-path coupling. Given the local nature of Cramér-Rao lower bound, the delay response is analyzed next. In the single-path case, the combined subband responses determine how delay-domain sidelobe levels are distributed. The dominant peak spacing is set primarily by the separation between subband center frequencies. In the two-path case, increased aperture sharpens the mainlobe but also intensifies sidelobes and leakage, yielding competing peaks and, in some regimes, a dominant peak shifted from the true delay. Finally, a normalized leakage metric is introduced to predict problematic separations and to identify regimes where local Cramér-Rao lower bound analysis does not capture practical peak-leakage behavior in delay estimation.

翻译：当无法获得宽连续频谱时，利用多个Wi-Fi频段的信道状态信息可提升测距与感知的时延分辨率。然而，频率间隔会塑造时延响应，引入旁瓣与次级峰值，从而可能掩盖紧密间隔的多径分量。本文研究了基于Wi-Fi兼容多频段配置、利用信道状态信息（CSI）的多径时延估计问题。针对具有未知复增益与时延的双径模型，推导并分析了时延分离的克拉美-罗下界（CRLB），证实了更大频率孔径的益处，同时揭示了由间隔几何结构与路径间耦合驱动的显著且依赖分离度的振荡特性。鉴于克拉美-罗下界的局部性质，本文进一步分析了时延响应。在单径情况下，合并子带响应决定了时延域旁瓣电平的分布方式，其主导峰值间距主要由子带中心频率间的间隔决定。在双径情况下，增大的孔径虽能锐化主瓣，但同时加剧了旁瓣与泄漏，导致竞争性峰值的出现，并在某些区间产生偏离真实时延的主导峰值。最后，本文引入了一种归一化泄漏度量，用于预测存在问题的分离区间，并识别那些局部CRLB分析未能捕捉时延估计中实际峰值泄漏行为的区域。