Fundamental Limits for Dynamic Path Parameter Estimation in Asynchronous ISAC Systems

Passive sensing based on the dynamic path signal is a key technology in integrated sensing and communications (ISAC), where clock asynchronism between transceivers poses a crucial challenge. While various passive sensing applications have been realized by analyzing the dynamic channel path signal reflected from the target, how accurately the dynamic path signal may be recovered from the noisy asynchronous sensing signal is yet known. This work investigates the error bounds for estimating the dynamic path angle-of-arrival and complex gain sequence (CGS). We provide mathematical analyses and numerical simulations to characterize the dependence of the error bounds on system configurations and multipath conditions. Our results demonstrate the increase of the error bounds due to the asynchronism and reveal the blind zone in dynamic path CGS estimation.