Hybrid Sensing Strategy Using Pilot and Frame for OTFS-Based ISAC Systems

Orthogonal Time Frequency Space (OTFS) modulation has emerged as a promising candidate for Integrated Sensing and Communication (ISAC) in high-mobility environments. This paper presents a hybrid sensing strategy that jointly leverages both embedded pilot signals and the full OTFS frame to enhance sensing accuracy and resource efficiency. Specifically, the proposed algorithm is mainly divided into two stages. In the first stage, a matched filter is applied to the pilot-only response to yield a coarse estimate of the delay and Doppler shifts. In the second stage, this initial estimate is refined via quasi-Newton iterative search using the full-frame signal in the delay-Doppler (DD) domain. The pilot facilitates fast localization of the target region, while the frame enables fine-grained Doppler refinement. The proposed hybrid method can significantly achieve better sensing performance compared to the existing two dimensional (2D) correlation algorithm. Simulation results confirm the effectiveness of this hybrid sensing approach for practical OTFS-ISAC implementations.