Barycenter Calibration With High Order Spectra of Windowed Delay-Doppler Signals for OTFS Based ISAC Systems

Integrated sensing and communication (ISAC) technology stands as a pivotal enabler for the sixth-generation mobile communication systems (6G) to enable high data rate communication while ensuring accurate target sensing. Orthogonal time-frequency space (OTFS) modulation has emerged as a promising candidate for ISAC, owing to its remarkable performance in doubly-selective channels. However, the sensing resolutions of OTFS are limited by the available bandwidth and frame time. In cases of insufficient delay and Doppler resolutions, the channel response is spread along delay and Doppler axes, resulting in substantial sensing inaccuracies. In our previous research, we introduced the amplitude barycenter calibration (A-BC) algorithm as an effort to improve the accuracy of parameter estimation, albeit without a strategic design for OTFS windows. In this work, we delve into the receive window design of the OTFS-ISAC system and develop a barycenter calibration algorithm that explores the high-order spectra (HOS) of the DD domain channels, called the HOS-BC algorithm. The simulation results indicate that the proposed algorithm not only improves the sensing resolution under the given bandwidth and frame time but also achieves a higher sensing accuracy at a low pilot signal-to-noise ratio compared with the A-BC algorithm.