OTFS-Based ISAC with Reduced Sampling Rate: Algorithm and Experiment

Integrated Sensing and Communication (ISAC) is emerging as a promising technique for future communication and radar systems. A high-resolution estimation is essential for radar applications, necessitating large bandwidth. However, a large bandwidth requires dedicated Analog-to-Digital Converters (ADCs) with high sampling rates and substantial storage capacities to fully capture waveform signals, making it prohibitively expensive and impractical for many commercial systems. Therefore, it is crucial to develop methods for radar estimation with reduced sampling rates. In this paper, we propose a method to achieve accurate radar estimations for Orthogonal Time Frequency Space (OTFS)-based ISAC systems with reduced sampling rates. Specifically, we design pilot symbols in the delay-Doppler domain to ensure that the pilots in the time-frequency (TF) domain occupy specific subcarriers, leaving the remaining ones inactive. By leveraging the aliasing effect caused by undersampling, the receiver captures all aliased active subcarrier information with a reduced ADC sampling rate, enabling the restoration of the original delay-Doppler signal. Finally, we introduce an iterative estimation and interference cancellation algorithm to mitigate the interference from data symbols and provide accurate estimation results. Extensive experiments demonstrate that our method effectively reduces the sampling rate without compromising the ISAC performance.