2D Pilot Signal Design for OTFS-ISAC Systems

This paper explores the design of two-dimensional (2D) sparse pilot signals for Orthogonal Time Frequency Space (OTFS)-based Integrated Sensing And Communication (ISAC) systems. In such dual-purpose systems, pilot design plays a critical role in enabling both highly accurate channel estimation and efficient data communication. Channel estimation in the Delay-Doppler (DD) domain is highly dependent on the OTFS-DD frame structure, which impacts pilot placement and performance. We propose a novel 2D pilot design framework in the DD domain to create a sparse pilot matrix superimposed on the OTFS data frame. This framework formulates an optimization problem that minimizes Ambiguity Function (AF) sidelobes for improved sensing accuracy, and reduces pilot-data or pilot-pilot interference, overhead, and Peak to-average Power Ratio (PAPR) for better communication performance. Simulation results demonstrate the designed pilot signal satisfactory sensing performance while effectively balancing communication requirements, such as higher Spectral Efficiency (SE), and lower PAPR and interference.