Joint Association and Localization of Multiple Targets in an OTFS-Based Multistatic ISAC System

Orthogonal Time Frequency Space (OTFS) modulation is a promising candidate for Integrated Sensing and Communication (ISAC) in high-mobility vehicular scenarios. It offers reliable performance under challenging channel conditions. In this work, a vehicle-to-infrastructure OTFS-based multistatic system with single or multiple transmitters is considered. The cell towers communicate to the intended target vehicle(s) and simultaneously estimate the location, velocity, and bistatic radar cross-section of other targets in the scene. The multistatic setup enables the exploitation of spatial diversity, improving target detection accuracy. Pilot sequences are chosen to ensure both spectral efficiency, and accurate detection and parameter estimation using signals from multiple transmitters. The prime problem in multistatic sensing, which is the association of data between multiple targets, is solved using a joint association and localization approach using a sparse recovery framework. Simulations are performed with real-time system and signal parameters. Performance of the algorithm across different OTFS delay- Doppler grid sizes and target configurations is demonstrated. Performance and complexity comparisons with other existing data association approaches are also furnished. The results highlight better accuracy with lesser complexity, thus aiding in the practical implementation of an ISAC system. Furthermore, the extension of our algorithm to accommodate fractional delay and Doppler measurements is also described to achieve enhanced performance even with modest bandwidth requirements.