Air-Ground OTFS in-Band-Full-Duplex Integrated Sensing and Communications Systems

In beyond fifth-generation and sixth-generation, integrated sensing and communications (ISAC) will benefit many aspects, especially for vehicle-to-everything (V2X) communications. However, the high mobility feature of the moving vehicles distorts the performance of the well-known orthogonal frequency division multiplexing (OFDM) modulation, which encourages the emergence of the orthogonal time frequency space (OTFS) modulation. Adopting the subarray-based hybrid beamforming, by leveraging the advantage of the strong line-of-sight link given by the air-ground channel, we design an unmanned aerial vehicle (UAV) supported in-band-full-duplex (IBFD)-OTFS-ISAC system operating in the frequency range 2 band for V2X communications, where the motion parameters are tracked by the maximum log-likelihood (ML) estimator. Simulation shows that the ML estimator can satisfactorily track the vehicles with similar accuracy under both OFDM and OTFS-based IBFD-ISAC systems. OTFS modulation outperforms the OFDM regarding spectral efficiency due to less cyclic prefix overhead paid.