MIMO OTFS With Arbitrary Time-Frequency Allocation for Joint Radar and Communications

This paper proposes a novel waveform, namely non-uniform OTFS (NU-OTFS), for joint radar and communication applications (Radcom) in multi-user/MIMO scenarios. Based on orthogonal time frequency space (OTFS) modulation, the proposed waveform is realized by using a non-uniform symplectic finite Fourier transform (NU-SFFT) to generate non-overlapping quasi-arbitrary time-frequency representations of OTFS messages. Non-uniform sampling and sparse reconstruction algorithms within the compressed sensing framework are employed to avoid (self-)interference and enhance radar target parameter estimation. The performance of NU-OTFS and its corresponding receivers is evaluated through numerical simulations and measurements, and compared with state-of-the-art MU/MIMO Radcom OTFS system concepts. NU-OTFS allows for increased flexibility in time-frequency resource allocation and larger unambiguous radar parameter estimation while showing comparable performance to state-of-the-art OTFS multi-user communication implementations in realistic high-mobility channel conditions.