Delay-Doppler and Angular Domain 4D-Sparse CSI Estimation in OTFS Aided MIMO Systems

A convenient delay, Doppler and angular-(DDA) domain representation of the multiple-input multiple-output (MIMO) wireless channel is conceived for deriving end to relationship in delay-Doppler (DD)-domain orthogonal time frequency space (OTFS)-based communications. Subsequently, a time-domain pilot based model developed estimating DDA-domain state information (CSI) our MIMO OTFS system. The key differentiating feature CSI estimation derived its ability exploit 4-dimensional (4D)-sparsity arising DDA-domain, given limited number dominant scatterers. Furthermore, training overhead proposed framework low, placement quite flexible, necessitating no guard-interval. Finally, an matching pursuit (OMP) employed 4D-sparse acquisition, followed by Oracle minimum mean squared error (Oracle-MMSE) Bayesian Cramer-Rao lower bound (BCRLB). Our simulation results confirm improved performance attained over benchmarks.