  We consider the estimation of three-dimensional (3D) radar parameters,
namely, bearing or angle-of-arrival (AoA), delay or range, and Doppler shift
velocity, under a mono-static multiple-input multiple-output (MIMO) joint
communications and radar (JCR) system based on Orthogonal Time Frequency Space
(OTFS) signals. In particular, we propose a novel two-step algorithm to
estimate the three radar parameters sequentially, where the AoA is obtained
first, followed by the estimation of range and velocity via a reduced
two-dimensional (2D) grid maximum likelihood (ML) search in the delay-Doppler
(DD) domain. Besides the resulting lower complexity, the decoupling of AoA and
DD estimation enables the incorporation of an linear minimum mean square error
(LMMSE) procedure in the ML estimation of range and velocity, which are found
to significantly outperform State-of-the-Art (SotA) alternatives and approach
the fundamental limits of the Cram`er-Rao lower bound (CRLB) and search grid
resolution.
