  This paper considers the design of beamforming for orthogonal time frequency
space modulation assisted non-orthogonal multiple access (OTFS-NOMA) networks,
in which a high-mobility user is sharing the spectrum with multiple
low-mobility NOMA users. In particular, the beamforming design is formulated as
an optimization problem whose objective is to maximize the low-mobility NOMA
users' data rates while guaranteeing that the high-mobility user's targeted
data rate can be met. Both the cases with and without channel state information
errors are considered, where low-complexity solutions are developed by applying
successive convex approximation and semidefinite relaxation. Simulation results
are also provided to show that the use of the proposed beamforming schemes can
yield a significant performance gain over random beamforming.
