  We investigate a coded uplink non-orthogonal multiple access (NOMA)
configuration in which groups of co-channel users are modulated in accordance
with orthogonal time frequency space (OTFS). We take advantage of OTFS
characteristics to achieve NOMA spectrum sharing in the delay-Doppler domain
between stationary and mobile users. We develop an efficient iterative turbo
receiver based on the principle of successive interference cancellation (SIC)
to overcome the co-channel interference (CCI). We propose two turbo detector
algorithms: orthogonal approximate message passing with linear minimum mean
squared error (OAMP-LMMSE) and Gaussian approximate message passing with
expectation propagation (GAMP-EP). The interactive OAMP-LMMSE detector and
GAMP-EP detector are respectively assigned for the reception of the stationary
and mobile users. We analyze the convergence performance of our proposed
iterative SIC turbo receiver by utilizing a customized extrinsic information
transfer (EXIT) chart and simplify the corresponding detector algorithms to
further reduce receiver complexity. Our proposed iterative SIC turbo receiver
demonstrates performance improvement over existing receivers and robustness
against imperfect SIC process and channel state information uncertainty.
