  The designing of efficient signal detectors is important and yet challenge
for orthogonal time frequency space (OTFS) systems in high-mobility scenarios.
In this letter, we develop an efficient message feedback interference
cancellation aided unitary approximate message passing (denoted as UAMPMFIC)
iterative detector, where the latest feedback messages from variable nodes are
utilized for more reliable interference cancellation and performance
improvement. A fast recursive scheme is leveraged in the proposed UAMP-MFIC
detector to prevent complexity increasing. To further alleviate the
error-propagation and improve the receiver performance, we also develop the
bidirectional symbol detection structures, where Turbo UAMP-MFIC detector and
iterative weight UAMP-MFIC detector are proposed to efficiently fuse the
estimation results of forward and backward UAMP-MFIC detectors. The simulation
results are finally provided to demonstrate performance improvement of our
proposed detectors over existing detectors.
