  Orthogonal time frequency space (OTFS) modulation has attracted substantial
attention recently due to its great potential of providing reliable
communications in high-mobility scenarios. In this paper, we propose a novel
hybrid signal detection algorithm for OTFS modulation. By characterizing the
input-output relationship of OTFS modulation, we derive the near-optimal
symbol-wise maximum a posteriori (MAP) detection algorithm for OTFS modulation,
which aims to extract the information of each transmitted symbol based on the
corresponding related received symbols. Furthermore, in order to reduce the
detection complexity, we propose a partitioning rule that separates the related
received symbols into two subsets for detecting each transmitted symbol,
according to the corresponding path gains. We then introduce a hybrid detection
algorithm to exploit the power discrepancy of each subset, where the MAP
detection is applied to the subset with larger channel gains, while the
parallel interference cancellation (PIC) detection is applied to the subset
with smaller channel gains. Simulation results show that the proposed
algorithms can not only approach the performance of the near-optimal
symbol-wise MAP algorithms, but also offer a substantial performance gain
compared with existing algorithms.
