Joint Data-Aided Channel Estimation and Expectation Propagation Detection for Superimposed-Pilot-Based MIMO-OTFS Systems

In this paper, we design a novel joint receiver that iteratively performs channel estimation (CE) and symbol detection for channel-coded multi-user multiple-input multiple-output systems with orthogonal time frequency space modulation (MIMO-OTFS). In particular, we first propose a two-stage CE method based on a single superimposed pilot (SP) with inter-user interference canceling (ICCE). The delay-Doppler domain SP is used to estimate path delays, Doppler shifts, and other channel parameters. Then the detected user symbols are utilized to update the channel parameters with mitigating inter-user and multipath interferences. Second, we construct a joint CE and signal detection scheme based on the expectation propagation (EP) algorithm (EP-ICCE). We exploit the relationship between CE and symbol detection, refining the estimated channel matrix with the detected data symbols. Finally, simulation results shows the proposed EP-ICCE can achieve performance gains up to 2 dB over the conventional methods for the different MIMO and modulations.