Gaussian Approximate Message Passing Detection of Orthogonal Time Frequency Space Modulation

Message passing (MP) aided detectors are designed for orthogonal time frequency space (OTFS) modulated system. We first characterize the transmit-receive relationship of our OTFS-modulated system in the delay-Doppler (DD) domain by designing a joint factor graph. Based on this joint factor graph, we then conceive a joint message passing aided (JMPA) detector. Furthermore, a novel low-complexity Gaussian approximate MP (GA-MP) detector is also conceived, which models the
a posteriori
probabilities propagated through the proposed joint factor graph by Gaussian distributions. Finally, we demonstrate that the proposed GA-MP detector outperforms the state-of-the-art MP detector by at least 1.5 dB at a bit error ratio (BER) of
$10^{-4}$
, while keeping the same complexity order.