  The recently proposed orthogonal time frequency space (OTFS) modulation
technique was shown to provide significant error performance advantages over
orthogonal frequency division multiplexing (OFDM) in Doppler channels. In this
paper, we derive the explicit input-output relation describing OTFS modulation
and demodulation (mod/demod) for delay-Doppler channels. We analyze the
interferences and develop a novel low-complexity yet efficient message passing
(MP) algorithm for joint interference cancellation (IC) and symbol detection.
The proposed MP algorithm can effectively compensate for a wide range of
channel Doppler spreads.
