Input-Output Relation Analysis of OTFS modulation over Rapid Linear Time-Variant Channels

Orthogonal time-frequency space (OTFS) is an emerging two-dimensional modulation technology, which converts the delay-Doppler domain symbols to the time domain signals through cascaded orthogonal transforms for transmission. OTFS has been verified to be effective against Doppler shift in quasistatic channels. However, the dynamic Doppler channels have not been paid attention to yet. Furthermore, the power of the received signal will change in some practical systems. A more general linear time-variant (LTV) channel is considered in this paper, where it is assumed that the signal propagating in each path has experienced a unique rapid amplitude fading and phase jitter. We derive the explicit input-output relation of OTFS in the delay-Doppler domain for the case of ideal pulse. Simulation results reveal that OTFS obtain time diversity gain and still outperforms orthogonal frequency-division multiplexing (OFDM) in rapid fading channels.