OTFS Performance on Static Multipath Channels

Orthogonal time frequency space (OTFS) modulation is known to achieve excellent error performance in delay-Doppler channels. However, its performance over static multipath channels has never been fully investigated. In this letter, we show that, in static multipath channels, the system structure of OTFS is equivalent to the asymmetric orthogonal frequency division multiplexing (A-OFDM), a scheme proposed by Zhang et al., bridging between cyclic prefix single carrier (CPSC) and traditional OFDM. We derive a condition on the parameters of OTFS to guarantee that all the transmitted symbols experience uniform channel gains, as in CPSC. Finally, we apply a low-complexity message passing detection to OTFS/A-OFDM and show a significant performance improvement over ZF and MMSE detection originally proposed for A-OFDM.