Spatial Modulation Based MIMO-OTFS Transmissions

Orthogonal time frequency space (OTFS) is a novel modulation scheme designed in delay-Doppler domain, which shows a strong Doppler-resilience over doubly-dispersive channels. The interaction between delay-Doppler channel and OTFS symbols allows a linear scaling of capacity with the multiple-input multiple-output (MIMO) order and simultaneously enables significant spectral efficiency improvements over traditional multicarrier modulations such as orthogonal frequency division multiplexing (OFDM). In this paper, we investigate the use of spatial modulation (SM) in MIMO-OTFS systems. With the structure of SM-OTFS, the overall spectral efficiency is increased by the base-two logarithm of the number of transmit antennas at least. We demonstrate that such an SM-OTFS system can achieve a higher spectral efficiency than space-time coded OTFS (STC-OTFS) while demand a lower detection complexity. Extensive simulations are carried out under various delay and Doppler conditions, our simulation results demonstrate significant performance gains of SM-OTFS compared to STC-OTFS with various MIMO settings.