IRS-Assisted High Mobility Communications using OTFS Modulation

Intelligent reflecting surface (IRS) has emerged as a promising technology for fifth generation (5G) and beyond wireless networks that are expected to support high mobility applications. Supporting IRS-assisted high mobility communications is nonetheless challenging due to the cascade of doubly-dispersive transmitter-IRS and IRS-receiver channels. To address this issue, we propose a multiple-input multiple-output orthogonal time frequency space (MIMO-OTFS) IRS-assisted communications system with MMSE detection. We present a general time-domain input-output relation, which is also applicable to single-input single-output OTFS (SISO-OTFS). We then design the IRS phase shifts to maximize the received signal-to-noise (SNR) for both SISO and MIMO cases. Numerical results show significantly lower error rates than orthogonal frequency division multiplexing (OFDM) IRS-assisted systems for terrestrial and non-terrestrial high-Doppler communications.