Simultaneously Transmitting And Reflecting (STAR) IRS-Aided OTFS System

We develop a novel and comprehensive model for a simultaneously transmitting and reflecting (STAR) intelligent reflecting surface (IRS)-aided orthogonal time frequency space (OTFS) system. We propose two novel algorithms, namely, equal split STAR IRS phase programming and two step amplitude and phase programming, to reconfigure both the transmission and reflection coefficient of the passive elements in an STAR IRS-aided OTFS system and also analyze their computational complexities. We show that the second algorithm performs noticeably better than the first at marginally higher complexity. We also elucidate that an STAR IRS outperforms a conventional IRS in an OTFS system as the number of passive elements increases. Our work also suggests that 3-bit discrete phase shifts at the STAR IRS can achieve the same BER performance as an STAR IRS with infinite phase precision.