OTFS and Delay-Doppler Domain Modulation: Signal Detection and Channel Estimation

It is envisioned that reliable communications in high-mobility scenarios at high carrier frequencies will play a vital role in the sixth-generation (6G) wireless networks. In these scenarios, the orthogonal frequency-division multiplexing (OFDM) modulation, which has been widely used in both the fourth-generation (4G) and the emerging fifth-generation (5G) wireless networks, is vulnerable to severe Doppler spread. Recently, the orthogonal time-frequency space (OTFS) modulation or general delay-Doppler domain modulation, which conveniently accommodates the channel dynamics via modulating information in the delay-Doppler domain, has emerged as a promising signal waveform for high-mobility wireless communications. In this chapter, we provide an overview of the OTFS waveform and discuss the most fundamental signal processing tasks in an OTFS system: signal detection and channel estimation. We also discuss a range of promising research opportunities and potential applications of delay-Doppler domain modulation in 6G wireless networks.