A review on orthogonal time–frequency space modulation: State-of-art, hotspots and challenges

High-speed mobility communication is one of the challenging scenarios because of the rapidly changing channel involved. In light of this, the orthogonal time–frequency space (OTFS) modulation technique is explored for meeting the high-Doppler communication requirements. This paper provides a comprehensive overview of the critical application technologies and state-of-art approaches to OTFS modulation. First, we summarize the input–output expression relation under the different domains and the interference analysis under different waveforms, which is significant for the follow-up research. Secondly, the comparison between the existing modulation methods and OTFS modulation is discussed, which provides a reference for the improvement of the OTFS system. Next, detailed and exhaustive reviews of current OTFS-based hotpots are provided, including channel estimation, signal detection, etc. Further, the OTFS technologies are applied to specific application scenarios and the corresponding advantages are analyzed. Based on the above research status, we present our vision on the research trends and open issues, highlighting the opportunity for OTFS to be a promising next-generation candidate in future communication.