Delay-Doppler Domain Multicarrier Modulation (DDMC) for Future Communications and Sensing

This article introduces delay-Doppler (DD) domain multicarrier modulation (DDMC), a promising new waveform for future wireless communications and sensing systems. We first provide an overview of the existing wireless communication waveforms and emerging use cases, followed by a discussion of doubly selective wireless channels in high-mobility environments. We then introduce the general form of multicarrier modulation, which covers the widely deployed orthogonal frequency division multiplexing (OFDM). Next we elaborate on DDMC solutions based on the delay-Doppler plane orthogonal pulse (DDOP). In particular, we introduce the orthogonal delay-Doppler division multiplexing (ODDM) waveform and show it simultaneously captures the features of orthogonal Doppler division multiplexing and orthogonal delay division multiplexing. We also highlight the properties and characteristics of ODDM, such as their basis functions, spectrum properties, implementations, pros and cons compared to alternative waveforms. We finally outline the standardization outlook as well as research challenges and opportunities related to DDMC.