Delay–Doppler Communications: Opportunities and Challenges

Delay-Doppler communications are considered a promising technique for high-mobility communication systems and integrated sensing and communication (ISAC) applications. This technique multiplexes information symbols in the delay-Doppler (DD) domain, where the channel’s sparse nature and characteristics can be easily captured. It guarantees superior performance against severe Doppler shifts, compared to traditional modulation techniques in the time-frequency (TF) domain. In this article, we present the basic principles of DD communications: DD channel response, signal basis functions, and the fundamental relation between TF and DD domains, and demonstrate the effectiveness of these principles in support of reliable communications and ISAC. We also compare transceiver architectures adopting DD versus TF modulation techniques, then discuss how the DD channel estimation can be mapped to scatters/targets sensing in ISAC. Finally, some emerging applications for high mobility communications and ISAC are discussed.