Multicarrier ISAC Advances in waveform design, signal processing, and learning under nonidealities

This article addresses the topic of integrated sensing and communications (ISAC) in 5G and emerging 6G wireless networks. ISAC systems operate within shared, congested, or even contested spectrum, aiming to deliver high performance in both wireless communications and radio-frequency (RF) sensing. The expected benefits include more efficient utilization of spectrum, power, hardware (HW), and antenna resources. Focusing on multicarrier (MC) systems, which represent the most widely used communication waveforms, this article explores the codesign and optimization of waveforms alongside multiantenna transceiver signal processing for communications and both monostatic and bistatic sensing applications of ISAC. Moreover, techniques of high practical relevance for overcoming and even harnessing challenges posed by nonidealities in actual transceiver implementations are considered. To operate in highly dynamic radio environments and target scenarios, both model-based structured optimization and learning-based methodologies for ISAC systems are covered, assessing their adaptability and learning capabilities under real-world conditions. This article presents tradeoffs in communication-centric and radar-sensing-centric approaches, aiming for an optimized balance in the densely used spectrum.