Rendezvous of ISAC and NOMA: Progress and Prospects of Next-Generation Multiple Access

Integrated sensing and communication (ISAC) has become a key strategy, where a comprehensive framework transcends a single radar functionality by incorporating various types of sensors, thus facilitating richer interactions between multimodal sensing and communication. As efforts to standardize ISAC intensify, this article embarks on an exploration of the integration of multiple access schemes with ISAC, with a special focus on non-orthogonal multiple access (NOMA). Various dimensions of ISAC-NOMA are covered, comprehensively spanning deployment scenarios, integration challenges, and synergistic opportunities, alongside other wireless communication technologies. In particular, the article delves into intricate aspects such as interference management, user-target clustering, power allocation (PA), beamforming, and cooperative communication schemes. To provide further clarity to our discussions, we introduce two case studies supported by simulation findings: joint PA and user-target clustering, and simultaneous beam codebook design for sensing and communication. Furthermore, the article elaborates on the potential application of ISAC-NOMA in cutting-edge wireless paradigms such as cell-free massive multiple input multiple output networks, reconfigurable intelligent surfaces, non-terrestrial networks, and ambient backscatter communication.