UDNs: Enhancing Environmental Monitoring with ISAC and NOMA

Abstract

This chapter explores the integration of sensing and communication (ISAC) in ultra-dense wireless networks enhanced by non-orthogonal multiple access (NOMA), with a focus on enabling environmental awareness. As next-generation networks evolve to support massive connectivity, low latency, and intelligent decision-making, ISAC emerges as a key enabler by combining radar-like sensing with data transmission capabilities. One of the leading concepts in this competitive environment is the ultra-dense network (UDN), where the access nodes and/or the communication links per unit area are densified, with the aim of improving overall network performance. In ultra-dense network deployments, where interference and mobility pose significant challenges, NOMA offers an efficient solution to support multiple users’ tasks over shared resources. This chapter presents the fundamental principles of ISAC and NOMA, their synergies in dense deployments, and the role of joint design in improving network adaptability, energy efficiency, and situational awareness. Use cases such as smart cities, autonomous systems, and the internet of things (IoT) are discussed to illustrate the practical benefits. Challenges and future research directions are also outlined to guide ongoing developments in this emerging area. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2026.