ISAC—A Survey on Its Layered Architecture, Technologies, Standardizations, Prototypes, and Testbeds

Integrated sensing and communication (ISAC) has emerged as a critical convergence of traditional communication and radar systems in terms of spectrum, software, and hardware platforms within a unified framework. This survey aims to provide a comprehensive overview on ISAC, beginning with its layered architecture and continuing to discuss about many key components, such as technologies, standardizations, prototypes and testbeds. ISAC architecture is divided into terminal and signal layer, resource layer, function layer, application layer, and computation layer, each of which is examined in detail to understand its roles and interplay within an ISAC ecosystem. Moving beyond the layered architecture, we explore various enabling technologies that empower ISAC, such as beamforming, antenna array design, etc.. Notably, this paper reviews emerging technologies such as reconfigurable intelligent surfaces (RIS), new materials, and innovative approach of software-defined radio/radar (SDR), as well as near-field (NF) ISAC. In addition, this survey covers the standardization efforts of international bodies, which are instrumental in shaping an evolutional trajectory of ISAC technologies. The prototypes and testbeds are presented to validate theoretical concepts and practical implementations of ISAC. Finally, the survey concludes with open issues and potential future directions for ISAC, providing a roadmap for its ongoing development and integration into next-generation networks.