A Survey on Integrated Sensing and Communication With Intelligent Metasurfaces: Trends, Challenges, and Opportunities

The emergence of technologies requiring high data rates and precise sensing information, such as autonomous vehicles and internet of things devices, has driven the growing popularity of integrated sensing and communication (ISAC). ISAC provides an efficient framework where communication and sensing occur simultaneously or in coordination, features two integration levels. First, radio-communications coexistence (RCC), which involves separate hardware, waveforms, and signal processing for communication and radar systems, but in a shared and coordinated spectrum use. Second, dual-function radar-communications (DFRC), which uses the same hardware, waveform, and other key racecourses for both functions. At the architectural level, intelligent metasurfaces are a key enabler for sixth-generation (6G) wireless communication due to their energy-efficient control of the propagation environment. Metasurfaces’ ability to enhance both communication and sensing has led to numerous studies on metasurface-assisted ISAC performance gains. Additionally, some ISAC frameworks address limitations of reconfigurable intelligent surfaces (RIS) in communications, making their integration mutually beneficial. This survey reviews metasurface-assisted ISAC literature, outlining challenges and opportunities. We begin with background on ISAC and metasurfaces fundamentals. The core sections summarize state-of-the-art studies, focusing on metasurfaces as separate entities between transmitter and receiver, i.e., as RISs, emphasizing RCC and DFRC operations. We also explore holographic ISAC. Each category includes challenges, opportunities, and future research directions.