RIS-Enabled ISAC in 6G: Exploring the Role of Wave Domain Computing

In preparation for the 6th generation (6G) of communication networks, the adoption of high-frequency spectrum in millimeter wave (mm-wave) and terahertz (THz) frequencies is expected to improve communication bandwidth, bolster capacity, and decrease latency. However, challenges such as high propagation losses and the need for direct line-of-sight (LoS) connections between base station (BS) and user equipment (UE) pose significant barriers to the deployment of mm-wave-based systems. Within this context, integrated sensing and communication (ISAC) and reconfigurable intelligent surfaces (RISs) have recently emerged as the key enabling technologies for high-frequency systems deployment. However, the fundamental trade-off between sensing and communications in ISAC has already been introduced in the literature, unveiling the inevitable resource competition between sensing and communication tasks. This paper explores the use of orbital angular momentum (OAM) to distinguish the sensing signal, allowing for autonomous handling of sensing operations, distinct from the linearly polarized communication signals. This framework uses wave domain computing (WDC) to perform sensing tasks independently of the BS, thereby reducing the computational load on the BS and enhancing the response time and accuracy of sensing tasks. This is achieved by processing the extensive data generated by high-frequency networks directly on the physical layer of the metasurface. This approach facilitates efficient environment mapping and channel propagation path construction, addressing latency issues inherent in previous systems. We also review the associated pre-standardization and subsequent commercialization efforts for the RIS and ISAC technologies that are taking place with the aim of commercial deployments in future 6G networks by 2030.