RIS for 6G THz Networks: Advances in Modeling, Hardware, Signal Processing, and Standardization

The integration of reconfigurable intelligent surfaces (RIS) with terahertz (THz) communication is emerging as a transformative enabler for sixth-generation (6G) wireless networks, offering unprecedented capacity, spectrum utilization, and propagation control. This paper presents a comprehensive survey of RIS-assisted THz systems, with a focus on their design, performance, and integration challenges. A unified taxonomy is introduced, organizing the discussion into key domains: system architectures, channel modeling, hardware implementation, signal processing, and experimental validation. The paper consolidates diverse technological perspectives by examining metasurface hardware, wideband and near-field propagation modeling, and signal processing tailored to THz-specific impairments. It further reviews advanced methods for beamforming, phase error mitigation, and channel estimation under practical hardware constraints. Beyond performance optimization, the work explores deployment paradigms including indoor coverage, autonomous aerial vehicles (AAV)-based relays, and RIS integration in joint communication and sensing frameworks. A major contribution of this survey is the detailed mapping between RIS design strategies and 6G use cases, offering deployment guidelines and highlighting trade-offs across different tuning mechanisms, fabrication techniques, and control architectures. The paper also addresses open research challenges such as hardware scalability and real-time reconfigurability, ultimately serving as a foundational reference for researchers and engineers developing next-generation RIS-enabled THz communication systems.