6G Early Prototypes with Sub-THz Links and RIS

Abstract

The sixth generation (6G) of wireless communication is envisioned to deliver ultra-high-speed, lowlatency, and ubiquitous connectivity. Central to this vision are sub-terahertz (sub-THz) links and Reconfigurable Intelligent Surfaces (RIS)—technologies that can overcome inherent propagation challenges of the THz band. This paper examines initial prototypes and theoretical developments of sub-THz communication augmented by RIS, presenting an integrated perspective on hardware feasibility and performance benefits. RIS prototypes at lower bands have demonstrated substantial gains. A 5.8 GHz RIS with over 1,000 elements achieved up to 27 dB power gain in practical indoor and outdoor scenarios arXiv. Simultaneously, emerging studies on THzrange RIS mechanisms have analyzed a range of tuning technologies—including CMOS transistors, graphene, phasechange materials, and MEMS—for dynamic beam steering and amplitude control in 6G sub-THz links MDPIEurope PMC. Moreover, hybrid beamforming methods leveraging RIS-assisted multi-hop links powered by deep reinforcement learning (DRL) have shown potential to expand THz coverage by approximately 50% in simulations arXiv. Additionally, the European research project 6G-TERARIS explores stochastic geometry-based modeling and RIS deployment strategies for sub-THz carrier frequencies aiming to guide novel ultra-massive MIMO architectures CORDIS. Through a structured methodology combining prototype analysis, simulation evaluation, and system modeling, the paper discusses the advantages of improved signal coverage, energy-efficient deployment, and cost-effective reconfigurability. Limitations include present fabrication constraints, limited real-world prototype demonstration at THz frequencies, and challenges in hardware integration. In conclusion, early RIS prototypes at microwave bands and theoretical frameworks for THz RIS integration illustrate the promise of sub-THz links in 6G systems. Future work should focus on hardware realization of THz RIS, large-scale field trials, and integrated design of RIS-enabled sub-THz networks.