Reconfigurable Intelligent Surfaces (RISs) are expected to play a pivotal role in future indoor ultra high data rate wireless communications as well as highly accurate three-dimensional localization and sensing, mainly due to their capability to provide flexible, cost- and power-efficient coverage extension, even under blockage conditions. However, when considering beyond millimeter wave frequencies where there exists GHz-level available bandwidth, realistic models of indoor RIS-parameterized channels verified by field-trial measurements are unavailable. In this article, we first present and characterize three RIS prototypes with 100×100 unit cells of half-wavelength inter-cell spacing, which were optimized to offer a specific non-specular reflection with 1-, 2-, and 3-bit phase quantization at 304 GHz. The designed static RISs were considered in an indoor channel measurement campaign carried out with a 304 GHz channel sounder. Channel measurements for two setups, one focusing on the transmitter-RIS-receiver path gain and the other on the angular spread of multipath components, are presented and compared with both state-of-the-art theoretical models as well as full-wave simulation results. The article is concluded with a list of challenges and research directions for RIS design and modeling of RIS-parameterized channels at THz frequencies.
@article{arxiv.2412.07359,
title = {Characterization of Indoor RIS-Assisted Channels at 304 GHz: Experimental Measurements, Challenges, and Future Directions},
author = {George C. Alexandropoulos and Bo Kum Jung and Panagiotis Gavriilidis and Sérgio Matos and Lorenz H. W. Loeser and Varvara Elesina and Antonio Clemente and Raffaele D'Errico and Luís M. Pessoa and Thomas Kürner},
journal= {arXiv preprint arXiv:2412.07359},
year = {2024}
}