Indoor Measurements for RIS-Aided Communication: Practical Phase Shift Optimization, Coverage Enhancement, and Physical Layer Security

Abstract

Practical experiments are a crucial step to demonstrate the viability of reconfigurable intelligent surface (RIS)-empowered communication, which is one of the emerging technologies for nextgeneration networks. In this paper, we present practical measurements to demonstrate the RIS capabilities for enhancing signal coverage and providing physical layer security (PLS) in an indoor environment. First, extensive measurements are performed in a single-user deployment using iterative, grouping, and codebookbased phase shift optimization methods. The iterative method achieves approximately 10 dB performance improvement in the received signal power through careful adjustments of RIS phase configurations when the receiver is placed at different locations. The grouping method reduces the training time to find a suitable RIS configuration by sacrificing only a few dBs in the received signal power. Another set of experiments is conducted for a multi-user deployment to exhibit PLS, where the RIS is partitioned into two regions serving the intended and unintended users. The results demonstrate that the codebook method can effectively boost the secrecy capacity on the move without utilizing feedback other than the users' positions during the phase shift optimization process, while the iterative method requires a continuous feedback channel for the received signal powers.INDEX TERMS Reconfigurable intelligent surface, indoor measurements, physical layer security, 6G.