A Simple Detection and Identification Scheme For Reconfigurable Intelligent Surfaces

Reconfigurable intelligent surface (RIS)-empowered communication is one of the promising physical layer enabling technologies for the sixth generation (6G) wireless networks due to their unprecedented capabilities in shaping the wireless communication environment. RISs are modeled as passive objects that can not transmit or receive wireless signals. While the passiveness of these surfaces is a key advantage in terms of power consumption and implementation complexity, it limits their capability to interact with the other active components in the network. Specifically, unlike conventional base stations (BSs), which actively identify themselves to user equipment (UEs) by periodically sending pilot signals, RISs need to be detected from the UE side. This paper proposes a novel RIS identification (RIS- ID) scheme, enabling UEs to detect and uniquely identify RISs in their surrounding environment. Furthermore, to assess the proposed RIS-ID scheme, we propose two performance metrics: the false and miss detection probabilities. These probabilities are analytically derived and verified through computer simulations, revealing the effectiveness of the proposed RIS-ID scheme under different operating scenarios.

Plug-In RIS: A Novel Approach to Fully Passive Reconfigurable Intelligent Surfaces

This paper presents a promising design concept for reconfigurable intelligent surfaces (RISs), named plug-in RIS, wherein the RIS is plugged into an appropriate position in the environment, adjusted once according to the location of both base station and blocked region, and operates with fixed beams to enhance the system performance. The plug-in RIS is a novel system design, streamlining RIS-assisted millimeter-wave (mmWave) communication without requiring decoupling two parts of the end-to-end channel, traditional control signal transmission, and online RIS configuration. In plug-in RIS-aided transmission, the transmitter efficiently activates specific regions of the divided large RIS by employing hybrid beamforming techniques, each with predetermined phase adjustments tailored to reflect signals to desired user locations. This user-centric approach enhances connectivity and overall user experience by dynamically illuminating the targeted user based on location. By introducing plug-in RIS's theoretical framework, design principles, and performance evaluation, we demonstrate its potential to revolutionize mmWave communications in limited channel state information (CSI) scenarios. Simulation results illustrate that plug-in RIS provides power/cost-efficient solutions to overcome blockage in the mmWave communication system and a striking convergence in average bit error rate and achievable rate performance with traditional full CSI-enabled RIS solutions.