Review of the Reconfigurable Intelligent Surfaces in Smart Cities: Opportunities, Challenges, and Applications

Abstract

This survey synthesises state-of-the-art advancements in Reconfigurable Intelligent Surfaces (RIS) and their transformation in urban wireless networks, focusing on addressing the challenges inherent to 5 G/mmWave communications. The authors begin by evaluating path loss, blockage, and interference in dense urban environments. The analysis comprehensively represents various RIS design, including phase-shift optimisation, material selection, and control mechanisms based on PIN and varactor diodes, whereas considering integration challenges such as scalability, energy efficiency, and real-world deployment constraints. The authors present an in-depth case study of RIS implementation in a smart city mmWave scenario, utilising both analytical modelling and simulation experiments to quantify performance improvements in beam steering and network reliability. This study highlights the potential of RIS to mitigate traditional propagation limitations and provide directions for future research, standardisation efforts, and the evolution of 6G wireless networks.