Reconfigurable Intelligent Surface Placement for Enhanced User Equipment Coverage

This paper addresses the coverage extension of User Equipment (UE) through the strategic placement of Reconfigurable Intelligent Surfaces (RISs). By considering Line-of-Sight (LOS) and surface orientation as key factors influencing RIS performance, we enhance existing models by incorporating 3D scenarios and more realistic wave propagation effects. Given that the RIS placement problem is NP-hard, we propose a low-complexity algorithm inspired by submodular optimization. Extensive numerical simulations in an urban environment demonstrate the scalability and effectiveness of the proposed approach, achieving coverage enhancements comparable to exhaustive search methods but with significantly reduced computational complexity. Furthermore, our results indicate that while RIS placement effectively extends LOS coverage, its primary benefit lies in basic coverage enhancement rather than delivering high data rates.