Practical Challenges for Reliable RIS Deployment in Heterogeneous Multi-Operator Multi-Band Networks

Reconfigurable intelligent surfaces (RISs) have been introduced as arrays of nearly passive elements with software-tunable electromagnetic properties to dynamically manipulate the reflection/transmission of radio signals. Research in this area focuses on two applications, namely user-assist RIS aiming to tune the RIS to enhance the quality-of-service (QoS) of target users and malicious RIS aiming for an attacker to degrade the QoS at victim receivers through generating intended destructive interference. While both user-assist and malicious RIS applications have been explored extensively, the impact of RIS deployments on imposing unintended interference on various wireless user-equipments (UEs) remains underexplored. This article investigates the challenges of integrating RISs into multi-carrier, multi-user, and multi-operator wireless networks. We discuss how RIS deployments intended to benefit specific users can negatively impact other users served at various carrier frequencies through different network operators. While not an ideal solution, we discuss how ultra-narrowband metasurfaces can be incorporated into the manufacturing of RISs to mitigate some challenges of RIS deployment in wireless networks. We also present a simulation scenario to illustrate practical challenges associated with the deployment of RISs in shared public environments.