Orchestration Framework for Open System Models with Autonomous RISs and Oblivious Base Stations

Autonomous reconfigurable intelligent surface (RIS) offers the potential to simplify deployment by reducing the need for real-time remote control between a base station (BS) and an RIS. However, we highlight two major challenges posed by autonomy. The first is implementation complexity, as autonomy requires hybrid RISs (HRISs) equipped with additional on-board hardware to monitor the propagation environment and conduct local channel estimation (CHEST), a process known as probing. The second challenge, termed probe distortion, reflects a form of the observer effect: during probing, an HRIS can inadvertently alter the propagation environment, potentially disrupting the operations of other communicating devices. While implementation complexity has been extensively studied, probe distortion remains largely unexplored. To further assess the potential of autonomous RISs, this paper comprehensively and pragmatically studies fundamental trade-offs posed by these challenges. We examine the robustness of an HRIS-assisted massive multiple-input multiple-output (mMIMO) system under minimal design choices that reflect the essential elements and stringent conditions, including (a) two extremes of implementation complexity realized through minimalist operational designs of two HRIS hardware architectures, and (b) an oblivious BS that fully embraces probe distortion. To make our analysis possible, we propose a physical-layer orchestration framework that aligns HRIS and mMIMO operations. We provide empirical evidence showing that autonomous RIS holds promise even under these strict conditions and propose new research directions, particularly for advancing the understanding of probe distortion.