The research on Reconfigurable Intelligent Surfaces (RISs) has dominantly been focused on physical-layer aspects and analyses of the achievable adaptation of the wireless propagation environment. Compared to that, questions related to system-level integration of RISs have received less attention. We address this research gap by analyzing the necessary control/signaling operations that are necessary to integrate RIS as a new type of wireless infrastructure element. We build a general model for evaluating the impact of control operations along two dimensions: i) the allocated bandwidth of the control channels (in-band and out-of-band), and ii) the rate selection for the data channel (multiplexing or diversity). Specifically, the second dimension results in two generic transmission schemes, one based on channel estimation and the subsequent optimization of the RIS, while the other is based on sweeping through predefined RIS phase configurations. We analyze the communication performance in multiple setups built along these two dimensions. While necessarily simplified, our analysis reveals the basic trade-offs in RIS-assisted communication and the associated control operations. The main contribution of the paper is a methodology for systematic evaluation of the control overhead in RIS-aided networks, regardless of the specific control schemes used.

翻译：关于可重构智能表面（RIS）的研究主要集中在物理层层面以及无线传播环境自适应调节的可实现性分析上。相比之下，与RIS系统级集成相关的问题受到的关注较少。我们通过分析将RIS作为新型无线基础设施元件进行集成所需的必要控制/信令操作来填补这一研究空白。我们构建了一个通用模型，用于从两个维度评估控制操作的影响：i) 控制信道分配的带宽（带内与带外），以及ii) 数据信道的速率选择方案（多路复用或分集）。具体来说，第二个维度衍生出两种通用传输方案：一种基于信道估计及后续RIS优化，另一种基于对预定义RIS相位配置进行扫描。我们沿着这两个维度在多种配置场景下分析了通信性能。尽管进行了必要简化，我们的分析揭示了RIS辅助通信及其相关控制操作中的基本权衡。本文的主要贡献在于提出了一种系统评估RIS辅助网络中控制开销的方法，该方法不依赖于具体的控制方案。