FARIS: Fluid-Active-RIS

In this paper, we introduce a fluid-active reconfigurable intelligent surface (FARIS) that combines fluid-based port repositioning with per-element active amplification to enhance the performance of 6G network. To characterize the performance, we formulate an ergodic-rate maximization problem that jointly optimizes both the active amplification-reflection vector and the discrete selection of fluid active elements under practical hardware constraints. The problem is addressed via an alternating optimization (AO) framework, which progressively improves the rate. Complexity and convergence analyses that follow furnish deeper insight into the algorithmic operation and performance enhancement. Numerical results confirm that the proposed FARIS with AO framework consistently outperforms conventional FRIS/ARIS, delivering higher rates across diverse environments, often even when using fewer active elements or a smaller physical aperture.