This letter introduces the concept of fluid integrated reflecting and emitting surface (FIRES), which constitutes a new paradigm seamlessly integrating the flexibility of fluid-antenna systems (FASs) with the dual functionality of simultaneous transmitting and reflecting reconfigurable intelligent surfaces (STAR-RISs). The potential of the proposed metasurface structure is studied though an FIRES-enabled multicast system based on the energy splitting protocol. In this model, the FIRES is divided into non-overlapping subareas, each functioning as a 'fluid' element capable of concurrent reflection and transmission and changing its position of radiation within the subarea. In particular, we formulate an optimization problem for the design of the triple tunable features of the surface unit elements, which is solved via a tailored particle swarm optimization approach. Our results showcase that the proposed FIRES architecture significantly outperforms its conventional STAR-RIS counterpart.

翻译：本文提出流体集成反射与发射表面（FIRES）的概念，这一新范式将流体天线系统的灵活性与同时透射反射可重构智能表面的双功能特性无缝融合。通过基于能量分割协议的FIRES使能多播系统，研究了所提超表面结构的潜力。在该模型中，FIRES被划分为互不重叠的子区域，每个子区域作为可同时实现反射与传输功能的“流体”单元，并能在子区域内改变其辐射位置。特别地，我们针对表面单元三重可调特性的设计构建了优化问题，并通过定制的粒子群优化算法进行求解。结果表明，所提出的FIRES架构在性能上显著优于传统的STAR-RIS方案。