This letter studies the performance of reconfigurable intelligent surface (RIS)-aided communications for a fluid antenna system (FAS) enabled receiver. Specifically, a fixed singleantenna base station (BS) transmits information through a RIS to a mobile user (MU) which is equipped with a planar fluid antenna in the absence of a direct link.We first analyze the spatial correlation structures among the positions (or ports) in the planar FAS, and then derive the joint distribution of the equivalent channel gain at the user by exploiting the central limit theorem. Furthermore, we obtain compact analytical expressions for the outage probability (OP) and delay outage rate (DOR). Numerical results illustrate that using FAS with only one activated port into the RIS-aided communication network can greatly enhance the performance, when compared to traditional antenna systems (TAS).

翻译：本文研究了可重构智能表面（RIS）辅助通信在配备流体天线系统（FAS）接收端中的性能。具体而言，一个固定单天线基站（BS）通过RIS向配备平面流体天线的移动用户（MU）传输信息，且不存在直射链路。我们首先分析了平面FAS中不同位置（或端口）之间的空间相关结构，然后利用中心极限定理推导了用户端等效信道增益的联合分布。此外，我们得到了中断概率（OP）和延迟中断率（DOR）的紧凑解析表达式。数值结果表明，与传统天线系统（TAS）相比，在RIS辅助通信网络中仅使用具有一个激活端口的FAS即可显著提升性能。