We propose a new reconfigurable intelligent surface (RIS) structure, referred to as interconnected RIS (I-RIS), which allows the RIS elements to be interconnected and share the incident signals using simple binary radio frequency (RF) switches and mix them into the reflecting signals. This structure enables multi-user scaling and requires fewer elements (i.e., a compact structure) compared to standard RIS (S-RIS), which assumes no interconnection between the elements. The I-RIS compact design makes it practical for deployment on space-limited nodes, e.g., unmanned aerial vehicles (UAVs). Hence, in this work, we propose a beamforming design based on I-RIS in a multi-user network, where we use binary RF switches as RIS elements. We show that our switch-based I-RIS offers a higher gain compared to an S-RIS using phase shifters. Finally, we introduce two optimization methods, sigmoid filled function (SFF) and semi-definite binary optimization (SBO), to optimize the RIS elements and evaluate their performance in terms of sum-rate and complexity.

翻译：本文提出了一种新型可重构智能表面（RIS）结构，称为互连RIS（I-RIS）。该结构通过简单的二进制射频（RF）开关实现RIS单元间的互连，使入射信号能够在单元间共享并混合至反射信号中。相较于假设单元间无互连的标准RIS（S-RIS），I-RIS结构能够实现多用户扩展，同时所需单元数量更少（即结构更紧凑）。这种紧凑设计使得I-RIS可部署于空间受限的节点，例如无人机（UAV）。因此，本研究提出了一种基于I-RIS的多用户网络波束成形设计方案，其中采用二进制RF开关作为RIS单元。研究表明，与使用移相器的S-RIS相比，基于开关的I-RIS能提供更高的增益。最后，本文引入两种优化方法——S型填充函数（SFF）和半定二进制优化（SBO）——对RIS单元进行优化，并从和速率与复杂度两个维度评估其性能。