The synergy of metasurface-based holographic surfaces (HoloS) and reconfigurable intelligent surfaces (RIS) is considered a key aspect for future communication networks. However, the optimization of dynamic metasurfaces requires the use of numerical algorithms, for example, based on the singular value decomposition (SVD) and gradient descent methods, which are usually computationally intensive, especially when the number of elements is large. In this paper, we analyze low complexity designs for RIS-aided HoloS communication systems, in which the configurations of the HoloS transmitter and the RIS are given in a closed-form expression. We consider implementations based on diagonal and non-diagonal RISs. Over line-of-sight channels, we show that the proposed schemes provide performance that is close to that offered by complex numerical methods.

翻译：基于超表面的全息表面（HoloS）与可重构智能表面（RIS）的协同作用被认为是未来通信网络的关键方面。然而，动态超表面的优化需要使用数值算法，例如基于奇异值分解（SVD）和梯度下降法的方法，这些算法通常计算强度大，特别是在元素数量众多的情况下。本文分析了RIS辅助HoloS通信系统中的低复杂度设计方案，其中HoloS发射机和RIS的配置以闭式表达式给出。我们考虑了基于对角和非对角RIS的实现方案。在视距信道下，我们证明所提出的方案能够提供与复杂数值方法相近的性能。