The cell-free networking paradigm constitutes a revolutionary architecture for future generations of wireless networks, which has been recently considered in synergy with Reconfigurable Intelligent Surfaces (RISs), a promising physical-layer technology for signal propagation programmability. In this paper, we focus on wideband cell-free multi-RIS-empowered Multiple-Input Single-Output (MISO) systems and present a decentralized cooperative active and passive beamforming scheme, aiming to provide an efficient alternative towards the cooperation overhead of available centralized schemes depending on central processing unit. Considering imperfect channel information availability and realistic frequency selectivity behavior of each RIS's element response, we devise a distributed optimization approach based on consensus updates for the RISs' phase configurations. Our simulation results showcase that the proposed distributed design is superior to centralized schemes that are based on various Lorentzian-type wideband modeling approaches for the RISs.

翻译：无小区网络范式构成了未来无线网络代际的革命性架构，近期已与可重构智能表面这一实现信号传播可编程性的前景广阔的物理层技术协同考虑。本文聚焦于宽带无小区多RIS赋能的MISO系统，提出一种去中心化的协作式主动与被动波束成形方案，旨在为依赖中央处理单元的现有集中式方案所面临的高协作开销提供高效替代方案。考虑到不完善的信道信息可用性及各RIS单元响应的实际频率选择性特性，我们基于共识更新机制为RIS相位配置设计了一种分布式优化方法。仿真结果表明，所提出的分布式设计优于基于多种洛伦兹型宽带RIS建模方法的集中式方案。