Reconfigurable intelligent surfaces (RISs) have drawn much attention recently for their appealing advantages in shaping wireless channels to improve the spectral and energy efficiencies of wireless communications. However, conventional fully-passive RISs generally suffer from the so-called ``multiplicative fading'' effect which thereby limits RISs' practicability and manufacturability. In this paper, a novel architecture of ``Reconfigurable Distributed Antennas and Reflecting Surfaces (RDARS)'' is first proposed to overcome this limitation from the ``multiplicative fading'' effect. Specifically, unlike existing active RIS variants, RDARS inherits the low-cost and low-energy-consumption benefits of fully-passive RISs by default configuring all the elements as passive to perform the reflection mode. On the other hand, based on the design of the additional direct-through state, any element of the RDARS can be dynamically programmed to connect with the base station (BS) via fibers and perform the connected mode as remote distributed antennas of the BS to receive signals. Consequently, a controllable trade-off between the reflection gain and the distribution gain can be achieved via RDARS at the BS. To unveil the system behavior of the RDARS-aided system, we analyze the received signal-to-noise ratio (SNR) under maximum ratio combining (MRC) at BS. Closed-form outage probability and ergodic achievable rate are also provided and are verified through extensive simulations. To demonstrate the superiority of the proposed RDARS, experiments are carried out using a prototype of RDARS with a total number of 256 elements which revealed extra 76% throughput improvement could be achieved by deploying RDARS with only three elements performing connected mode. This thus confirms the effectiveness of the proposed RDARS and envisions it as a promising candidate for future 6G wireless systems.

翻译：可重构智能表面（RIS）近期因其在塑造无线信道以提升通信频谱和能量效率方面的显著优势而备受关注。然而，传统的全无源RIS普遍存在所谓的“乘性衰落”效应，这限制了RIS的实用性和可制造性。本文首次提出一种名为“可重构分布式天线与反射表面（RDARS）”的新型架构，以克服“乘性衰落”效应带来的限制。具体而言，与现有的有源RIS变体不同，RDARS默认将所有元件配置为无源模式执行反射，从而继承了全无源RIS的低成本与低能耗优势。另一方面，基于额外设计的直通状态，RDARS中的任意元件均可通过光纤动态编程连接至基站（BS），以BS远程分布式天线的角色执行连接模式进行信号接收。由此，RDARS可在基站端实现反射增益与分布增益的可控权衡。为揭示RDARS辅助系统的行为特性，我们分析了基站采用最大比合并（MRC）时的接收信噪比（SNR）。同时推导了闭式中断概率和遍历可达速率，并通过大量仿真进行了验证。为展示所提RDARS的优越性，我们利用包含256个元件的RDARS原型开展实验，发现仅需将三个元件配置为连接模式，部署RDARS即可实现76%的吞吐量提升。这证实了所提RDARS的有效性，并预示其有望成为未来6G无线系统的候选方案。