In this paper, we propose a distributed flexible coupler antenna (FCA) array to enhance communication performance with low hardware cost. At each FCA, there is one fixed-position active antenna and multiple passive couplers that can move within a designated region around the active antenna. Moreover, each FCA is equipped with a local processing unit (LPU). All LPUs exchange signals with a central processing unit (CPU) for joint signal processing. We study an FCA-aided multiuser multiple-input multiple-output (MIMO) system, where an FCA array base station (BS) is deployed to enhance the downlink communication between the BS and multiple single-antenna users. We formulate optimization problems to maximize the achievable sum rate of users by jointly optimizing the coupler positions and digital beamforming, subject to movement constraints on the coupler positions and the transmit power constraint. To address the resulting nonconvex optimization problem, the digital beamforming is expressed as a function of the FCA position vectors, which are then optimized using the proposed distributed coupler position optimization algorithm. Considering a structured time domain pattern of pilots and coupler positions, pilot-assisted centralized and distributed channel estimation algorithms are designed under the FCA array architecture. Simulation results demonstrate that the distributed FCA array achieves substantial rate gains over conventional benchmarks in multiuser systems without moving active antennas, and approaches the performance of fully active arrays while significantly reducing hardware cost and power consumption. Moreover, the proposed channel estimation algorithms outperform the benchmark schemes in terms of both pilot overhead and channel reconstruction accuracy.

翻译：本文提出了一种分布式柔性耦合天线（FCA）阵列，以低成本硬件提升通信性能。每个FCA包含一个固定位置的有源天线和多个可在有源天线周围指定区域内移动的无源耦合器。此外，每个FCA配备一个本地处理单元（LPU），所有LPU通过中央处理单元（CPU）进行信号交换以实现联合信号处理。我们研究了一种FCA辅助的多用户多输入多输出（MIMO）系统，其中部署FCA阵列基站（BS）以增强BS与多个单天线用户之间的下行链路通信。我们构建优化问题，通过联合优化耦合器位置和数字波束成形来最大化用户的可达和速率，同时满足耦合器位置的移动约束和发射功率约束。针对产生的非凸优化问题，将数字波束成形表示为FCA位置向量的函数，并利用所提出的分布式耦合器位置优化算法对其进行优化。考虑导频和耦合器位置的结构化时域模式，在FCA阵列架构下设计了导频辅助的集中式和分布式信道估计算法。仿真结果表明，在无移动有源天线的多用户系统中，分布式FCA阵列相较于传统基准方案实现了显著的速率增益，其性能接近全有源阵列，同时大幅降低了硬件成本和功耗。此外，所提出的信道估计算法在导频开销和信道重建精度方面均优于基准方案。