In this paper, we investigate reconfigurable pixel antenna (RPA)-based electronic movable antennas (REMAs) for multiuser communications. First, we model each REMA as an antenna characterized by a set of predefined and discrete selectable radiation positions within the radiating region. Considering the trade-off between performance and cost, we propose two types of REMA-based arrays: the partially-connected RPA-based electronic movable-antenna array (PC-REMAA) and fully-connected REMAA (FC-REMAA). Then, we formulate a multiuser sum-rate maximization problem subject to the power constraint and hardware constraints of the PC-REMAA or FC-REMAA. To solve this problem, we propose a two-step multiuser beamforming and antenna selection scheme. In the first step, we develop a two-loop joint beamforming and antenna selection (TL-JBAS) algorithm. In the second step, we apply the coordinate descent method to further enhance the solution of the TL-JBAS algorithm. In addition, we revisit mechanical movable antennas (MMAs) to establish a benchmark for evaluating the performance of REMA-enabled multiuser communications, where MMAs can continuously adjust the positions within the transmission region. We also formulate a sum-rate maximization problem for MMA-enabled multiuser communications and propose an alternating beamforming and antenna position optimization scheme to solve it. Finally, we analyze the performance gap between REMAs and MMAs. Based on Fourier analysis, we derive the maximum power loss of REMAs compared to MMAs for any given position interval. Specifically, we show that the REMA incurs a maximum power loss of only 3.25\% compared to the MMA when the position interval is set to one-tenth of the wavelength. Simulation results demonstrate the effectiveness of the proposed methods.

翻译：本文研究基于可重构像素天线的电子可移动天线用于多用户通信。首先，我们将每个电子可移动天线建模为一种天线，其特征是在辐射区域内具有一组预定义且离散的可选辐射位置。考虑到性能与成本之间的权衡，我们提出两种基于电子可移动天线的阵列结构：部分连接的可重构像素天线电子可移动天线阵列与全连接电子可移动天线阵列。随后，我们构建了一个在部分连接或全连接电子可移动天线阵列的功率约束与硬件约束下的多用户和速率最大化问题。为解决该问题，我们提出了一种两步式多用户波束成形与天线选择方案。第一步，我们开发了一种双循环联合波束成形与天线选择算法。第二步，我们应用坐标下降法进一步优化该算法的解。此外，我们重新审视机械可移动天线，以建立评估电子可移动天线支持的多用户通信性能的基准，其中机械可移动天线可在传输区域内连续调整位置。我们也为机械可移动天线支持的多用户通信构建了一个和速率最大化问题，并提出一种交替波束成形与天线位置优化方案进行求解。最后，我们分析了电子可移动天线与机械可移动天线之间的性能差距。基于傅里叶分析，我们推导出对于任意给定位置间隔，电子可移动天线相较于机械可移动天线的最大功率损耗。具体而言，我们证明当位置间隔设置为波长的十分之一时，电子可移动天线相比机械可移动天线的最大功率损耗仅为3.25%。仿真结果验证了所提方法的有效性。