Movable antenna (MA) 是一种极具前景的技术，它通过在收发机的给定有限区域内改变天线位置来创造更有利的信道条件，从而提升无线通信性能。本文研究了 MA 增强的多址接入信道（MAC），该信道用于从每个配备单根 MA 的多个用户到配备固定位置天线（FPA）阵列的基站（BS）的上行传输。我们采用基于场响应的信道模型来表征 BS 天线阵列与每个用户具有灵活位置的 MA 之间的多径信道。为了评估 MA 提供的 MAC 性能增益，我们构建了一个优化问题，旨在最小化用户的总发射功率，同时满足每个用户的最小可达速率要求，其中 MA 的位置、用户的发射功率以及 BS 的接收合并矩阵被联合优化。为了解决这一涉及复杂耦合变量的非凸优化问题，我们分别开发了基于零强迫（ZF）和最小均方误差（MMSE）合并方法的两种算法。具体而言，对于每种算法，BS 的合并矩阵和用户的总发射功率均被表示为 MA 位置向量的函数，随后利用所提出的多方向下降（MDD）框架对其进行优化。结果表明，所提出的基于 ZF 和基于 MMSE 的 MDD 算法能够以较低的计算复杂度收敛到高质量的次优解。仿真结果证明，与在完美和不完美的场响应信息下均采用天线选择的传统 FPA 系统相比，所提出的 MA 增强多址接入系统解决方案能够显著降低用户的总发射功率。
英文摘要：
Movable antenna (MA) is a promising technology to improve wireless communication performance by varying the antenna position in a given finite area at the transceivers to create more favorable channel conditions. In this paper, we investigate the MA-enhanced multiple-access channel (MAC) for the uplink transmission from multiple users each equipped with a single MA to a base station (BS) with a fixed-position antenna (FPA) array. A field-response based channel model is used to characterize the multi-path channel between the antenna array of the BS and each user's MA with a flexible position. To evaluate the MAC performance gain provided by MAs, we formulate an optimization problem for minimizing the total transmit power of users, subject to a minimum-achievable-rate requirement for each user, where the positions of MAs and the transmit powers of users, as well as the receive combining matrix of the BS are jointly optimized. To solve this non-convex optimization problem involving intricately coupled variables, we develop two algorithms based on zero-forcing (ZF) and minimum mean square error (MMSE) combining methods, respectively. Specifically, for each algorithm, the combining matrix of the BS and the total transmit power of users are expressed as a function of the MAs' position vectors, which are then optimized by using the proposed multi-directional descent (MDD) framework. It is shown that the proposed ZF-based and MMSE-based MDD algorithms can converge to high-quality suboptimal solutions with low computational complexities. Simulation results demonstrate that the proposed solutions for MA-enhanced multiple access systems can significantly decrease the total transmit power of users as compared to conventional FPA systems employing antenna selection under both perfect and imperfect field-response information.
Does Movable Antenna Present A Dual-edged Nature? From the Perspective of Physical Layer Security: A Joint Design of Fixed-position Antenna and Movable Antenna
Suppressing Beam Squint Effect For Near-Field Wideband Communication Through Movable Antennas
Shanghai Jiao Tong University（上海交通大学）；Dalian University of Technology（大连理工大学）；Tongji University（同济大学）；Shenzhen Research Institute of Big Data（深圳大数据研究院）
