Movable antenna (MA) array is a novel technology recently developed where positions of transmit/receive antennas can be flexibly adjusted in the specified region to reconfigure the wireless channel and achieve a higher capacity. In this letter, we, for the first time, investigate the MA array-assisted physical-layer security where the confidential information is transmitted from a MA array-enabled Alice to a single-antenna Bob, in the presence of multiple single-antenna and colluding eavesdroppers. We aim to maximize the achievable secrecy rate by jointly designing the transmit beamforming and positions of all antennas at Alice subject to the transmit power budget and specified regions for positions of all transmit antennas. The resulting problem is highly non-convex, for which the projected gradient ascent (PGA) and the alternating optimization methods are utilized to obtain a high-quality suboptimal solution. Simulation results demonstrate that since the additional spatial degree of freedom (DoF) can be fully exploited, the MA array significantly enhances the secrecy rate compared to the conventional fixed-position antenna (FPA) array.

翻译：可移动天线（MA）阵列是一种新兴技术，通过在指定区域内灵活调整发射/接收天线的位置，可重新配置无线信道并实现更高的容量。本文首次研究了可移动天线阵列辅助的物理层安全场景：在存在多个单天线且共谋的窃听者的情况下，由配备可移动天线阵列的Alice向单天线Bob传输机密信息。我们旨在通过联合设计Alice处的发射波束赋形与所有天线的位置，在满足发射功率预算及所有发射天线位置指定区域约束的前提下，最大化可达保密速率。该问题具有高度非凸性，我们采用投影梯度上升（PGA）与交替优化方法获取高质量次优解。仿真结果表明，由于可移动天线阵列能够充分挖掘额外的空间自由度（DoF），相较于传统固定位置天线（FPA）阵列，其显著提升了保密速率性能。