In this paper, we propose a novel antenna architecture called movable antenna (MA) to improve the performance of wireless communication systems. Different from conventional fixed-position antennas (FPAs) that undergo random wireless channel variation, the MAs with the capability of flexible movement can be deployed at positions with more favorable channel conditions to achieve higher spatial diversity gains. To characterize the general multi-path channel in a given region or field where the MAs are deployed, a field-response model is developed by leveraging the amplitude, phase, and angle of arrival/angle of departure (AoA/AoD) information on each of the multiple channel paths under the far-field condition. Based on this model, we then analyze the maximum channel gain achieved by a single receive MA as compared to its FPA counterpart in both deterministic and stochastic channels. First, in the deterministic channel case, we show the periodic behavior of the multi-path channel gain in a given spatial field, which can be exploited for analyzing the maximum channel gain of the MA. Next, in the case of stochastic channels, the expected value of an upper bound on the maximum channel gain of the MA in an infinitely large receive region is derived for different numbers of channel paths. The approximate cumulative distribution function (CDF) for the maximum channel gain is also obtained in closed form, which is useful to evaluate the outage probability of the MA system. Moreover, our results reveal that higher performance gains by the MA over the FPA can be acquired when the number of channel paths increases due to more pronounced small-scale fading effects in the spatial domain. Numerical examples are presented which validate our analytical results and demonstrate that the MA system can reap considerable performance gains over the conventional FPA systems with/without antenna selection (AS).

翻译：本文提出一种名为可移动天线（MA）的新型天线架构，用于提升无线通信系统性能。与传统固定位置天线（FPA）经历随机无线信道变化不同，MA具备灵活移动能力，可部署在信道条件更优的位置以实现更高的空间分集增益。为刻画部署MA的给定区域或场中的通用多径信道，本文利用远场条件下每条多径信道的幅度、相位和到达角/离开角（AoA/AoD）信息，建立了一种场响应模型。基于该模型，我们进一步在确定性信道与随机信道中，分析单个接收MA相较于FPA所能达到的最大信道增益。首先，在确定性信道情形下，我们揭示了多径信道增益在给定空间场中的周期性行为，该特性可用于分析MA的最大信道增益。其次，在随机信道情形下，针对不同数量的信道径数，推导了无限大接收区域内MA最大信道增益上界的期望值。同时，以闭合形式近似获得了最大信道增益的累积分布函数（CDF），这有助于评估MA系统的中断概率。此外，研究结果表明：随着信道径数增加，空间域小尺度衰落效应更加显著，MA相较于FPA可获得更高的性能增益。数值示例验证了我们的分析结果，并表明MA系统相较于传统FPA系统（无论是否采用天线选择（AS））均能获得显著的性能提升。