Movable antenna (MA) has emerged as a promising technology to enhance wireless communication performance by enabling the local movement of antennas at the transmitter (Tx) and/or receiver (Rx) for achieving more favorable channel conditions. As the existing studies on MA-aided wireless communications have mainly considered narrow-band transmission in flat fading channels, we investigate in this paper the MA-aided wideband communications employing orthogonal frequency division multiplexing (OFDM) in frequency-selective fading channels. Under the general multi-tap field-response channel model, the wireless channel variations in both space and frequency are characterized with different positions of the MAs. Unlike the narrow-band transmission where the optimal MA position at the Tx/Rx simply maximizes the single-tap channel amplitude, the MA position in the wideband case needs to balance the amplitudes and phases over multiple channel taps in order to maximize the OFDM transmission rate over multiple frequency subcarriers. First, we derive an upper bound on the OFDM achievable rate in closed form when the size of the Tx/Rx region for antenna movement is arbitrarily large. Next, we develop a parallel greedy ascent (PGA) algorithm to obtain locally optimal solutions to the MAs' positions for OFDM rate maximization subject to finite-size Tx/Rx regions. To reduce computational complexity, a simplified PGA algorithm is also provided to optimize the MAs' positions more efficiently. Simulation results demonstrate that the proposed PGA algorithms can approach the OFDM rate upper bound closely with the increase of Tx/Rx region sizes and outperform conventional systems with fixed-position antennas (FPAs) under the wideband channel setup.

翻译：移动天线技术通过允许发射端和/或接收端天线局部移动以获得更有利的信道条件，已成为增强无线通信性能的前沿技术。鉴于现有关于移动天线辅助无线通信的研究主要考虑平坦衰落信道中的窄带传输，本文研究了在频率选择性衰落信道中采用正交频分复用技术的移动天线辅助宽带通信。在通用多抽头场响应信道模型下，我们刻画了移动天线处于不同位置时信道在空间和频率上的联合变化特性。与窄带传输中发射端/接收端最优天线位置只需最大化单抽头信道幅度不同，宽带场景下的天线位置需权衡多个信道抽头的幅度与相位，以最大化多个频率子载波上的正交频分复用传输速率。首先，当发射端/接收端天线运动区域尺寸任意大时，我们推导出正交频分复用可达速率的闭式上界。其次，针对有限尺寸发射端/接收端区域，我们提出一种并行贪心上升算法以获得天线位置的局部最优解，从而最大化正交频分复用速率。为降低计算复杂度，进一步给出简化版并行贪心上升算法以更高效地优化天线位置。仿真结果表明，所提并行贪心上升算法在增加发射端/接收端区域尺寸时可紧密逼近正交频分复用速率上界，且在宽带信道场景下性能优于采用固定位置天线的传统系统。