Due to the ultra-dense constellation, efficient beam coverage and interference mitigation are crucial to low-earth orbit (LEO) satellite communication systems, while the conventional directional antennas and fixed-position antenna (FPA) arrays both have limited degrees of freedom (DoFs) in beamforming to adapt to the time-varying coverage requirement of terrestrial users. To address this challenge, we propose in this paper utilizing movable antenna (MA) arrays to enhance the satellite beam coverage and interference mitigation. Specifically, given the satellite orbit and the coverage requirement within a specific time interval, the antenna position vector (APV) and antenna weight vector (AWV) of the satellite-mounted MA array are jointly optimized over time to minimize the average signal leakage power to the interference area of the satellite, subject to the constraints of the minimum beamforming gain over the coverage area, the continuous movement of MAs, and the constant modulus of AWV. The corresponding continuous-time decision process for the APV and AWV is first transformed into a more tractable discrete-time optimization problem. Then, an alternating optimization (AO)-based algorithm is developed by iteratively optimizing the APV and AWV, where the successive convex approximation (SCA) technique is utilized to obtain locally optimal solutions during the iterations. Moreover, to further reduce the antenna movement overhead, a low-complexity MA scheme is proposed by using an optimized common APV over all time slots. Simulation results validate that the proposed MA array-aided beam coverage schemes can significantly decrease the interference leakage of the satellite compared to conventional FPA-based schemes, while the low-complexity MA scheme can achieve a performance comparable to the continuous-movement scheme.

翻译：针对超密集星座带来的挑战，波束高效覆盖与干扰抑制对低轨卫星通信系统至关重要，而传统定向天线和固定位置天线（FPA）阵列在波束赋形中自由度有限，难以适应地面用户时变的覆盖需求。为解决该问题，本文提出利用可移动天线（MA）阵列增强卫星波束覆盖与干扰抑制能力。具体而言，给定卫星轨道及特定时间间隔内的覆盖需求，通过联合优化星载MA阵列的天线位置向量（APV）和天线权重向量（AWV）来最小化卫星干扰区域的平均信号泄漏功率，同时满足覆盖区域最小波束赋形增益、MA连续运动及AWV恒模约束。首先将APV和AWV的连续时间决策过程转化为更易处理的离散时间优化问题，随后提出基于交替优化（AO）的算法：通过迭代优化APV与AWV，并利用逐次凸近似（SCA）技术获得迭代过程中的局部最优解。为进一步降低天线移动开销，提出一种低复杂度MA方案，在所有时隙采用优化后的公共APV。仿真结果表明，与基于FPA的传统方案相比，所提MA阵列辅助波束覆盖方案能显著降低卫星干扰泄漏，而低复杂度MA方案可获得与连续运动方案相近的性能。