With the surging demand for ultra-reliable, low-latency, and ubiquitous connectivity in Sixth-Generation (6G) networks, Non-Terrestrial Networks (NTNs) emerge as a key complement to terrestrial networks by offering flexible access and global coverage. Despite the significant potential, NTNs still face critical challenges, including dynamic propagation environments, energy constraints, and dense interference. As a key 6G technology, Fluid Antennas (FAs) can reshape wireless channels by reconfiguring radiating elements within a limited space, such as their positions and rotations, to provide higher channel diversity and multiplexing gains. Compared to fixed-position antennas, FAs can present a promising integration path for NTNs to mitigate dynamic channel fading and optimize resource allocation. This paper provides a comprehensive review of FA-assisted NTNs. We begin with a brief overview of the classical structure and limitations of existing NTNs, the fundamentals and advantages of FAs, and the basic principles of FA-assisted NTNs. We then investigate the joint optimization solutions, detailing the adjustments of FA configurations, NTN platform motion modes, and resource allocations. We also discuss the combination with other emerging technologies and explore FA-assisted NTNs as a novel network architecture for intelligent function integrations. Furthermore, we delve into the physical layer security and covert communication in FA-assisted NTNs. Finally, we highlight the potential future directions to empower broader applications of FA-assisted NTNs.

翻译：随着第六代（6G）网络对超可靠、低延迟及泛在连接需求的激增，非陆地网络（NTNs）凭借其灵活接入与全球覆盖能力，成为地面网络的关键补充。尽管潜力巨大，NTNs仍面临动态传播环境、能量约束及密集干扰等严峻挑战。作为6G关键技术，流体天线（FAs）可通过在有限空间内重构辐射单元（如位置与旋转角度）重塑无线信道，从而提供更高的信道分集与复用增益。相较于固定位置天线，FAs为NTNs提供了极具前景的集成路径，可缓解动态信道衰落并优化资源分配。本文对FA辅助NTNs进行了全面综述。我们首先简要概述现有NTNs的经典结构与局限性、FAs的基础原理与优势，以及FA辅助NTNs的基本架构。继而深入探讨联合优化方案，详细阐述FA配置调整、NTN平台运动模式与资源分配的协同机制。同时分析其与其他新兴技术的融合，探索FA辅助NTNs作为智能功能集成的新型网络架构。此外，我们深入研究FA辅助NTNs的物理层安全与隐蔽通信技术。最后，展望赋能FA辅助NTNs更广泛应用的前沿发展方向。