From fifth-generation (5G) communication technology onward, non-terrestrial networks (NTNs) have emerged as a key component of future network architectures. Especially through the rise of low-Earth-orbit satellite constellations, NTNs enable a space Internet and present a paradigm shift in delivering reliable services to even the most remote regions on Earth. However, the extensive coverage and rapid movement of satellites pose unique challenges in user equipment access and inter-satellite transmission, impacting the quality of service and service continuity. This paper offers an in-depth review of NTN networking technologies in the context of six-generation (6G) mobile networks evolution, focusing on access management, satellite mobility, and hetero-network slicing. Building on this foundation and considering the latest trends in NTN development, we then present innovative perspectives on emerging challenges, including satellite beamforming, handover mechanisms, and service delivery. Lastly, we identify key open research areas and propose future directions to improve NTN performance and accelerate satellite Internet deployment.

中文翻译：

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面向 6G 的非地面网络：演进、机遇和未来方向

从第五代 （5G） 通信技术开始，非地面网络 （NTN） 已成为未来网络架构的关键组成部分。特别是通过低地球轨道卫星星座的兴起，NTN 实现了太空互联网，并实现了向地球上最偏远地区提供可靠服务的范式转变。然而，卫星的广泛覆盖和快速移动对用户设备接入和星间传输提出了独特的挑战，影响了服务质量和业务连续性。本文深入回顾了六代 （6G） 移动网络演进背景下的 NTN 网络技术，重点介绍了接入管理、卫星移动性和异质网络切片。在此基础上，我们考虑了 NTN 发展的最新趋势，然后就新出现的挑战提出了创新观点，包括卫星波束成形、切换机制和服务交付。最后，我们确定了关键的开放研究领域，并提出了提高 NTN 性能和加速卫星互联网部署的未来方向。