Satellite networks are expected to support global connectivity and services via future integrated 6G space-terrestrial networks (STNs), as well as private non-geostationary satellite orbit (NGSO) constellations. In the past few years, many such private constellations have been launched or are in planning, e.g. SpaceX and OneWeb to name a few. In this article we take a closer look at the private constellations and give a comprehensive overview of their features. We then discuss major technical challenges resulting from their design and briefly review the recent literature addressing these challenges. Studying the emerging private constellations gives us useful insights for engineering the future STNs. To this end, we study the satellite mobility and evaluate the impact of two handover strategies on the space-to-ground link performance of four real private NGSO constellations. We show that the link capacity, delay, and handover rate vary across the constellations, so the optimal handover strategy depends on the constellation design. Consequently, the communications solutions of future STNs should be compliant with the constellation specifics, and the STN standards need to be flexible enough to support satellite operation with the large parameter space observed in the emerging private constellations.

中文翻译：

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走向全球和无限连接：私有 NGSO 卫星星座在未来天地网络中的作用

卫星网络有望通过未来的 6G 天地一体化网络 (STN) 以及私有非对地静止卫星轨道 (NGSO) 星座来支持全球连接和服务。在过去几年中，许多此类私人星座已经发射或正在规划中，例如 SpaceX 和 OneWeb 等等。在本文中，我们将仔细研究私有星座，并对其功能进行全面概述。然后，我们讨论了由它们的设计带来的主要技术挑战，并简要回顾了最近解决这些挑战的文献。研究新兴的私人星座为我们设计未来的 STN 提供了有用的见解。为此，我们研究卫星移动性并评估两种切换策略对四个真正私有 NGSO 星座的空对地链路性能的影响。我们表明链路容量、延迟和切换率在不同的星座中有所不同，因此最佳切换策略取决于星座设计。因此，未来 STN 的通信解决方案应符合星座特性，并且 STN 标准需要足够灵活，以支持在新兴私有星座中观察到的大参数空间的卫星操作。