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.
Download