Non-geostationary orbit constellation design for global connectivity

Abstract

In this chapter, we described relevant aspects of NGSO constellation design to achieve global connectivity. That is, to provide global service availability to ground terminals but also to ensure inter-satellite connectivity can be achieved along the constellation. We emphasised that the constellation geometry, the altitude of deployment and the density of satellites have a major impact on these and other relevant KPIs and compared the performance of three commercial designs: Kepler, OneWeb and the Starlink orbital shell at 550 km. We observed that, while the Starlink orbital shell has a greater number of satellites than the other two constellations, it still requires an additional orbital shell with nearly-polar orbital planes to provide connectivity near-polar regions. On the other hand, around 45 satellites from the OneWeb constellation are simultaneously within communication range in the near-polar regions, which may lead to waste of communication resources. Finally, the Kepler constellation may suffer from coverage holes near the Equator where, on average, less than one satellite is within communication range from the Earth's surface. To provide ubiquitous global coverage, a constellation similar to Kepler but with slightly larger number of orbital planes and satellites would be sufficient. Still, the NGSO constellations that aim to provide broadband services would benefit from further increasing the density of deployment, which would lead to greater data rates both in the inter- and intra-plane RF ISLs.Besides the impact of the main parameters for constellation design, we elaborated on the major challenges and technologies to achieve global connectivity at the physical layer for link establishment and routing. These arise from the distinctive characteristics of NGSO constellations, which are greatly dynamic yet fully predictable large-scale infrastructures.

Topics & Concepts