Very Low Earth Orbit Telecommunications Constellations for Non-Terrestrial Network Connectivity

This work assesses the benefits and challenges for direct-to-cellular (DtC) telecommunications service delivery through satellite operation in Very Low Earth Orbits (VLEO), defined as those below 450 km. Deploying spacecraft in VLEO presents technical challenges due to interaction with the upper atmosphere, causing both orbital drag and atomic oxygen erosion. However technological developments have begun to open this regime for practical use and it may best be realised in the extension of terrestrial cellular services through space based non-terrestrial networks (NTN), providing ubiquitous connectivity to low power user handsets.
Modelling a representative network across a range of altitudes, user elevations, and antenna beamwidths it is shown that there are significant benefits for reduced latency and free space loss that will assist commercial handset use. Individual spacecraft will also be able to greatly increase the number of cells and subscribers hosted per satellite, whilst simultaneously reducing onboard payload power demands. For example, moving from 800 to 400 km whilst employing variable beamwidth antennae can deliver almost 3800 channels for the same payload power needed for under 1100 channels at the higher altitude, more than tripling capacity. Similarly, across the network spectral efficiency can be increased through greater frequency reuse, with order of magnitude level performance increases possible dependent on chosen configuration. These benefits however demand larger constellation sizes greatly influenced by reduced altitudes and increased user elevations. A service provider must weigh their desired performance against operational and commercial deployment capacity to find the most effective DtC NTN design solution.