Optimizing resource allocation in large communications satellite constellations

Abstract

Satellite communications are becoming a key technology for maintaining connectivity in a world driven by information. In the recent years, established players (such as SES and Telesat), as well as new competitors (such as SpaceX and Amazon) have proposed constellations able to serve hundreds of thousands of users, using thousands of satellites. While the orbital configuration of each design is different, the next generation of satellite communications relies on highly flexible digital payloads, such as phased array antennas, on-board processing, and adaptive modulation and coding schemes. Several approaches have been proposed to deal with the complexity of the added flexibilities at the spacecraft level. Nevertheless, how to address the flexibilities at the constellation level, critical to operate the next generation of systems, remains an open question. This dissertation develops optimization-based decision-making frameworks for designing and operating the next generation of communication constellations. In particular, novel methods for the Beam Shaping, User Grouping, Satellite Routing, Frequency Assignment, and Gateway Routing problems are proposed, tailored for large non-geostationary orbit constellations with satellites at multiple altitudes, referred to as hybrid systems. The methods leverage optimization to find an optimized set of decisions that maximize capacity and quality of service and minimize necessary ground infrastructure, all while avoiding interference. The proposed methods are then combined, tested, and evaluated using existing constellation designs under representative operational conditions with hundreds of thousands of users. The reported results prove that the proposed techniques are able to multiply by two the capacity of these systems, with favorable trade-offs in quality of service and necessary ground infrastructure. By testing existing designs, it is concluded that the number of satellites, as well as the link quality are the main drivers of performance. Furthermore, the analysis shows that hybrid constellations offer advantages over other designs, thanks to the combination of high quality links on low altitude satellites, and high coverage on high altitude satellites. Additionally, this dissertation studies the optimal proportion of satellites across various altitudes in hybrid LEO-MEO constellations. Results show that hybrid constellations are desirable when the cost of MEO and LEO satellites are comparable and interference is minimal.