Optimization of a LEO-PNT Constellation: Design Considerations and Open Challenges

As the satellite launch and manufacturing costs have become affordable, the industrial and academic interest in low-Earth orbit (LEO) satellites has increased in recent years. With this interest, the concept of LEO-based positioning, navigation, and timing (LEO-PNT) has also gained popularity as a complementary and/or standalone system in addition to the already existing Global Navigation Satellite Systems (GNSS). This article proposes a LEO constellation optimization methodology from the perspective of a LEO-PNT design, identifies and discusses the state-of-art of the LEO satellite constellation optimization approaches, introduces relevant performance- and feasibility-related metrics and parameters, and addresses key concepts and trade-offs that must be considered for any LEO-PNT constellation design. In addition, a case study for a LEO-PNT constellation optimization is presented, where we showcase the discussed trade-offs. We present optimization results obtained with the adaptive weighting algorithm “ADaW” applied to the Pareto-optimization algorithm nondominated sorting genetic algorithm III (“NSGA-III”). A detailed performance analysis is done for six relevant scenarios with varying receiver location properties, namely, by considering indoor/outdoor, rural/urban and line of sight/non–line of sight (NLOS) cases.