Low Earth Orbit-Supported Non-Terrestrial Networks in 6G: Challenges and Future Research Directions
Sixth-generation (6G) communication systems require new network architectures capable of delivering global coverage, ultra-low latency, high data rates, and high reliability. However, terrestrial infrastructures remain insufficient in rural areas, oceans, mountainous regions, and disaster scenarios. For this reason, Non-Terrestrial Networks (NTNs), particularly those supported by Low Earth Orbit (LEO) satellite constellations, have emerged as a key enabler for the coverage and accessibility goals of 6G. Nevertheless, LEO-based NTN systems introduce major challenges, including high mobility, dynamic topology, frequent handovers, and complex resource management. This survey reviews LEO-supported NTN architectures, communication characteristics, and network management mechanisms for 6G, comparatively analyzes solutions for mobility, resource, beam, and routing management, and highlights current limitations as well as future research directions.