Coverage enhancement for 6G satellite-terrestrial integrated networks: performance metrics, constellation configuration and resource allocation

Since the base station-centric wireless coverage mode of 5G is difficult to support future stereoscopic global wireless coverage demands, the future infrastructure of 6G satellite-terrestrial integrated network (STIN) with mega constellations will extend from the terrestrial network to the integrated satellite-terrestrial architecture, so as to realize the improvement of wireless coverage capability through extending the spatial and temporal coverage. However, what are the specific quantitative indicators of wireless coverage? What is the basis for the effect of network configuration with mega constellations on coverage performance? How to form non-uniform coverage through intelligent resource scheduling to match non-uniformly distributed service requirements in the future 6G STIN? The aforementioned unknown fundamental problems have become a bottleneck restricting the further development of coverage expansion in the future 6G STIN. In this paper, we start with the evolution route of wireless coverage and the vision of 6G coverage and propose coverage performance evaluation metrics in 6G STINs from the perspective of signal coverage, capacity coverage, and service coverage. Furthermore, we investigate the relationship between coverage structure and coverage capability in 6G STINs with mega constellations and we find network structure characteristics suitable for 6G non-uniform service requirements, thus guiding constellation design in 6G STINs by analyzing and comparing the coverage performance of several typical mega constellations. Afterwards, we explore the application of artificial intelligence in resource collaboration to provide technology reference to enhance coverage capability for dynamic 6G service demands. Finally, we analyze possible technical challenges for improving service coverage performance in 6G STINs to provide researchers with new ideas.