A Survey on Satellite and Ground Integrated Network Systems

Low-earth orbit (LEO) satellite networks enable communication services in areas beyond the coverage of terrestrial base stations. This system is considered a key technology for 6G communications as it offers lower latency and less signal attenuation compared to geostationary satellites, achieving high throughput. By integrating these satellite networks with terrestrial base stations, a network structure can be created that combines the wide coverage of satellites with the data processing capabilities of terrestrial base stations, providing a more reliable and flexible communication environment. Therefore, to address the increasing number of connected devices and the rise in network density due to the growth of IoT, recent research on integrated satellite-terrestrial network systems is actively being conducted. In this paper, we investigate the latest research topics, such as space-air-ground integrated networks (SAGIN), RIS-integrated systems, security issues, and semantic-aware SAGIN systems.