Space–Air–Ground Integrated Networks for 6G

Dear Colleagues,

Space–air–ground integrated networks (SAGINs) have been an important research direction for 6G. Terrestrial networks are insufficient for fulfilling Internet service demand, and there are 3 billion people all over the world living without Internet access. Satellite communication makes up for the shortage of terrestrial networks, with its advantages including wide coverage and support for massive access services. With the fast development of low-Earth-orbit (LEO) satellite constellations, e.g., Starlink and OneWeb, satellite communication has become an indispensable part of space-air-ground integrated networks. On the other hand, unmanned aerial vehicle (UAV) communication plays a multifaceted role in SAGINs, offering a versatile and adaptable solution for extending communication capabilities across the space, air, and ground domains. UAVs can serve as data relays between various nodes in the network, including ground stations, satellites, and other UAVs. They can extend communication ranges and provide connectivity to remote or inaccessible areas where traditional communication infrastructure is lacking. UAVs offer the advantages of mobility and flexibility in deployment. They can be rapidly deployed to specific locations based on demand or operational requirements, providing on-demand communication services where needed. By integrating UAV communication into SAGINs, additional bandwidth can be made available for data transmission, thereby improving the overall network capacity and performance, especially in scenarios with high data traffic or congestion.

Research challenges in SAGINs for 6G communications encompass several key areas:

• Developing seamless integration mechanisms for satellite, UAV, and terrestrial networks, ensuring interoperability between different communication platforms and technologies.
• Designing efficient resource allocation algorithms to dynamically manage spectrum, power, and bandwidth across diverse network segments, considering varying user demands and environmental conditions.
• Addressing challenges related to mobility management in heterogeneous environments, including handover optimization, trajectory prediction, and seamless connectivity during transitions between different network segments.
• Enhancing security mechanisms to protect sensitive data and communication links against cyberattacks, physical tampering, and interception, while also preserving user privacy in multi-domain communication scenarios.
• Developing QoS-aware routing and scheduling algorithms to optimize communication performance metrics such as latency, throughput, and reliability across space, air, and ground segments, while meeting diverse application requirements.
• Investigating spectrum sharing techniques and cognitive radio technologies to efficiently utilize available frequency bands, mitigate interference, and enable coexistence between different communication systems operating in the same spectrum.
• Designing energy-efficient communication protocols, transmission techniques, and power management strategies to minimize energy consumption and extend the operational lifetime of battery-powered devices, especially in resource-constrained environments.
• Developing scalable network architectures and management frameworks to support the growing number of connected devices and services in SAGINs, while ensuring robustness, scalability, and ease of deployment.

Addressing these research challenges will be crucial for realizing the full potential of SAGINs in enabling advanced communication capabilities for 6G networks. The research for SAGINs has become a hot topic in both academia and industry, and this Special Issue aims to discuss the advances in space–air–ground integrated networks for 6G communications. Prospective authors with original research articles and reviews are invited to submit articles on topics related to “Space–Air–Ground Integrated Networks for 6G”. We look forward to receiving your contributions.

Dr. Sai Huang
Dr. Weiwei Jiang
Dr. Yafeng Zhan
Prof. Dr. Ray E. Sheriff
Prof. Dr. Zhiyong Feng
Guest Editors

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• satellite- and UAV-assisted 6G communications
• space–air–ground integrated network
• integrated sensing and communications
• trajectory optimization and resource allocation
• physical layer security and radio monitoring
• artificial intelligence in SAGINs for 6G communications
• unmanned aerial vehicles
• drone communications
• UAV ad hoc networks
• unmanned aerial systems