Space-Air-Ground Integrated Network (SAGIN) has emerged as a comprehensive solution to address the increasing demand for ubiquitous and resilient communication networks. This architecture is particularly relevant for extending coverage in remote and traditionally underserved areas beyond the scope of conventional ground-based networks.

At the forefront of this integrated approach are the combined Airspace and NTN (non-terrestrial network), abbreviated as combined ASN, which leverages the synergistic capabilities of unmanned aerial vehicles (UAVs), high-altitude platform stations (HAPSs), and low Earth orbit (LEO) satellite networks. The combination of airspace and non-terrestrial networks (combined ASN) creates a transformative 6G connectivity infrastructure. 

The envisioned architecture combines the strengths of these technologies in a hierarchical network, addressing coverage, especially in remote areas not served today. In an article published in IEEE Communications Magazine, researchers conduct a techno-economic analysis of the non-terrestrial enabling technologies of combined ASN.

This ASN-integrated system delivers superior throughput, resilience, and extended coverage, serving rural and remote areas, augmenting ground stations, and enabling smart urban infrastructure. A techno-economic assessment of the proposed architecture focusing on its enabling aerial technologies is essential to assess its real-world feasibility.

The combined ASN architecture proposed for 6G.

 

Combined ASN Use Cases

Each component of the combined ASN has unique strengths and limitations: 

  • LEO satellite constellations offer continuous global coverage, adequate latency for real-time applications owing to their proximity to Earth, and resilience against service interruptions. Satellites have a long lifespan and tolerate weather effects well, but they have fixed orbits and substantial setup times due to launches. 
  • HAPS excels in providing spatiotemporally focused, semi-permanent communications services catering for significant regional events and sustained emergency response situations; however, their coverage, mobility, and longevity are moderate. 
  • UAVs add responsiveness, facilitating rapid deployment for temporary service gaps and disaster recovery. Flying at low altitudes and equipped with sensors, they can provide real-time data for environmental monitoring and infrastructure inspection, thereby instantiating the joint communication and sensing vision of 6G networks. On the other hand, large-scale UAV deployments pose complex fleet and air traffic management challenges.
  • Although limited on their own, integrating LEO satellites, HAPSs, and UAVs into the combined ASN architecture creates a dynamic network capable of adjusting to a wide range of spatial and temporal demands. This layered approach maximizes network coverage, bandwidth, and resilience, ensuring reliable 6G communications even under challenging conditions.

 

6G connectivity services provided by the combined ASN are categorized into two main types: 

  • The first category focuses on airspace communications. Uses cases include connectivity for airline passengers, urban air mobility, safety services in smart cities, and integrating digital airspace with terrestrial networks for air traffic and national security management. 
  • The second category aims to connect terrestrial users, enhancing either capacity or coverage. Uses cases include extending mobile connectivity to remote areas, boosting ground communication capacity as needed, supporting non-3GPP traffic like Earth observation and disaster management, and enhancing IoT connectivity through extended coverage.

Techno-Economic Analysis of LEO Satellite, HAPS, and UAV Technologies

Examining the techno-economic aspects of LEO constellations, HAPS units, and UAV-based solutions in the combined ASN ecosystem is crucial, given the delicate balance between technological capabilities and financial viability. The researchers looked at manufacturing, deployment, maintenance, and operating costs for the analysis.

Opting for HAPS within cities or smaller countries can be cost-effective for service providers; even a few HAPS units can provide coverage for a large area. However, if a provider aims to expand its services to a continent or a global scale, the significant investment cost of a LEO constellation may be justifiable due to its extensive coverage capabilities.

HAPS excels over LEO satellites in network augmentation scenarios in applications requiring near-real-time latency and high data rates due to their proximity to the ground and user equipment. However, UAV-based solutions offer a more economical alternative for smaller, localized coverage areas, provided they effectively cover the designated area. 

Network augmentation costs in small-scale scenarios.

 

Network augmentation costs in large-scale scenarios.

 

Challenges and Considerations

This research examines the complex field of non-terrestrial technologies within the combined ASN architecture, highlighting their potential to revolutionize ubiquitous connectivity. The integration of these technologies addresses various geographical and operational needs.

While High Altitude Platform Stations (HAPS) represent a novel advancement in telecommunications infrastructure, they face numerous technological, regulatory, and economic challenges, as outlined by the authors. The researchers suggest that HAPS may only be advantageous in very specific scenarios. 

The researchers recommend that a combination of a Low Earth Orbit (LEO) constellation and well-managed Unmanned Aerial Vehicles (UAVs) is more suitable for addressing the majority of the identified use cases.

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