The Integration of Terrestrial Networks and NTNs

- Overview

Terrestrial networks (TNs) in 5G and beyond focus on dense, high-speed, and low-latency communication using land-based infrastructure (sub-6 GHz, mmWave). Moving toward 6G, these networks are increasingly integrating with non-terrestrial networks (NTN) like LEO/GEO satellites and HAPS to provide ubiquitous, seamless global coverage. 

1. Key Aspects of Terrestrial Networks (TNs) in 5G & Beyond:

• Architecture & Evolution: 5G networks utilize gNodeB base stations to deliver enhanced Mobile Broadband (eMBB) and Massive Machine Type Communications (mMTC). Beyond 5G, this evolves into a fully integrated space-air-ground network to eliminate coverage gaps.
• Integration with NTN (6G Vision): Future networks will seamlessly blend terrestrial and satellite systems, enabling direct-to-device communication even in remote, maritime, or aerial locations.
• Key 5G Features: High-capacity data, ultra-low latency, and network slicing for specialized services.
• Applications Beyond 5G: Enhanced IoT,, critical communications (E911, WEA), and 6G, which aims to provide connectivity across all domains (sea, air, land).

2. Key Takeaways:

• 3GPP Standardization: 3GPP Rel-18 5G Advanced and future releases are key for integrating NTN with terrestrial infrastructure.
• Coverage Expansion: Satellite-based NTN allows for bridging the digital divide in rural areas.
• Future Trends: 6G systems will require a fully integrated control plane for both terrestrial and non-terrestrial domains.

- The Integration of TNs and NTNs for 5G and Beyond

The integration of Terrestrial Networks (TNs) and Non-Terrestrial Networks (NTNs)—including LEO/GEO satellites, UAVs, and HAPs - is critical for 5G-Advanced and 6G, enabling ubiquitous, high-quality, and 3D coverage. 

By standardizing NTN in 3GPP Release 17, this convergence extends connectivity to remote areas, enhances IoT, and provides reliable emergency services, with future enhancements like 5G-Advanced (Rel-18) supporting Ka-band and improved bandwidth for integrated architectures. 

(A) Key Aspects of TN-NTN Integration: 

• 3GPP Standardization: Release 17 and 18 establish the framework for integrating NTNs, allowing mobile devices to connect directly to satellites, improving global coverage and reducing the digital divide.
• Architecture & Components: The architecture merges ground-based infrastructure with space/airborne components, utilizing edge caching at both satellite and terrestrial levels to optimize content delivery. 

2. Key Use Cases:

• Ubiquitous Coverage: Extending service to rural, remote, and maritime areas where terrestrial infrastructure is unfeasible. 
• IoT & M2M Support: Enabling massive machine-type communications (mMTC) via satellite for tracking, monitoring, and sensing.
• Service Continuity & Reliability: Providing resilient, backup communication in disaster-stricken areas. 
• Backhaul: Using satellites for backhaul, augmenting terrestrial cell sites.

3. Challenges: Key challenges include managing high latency, Doppler shifts due to satellite mobility, power constraints for IoT devices, and maintaining seamless handover between satellite and terrestrial networks.

(B) Future Outlook (5G and Beyond): 

The future of NTN involves further integration into 6G, focusing on intelligent 3D orchestration, increased data throughput, and lower latency through advanced technologies like integrated access and backhaul (IAB).