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.

Please refer to the following for more information:

• Wikipedia: SpaceX

- Non-terrestrial Networks: The Future of 6G Connectivity

Non-Terrestrial Networks (NTN) will natively merge with terrestrial systems, transforming the internet into a seamless, planetary communication fabric. This 6G evolution introduces multi-layer architectures across Low Earth Orbit (LEO) satellites, High-Altitude Platforms (HAPS), and drones, delivering reliable, ubiquitous coverage to unserved regions. 

To achieve this, the industry is focusing on the following key advancements:

• Intelligent 3D Orchestration: Future networks utilize Artificial Intelligence (AI) and Machine Learning (ML) for network automation. This allows the system to autonomously predict handovers, manage resources, and route traffic dynamically across space, air, and ground segments. 

• Integrated Access and Backhaul (IAB): Advanced IAB permits the same radio infrastructure to handle both user access and wireless backhaul. By enabling HAPS and satellites to act as flexible, intermediate relay nodes, this minimizes the need for hardwired terrestrial backhaul. 

• Increased Data Throughput: By tapping into higher radio frequency bands (such as the sub-THz spectrum), future NTN configurations are expected to handle terabit-per-second transmission rates to meet massive global data demands. [1, 2]

• Lower Latency: Transitioning from 5G to 6G aims to bring hyper-reliable, low-latency communication (HRLLC). Using mega-constellations of LEO satellites and integrating Mobile Edge Computing (MEC) directly onboard aerial vehicles dramatically cuts propagation delays. 

- 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: 

1. 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. 

2. 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. 

3. 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.

4. 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).

- MNOs vs. SpaceX

Major mobile network operators (MNOs) like AT&T Wireless maintain physical cell towers on the ground using highly concentrated spectrum to provide fast, continuous, indoor 5G data. In contrast, SpaceX (Starlink) uses low-Earth orbit (LEO) satellites as "cell towers in space" to beam coverage directly to standard, unmodified mobile phones. 

The fundamental differences across their core business models and technologies include: 

1. Network Infrastructure & Coverage: 

• AT&T: Relies on millions of localized terrestrial cell sites. They offer near-perfect urban and suburban coverage, but their signals struggle in remote, rugged, or rural topographies. 
• SpaceX: Orbits thousands of satellites at an altitude of roughly 340 to 550 kilometers. Because coverage requires a direct line of sight to the sky, they excel in providing service in oceans, deserts, and vast geographic areas that lack physical towers. 

2. Speeds & Capacity:

• AT&T: Terrestrial 5G and fiber backhaul allow for high-speed streaming, gaming, and heavy data usage.
• SpaceX: Space-based connections are a supplementary layer. While SpaceX’s next-gen Starlink satellites provide up to 1 Tbps of capacity, physics dictates that space connections yield significantly slower speeds (e.g., in the lower Mbps) and are best used for emergency messaging, texting, and basic voice calls.

3. Market Role & Partnerships:

• AT&T: Acts as a traditional Mobile Network Operator (MNO), selling directly to consumers and businesses and occasionally using partner satellites to supplement rural gaps.
• SpaceX: While they hold their own dedicated radio spectrum, they primarily act as a wholesaler or partner to existing terrestrial carriers (like T-Mobile), routing space-based traffic to fill network dead zones without requiring users to switch carriers.