Types of Non-Terrestrial Network (NTNs) Platforms
Introduction Non-Terrestrial Networks (NTNs)
Non-Terrestrial Networks (NTNs) provide significant flexibility to network operators by supporting different types of non-terrestrial platforms.
Unlike a traditional Terrestrial Network (TN), where radio equipment is primarily deployed on the Earth's surface, an NTN can use radio network equipment placed on spaceborne or airborne platforms.Non-Terrestrial Networks (NTNs)
The choice of platform can depend on factors such as:
Coverage requirements
Data-rate requirements
Propagation delay
Mobility
Deployment scenario
Power limitations
Service requirements
Target geographical area
Examples of NTN platforms include:
Geosynchronous Earth Orbit (GEO) satellites
Medium Earth Orbit (MEO) satellites
Low Earth Orbit (LEO) satellites
High-Altitude Platform Stations (HAPSs)
Each platform has distinct characteristics and can be suitable for different NTN applications.
1. What Is an NTN Platform?
An NTN platform is the airborne or spaceborne vehicle on which the NTN payload is deployed.
The payload provides the radio connectivity required to serve users and devices on the Earth's surface.
Depending on the platform and system design, an NTN can provide coverage over a very large geographical area.
A simplified communication path can be represented as:
UE → NTN Payload → NTN Gateway → Terrestrial Network/Core Network
The NTN platform therefore becomes an important part of the overall network architecture.
2. Major Types of NTN Platforms
The major NTN platforms discussed in the context of 3GPP NTN include:
1. GEO Satellites
2. MEO Satellites
3. LEO Satellites
4. HAPS
Each platform operates under different physical and operational conditions.
3. Geosynchronous Earth Orbit (GEO) Satellites
Geosynchronous Earth Orbit (GEO) satellites operate at an altitude of approximately:
35,786 km above the Earth's surface
A GEO satellite has a very large coverage footprint.
This makes GEO particularly attractive for applications requiring broad-area coverage.
Key Characteristics
GEO satellites provide:
Very large coverage areas
Wide geographical reach
Relatively stable coverage from the perspective of a fixed location on Earth
Reduced need for frequent satellite-related mobility management for fixed users
Because of their high altitude, however, communication signals must travel a very long distance.
This results in relatively high propagation delay compared with lower-orbit satellite systems.
Potential Applications
GEO systems can be useful for:
Wide-area coverage
Broadcast services
Multicast services
Large-scale IoT coverage
Remote-area connectivity
The very large coverage footprint is one of the major advantages of GEO systems.
4. Medium Earth Orbit (MEO) Satellites
Medium Earth Orbit (MEO) satellites operate at altitudes between approximately:
7,000 km and 25,000 km
MEO satellites occupy an orbital region between GEO and LEO.
As a result, their characteristics can fall between the two.
Compared with GEO satellites, MEO satellites operate at lower altitudes and therefore can provide:
Lower propagation delay
Different coverage characteristics
Potentially different capacity and constellation requirements
At the same time, MEO satellites generally cover a larger area than LEO satellites operating at much lower altitudes.
Potential Applications
MEO systems can be considered for applications requiring a balance between:
Coverage + Propagation Delay + Satellite Constellation Size
The exact characteristics depend on the orbital altitude and system design.
5. Low Earth Orbit (LEO) Satellites
Low Earth Orbit (LEO) satellites typically operate at altitudes between approximately:
300 km and 1,500 km
LEO satellites are significantly closer to the Earth's surface than GEO and MEO satellites.
This provides several important advantages.
Lower Propagation Delay
Because the satellite is much closer to the Earth, the propagation distance is shorter.
Therefore, LEO systems can provide significantly lower propagation delay compared with GEO systems.
Higher Potential Data Rates
The lower altitude can also support communication systems designed for higher data rates.
Smaller Coverage Area
A LEO satellite generally covers a smaller geographical area than a GEO satellite.
As a result, a large number of LEO satellites may be required to provide continuous or near-continuous coverage across a large geographical region.
6. LEO and Satellite Mobility
One of the important characteristics of LEO systems is that the satellites move rapidly relative to a fixed point on Earth.
Therefore, the coverage area associated with a LEO satellite also moves across the Earth's surface.
This introduces additional requirements related to:
Mobility management
Handover
Timing
Frequency compensation
Tracking
Satellite constellation management
These factors are particularly important for cellular NTN deployments.
7. High-Altitude Platform Stations (HAPS)
Another important type of NTN platform is the High-Altitude Platform Station (HAPS).
A HAPS is an airborne platform that operates at an altitude between approximately:
8 km and 50 km
above the Earth's surface.
Unlike satellites, HAPS platforms operate within the Earth's atmosphere.
They can potentially be deployed using different types of airborne systems.
8. HAPS Characteristics
Because HAPS platforms operate much closer to the Earth than satellites, they can have different propagation characteristics.
Potential advantages include:
Lower propagation delay than satellite systems
Large coverage compared with conventional terrestrial cells
Flexible deployment
Ability to provide connectivity over challenging geographical areas
HAPS can therefore provide another layer between conventional terrestrial infrastructure and spaceborne satellite systems.
9. Comparing NTN Platforms
The major NTN platforms can be broadly compared as follows:
Platform | Approximate Altitude | Key Characteristic |
LEO | 300–1,500 km | Lower delay, moving coverage |
MEO | 7,000–25,000 km | Intermediate coverage and delay |
GEO | 35,786 km | Very large, relatively stable coverage |
HAPS | 8–50 km | Airborne platform with wide coverage |
These values provide a general understanding of the different platform types. Actual system characteristics depend on the specific deployment and orbital configuration.
10. NTN Beams and Coverage
The NTN platform does not simply provide coverage uniformly over the entire area below it.
The NTN payload uses a specific type of beam to illuminate its target geographical coverage area.
The beam design and behavior depend on:
Platform type
Antenna configuration
Payload capabilities
Coverage requirements
Satellite movement
Network design
Three important beam types are considered:
Earth-Fixed Beams
Earth-Moving Beams
Quasi-Earth-Fixed Beams
Understanding these beam types is essential for understanding NTN mobility and coverage behavior.
11. Earth-Fixed Beams
An Earth-fixed beam maintains its coverage area approximately fixed relative to the Earth's surface.
In other words, the beam is designed so that the illuminated geographical area remains relatively stationary.
This type of beam can be particularly useful for services where a stable coverage region is desired.
From the perspective of users on the ground, the coverage area remains associated with a particular geographical region.
12. Earth-Moving Beams
An Earth-moving beam moves across the Earth's surface.
This can occur when the beam is associated with a moving satellite and is not maintained at a fixed geographical location.
As the satellite moves along its orbit, the coverage area also moves.
This creates an important difference compared with terrestrial networks.
A UE may experience:
Beam A → Beam B → Beam C
as the satellite and its coverage move relative to the Earth.
This can introduce additional requirements for:
Mobility management
Handover
Tracking
Cell selection
Timing
Network coordination
Earth-moving beams are therefore particularly relevant to systems using non-geostationary satellites such as LEO satellites.
13. Quasi-Earth-Fixed Beams
A quasi-Earth-fixed beam attempts to maintain a coverage area that is approximately fixed relative to the Earth's surface for a certain period or under specific system conditions.
It can be considered between the concepts of a completely Earth-fixed beam and an Earth-moving beam.
The objective is to reduce the apparent movement of the coverage area from the perspective of users on Earth.
The exact behavior depends on:
Satellite orbit
Beam steering
Antenna capabilities
Payload design
Network configuration
14. Why Beam Type Matters
The beam type has a direct impact on NTN network operation.
For example, if the beam moves relative to the Earth, the network may need to manage changes in:
Serving cell
Neighbor cells
UE location
Handover
Timing
Frequency
Registration/tracking areas
Therefore, beam behavior is closely connected with NTN mobility management.
This is one reason why NTN requires additional mechanisms compared with a conventional terrestrial network.
15. Satellite Systems Before 3GPP NTN
Satellite communication systems existed long before the introduction of the 3GPP NTN specifications.
Traditional satellite systems have been used for applications such as:
Television broadcasting
Satellite Internet
Remote communications
Navigation
Maritime communications
Aviation
Enterprise connectivity
Remote-area connectivity
These systems established significant experience in satellite communications.
However, the integration of satellite connectivity with the 3GPP cellular ecosystem introduces additional requirements.
The 3GPP NTN work focuses on enabling non-terrestrial connectivity using technologies and architectures aligned with the cellular system.
16. NTN Platforms and 3GPP
The 3GPP NTN specifications primarily focus on specific non-terrestrial platforms, including:
LEO satellites + MEO satellites + GEO satellites + HAPS
These platforms can support different deployment scenarios.
The appropriate platform depends on the target application and requirements.
For example:
Wide-Area Broadcast
GEO can be attractive because of its very large coverage footprint.
Lower-Latency Services
LEO can be attractive because of its lower altitude and shorter propagation distance.
Intermediate Requirements
MEO can provide characteristics between LEO and GEO.
Airborne Coverage
HAPS can provide wide-area coverage from a much lower altitude than satellites.
17. One NTN Ecosystem, Multiple Platforms
The future NTN ecosystem does not necessarily have to depend on only one type of platform.
Different platforms can potentially complement each other.
A future communication system could combine:
Terrestrial Networks
HAPS
LEO
MEO
GEO
This can create multiple layers of connectivity.
Each layer can serve different requirements related to:
Coverage
Capacity
Latency
Mobility
Reliability
Cost
Service type
This multi-layer approach can become particularly important as NTN evolves toward 5G-Advanced and 6G.
18. Key Takeaways
The most important points from this chapter are:
1. NTN Supports Multiple Platforms
NTN provides flexibility by supporting different airborne and spaceborne platforms.
2. Major Platform Types
The key platforms discussed are:
GEO
MEO
LEO
HAPS
3. Each Platform Has Different Characteristics
Altitude strongly influences:
Propagation delay
Coverage
Mobility
Deployment requirements
Network architecture
4. LEO Offers Lower Propagation Delay
Because LEO satellites operate closer to Earth, they can provide lower propagation delay compared with higher-orbit satellites.
5. GEO Provides Very Large Coverage
GEO satellites can cover very large geographical regions and are useful for wide-area services.
6. HAPS Provides Airborne Coverage
HAPS operates between approximately 8 km and 50 km, providing another option between terrestrial networks and satellites.
7. Beam Type Is Important
NTN platforms can use:
Earth-fixed beams
Earth-moving beams
Quasi-Earth-fixed beams
8. Beam Behavior Affects Mobility
Earth-moving coverage can introduce additional requirements for:
Handover
Cell selection
Tracking
Timing
Network management
Conclusion
The concept of Non-Terrestrial Networks is closely connected with the different platforms used to provide non-terrestrial radio coverage.
GEO, MEO, LEO satellites, and HAPS each offer distinct characteristics and can be used for different communication requirements.
GEO satellites provide extremely wide coverage, MEO systems provide an intermediate solution, LEO satellites offer lower propagation delay with moving coverage, and HAPS provides airborne connectivity at significantly lower altitudes.
At the same time, the behavior of the NTN beam is critical.
The three important beam concepts—Earth-fixed, Earth-moving, and Quasi-Earth-fixed beams—help explain how NTN coverage behaves relative to the Earth's surface and why NTN mobility management differs from conventional terrestrial networks.
Together, these platforms and beam configurations provide operators with a flexible set of options for extending wireless connectivity beyond the limitations of terrestrial infrastructure.
As NTN continues to evolve through 5G, 5G-Advanced, and future 6G, understanding these platform types, their characteristics, and their coverage behavior will be essential for telecom professionals working with next-generation networks.
Learn NTN, 5G & Telecom Technologies in Depth
To learn the complete NTN course and build practical, industry-oriented expertise in modern telecom technologies, join Apeksha Telecom with Bikas Kumar Singh.
📞 Contact: +91-8800669860
Learn in depth about 5G NR, NTN, 5G-Advanced, 6G, Protocol Testing, Log Analysis, O-RAN, Telecom Architecture and other next-generation telecom technologies with industry-focused training.
Comments