Motivation for Non-Terrestrial Networks (NTN): Why Do We Need NTN?

Introduction Non-Terrestrial Networks

 Non-Terrestrial Networks  A Terrestrial Network (TN) can provide high-quality communication services when users are located within its radio coverage area. Cellular service providers carefully perform coverage and capacity planning to determine the number and locations of base stations required to serve a particular geographical area and meet expected traffic demands.

However, terrestrial cellular networks have practical limitations. Non-Terrestrial Networks 

Deploying base stations and the associated transport infrastructure is not always technically or economically feasible, particularly in remote, sparsely populated, and geographically challenging areas.

This is one of the key motivations behind the development and deployment of Non-Terrestrial Networks (NTNs).

NTN platforms can extend radio coverage beyond the geographical limitations of traditional terrestrial networks and provide connectivity in locations where deploying conventional cellular infrastructure may be difficult, expensive, or impractical.

Non-Terrestrial Networks

Limitations of Traditional Terrestrial Networks

A traditional terrestrial cellular network requires more than just base stations.

Base stations need to communicate with other base stations to support important functions such as handover.

They also need connectivity toward the core network, because the core network ultimately interfaces with data networks such as the Internet.

Therefore, a terrestrial cellular deployment generally requires:

• Base stations

• Radio infrastructure

• Transport network

• Backhaul connectivity

• Core network connectivity

• Power and supporting infrastructure

In densely populated areas, these investments can be economically justified because a large number of users generate sufficient traffic and revenue.

However, the situation changes dramatically in remote areas.

The Challenge of Remote and Vast Areas

Cost-effective deployment of base stations and their associated transport networks can be difficult in areas with:

• Sparse populations

• Vast geographical areas

• Mountains

• Deserts

• National parks

• Remote islands

• Oceans

For example, deploying fiber or other terrestrial transport infrastructure across a remote mountain region can require significant investment.

Similarly, building a conventional cellular network across large portions of the ocean is extremely challenging because there may be little or no terrestrial infrastructure available.

In remote islands, the lack of sufficient infrastructure and a limited business case can also make terrestrial cellular deployment difficult.

These limitations create a strong motivation for using Non-Terrestrial Networks.

How NTN Addresses These Challenges

An NTN provides an attractive solution for challenging environments where traditional terrestrial networks cannot adequately address connectivity requirements.

Instead of requiring radio equipment to be physically located near or inside the geographical area being served, an NTN platform can provide coverage from the air or space.

This fundamentally changes the way coverage can be delivered.

The three major NTN use-case categories identified by 3GPP are:

1. Service Ubiquity

2. Service Continuity

3. Service Scalability

These categories represent some of the key motivations behind the design and deployment of NTN.

1. Service Ubiquity

Service ubiquity refers to the ability to provide communication services over very large geographical areas, including locations where terrestrial networks are unavailable or difficult to deploy.

An NTN platform can create large radio beams capable of providing coverage across extensive areas of the Earth's surface.

This can help provide connectivity to:

• Remote rural areas

• Underserved communities

• Homes in sparsely populated regions

• Mountains

• Oceans

• Remote islands

• IoT devices

• Smart farms

• Remote manufacturing plants

For example, IoT devices deployed in a smart farm located far from terrestrial cellular infrastructure could potentially be connected through an NTN platform.

Similarly, remote manufacturing facilities can benefit from connectivity without requiring a complete terrestrial cellular infrastructure to be constructed around the facility.

NTN During Natural Disasters

Service ubiquity becomes particularly valuable when terrestrial infrastructure is damaged or destroyed.

Natural disasters such as:

• Earthquakes

• Floods

• Cyclones

• Other major disasters

can damage terrestrial cellular infrastructure.

Similarly, armed conflicts and wars can destroy or disrupt terrestrial communication infrastructure.

In such situations, an NTN platform can potentially provide an alternative communication path.

A suitable NTN architecture can allow the platform to connect to data networks on Earth's surface through a gateway.

This means the radio equipment does not necessarily need to be located near the geographical area being served.

That is a fundamental advantage of NTN.

NTN Removes the Geographic Constraint of Terrestrial Networks

In a traditional terrestrial network, radio equipment generally needs to be located near or inside the area being served.

This creates a strong geographical constraint.

NTN changes this model.

An NTN platform can be located far above the service area and use its radio beams to provide coverage over a large geographical region.

Therefore:

Terrestrial Network:Radio infrastructure needs to be near the service area.

Non-Terrestrial Network:Radio coverage can be provided from an airborne or spaceborne platform located far from the service area.

This capability makes NTN particularly attractive for remote and difficult-to-reach locations.

2. Service Continuity

The second major motivation for NTN is service continuity.

There are many situations where a cellular subscriber or IoT device moves outside the radio coverage of a terrestrial network.

For example, a user may:

• Move from a suburban area into a rural region

• Board a cruise ship

• Travel through an area without terrestrial coverage

• Experience loss of coverage during certain phases of air travel

In these situations, conventional terrestrial coverage may become unavailable.

NTN can help provide service continuity by extending radio coverage into areas that are not adequately covered by terrestrial networks.

Connectivity for Moving Platforms

Service continuity is especially important because users and IoT devices are not always stationary.

They can operate on different types of moving platforms.

Land Platforms

Examples include:

• Cars

• Trains

• Trucks

Airborne Platforms

Examples include:

• Commercial aircraft

• Private aircraft

Maritime Platforms

Examples include:

• Cruise ships

• Container ships

• Cargo ships

These platforms can travel across areas where terrestrial cellular coverage is limited or completely unavailable.

NTN can provide radio coverage in such areas and therefore help maintain connectivity.

Example: Maritime Connectivity

Consider a cruise ship traveling far away from the coastline.

Near the coast, the ship may be within terrestrial cellular coverage.

As it moves farther into the ocean, terrestrial coverage may disappear.

An NTN platform can provide radio coverage over the ocean and help maintain communication services.

The same principle can apply to container ships, cargo vessels, and other maritime platforms.

Example: Rural Mobility

Consider a person traveling from a well-connected suburban region into a remote rural area.

As the person moves beyond terrestrial network coverage, the cellular service may become unavailable.

An NTN can provide coverage in areas that are not served by the terrestrial network, helping support service continuity.

This illustrates how TN and NTN can work together rather than necessarily operating as completely independent systems.

3. Service Scalability

The third major motivation for NTN is service scalability.

Modern cellular systems are designed to use network resources efficiently.

Operators must optimize:

• Network performance

• User experience

• Radio resources

• Spectrum utilization

• Network capacity

Spectrum is a particularly valuable and limited resource.

Therefore, the network needs to use its available radio resources efficiently.

Large-Area Broadcast with NTN

Consider a situation where the same service content needs to be delivered to a large number of users spread across a wide geographical area.

In a conventional terrestrial network, multiple base stations across that geographical area may need to consume radio resources to deliver the same content.

This can result in significant resource consumption.

An NTN cell, however, can cover a much larger geographical area compared with a typical terrestrial cell.

This creates an opportunity for increased efficiency when distributing the same content to many users across a large area.

Examples of Services Benefiting from Large-Area Broadcast

Large-area NTN coverage can be particularly useful for services where the same information needs to reach many users.

Examples include:

• Over-the-air software updates

• Selected entertainment programs

• Live games

• Prescheduled movies

• Other broadcast-type services

For example, if the same software update needs to be distributed to devices across a very large geographical area, an NTN platform could potentially broadcast the content over a large coverage area.

Similarly, entertainment content or live events can benefit from large-area distribution.

Why NTN Can Improve Efficiency

The key concept behind NTN service scalability is coverage area.

A traditional terrestrial cell generally covers a comparatively smaller geographical area.

An NTN cell can cover a much larger area.

Therefore, when identical content needs to be delivered to users distributed across a large region, NTN can potentially reduce the need for repeated transmission from many terrestrial base stations.

The basic concept can be represented as:

Large Geographic Area + Same Content + Many Users → Large-Area NTN Broadcast

This makes service scalability an important motivation for NTN deployment.

Three Key Motivations for NTN

The three major use-case categories can be summarized as follows:

NTN Motivation	Main Objective	Example
Service Ubiquity	Provide connectivity where TN coverage is unavailable	Remote mountains, oceans, rural areas
Service Continuity	Maintain connectivity while users move beyond TN coverage	Ships, aircraft, trains, vehicles
Service Scalability	Efficiently serve large numbers of users across large areas	Software updates, live games, broadcast content

These three categories highlight the fundamental limitations of terrestrial networks that NTN technology aims to address.

NTN and Terrestrial Networks Can Work Together

It is important to understand that NTN is not necessarily intended to replace terrestrial networks.

Instead, NTN can complement terrestrial networks.

Terrestrial networks are highly effective in areas where sufficient infrastructure, population density, and business justification exist.

NTN becomes particularly valuable where terrestrial deployment is difficult, expensive, or impractical.

The combination can therefore provide a more comprehensive connectivity ecosystem:

Terrestrial Network + Non-Terrestrial Network = Wider and More Flexible Connectivity

A Word of Caution

Although NTN has the potential to support a wide range of use cases, not every NTN use case will necessarily be supported in the initial deployments.

NTN technology and deployments will continue to evolve.

As NTN platforms become:

• More capable

• More widely deployed

• More integrated with terrestrial networks

• More efficient

• More commercially mature

additional use cases are expected to become feasible.

Therefore, the NTN ecosystem should be viewed as an evolving technology rather than a solution where every possible use case is immediately available.

The Future of NTN

The motivations behind NTN demonstrate why non-terrestrial connectivity is becoming an important part of the evolution of cellular networks.

The technology can address situations where traditional terrestrial infrastructure faces geographical, economic, or operational limitations.

From remote communities and smart farms to ships, aircraft, IoT devices, disaster zones, and large-area broadcast services, NTN can expand the reach and flexibility of wireless communication.

As the industry progresses from 5G to 5G-Advanced and eventually 6G, the integration between terrestrial and non-terrestrial networks is expected to become increasingly important.

Conclusion

The motivation for Non-Terrestrial Networks (NTNs) comes from the limitations of conventional terrestrial cellular networks.

Deploying base stations and transport infrastructure is not always cost-effective in sparse, remote, and geographically challenging areas such as mountains, deserts, national parks, oceans, and remote islands.

NTN provides an attractive alternative by delivering radio coverage from airborne and spaceborne platforms.

The three major motivations identified by 3GPP are:

1. Service Ubiquity

Providing connectivity across remote, underserved, or unserved areas.

2. Service Continuity

Maintaining connectivity for users and IoT devices moving beyond terrestrial coverage.

3. Service Scalability

Efficiently delivering the same content to users across very large geographical areas.

However, not all NTN use cases will necessarily be supported in the initial deployments. As NTN platforms become more capable and widespread, additional applications and use cases are expected to become feasible.

Understanding these motivations is fundamental to understanding why NTN has become an important part of 5G, 5G-Advanced, and the future 6G communication ecosystem.

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