Satellite communication has come a long way since its experimental beginnings, evolving into a sophisticated global network that plays a crucial role in modern telecommunications. The journey of non-terrestrial networks (NTNs) is marked by significant milestones, particularly the transition from geostationary (GEO) satellites to medium Earth orbit (MEO) and low Earth orbit (LEO) constellations. This evolution not only highlights the advancements in satellite technology but also underscores the promise of LEO constellations in providing mobile broadband services on a global scale. In this blog series, we will explore the development of NTNs, the differences between GEO, MEO, and LEO constellations, and the potential of LEO satellites to revolutionize mobile connectivity.

Advancing Satellite Communication Through 3GPP Standardization

Historically, satellite communication operated on proprietary systems, limiting interoperability and hindering widespread adoption. However, the industry is undergoing a transformative shift towards standardization under the 3GPP framework. This evolution is driven by the need for seamless integration between terrestrial and non-terrestrial networks, enabling ubiquitous connectivity and providing connectivity direct-to-device besides very-small-aperture terminals (VSAT). 

Traditional satellite NTN deployment often involves proprietary systems with limited interoperability, resulting in fragmented networks and inconsistent user experiences. In contrast, the use of 3GPP standards in NTN deployment offers seamless integration with terrestrial networks allowing them to easily connect with land-based networks, making them more reliable and providing better global coverage. By adopting 3GPP standards, satellite operators can drive convergence of satellite and cellular networks and leverage economies of scale, improve network efficiency, and offer a wider range of new applications in various sectors such as IoT, emergency response, and rural connectivity.

Key benefits of this convergence include:

Below are some of the key benefits of the convergence of the terrestrial and non-terrestrial network.

• Standardized protocols: Ensuring compatibility and interoperability.
• Economies of scale: Leveraging shared technologies and components.
• Expanded coverage: Combining terrestrial and satellite networks for seamless connectivity.
• New services and applications: Enabling innovative use cases

Non-Terrestrial Networks (NTN) Use Cases

NTNs based on 3GPP standards open a wide range of applications across various sectors, offering innovative solutions to enhance connectivity and support advanced technological developments. (Figure 1). These use cases range from maritime and aircraft communication to IoT applications like continuous asset tracking. Additionally, NTNs can be leveraged to deliver mobile and fixed broadband communication services, providing internet access, enhancing mobile broadband services, and supporting emergency response operations to rural and remote, underserved areas.  Furthermore, for resilient communication NTN could provide a vital cog by providing ubiquitous communication link between communication entities across land, sea and air, thus supporting tactical communication needs. 

Advantages of 3GPP-defined 5G NR NTN Technology

The 3GPP Release-17 introduced NTNs to provide SATCOM services across GEO/MEO/LEO satellite constellations and via other air-borne vehicles like high-altitude platform station (HAPS), drones and unmanned aerial vehicles (UAVs) direct to the standard mobile devices.

Overall, the 3GPP NTN solution is broadly categorized into Cellular and SATCOM infrastructure elements. The 3GPP defined cellular infrastructure is comprised of Network Elements (NE) and Network Functions (NF) of gNodeB and 5G Core Network. Traditional SATCOM infrastructure is comprised of ground stations or gateways that track one or multiple visible or on-horizon satellites and provide feeder link connection as transport between Cellular Infrastructure NE/NF. SATCOM infrastructure also consists of logical entities like NTN Control Function (NCF) which interface with cellular Infra NE/NF and also control the satellite spot beams which provide service link using 5G NR air interface directly to mobile handsets. 

NTN primarily supports two deployment architectures (refer to Figure 2): Transparent/Bent Pipe in 3GPP Releases 17 and 18 and Regenerative Payloads in 3GPP Release 19. A transparent payload has all the cellular infrastructure components, gNode Base Station (gNB)and 5G core network (5GCN), hosted on the ground with the satellite payload providing a transparent transport for the NR waveform to the mobile device. 

A regenerative payload solution could have either the complete gNodeB (CU/DU/RU) or part of gNodeB (e.g.: RU/DU) hosted on the satellite payload with the remaining cellular infrastructure network functions (5GCN or CU with 5GCN) hosted on ground and connected to the DU/RU via the feeder link between the ground station and satellite.

The evolution of non-terrestrial networks (NTNs) represents a transformative shift in satellite communications. Traditional satellite networks, often hampered by proprietary systems and limited interoperability, are being replaced by flexible NTNs based on 3GPP standards. This transition not only ensures seamless integration with terrestrial networks, enhancing compatibility and reliability but also opens significant opportunities for telecom operators. With 3GPP standards, operators can extend their reach to underserved rural areas, offering new services that bridge the digital divide. This evolution enables communication service providers to explore innovative applications and create new revenue streams, such as enhanced mobile broadband, IoT services, and global connectivity solutions. As NTNs continue to advance, they hold the promise of revolutionizing the telecom landscape, driving both technological progress and economic growth.