The Definitive Guide to Non-Terrestrial Networks

The Case for Non-Terrestrial Networks (NTNs)

Non-terrestrial networks (NTNs) are not new, given the decades-long existence of satellite communications (SATCOM). The term “non-terrestrial network” often refers to the newer integration of terrestrial cellular communications with air-borne assets or satellite constellations, which largely operate in the rapidly expanding lower earth orbit (LEO). NTN platforms may include multiple types of satellites as well as assets like high-altitude platform stations (HAPS) and drones.

As 5G and future 6G networks incorporate NTNs into their design, pushing past the boundaries of terrestrial-based infrastructure, the impact of NTNs will become even more significant. Because of their ability to connect the unconnected (theoretically anywhere in the world), NTNs continue to play an increasingly prominent role in wireless communications, enabling ubiquitous connectivity and supporting emerging technologies like autonomous vehicles and IoT.

LEO-Driven Use Cases

The current explosive growth in LEO satellites provides the foundation for many NTN use cases across the commercial, government, and military industries. NTNs have the potential to overcome infrastructure challenges in developing regions, empowering communities with access to education, healthcare, and economic opportunities. By supplying reliable connectivity, these networks foster social and economic development on a global scale.

NTN Basics

This eBook covers the non-terrestrial network basics, including the various potential orbits, network architectures, and network aspects from user equipment through the base station and satellite. Each orbit creates different challenges in communication networks. With LEO, the satellite operates at a nearer distance but moves more quickly. Due to the proximity, you can have low-latency communications from satellite to ground.

Every NTN has several points of presence where the non-terrestrial network connects to the terrestrial internet. Each orbit creates different challenges in communication networks. Fiber-optic links connect land stations together, while laser-optical links are used between satellites.

What Advantages Do Non-Terrestrial Networks Provide?

The rapid growth of LEO satellite networks invites new applications for NTNs ranging from hybrid fifth-generation (5G) cellular and satellite networks through industrial, emergency response, agriculture, earth monitoring, and smart cities. With increasing focus on direct-to-cell-phone capability, NTN will support capabilities across commercial and government organizations.

NTNs bring mobile communications to remote and under-served regions, bridging communication gaps to last-mile rural areas and boosting coverage in emergencies and other scenarios. In addition, non-terrestrial networks increase global sensing capabilities through narrowband-Internet of Things (NB-IoT) over NTN, enabling various industries to leverage the resulting data.

Much of the focus on NTN currently centers on direct-to-device capability. This capability allows cellular phones to connect to satellites when they are out of range of terrestrial base stations. For example, future 3GPP releases will include very short aperture terminals (VSATs), which consist of high-gain antennas, such as dish or array panels,  and higher power modems in fixed installations.

The Role of Phased Array Antennas in NTNs

Communication with a low Earth orbit satellite occurs by tracking one satellite, then tracking another as the first satellite starts to go out of view. A successful connection must seamlessly connect between the two satellites. Phased array antennas perform this task well, tracking multiple LEO satellites and enabling backups to ensure continuous connectivity. A phased array comprises many antenna elements arranged in a matrix to provide desired characteristics or features not available in a single antenna.

Challenges Facing NTNs

Spectrum crowding presents a major challenge for LEO satellites. Limited availability in reserved satellite bands and requirements for wider bandwidth communications through satellite links have increasingly pushed deployment into higher frequencies, which demand new design requirements and methods to ensure satellite performance. However, wider bandwidth and higher-order modulation schemes introduce challenges that can affect link quality at millimeter-wave frequencies.

Non-terrestrial networks must meet higher performance requirements despite the harsh operating environment of space and the need to launch systems into orbit successfully. Building mesh networks in space exacerbates these complexities by multiplying the chances for problems. A distributed LEO satellite constellation spreads risks and costs across hundreds or thousands of satellites.

Optical communications can overcome some NTN challenges. By using light to transmit information, optical communications provides several benefits over traditional radio frequency (RF) communications. The benefits of this technology include increased bandwidth, higher frequencies, improved security, and the capability to transmit data without signal degradation.

The Standards Driving 5G NTN Development

Not all NTN solutions and services will operate within the standards set by the 3GPP, which has overseen cellular standardization worldwide. Many vendors outside 3GPP already rely on proprietary waveforms, with more in development. DVB-S2X is the Digital Video Broadcasting Project Second Generation Satellite Extension, offering alternatives to wideband data transfer via NTNs.

For its part, the 3GPP set the standards and targets for NTNs within 5G and future 6G networks for direct-to-handset communications and IoT devices. From 2022, when 3GPP Release 17 accounted for ground-based terrestrial networks and non-terrestrial network platforms in 5G specifications, newer efforts set the standards and targets for NTNs within 5G and future 6G networks for direct-to-handset communications and IoT devices.

The 3GPP is currently defining Release 19, and finalization will occur in late 2025. Although 3GPP plans to limit the score of the overall enhancements in Release 19, it will include additional NTN enhancements. Several proposals are under consideration for Release 19, including a specification for a regenerative architecture for NTNs that includes distributed unit processing on board the satellite supporting inter-satellite links.

NTN Testing Challenges and Solutions

To realize the mobile communications industry’s vision of integrating cellular networks with NTNs over the next several years, device makers and mobile network operators must test NTN wireless links with actual base stations and real devices.

Significant challenges include simulating life-like conditions for satellite end-to-end links and the ability to connect NTN nodes and terminals before system deployment. NTN development projects need the ability to test and connect network entities and terminals in the prototyping phase and before and during deployments to avoid costly delays.

Download “The Definitive Guide to Non-Terrestrial Networks” for an in-depth view into what constitutes an NTN, what challenges remain to be overcome, and what the future holds for these hybrid and space-based networks. You also will learn how network and device vendors can verify system performance under real-life operating conditions in the lab, before launching devices and networks.