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Non-Terrestrial Networks: 5G’s T.N.T.
December 22, 2020 Blog


Authored by: Jessy Cavazos, 5G Industry Solutions Manager, Keysight Technologies

The focus on non-terrestrial networks (NTN) is growing. Part of 3rd Generation Partnership (3GPP) Release 17, NTN will expand the reach of cellular networks through satellite connectivity. With NTN, cellular networks will expand through satellite communications for the first time. And that’s dynamite. 5G will drive enormous growth in the satellite industry: a new study by Northern Sky Research (NSR) indicates that close to 10 million active revenue sources will help provide $32.5 billion of extra revenue by 2029.

Why introduce satellite links in the 5G New Radio (5G NR) standard? There are many reasons for this, but the main one relates to network infrastructure. NTN enables delivering services in areas lacking network infrastructure or availability like during natural disasters.

Satellite links can provide coverage for isolated or moving platforms such as aircrafts, ships, oil platforms, and trains, and support machine-to-machine communications (M2M) for the Internet of Things (IoT). Mobile operators can also use satellite links to cover the edge of their networks.

One of the main benefits of 5G NTN is multi-connectivity. Customers connect through terrestrial and satellite links, the terrestrial links handling low-latency traffic and the satellite ones carrying high-latency traffic.

5G NTN can also be dynamite with a not-so-positive connotation. Latency is a major concern because 5G has much stricter latency requirements than 4G Long Term Evolution (LTE). Even though satellite communications (SATCOM) only aim to support terrestrial networks for specific applications, latency remains a major consideration for modern SATCOM systems.

In addition, errors in operational SATCOM systems can incur high costs for solution providers. It is much more expensive to address an error in an operational system than fixing it during the requirement specification phase of the system. Studies such as NASA’s Error Cost Escalation Through the Project Life Cycle indicate that it is about 1,000 times more expensive to fix issues in an operational system than in the requirement specification phase, and 25 times more than in the research and development (R&D) phase.

Satellite link modelling has also traditionally been performed for unidirectional communications links, one link at a time. Modern satellite systems use terrestrial and satellite links and have more than one link active between the devices under test at a time, with signalling changing over time between the devices and the networks.

Testing SATCOM systems with realistic environmental models is certainly challenging but it is crucial to ensure performance and avoid unwanted costs later. Simulating link distance the traditional way adds buffering through delaying signals. Creating realistic satellite kinematics requires simulating the sliding delay.

Modern SATCOM systems use satellite mesh networks consisting of multiple interconnected satellites with several transponders per satellite. These systems are much more complex than single-link satellite ones, making them harder to test but solutions to overcome these challenges exist.

A channel emulator can simulate a whole network of devices (Figure 2), enabling you to compare hardware variants and software versions during development. It can also help you compare devices from different vendors objectively while integrating full solutions during the development process.

For more information on this topic, you can view Keysight’s webinar 5G Non-Terrestrial Networks – Overview & Focus on Satellite Link Simulation available on-demand and hosted on Keysight’s Assess 5G Real-World Performance web page.