5G Non-Terrestrial Networks (NTN) are on the verge of dramatically improving global connectivity. Dylan MGrath from Keysight Technologies shares his enthusiasm for 5G NTNs and their powerful use-cases for broadband and IoT applications.
How do non-terrestrial networks boost mobile networks?
Patchy coverage, dropped calls, voice distortions, and inconsistent data speeds are some common problems with current 4G and 5G networks.
Some of these issues are due to the inherent problems of terrestrial networks.
About the Author: Dylan McGrath is the industry solutions manager for 5G at Keysight Technologies. Prior to joining Keysight, Dylan spent more than 20 years in technology journalism and marketing. He spent more than 10 years as an editor at EE Times, including several years as editor-in-chief of the 50-year-old electronics industry trade publication. His career has also included stints at Electronic News, IHS Markit, and the Hoffman Agency.
Non-terrestrial networks (NTNs) can not only alleviate these problems but also potentially expand 5G coverage to the entire planet.
While NTN technologies use satellite systems or airborne platforms to provide telecommunication services in remote areas that are impractical for traditional terrestrial networks, a drawback of current NTNs is that they’re incompatible with traditional terrestrial networks.
For example, SpaceX’s Starlink is an NTN that provides internet access to millions of users around the world through its satellite constellation.
But even if users have smartphones and tablets equipped with perfectly capable radio transceivers, they still need an additional gateway device for Starlink internet access.
Fortunately, the 3rd Generation Partnership Project (3GPP), the organisation that creates mobile communication standards, is addressing this incompatibility by bringing the NTN ecosystem under the umbrella of the 5G standards.
This will enable 5G-compliant non-terrestrial networks to interwork seamlessly with terrestrial mobile networks and allow users direct access to satellite mobile services from their smartphones and tablets.
The architecture of 5G non-terrestrial networks
5G NTNs are on the verge of dramatically improving global connectivity.
A typical terrestrial 5G telecommunications network consists of the following.
- User equipment (UE): UEs are your devices that communicate with a 5G network, like your smartphones or 5G Wi-Fi routers.
- Radio access network (RAN): To receive calls or data, the UEs communicate with a 5G RAN, a wireless network of radio transceivers (called base stations, gNodeBs, or gNBs) installed on towers in areas where 5G coverage is desired. The 5G New Radio, or 5G NR, standard specifies the radio frequencies they can use, which are either below 6 GHz (called FR1) or in the 28-60 GHz range (known as mmWave or FR2). Typically, RANs also support older standards like 4G Long-Term Evolution (LTE) and 3G.
- 5G core: This is the brain of a 5G network. RANs essentially relay voice and data from the UEs to the 5G core and back. The core consists of network devices and software systems to support all the essential mobile network capabilities like voice calls, text messaging, internet connectivity, and more.
A gNB has a limited capacity to serve multiple users. So, network operators install one every 300-800 meters in densely populated areas and every 2-3 kilometers elsewhere.
Obviously, covering every part of a country this way, let alone the planet, is impractical and expensive.
A typical terrestrial 5G telecommunications network.
5G non-terrestrial networks, specified in the 3GPP 5G NR Release 17 standard, overcome such drawbacks by using satellites or airborne vehicles as radio transceivers in their RANs.
This dramatically expands the coverage of 5G networks to most parts of the planet.
A satellite-based NTN consists of the following components.
- Satellite network: A constellation of satellites acts as a space-based segment of a 5G RAN.
- NTN gateways: These are ground stations to relay data between the satellites and the 5G terrestrial infrastructure.
- NTN payloads: An NTN payload consists of components installed in each satellite to provide 5G capabilities based on the satellite’s role.
- Service links: The radio link set-up between a UE and a satellite is called a service link.
- Feeder links: The radio downlink between a satellite and a ground-based gateway is called a feeder link.
NTNs can serve 5G network roles as transparent relays, base stations, or backhauls.
But satellites aren’t the only option in 5G NTNs because the standard also supports airborne vehicles.
Airborne vehicles are faster, easier, and cheaper to launch than satellites are.
A basic 5G NTN illustrating Non-terrestrial Elements in the Flow of SM Internet into Satellite Constellation.
They can typically stay airborne only for a few hours, or a few days at best, but that is sufficient for many use cases.
The 5G standard supports high altitude platforms (HAPs), which may be manned or unmanned aircraft systems flying at altitudes of 8 kilometers to 50 kilometers.
They may be heavier-than-air systems like airplanes or drones that work on aerodynamic principles, or lighter-than-air systems like airships or balloons that work on the principle of buoyancy in air.
In the 5G architecture, they have similar roles as the satellites, as transparent relays, base stations, or backhauls.
5G non-terrestrial network operations
The non-terrestrial elements of NTNs are expected to operate like their terrestrial counterparts. This implies outcomes such as the following.
- Seamless handovers: Even if a user is moving fast, voice calls and data links must remain intact and seamlessly transfer between cells. Unlike ground-based RANs, the satellites or airborne vehicles may also be moving at high speeds.
- Low latencies: Users expect performance on par with ground-based networks.
- High bandwidths: Their bandwidths must be in the same range as ground-based networks.
Broadband use cases for 5G non-terrestrial networks
Maritime 5G services. People who are out on the ocean for long periods can remain in touch with their families or offices back home without any special devices.
Direct air-to-ground communications (DA2GC) for airlines. While flying, crew and passengers can communicate with people on land and access the internet.
Automotive industry. Connectivity is becoming increasingly important as cars, trucks, and cargo vehicles evolve toward self-driving powered by artificial intelligence, cooperative driving using vehicle-to-everything communications, continuous monitoring of vehicle performance metrics, and dashcam recording for security and insurance purposes.
5G NTNs can ensure that these capabilities work seamlessly even in remote areas with high bandwidth.
What are the challenges of 5G non-terrestrial networks?
5G NTNs face some unique challenges that don’t apply to their terrestrial counterparts.
Some technical challenges include relatively higher latencies, especially with satellite communications due to their altitudes; doppler shifts in radio frequencies due to the fast speeds of orbiting satellites and aerodynamic platforms like airplanes and drones, and the complexity of handovers since users and satellites or airplanes are moving simultaneously.
Disaster Response. Reliable voice calling and data access are invaluable during disasters like floods, forest fires, and earthquakes. They enable public safety officials and rescue teams to coordinate better and share critical information efficiently. For example, drones are a quick and cost-effective way to launch an airborne 5G element that hovers over a disaster zone and provides connectivity to victims and rescue personnel.
National security and defense. Since defense and national security industries often operate in remote areas, they can expand their private 5G networks with 5G non-terrestrial networks for better connectivity and improved efficiency of their workflows.
Broadcasting. Satellites are particularly suited for broadcasting information over wide areas to many edge devices. Examples include public service announcements, entertainment content, sports content, mobile gaming content, and more. 3GPP’s Release 17 introduced enhancements to support 5G multicast-broadcast service (MBS), which can be used to transmit content to multiple users via both NTNs and terrestrial networks.
IoT applications of 5G non-terrestrial networks
IoT applications typically work at low data rates and involve periodic bursts of data transmission. This means that radio bandwidth and other demands on 5G networks are far lower than for broadband use cases.
3GPP specifies multiple IoT standards, including the following.
- Narrowband IoT (NB-IoT): NB-IoT uses very little bandwidth, costs little, ensures long battery life, and is suited to indoor coverage.
- Enhanced machine-type communication (eMTC): This is a part of the LTE machine type communication (LTE-M) standard for machine-to-machine and IoT applications. It uses more bandwidth, is faster than NB-IoT, and is suitable for frequent or continuous communication.
- Reduced capability (RedCap): Also known as NR-Lite, RedCap is a lightweight version of the 5G standard for use cases where ultra-low latency is not essential but reasonable throughput is necessary.
Some industrial use cases of 5G IoT include:
Real-Time asset tracking. Companies can continuously track their assets, such as shipping containers or trucks, around the planet in real time.
Agriculture. Farmers can use 5G NTNs to run unmanned tractors or for livestock monitoring in remote rural areas.
Equipment monitoring. Sensors and trackers in remote locations like oil rigs can be continuously monitored.
The future of non-terrestrial networks
The future will likely see seamless convergence of non-terrestrial networks with terrestrial networks, ushering in a communications revolution with 24/7 connectivity everywhere in the world.
Planned enhancements to non-terrestrial networks include deeper integration of terrestrial and non-terrestrial 5G networks for a seamless user experience, phased array beamforming for far higher data rates, more efficient waveform and transmission techniques for better coverage, reduced transmission losses, and better spectrum sharing with terrestrial networks.
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