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.
Non-terrestrial networks (NTNs) can not only alleviate these problems but also potentially expand 5G coverage to the entire planet. In this article, you will:
- find out what non-terrestrial networks are
- understand their architecture
- learn their use cases in different industries
What Is a Non-Terrestrial Network?
Non-terrestrial networks (NTN) are wireless communication systems whose components are deployed in the Earth's atmosphere or in space around the Earth instead of on land.
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 organization 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. 5G NTNs are on the verge of dramatically improving global connectivity.
The Architecture of 5G Non-Terrestrial Networks
A typical terrestrial 5G telecommunications network is shown below.
It consists of:
- 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.
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 basic 5G NTN is shown below:
Non-terrestrial Elements Illustration | Flow of SM Internet into Satellite Constellation
Let's look at these non-terrestrial elements in more depth.
How Are Satellites Used in Non-Terrestrial Networks?
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.
One possible role is as a relay satellite link between UEs and NTN gateways, as shown below:
A second possible role is as a full gNB base station:
A third possibility is as a backhaul between a remote terrestrial RAN and a 5G core:
What Types of Satellites Are Used in Non-Terrestrial Networks?
Depending on their orbits and heights, NTN satellites can be one of the following types:
- Geosynchronous orbit (GSO): Since their orbital speeds match the Earth's rotation, they appear stationary over a certain longitude.
- Geosynchronous equatorial orbit (GEO): This is a special GSO around the equator, making it seem stationary from anywhere on the planet — so it's also called geostationary orbit.
- Low Earth orbit (LEO): A LEO satellite has a non-geosynchronous orbit (NGSO) at an altitude between 300 kilometers and 1,500 kilometers.
- Medium Earth orbit (MEO): This is an NGSO at an altitude between 7,000 kilometers and 25,000 kilometers.
Satellites aren't the only option in 5G NTNs because the standard also supports airborne vehicles.
How Are Airborne Vehicles Used in 5G Non-Terrestrial Networks?
As compared to satellites, airborne vehicles are faster, easier, and cheaper to launch. 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. Further, they may be:
- heavier-than-air systems like airplanes or drones that work on aerodynamic principles
- 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.
In the next section, we explore various applications of 5G NTNs in different industries and see how these architectures and operational aspects play out.
Broadband Use Cases for 5G Non-Terrestrial Networks
The 3GPP standard supports two distinct categories of applications:
- High-data-rate communications like voice and video calls
- Low-data-rate messaging suitable for Internet of Things (IoT) use cases
We'll look at the high-data-rate broadband applications here.
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. Those in this category that benefit from non-terrestrial communication services:
- oil and gas industry, especially workers on offshore oil rigs
- merchant shipping
- research vessels
- fishing and whaling industries
- cruise ships
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
- dashcam recording for security and insurance purposes
5G NTNs ensure that these capabilities work seamlessly even in remote areas with high bandwidth.
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 of the planet, 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. Let's explore some industrial uses of 5G IoT.
3GPP specifies multiple IoT standards:
- 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.
The 5G NTN specification is designed to support all these standards for the use cases described below.
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.
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
- the complexity of handovers since users and satellites or airplanes are moving simultaneously
What Is the Future of Non-Terrestrial Networks?
Enhancements to non-terrestrial networks are planned both under future releases of the 5G NR standards and the new 6G standard. They 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
- better spectrum sharing with terrestrial networks
Keysight Solutions for 5G Non-Terrestrial Networks
Keysight offers an extensive set of products and solutions for 5G non-terrestrial network testing and measurements. State-of-the-art products are available to assist network equipment manufacturers, satellite service providers, network operators, device manufacturers, and chipset makers.
Radio Frequency Testing
Keysight solutions for testing radio communications and satellite connectivity include:
- E7515B/E7515R UXM 5G Wireless Test Platforms for comprehensively emulating a 5G RAN
- S8825A Satellite and Aerospace Channel Emulation Toolset, a comprehensive solution, based on Keysight's PROPSIM channel emulation platform, to test the performance of both non-terrestrial and terrestrial links
- SJ001A WaveJudge Wireless Analyzer Toolset to analyze wireless transmissions between UE-satellite, satellite-gateway, and gateway-gNB
End-to-End Testing
Facilitate your acceptance testing with:
- S8707A RF/RRM Carrier Acceptance Toolset with carrier acceptance test plans and test scenarios mandated by the world’s major 5G mobile network operators, including NTN carrier acceptance 3GPP requirements
- S8711A UXM 5G Test Application with NTN and RedCap support for 5G NR chipset and device development
UE simulation
Simulate realistic user equipment loads with:
- P8800S UeSIM UE EmulationRAN Solutions to validate end-to-end RAN performance by emulating real network traffic over both radio and O-RAN interfaces
In addition, we have products for:
- satellite power testing
- satellite solar array simulations
- space system simulations
- ground system simulations
- edge-to-core solutions
- core network simulation
Cutting-Edge 5G Non-Terrestrial Networks With Keysight
This article explained the basics of 5G NTNs and where they're headed with upcoming standards. 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. Contact us for guidance on your 5G requirements.