Matthew BoyleAs we move towards creating international 5G service coverage, non-terrestrial networks (NTN) technology has the potential to eliminate various challenges. Over the past two decades, the world has experienced widespread innovation in mobile technologies. We have seen breakthroughs in Wi-Fi connectivity, biological, and considerable growth in attached devices. But patchy coverage, dropped calls, and inconsistent data speeds continue to challenge 4G and 5G networks, stemming from the natural limitations of earth networks.
Terrestrial over non-terrestrial networks (NTN)
Network providers deploy earth networks on the ground, as their names imply, and NTNs are deployed in Earth orbit. NTNs enable telecommunication services to reach remote areas that are not possible with standard ground-based networks by using satellite systems or flying platforms. Below is a typical 5G telecommunications network with user equipment (UE), radio access network (RAN), and core. In essence, UEs must communicate with a 5G RAN, which sends voice and data from the UEs to the 5G core and up. The issue is that this relies on cell towers that can only provide a minimal number of users at once.
To overcome this challenge, network operators usually install one cell tower every 300-800 meters in densely populated areas and every 2-3 kilometers abroad. But covering a country this way, or the planet, proves impractical and extremely costly.
NTNs offer a more practical solution, considerably expanding 5G coverage worldwide. Making use of satellites or flying vehicles as RAN transceivers increases demand and traffic and provides connectivity in difficult-to-reach areas. But, there are also challenges when it comes to NTN networks. One of the crucial hurdles to overcome is ensuring natural, system, and application layer compatibility, as well as addressing issues related to standards compliance and performance benchmarks.
NTN was introduced into the 5G standard thanks to standards like the 3rd Generation Partnership Project (3GPP ). This means that engineers can add satellite links to 5G devices, enabling connectivity whether it is from earth-based or non-terrestrial infrastructure. The market for satellite communications has expanded with the introduction of 3GPP 5G NTNs to include earth cellular network operators as well. This enables users to have immediate access to satellite mobile services between 5G-compliant NTNs and terrestrial wireless networks.
Although this is a wonderful step forward, amazing NTNs that operate outside of accepted standards also present challenges. For example, SpaceX’s Starlink offers global internet access, but because Starlink operates outside of 3GPP standards, users also need an extra gateway device for Starlink internet access.
Satellites and aerial vehicles
When it comes to satellite-based NTNs these consist of NTN gateways, service links, and feeder links. The satellite can play a number of different roles, including serving as a relay link between UEs and NTN gateways, as depicted in Figure 2 below.
Additionally, network developers could use the satellite as a gNB base station, as seen in Figure 3. Also, as shown in Figure 4, satellites may serve as a backhaul between a distant terrestrial RAN and a 5G core. A network operator might use a satellite as a relay, gNB, or backhaul to extend network coverage to rural areas, provide redundancy in case of earth network failures, and support high-capacity, high-speed data transmission.
With the standards even allowing flying vehicles, satellites are not the only option when it comes to 5G NTNs. The 5G standard includes high altitude platforms (HAPs) flying at altitudes of 8 – 50 kilometers, including heavier-than-air systems like airplanes or drones and lighter-than-air systems like airships or balloons. Similar to satellites, they function as open relays, base stations, or backhauls. HAPs enable faster, easier, and cheaper launches compared to satellites. However, they usually only stay aerial for hours or days, simply enabling momentary coverage.
The future
Users can expect the same level of service regardless of whether they use geological networks or NTNs. NTNs come with their own distinct set of challenges, including latency issues brought on by satellite altitude, handover complexity given the continuous movements of users and satellites, and a Doppler shift in frequency due to the speed of satellite orbit.
NTNs are widely discussed when it comes to use cases for national security, defense, and disaster response. NTNs might prove even more potent commercially, especially for transportation and business IoT applications, despite the fact that these emergency scenarios would undoubtedly benefit from widespread network coverage. When it comes to supporting offshore oil rigs, merchant shipping, fishing crews, or airline communication, enabling communication in hard to reach places will have a big impact. When it comes to business IoT applications, most use cases relate to tracking and sensing technologies, such as real-time asset tracking, equipment monitoring, and bright farming. Although these applications typically operate at lower data rates, they do need to adhere to the standards that 5G NTN was created to support.
Ultimately, NTNs are not a magic bullet for delivering global connectivity. But, standards bodies are considering adding new features to the NTNs in upcoming 5G New Radio and 6G standards releases. Enhancements include increased coverage and increased data rates achieved by using phased array beamforming and more effective transmission methods. Also, custom NTNs will continue innovating based on market demands. NTNs will revolutionize wireless connectivity and make a quick, reliable network coverage available for both business and professional IoT applications.
