By Kelly Hill
5G has become more broadly deployed across the planet, but the technology may also eventually end up in the skies. 3GPP has established, and is continuing to build upon, standards that will enable 5G services to be delivered over satellite infrastructure, otherwise referred to as 5G New Radio over non-terrestrial networks (NTN).
How might 5G NR over non-terrestrial networks be used? It depends on which type of satellite network is used: Geostationary Earth Orbit (GEO), Medium Earth Orbit (MEO), or Low Earth Orbit (LEO) systems, each of which inhabit a different range of distances from Earth, with LEO systems the closest and GEO systems that furthest away. Depending on the system, satellites can also be stationary or in orbit in relation to earth, which leads to tradeoffs in performance (particularly latency) and complexities of deployment and continuity of coverage, according to a recently published white paper on 5G and non-terrestrial networks from 5G Americas.
Work on NTN began in 2017 with a study item in 3GPP’s Release 15, and 3GPP’s Systems Aspects working group has built upon that work by outlining categories of use cases. 3GPP is “now concentrating on the normative work for support of LEO and GEO satellites using 5G,” according to the white paper.
The use cases for 5G NR over non-terrestrial networks fall into three main categories: Service continuity, where terrestrial 5G networks alone cannot provide sufficient coverage for a 5G service; service ubiquity across unserved or under-served areas; and service scalability, for use cases such as multicasting or broadcasting that would leverage the large areas covered by satellites.
More specifically, 5G Americas outlined a series of 5G enhanced mobile broadband (eMBB) and massive machine-type communication (MMTC) use cases that could be well-served by having 5G NR over non-terrestrial networks capabilities. Those include:
-Satellite connectivity providing a backhaul link between the network core and 5G cells that are isolated from the rest of the network. These would be primarily eMBB use cases, either fixed or mobile. For instance, satellite infrastructure could link a 5G site that is providing fixed wireless broadband to an isolated village or a mining or industrial site, to the network core.
-Alternatively, 5G NR over satellite infrastructure could connect 5G nodes on moving aircraft or ships, which travel where there simply is no existing infrastructure.
-A third scenario would be a multi-connectivity environment, where there are users in underserved areas—which could be rural areas, small office buildings, or places like temporary festival grounds—are connected to 5G by multiple network types. Traffic which can tolerate latency could be routed over the 5G-NR-over-non-terrestrial-networks path, while latency-sensitive traffic could take a terrestrial route in order to increase the overall system performance and capacity.
-5G NR over non-terrestrial networks could also help to prevent network outages by offering a backup network connection, although that connection may not be quite as high-performance as the terrestrial network option. This would have utility for public safety connectivity, as well as increasing overall network resilience.
-5G NR over non-terrestrial networks could also serve as a trunking technology in environments where operators want to connect multiple “islands” of 5G sites that are not otherwise connected, or that have been deployed for, say, disaster relief or in isolated areas. This is another 5G eMBB use case.
-5G NR over non-terrestrial networks could also make use of the 5G Broadcast/Multicast function and actually be used for satellite-based television or multimedia services, delivering content to either fixed or mobile end user devices.
-3GPP is also exploring 5G IoT use cases for 5G NR over non-terrestrial networks. This could be particularly useful for telematics use cases in automotive or transportation use cases, like the ability to maintain automated vehicle platoons in areas without terrestrial 5G coverage, to distribute vehicle software updates to geographically isolated areas, or to gather information from far-flung fixed or mobile sensors around the globe that must report to a central server.
