The battle for market share for satellite connectivity, delivered by non-terrestrial networks (NTNs), is well underway, with satellite companies, telcos and handset vendors all vying for a position in this rapidly growing market. We’ve already seen pioneering moves from a number of high-profile names, with early partnerships beginning to form that will ultimately enable seamless 5G NTN connectivity to become a reality.
This includes T-Mobile and SpaceX announcing their intention to join forces to serve T-Mobile customers in rural or remote locations. Apple’s iPhone 14 also made waves as the first major smartphone to offer messaging via satellite connectivity for emergency situations. And interest isn’t waning as in March Amazon shared plans to launch its first internet satellites to compete with SpaceX, and OneWeb completed a constellation that it says will offer global coverage as early as later this year.
The recent flurry of satellite-focused activity can be attributed in part to the 3GPP’s standardization on 5G NTNs, which has been ongoing for around four years. 3GPP Release 17 was approved in 2022 and has already enabled major chipset suppliers such as MediaTek and Qualcomm to deliver solutions covering the integration of TNs and NTNs for use in consumer handsets. While this is welcome, it does mean the developments that have been made with earlier designs have come before the industry has been fully standardized, which limits their potential.
Until 3GPP Release 17, NTNs have been developed based on siloed approaches and proprietary technology. This means that handset providers and chipset manufacturers looking to offer satellite connectivity have only partnered with a single NTN provider. For example, Apple has partnered with Globalstar, and Qualcomm with Iridium. The result is that the satellite capabilities they offer are restricted by the individual networks and the coverage and performance they offer.
However, T-Mobile and SpaceX’s pledge to provide near complete coverage in the U.S. — using T-Mobile’s spectrum compatible with existing handsets — signifies an intent to open up satellite connectivity to a wider audience by creating networks that converge with terrestrial networks (TNs) and are built-on industry standards.
The 3GPP’s standards will eventually allow for 5G NTN-enabled chipsets and handsets to be released that will be compatible with multiple satellite providers. This will enable them to provide wider coverage, but certain network challenges still need to be overcome to achieve this.
So, what does 3GPP standardization mean for the way that networks are being built?
Satellite payloads operate in very harsh, constrained environments. Until recently, each constellation has tried to overcome these challenges with unique architectures and operational requirements, taking time and considerable financing. To battle these challenges, the 3GPP has defined two architectures for how 5G NTNs connect to terrestrial infrastructure: ‘transparent’ and ‘regenerative.’
The transparent architecture is composed of connectivity via a satellite acting as a repeater with the gNB on the ground. This still meets link-budget requirements, but since each satellite is only repeating the signal, there is additional latency and greater feeder-link demands to operate multiple beams.
The regenerative model, on the other hand, sees the gNB installed on the satellite. It is generally preferred as it provides greater performance enhancements than the transparent model by avoiding some of the latter’s pitfalls, whilst improving link budget management and avoiding the need for each satellite to have good visibility of a ground station.
This model takes inspiration from O-RAN architecture, and splits RAN processing across the radio unit, distributed unit and centralised unit. RAN components can therefore be more easily located within the satellite infrastructure and multiple satellites are able to connect to a single gateway, communicating via satellite links allowing for a denser deployment of satellites in space. This leads to greater coverage and better performance, such as reduced latency and increased bandwidth efficiency.
However, while designing NTNs based on the regenerative model will enhance their performance, it won’t remove their complexity. These networks will need to comprise vast numbers of satellites and beams, which must be properly coordinated to interoperate with TNs and provide universal coverage. As well as working together on system engineering and modeling to tackle these issues, terrestrial and non-terrestrial players will need to coordinate to overcome the problem of spectrum constraint.
Fortunately, the FCC recently came out in support of 5G satellite connectivity by proposing a framework that will allow satellites to re-use MNO spectrum in areas not covered by TNs. In essence, this will see satellite-enabled handsets being served by satellite signals when terrestrial signal isn’t available. This so-called ‘supplemental coverage from space’ approach will enable satellite operators to use spectrum that is currently licensed to terrestrial services in a move that will mitigate the challenges of limited spectrum availability.
Just as with the performance transitions from 2G to 5G, we’ll soon come to rely on the ubiquitous coverage provided by 5G NTNs to fill coverage gaps worldwide. Together, standardization and the allocation of additional spectrum for satellite use cases are the key to enabling this, as these two factors are essential to achieve the performance and economies of scale that will make widespread NTN access a real possibility in the future.
As the industry standardizes and NTNs become more economically viable, satellite operators, telcos, equipment and handset vendors can invest in overcoming the remaining network challenges associated with their development – such as how to optimize performance – safe in the knowledge that they are working towards a shared goal, with the potential for integration and deeper partnerships. Therefore, a defined 3GPP roadmap that will increase the available performance of NTNs and facilitate this sector’s momentum can’t come soon enough.