By: Paul Tindall

Mobile Network Operators (MNOs) have spent decades navigating challenges surrounding interoperability to deliver services to customers. An MNO user can access networks around the world using the same handset. To get to this point, all networks and manufacturers have worked to a standards-based approach to guarantee interoperability. This is markedly different from the structure of satellite operations. Satellite Network Operators (SNOs) utilise proprietary infrastructure, allowing these organisations to maximise spectral efficiency through their physical infrastructure, resulting in operational and cost efficiency whilst maintaining full control over their assets.  These vastly different approaches bring a new challenge to both industries: how should networks be structured to encompass both types of operator? 

The need for convergence  

It is important to consider why MNOs and SNOs are looking towards a future in which their services are linked. MNOs deliver low-cost connectivity to a high number of users using terrestrial infrastructures. This provides reliable, mobile, low-latency services to users, with a well-established ecosystem ensuring that regular devices can connect easily when in range of a mast. However, coverage is limited by infrastructure; remote areas are often underserved or even unserved , whilst geographical topography can impinge on signal availability. On the other hand, SNOs deliver wide-reaching coverage with high-bandwidth, this has traditionally been delivered at a higher price whilst requiring specialist equipment to access the network. It is clear to see why SNOs and MNOs will benefit from working alongside one another; each delivers what the other is limited by. But this leads us on to the question: how?  

In 2022, the 3GPP initiative delivered Release 17, the first to cover 5G NTN. 3GPP specifications cover cellular telecommunications technologies, including radio access, core network , and service capabilities. The telecommunications industry has been built upon 3GPP standards to ensure seamless interoperability amongst networks and devices. From a terrestrial perspective, 5G NTN has introduced changes to assumptions that cellular networks have relied upon for decades, including fixed cells, short propagation delays, continuous coverage, modest Doppler , and largely national operating domains.   

Release 17 introduced normative requirements for NTN networks in 3GPP specifications. This formally introduced requirements for satellites to become a part of the 5G network, laying out how technologies must be orchestrated to ensure interoperability, including satellite access, service continuity between terrestrial and satellite networks, roaming/network selection for satellite-capable UEs, UE location support, and NR operation over NTN. Release 18 has continued to build on this, driving the integration of NTN more deeply into 5G-Advanced, including satellite IoT/MTC support, additional spectrum, work, and satellite backhaul considerations.   

As two communications industries expand to encompass one another, are MNOs and SNOs facing the same challenge to achieve interoperability?  

MNOs: simply adapting already agile networks?   

Having developed in isolation from one another, MNO and SNO networks are built on incredibly different infrastructures. Adapting to deliver 5G NTN to deliver interoperability between the two industries is set to pose different challenges for each. Modern MNO networks are already built upon modularity and interoperability, and are therefore in a strong position to adapt to the new demands of 5G NTN. The handset, RAN, core, transport, OSS/BSS, and service platforms are separated by standardised interfaces, with independent conformance testing and certification keeping the ecosystem working efficiently. Due to the nature of the industry, MNOs are used to multi-vendor procurement, software upgrades, cloud-native cores, virtualised network functions, orchestration platforms, and continuous lifecycle management.   

Although it will not require a complete reinvention of the MNO network, NTN adds new physics into a system designed around terrestrial assumptions. Networks must cope with long and variable delays, high Doppler, moving beams, intermittent coverage, weaker link budgets, and more complex spectrum coexistence. This impacts mobility management, timing, random access, scheduling, RF performance, device testing, orchestration, and service assurance. The move to NTN is going to require a shift in working for MNOs, especially surrounding RF, mobility, spectrum, interference, and assurance which is a challenge the magnitude of which we don’t yet fully realise. However, these changes are being added to operating systems which are already agile, reducing the scale of the challenge for the industry. Flexibility is a key attribute within the telco industry, and MNOs are comfortable in adapting to the demand of industry standards to access global networks. 5G NTN is an extension of this demand, albeit a significant and emerging one.