One of the new topics covered in the MSSA’s MSS Reference Architecture 2.0 is how satellite systems can support both 5G NR and NB-IoT within a shared non-terrestrial network (NTN) architecture. This matters because, as NTN D2D networks evolve from supporting limited narrowband service offerings to multi-service platforms supporting low-intensity IoT to consumer and enterprise broadband services and everything in between, operators will need to develop technology approaches that efficiently converge multiple high-performance NTN protocols.
Reference Architecture 2.0 looks at this convergence because both NR and NB-IoT are 3GPP-standardized technologies for NTN, and each brings different strengths to the NTN service mix. NB-IoT is well suited to low-power, low-cost, low-data-rate applications for lower-cost devices, while 5G NR provides the broader performance envelope needed for richer mobile experiences and higher-throughput use cases.3GPP has addressed how NB-IoT operations can coexist within wider NR carriers in the standards. Reference Architecture 2.0 examines what this multi-service coexistence means in mobile satellite architectures, where spectrum, payload resources, and beam capacity are more constrained.
For direct-to-device services, this pairing creates a practical evolution path. NB-IoT can continue to support essential use cases such as basic messaging, emergency alerting, wearables, and traditional IoT connectivity. As demand grows for more interactive and broadband-like services, operators can introduce wider-band NR capabilities while still supporting the installed base of narrowband devices and growing their IoT business.
However, supporting both radio access technologies is not simply a matter of turning on two services at once. NR and NB-IoT have different bandwidth profiles, timing behavior, duty-cycle expectations, and capacity requirements. These differences become especially important in satellite payloads, where mass, power, antenna resources, RF chains, and beamforming capability are all tightly constrained.
Radio Unit (RU) sharing is therefore a central design question. In this context, RU sharing means using a common set of payload resources – RF chains, antenna elements, and beamforming assets – to support more than one access technology. Duplicating hardware for each service layer would increase payload complexity, cost, power consumption, and risk. The challenge is that every shared-resource decision introduces trade-offs.
One design path gives NB-IoT a larger share of available RU resources, such as transmit and receive chains or simultaneously active beams, to support its service continuity and higher duty-cycle needs. Another path uses wider beams or alternative beamforming strategies for NB-IoT, reducing the number of dedicated chains while accepting potential compromises in spatial efficiency or link performance. Neither approach is universally right; each reflects a different balance among coverage, capacity, hardware efficiency, and service agility.
These choices ripple through the rest of the system. They influence beam-hopping patterns, scheduler behavior, traffic prioritization, and how quickly resources can be shifted between NR and NB-IoT as demand changes. An architecture tuned mainly for NR throughput may limit NB-IoT scale. A design optimized around NB-IoT coverage and persistence may reduce total NR capacity. The optimal answer depends on the constellation, payload limits, target markets, and expected service mix.
By adding this topic, Reference Architecture 2.0 helps frame a key design question for next-generation NTN systems: how to support multiple service types efficiently within limited satellite and spectrum resources. It evaluates the system-level trade-offs associated with shared NR and NB-IoT deployments, helping operators and vendors align RU designs with service priorities, payload constraints, and long-term evolution strategies while maintaining overall efficiency and flexibility.