LEO Satellites for Remote Regions IoT Devices Communicate with Satellites via Standard Mobile Network Protocols

The integration of Non-Terrestrial Networks (NTN) with LEO satellites enables a global, seamless connection to remote areas. With their direct-to-device communication, Nordic Semiconductor and Sateliot have achieved an important development milestone. Now, demanding RF measurement and validation procedures are the focus of device development.

The latest developments in communication via Non-Terrestrial Networks (NTN) in conjunction with LEO satellite constellations complement terrestrial mobile networks and enable data transmission even in remote regions.

Nordic Semiconductor is combining the LTE-M/NB-IoT-compatible nRF9151 System-in-Package with Sateliot's LEO satellite network in current projects. This enables so-called direct-to-device communication, where IoT devices can connect directly to the satellite using standard-compliant mobile network protocols (3GPP Release 17 for NTN-IoT).

"This successful test confirms Nordic's commitment to pushing the boundaries of satellite communications," says Oyvind Birkenes, EVP Long Range BU at Nordic Semiconductor. The satellites function as flying radio cells, handling signaling and data transmission via an extended terrestrial core network. Ground infrastructure remains an essential component. Gateways and core network interworking units manage routing and network synchronization. A fully direct chip-to-cloud connection without terrestrial gateways is possible via a hybrid model.

The nRF9151 module is characterized by very low idle current and optimized power-saving mechanisms. This allows acceptable energy efficiency to be achieved despite the higher link budgets in satellite operations, particularly during periodic or event-driven data transmission with long standby phases.

Lack of terrestrial network coverage

The integration of an LEO-NTN connection creates application opportunities in areas where terrestrial network coverage is patchy or economically unfeasible, such as precision agriculture (smart farming), maritime logistics and fisheries data transmission, environmental and climate monitoring in polar or desert regions, and global asset and container tracking. As Jaume Sanpera, CEO and co-founder of Sateliot, emphasizes: "We are delighted to collaborate with Nordic Semiconductor to achieve such a democratization of satellite connectivity."

Future devices must implement mechanisms for satellite handover, Doppler correction, and link quality monitoring. On the hardware side, frontends with high frequency stability, efficient LNA/RF path architecture, and frequency-agile PLL are essential to ensure consistent reception quality.

Requirements for RF measurement technology

LEO-based NTN connections bring entirely new requirements to RF measurement technology. The key measurement parameters include:

• Doppler shift and frequency drift: Due to the high relative motion (typically 7 to 8 km/s, approx. 4 to 5 miles/s) between the satellite and the end device, Doppler shifts of ±40 kHz occur at frequencies around 2 GHz. The measurement approach involves the use of frequency-stable signal generators (rubidium-referenced) and real-time spectrum analyzers with Doppler tracking functionality to dynamically capture frequency drift and signal distortion.
• Link budget and path loss analysis: LEO links exhibit variable attenuation profiles due to changing elevation angles. Developers use RF vector signal analyzers, coupled with correction algorithms for atmospheric attenuation and polarization effects, to conduct accurate measurements.
• EVM and modulation analysis: The quality of the transmitted NB-IoT or LTE-M signals in the satellite link is determined using Error Vector Magnitude (EVM) and modulation errors. Digital downconverters with real-time demodulation software are used to characterize bit error rates and modulation integrity over time.
• Spectral adjacent signals and interference analysis: As multiple satellites operate on the same frequency bands, spectral purity is critical. Multi-channel spectrum measurements with high dynamics (ENOB > 10 bits) are used to capture side lobe, IM3, and Adjacent Channel Leakage Power (ACLR) effects.
• Timing and synchronization measurement: Due to variable propagation delays between the satellite and the device, timing deviations must be precisely analyzed. Cross-correlation methods between uplink and downlink references using phase noise analysis are employed for this purpose.

These parameters are essential for the validation of communication modules and form the basis for pre-compliance tests as well as subsequent certification processes according to 3GPP NTN guidelines. Jesper Noer, VP Commercial at Gatehouse Satcom, summarizes the progress as follows: "This breakthrough in satellite-based IoT connectivity, achieved in collaboration with Nordic Semiconductor and Sateliot, underscores the potential of teamwork."

Nordic, Sateliot, and Gatehouse Satcom will continue working in the coming months to make the solution available to developers and companies looking to test and develop commercial components with NTN-LEO connectivity. The nRF9151 with NTN support is expected to be available from early 2026. (heh)