Narrowband Internet of Things over Non-Terrestrial Networks for Remote Renewable-Energy Management: Architecture and Performance Evaluation

Reliable communication is essential for monitoring and supervisory operation of renewable-energy facilities beyond terrestrial-network coverage. This study proposes a four-layer Internet of Things (IoT) architecture aligned with 3GPP Release 17, integrating sensors, an edge gateway, Narrowband IoT (NB-IoT) access through a transparent satellite payload, terrestrial core-network functions, and centralized IoT, Energy Management System (EMS), and Supervisory Control and Data Acquisition (SCADA) applications. A 3GPP-aligned analytical framework evaluates satellite geometry, transparent-path propagation delay, deterministic uplink and downlink margins, and pass-level outage probability for Low Earth Orbit (LEO) satellites at 600 and 1200 km, medium Earth orbit (MEO) at 10,000 km, and geostationary Earth orbit (GEO) at 35,786 km, complemented by a waveform-level Narrowband Physical Downlink Shared Channel (NPDSCH) reliability experiment for a representative LEO-600 downlink. At a 50∘ elevation angle, the one-way satellite-induced propagation delay ranges from 5.08 ms (LEO-600) to 247.35 ms (GEO). With single transmission, the uplink is the limiting direction and does not achieve link closure in any evaluated scenario. The LEO downlinks achieve positive margins at sufficiently high elevation angles. A 1% pass-averaged outage probability requires approximately 17 dB of uplink coverage enhancement for LEO-600, whereas the MEO and GEO requirements exceed the standardized repetition range. Realized NPDSCH repetition gains (approximately 5.5 and 9 dB for 8 and 32 repetitions) remain below the ideal values. The findings identify the link-budget and delay conditions under which NTN-assisted IoT may support periodic monitoring, alarm and maintenance traffic, and non-time-critical supervisory communication, while protection functions remain local.