Open NTN Testbed Release 4: Network-Verified UE Positioning with Multi-RTT and Dynamic LEO Geometry
Open NTN Testbed Release 4 provides network-verified UE positioning within a software-defined Low Earth Orbit (LEO) NTN environment, integrating OAI Location Management Function and 3GPP Release 18 NTN Multi-RTT positioning protocols. The system derives UE position solely from NTN link measurements, utilizing a common orbital model to synchronize satellite ephemeris data across signaling, channel simulation, and the positioning solver. Three positioning scenarios are demonstrated: single-satellite, cross-plane satellite switching, and concurrent dual-satellite positioning, achieving approximately 32 meter positioning error with a 10 meter uncertainty after 601 seconds. Validation confirms positioning ambiguity resolution within 15 seconds of a satellite switch and a 13.6 meter error post-resolution, while also verifying the positioning chain against emulator references and round-trip timing measurements.