Enabling Passive Localization with a Single Moving Receiver through Periodic 5G Reference Signals

Abstract

Passive Time Difference of Arrival (TDoA) localization conventionally requires multiple synchronized receivers to obtain spatially diverse observations. In this paper, we show that the periodic nature of the 5G NR downlink Positioning Reference Signals (PRS), combined with receiver motion, provides an alternative source of timing diversity. A single passive receiver identifies consecutive PRS occasions, estimates their periodicity, and exploits observations collected at known positions to synthesize a motion-induced self-TDoA without transmitter synchronization. This measurement is fused with Angle of Arrival (AoA) estimates obtained using MUSIC to determine the transmitter location. Experiments with USRP X310 software-defined radios in a controlled outdoor line-of-sight scenario validate the approach both with full prior knowledge of the PRS sequence and without it, by recovering the required scheduling information and periodicity at runtime from passive observations. Results show that periodicity and motion turn a single receiver into a source of virtual timing diversity, with sub-nanosecond self-TDoA errors in all tests.