Receiver Autonomous Signal Authentication (RASA) based on clock stability analysis

Abstract

Deceptive interference of Global Navigation Satellite System (GNSS) receivers, including deliberate spoofing of GNSS signals, is an increasing concern. Detection and isolation of deceptive interference signals from true GNSS signals is required to assure Position, Navigation, and Time (PNT) integrity and is a particular concern for unencrypted, Open Service GNSS users. A Receiver Autonomous Signal Authentication (RASA) approach is presented which is based on detecting the presence of a deceptive interference signal artifact due to the variation in the propagation delay from the threat transmitter to a moving target receiver. This artifact is not readily observable in the erroneous position solution, but can be observed in the estimated receiver clock state. This paper describes methods to analyze the stability of receiver clock over a short duration to determine the presence of dynamic artifacts that occur due to relative motion between the deceptive interference source and the GNSS receiver. The paper presents a discussion of the statistical decision testing involved with declaring the signals as “authentic” and presents results from a simulation model on the detection performance as well as live data characterization to validate the method described. The proposed RASA capability has the advantages that it can be implemented in receiver software and does not require coordination with other user receivers or require additional hardware.