GPS Spoofing Resilience via NMA/Watermarks Authentication and IMU Prediction

Abstract

A tightly coupled GPS/IMU estimation algorithm is developed assuming that all received measurements must first be authenticated by CHIps MEssage Robust Authentication (CHIMERA). CHIMERA is designed to authenticate incoming GPS signals through two methods referred to as the fast and slow channels. This paper analyzes the accuracy of estimation algorithms for both of these channels when using an Inertial Measurement Unit (IMU) to compensate for authentication delay, and it considers the effects of different quality IMUs. This paper also introduces a concept of authentication staggering as a possible approach to improve location and attitude accuracy. The estimation algorithm is modified to account for authentication staggering and different possible estimation architectures are developed for this purpose. The results indicate that the fast channel produces typical GPS navigation accuracy for different quality IMUs while the slow channel has moderately degraded navigation accuracy even with a navigation-grade IMU and highly degraded accuracy with tactical- and MEMS-grade IMUs. Staggering the authentication times of the GPS satellites can be used to improve navigation accuracy for the slow channel.