PNT Trust Inference Engine Reference Architecture

The ever-increasing set of threats to positioning, navigation, and timing (PNT) has led to the need for resilient PNT user equipment (UE), which in turn has led to efforts from the Department of Homeland Security (DHS) to define a framework for resilient PNT UE [1]. Fundamental to resilient PNT UE is the need to measure trust in both the PNT sources and the PNT solution computation. These trust assessments should encompass all relevant information, including prior assumptions of the environment, possible threats, and any situational awareness (SA). Previous work has proposed a PNT Trust Inference Engine (PNTTING) to provide such trust measures [2][3]. The relationship between the PNT computation and PNTTING assessments leads to the hierarchical recursive structure, which defines the PNTTING reference architecture. The core piece in the PNTTING reference architecture is the computational block, which is defined in sufficient generality to allow one or more inputs from the PNT engine, such as observations and statistical tests, and combine them as needed to yield the trust assessments. This computation maintains internal state as needed and potentially has any side information as input. Since PNTTING computational blocks can take as input the results of other blocks, a recursive architecture can be built up. The structure culminates in a final block, called the PNTTING controller, which aggregates the trust information and provides for decisions needed by the PNT UE. We show some initial examples of how this could work in practice.