Project Members: Zak Kassas and Todd Humphreys

Summary: Opportunistic navigation (OpNav) aims to extract positioning and timing information from ambient radio-frequency signals of opportunity (SOPs). OpNav radio receivers continuously search for opportune signals from which to draw navigation and timing information, while employing on-the-?y signal characterization as necessary. Signals from discovered SOPs are down-mixed and sampled coherently, yielding a tight coupling between signal streams that permits carrier-phase-level fusion of observables from the various streams within a single or distributed state estimator. Multiple OpNav receivers can share information to construct and continuously refine a global signal landscape. This gives rise to cooperative opportunistic navigation (COpNav). Such information sharing can be accomplished through peer-to-peer communication or via a signal characterization database (SCD) and a central estimator.

The first two papers below analyze various scenarios that a COpNav environment comprising multiple receivers and multiple SOPs may exhibit. Subsequently the observability conditions under which a COpNav environment is fully observable are derived. Notions of nonlinear and linear observability of dynamic systems are invoked to rigorously prove such conditions. For scenarios where the COpNav environment is not observable, the unobservable directions in the state space are specified. Moreover, the degree of observability, also known as estimability, of the various states is assessed. The observability and estimability results offered are verified through simulations.

Related Publications:

Observability and Estimability of Collaborative Opportunistic Navigation with Pseudorange Measurements

Observability Analysis of Opportunistic Navigation with Pseudorange Measurements

Highlight: Collaborative Opportunistic Navigation