Clock-aided satellite navigation receiver system for monitoring the integrity of satellite signals

A satellite navigation receiver system detects faulty range measurement signals from navigation satellites and excludes them from future position estimates. This system includes a receiver coupled to a movable object. The receiver includes a stable clock with a constant frequency drift rate over a predetermined period of time. A processor coupled to the receiver models the behavior of the clock over a time period equivalent to the period of constant frequency drift rate. The processor then generates predicted clock bias estimates over a future period of time equivalent in length to the period modeled, generates an instantaneous clock bias estimate using satellite signals, and determines the difference between the instantaneous clock bias estimate and a predicted instantaneous clock bias estimate. If the difference does not fall within an acceptable limit, one or more signals are determined to be faulty. When at least five satellites are in view, the processor determines which satellites have generated the faulty signals by generating sets of position and clock bias estimates and performing four- and three-dimensional estimation to determine consistency of the sets. An inconsistent set suggests the existence of a malfunctioning satellite. Signals from malfunctioning satellites are excluded from future position estimates.