Method and apparatus for estimating clock deviations, for virtual synchronization of free-running clocks and for determining the position of a movable object

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This invention describes a method and apparatus for estimating the time deviations between free-running (unsynchronized) transmitter clocks and a reference clock, enabling the virtual synchronization of multiple low-cost transmitters. Instead of using expensive, tightly synchronized transmitters, this technique relies on a stationary reference receiver to model and estimate clock errors using stochastic processes (like a second order Markov process and Kalman filters), and then shares these corrections with movable objects (such as rovers or receivers) for accurate position determination. The approach enables precise position calculations in systems that use unsynchronized transmitters and cheap oscillators.

Use CasesContent extracted from patent full text and abstract with AI.

• Indoor and outdoor positioning systems (e.g., for robotics, drones, or asset tracking) using local radio or microwave beacons with inexpensive hardware.
• Location-based services in environments where GPS is unavailable or unreliable, such as underground, inside buildings, or in urban canyons.
• Sport and athlete tracking on playfields using fixed beacons and mobile trackers.
• Logistics and warehouse navigation of AGVs (Automated Guided Vehicles) using local transmitter networks.
• Synchronizing networks of wireless sensors in industrial monitoring or scientific experiments without high-cost clock hardware.

BenefitsContent extracted from patent full text and abstract with AI.

• Enables cost-effective deployment of accurate positioning systems by allowing the use of unsynchronized, low-cost transmitters instead of expensive synchronized ones.
• Eliminates the need for physical synchronization connections (like cables) or complex communication between transmitters, reducing infrastructure complexity and installation cost.
• Improves position accuracy for mobile receivers by dynamically correcting for clock errors, even with long correction intervals via predictive models (Kalman filters).
• Facilitates scalable and flexible positioning deployments, as adding transmitters requires minimal setup and coordination.
• Enables robust operation in environments where traditional GPS or GNSS signals are unavailable or degraded.

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Patent Abstract

In a method for estimating a deviation between a free-running transmitter clock and a reference clock, at a receiver (12) stationary with respect to a transmitter (10), a transmitter signal generated by the transmitter (10) on the basis of the transmitter clock is received. On the basis of the reference clock, a time of arrival of the transmitter signal and a beat phase of the transmitter signals carrier is determined. On the basis of a clock error model, the time of arrival and the beat phase, the deviation between the transmitter clock and the reference clock is estimated. The clock error model is derived by fitting a correlation function of a stochastic model to a measured auto correlation function of the transmitter clock. Deviations for a plurality of transmitters may be estimated and the transmitters may be virtually synchronized based on the estimations.