Back to results
US 8,818,406 B2Granted
TDOA based positioning with calculation of correction factors for compensating the clock offsets of unsynchronized network stations
OwnerDavid Bevan, Simon Galeinventors
Life of this patent
Estimating the term…
Abstract
The present invention presents a method, arrangement and computer program product for clocking exploiting the relative behavior of clocks of individual receiving stations as well as a corresponding modeling to derive a time difference of arrival of a signal from a user device which can be used to correct the time difference of arrival based on the modeled clock behavior and leads to a correct clocking of received user signals without the need of synchronization of the clocks in the various receiving stations. This principle is applicable to a plurality of pairs of receiving stations and beacon signals transmitted amongst them and allows for a correct location estimation of a user device.
Claims17
Method for clocking involving at least a first device, a second device and a third device in a fixed positional relationship, the method comprising:
- at least the first device transmitting a sequence of unique signals comprising at least a first and a second signal having a unique identification;
- measuring the reception times of the uniquely identified signals at at least the second and third device with a respective second and third local clock of the second and third devices,
- at least the second and third device associating a reception time of the second and third device to respectively the first and the second signal upon reception thereof, leading to at least two value pairs of local clocks of the second and third device;
- based on the value pairs of local clocks, modeling a time function of a dependency of the second and third local clock over time as a first model curve;
- at an arbitrary point in time receiving a user signal from a user device at the second and third device and associating a reception time measured by the respective second and third local clock of the second and third device to the user signal upon its reception, leading to a user value pair of local clocks of the second and third device;
- calculating a reference time difference of arrival RTDOA for a signal from the first device received at the second and third device from the fixed positional relationship, based on the respective distance between the first and the second device and the first and the third device and the known signal propagation speed;
- calculating a user time difference of arrival UTDOA from the user value pair;
- at the arbitrary point in time determining a value from the first model curve and based on this value calculating a determined time difference of arrival DTDOA;
- relating the RTDOA to the DTDOA to determine a current correction factor;
- and
- for clocking using the current correction factor to correct the UTDOA.
8 more elements
Arrangement for clocking comprising:
- at least a first, a second and a third device in a fixed positional relationship;
- the first device having a transmitter for transmitting a sequence of unique signals comprising at least a first and a second signal with a unique identification;
- the second and third devices having a receiver for receiving the at least first and second signals and a respective second and third local clock of the second and third device for measuring the reception times of the uniquely identified signals at at least the second and third device, and a processor for associating a reception time measured by the respective second and third local clock of the second and third device to respectively the first and second signal it upon reception thereof, leading to at least two value pairs of local clocks of the second and third device;
- the processor for modeling based on the value pairs of local clocks a time function of a dependency of the second and third local clocks over time as a first model curve;
- the second and third device further being adapted for receiving at an arbitrary point in time a user signal from a user device at the second and third devices and associating a reception time measured by the respective second and third local clocks of the second and third devices to the user signal upon its reception, leading to a user value pair of local clocks of the second and third devices,
- the processor being adapted to calculate a reference time difference of arrival RTDOA for a signal from the first device received at the second and third devices from the fixed positional relationship, based on the respective distance between the first and the second devices and the first and the third devices and the known signal propagation speed;
- and to calculate a user time difference of arrival UTDOA from the user value pair;
- the processor further being adapted to determine at the arbitrary point in time a value from the first model curve and based on this value to calculate a determined time difference of arrival DTDOA;
- wherein the processor is further adapted to relate the RTDOA and DTDOA to determine a current correction factor;
- and
- for clocking to use the current correction factor to correct the UTDOA.
8 more elements
Arrangement for clocking comprising:
- at least a first, a second and a third device in a fixed positional relationship;
- the first device having transmitting means for transmitting a sequence of unique signals comprising at least a first and a second signal with a unique identification;
- the second and third devices having receiving means for receiving the at least first and second signals, a respective second and third local clock of the second and third device for measuring the reception times of the uniquely identified signals at at least the second and third device, and processing means for associating a reception time measured by the respective second and third local clocks of the second and third device to respectively the first and second signal upon reception thereof, leading to at least two value pairs of local clocks of the second and third devices;
- modeling means for modeling based on the value pairs of local clocks a time function of a dependency of the second and third local clock over time as a first model curve;
- the second and third devices further being adapted for receiving at an arbitrary point in time a user signal from a user device at the second and third devices and associating a reception time measured by the respective second and third local clocks of the second and third devices to the user signal upon its reception, leading to a user value pair of local clocks of the second and third devices,
- processing means for calculating a reference time difference of arrival RTDOA for a signal from the first device received at the second and third devices from the fixed positional relationship, based on the respective distance between the first and the second device and the first and the third device and the known signal propagation speed;
- and for calculating a user time difference of arrival UTDOA from the user value pair;
- means for determining at the arbitrary point in time a value from the first model curve and based on this value calculating a determined time difference of arrival DTDOA;
- wherein the processing means is adapted to relate the RTDOA and DTDOA to determine a current correction factor;
- and
- for clocking to use the current correction factor to correct the UTDOA.
8 more elements
Dependencies are inferred from the claim text.