Low-energy consumption location of movable objects

• US 9,606,238 B2
• Filed: 03/03/2016
• Issued: 03/28/2017
• Est. Priority Date: 03/06/2015
• Status: Active Grant

• Current Assignee: Gatekeeper Systems, Inc.
• Original Assignee: Gatekeeper Systems, Inc.
• Inventors: Carter, Scott J.
• Primary Examiner(s): Gregory, Bernarr
• Assistant Examiner(s): Mull, Fred H
• Application Number:
  US15/060,442
• Publication Number:
  US 20160259061A1
• Time in Patent Office: 390 Days
• US Class Current: 1/1
• CPC Class Codes: G01S 19/05 providing aiding data
• CPC Class Codes: G01S 19/06 employing an initial estimate of the location of the receiver as aiding data or in generating aiding data
• CPC Class Codes: G01S 19/09 providing processing capability normally carried out by the receiver
• CPC Class Codes: G01S 19/11 wherein the cooperating elements are pseudolites or satellite radio beacon positioning system signal repeaters
• CPC Class Codes: G01S 19/14 specially adapted for specific applications
• CPC Class Codes: G01S 19/252 Employing an initial estimate of location in generating assistance data
• CPC Class Codes: G01S 19/28 Satellite selection
• CPC Class Codes: G01S 19/34 Power consumption
• CPC Class Codes: G01S 19/41 Differential correction, e.g. DGPS [differential GPS]
• CPC Class Codes: G01S 19/485 whereby the further system is an optical system or imaging system
• CPC Class Codes: G01S 19/49 whereby the further system is an inertial position system, e.g. loosely-coupled
• CPC Class Codes: H04W 4/02 Services making use of location information
• CPC Class Codes: H04W 4/029 Location-based management or tracking services

Abstract

Low-energy consumption techniques for locating a movable object using a global satellite navigation system (GNSS) are provided. A mobile station attached to or included in a movable object can communicate bidirectionally with a fixed base station to determine a location of the movable object. The mobile station may communicate an estimated position to the base station and receive from the base station a set of GNSS satellites that are visible to the mobile station. The mobile station can acquire satellite timing information from GNSS signals from the set of satellites and communicate minimally-processed satellite timing information to the base station. The base station can determine the position of the mobile station and communicate the position back to the mobile station. By offloading much of the processing to the base station, energy consumption of the mobile station is reduced.

Claims

1. A system for locating a movable object, the system comprising:

a mobile station configured to be associated with the movable object, the mobile station comprising;

a radio frequency (RF) mobile communication system configured to operate an RF link having an RF link frequency in an RF band that is not licensed for cellular communications;

a mobile station clock;

a mobile global navigation satellite system (GNSS) receiver; and

a dead reckoning system including a non-GNSS sensor, the dead reckoning system configured to use measurements from the non-GNSS sensor to provide an estimated position for the mobile station; and

a base station located at a fixed position, the base station comprising;

a base RF communication system configured to bidirectionally communicate with the mobile communication system over the RF link;

a base station clock;

a base GNSS receiver; and

a hardware processor,

wherein the base station is configured to;

receive, from the mobile station over the RF link, the estimated position of the mobile station determined by the dead reckoning system;

determine satellite acquisition information that includes a set of GNSS satellites predicted to be viewable at the estimated position of the mobile station and GNSS code phases associated with each GNSS satellite in the set, the set of GNSS satellites including at least a minimum number of GNSS satellites;

synchronize the base station clock to a time representative of the set of GNSS satellites;

communicate, to the mobile station over the RF link, the satellite acquisition information;

receive, from the mobile station over the RF link, chip transition time information associated with the set of GNSS satellites;

determine, based at least in part on the chip transition time information, an updated position for the mobile station; and

communicate, to the mobile station over the RF link, the updated position, and

wherein the mobile station is configured to;

communicate, to the base station over the RF link, the estimated position of the mobile station determined by the dead reckoning system;

exchange, with the base station over the RF link, clock timing information;

synchronize, based at least partly on the clock timing information, the mobile station clock to the base station clock that is representative of the time for the set of GNSS satellites;

receive, from the base station over the RF link, the satellite acquisition information;

wake up the mobile GNSS receiver;

acquire, by the mobile GNSS receiver based on timing of a GNSS code phase transition, GNSS signals from at least some of the GNSS satellites in the set of GNSS satellites;

put the mobile GNSS receiver to sleep;

determine, from the acquired GNSS signals, the chip transition time information associated with the GNSS code phases for the at least some of the GNSS satellites in the set; and

communicate, to the base station over the RF link, the chip transition time information.

2. The system of claim 1, wherein the movable object comprises a human-propelled cart having a wheel, and the non-GNSS sensor comprises a magnetic heading sensor and a wheel rotation sensor.

3. The system of claim 1, wherein the movable object comprises a human or an animal, and the non-GNSS sensor comprises a pedometer and a magnetic heading sensor.

4. The system of claim 1, wherein the RF link frequency is in a range from 426 MHz to 435 MHz, 779 MHz to 787 MHz, 863 MHz to 870 MHz, 900 MHz to 928 MHz, 2.400 GHz to 2.483 GHz, or 5.725 GHz to 5.875 GHz.

5. The system of claim 1, wherein the satellite acquisition information further comprises Doppler shift information associated with the satellite in the set of GNSS satellites.

6. The system of claim 1, wherein the base station is configured to rank the set of GNSS satellites according to one or more ranking criteria, wherein the ranking criteria include one or more of:

whether a satellite is along a direction of movement or a direction of interest of the mobile station, whether a satellite is near a horizon of the mobile station, an altitude of a satellite above the horizon of the mobile station, a Doppler shift for a satellite, ionospheric propagation errors for a satellite, positional proximity information for at least two satellites, an antenna pattern of a mobile station GNSS antenna, or presence of obstructions near a mobile station that can inhibit reception of GNSS signals from a satellite.

7. The system of claim 1, wherein the satellite acquisition information includes selection information associated with an order in which the mobile station should attempt to capture GNSS signals from satellites in the set of GNSS satellites.

8. The system of claim 7, wherein the order is based at least in part on whether a contingency occurs.

9. The system of claim 1, where the base station is configured to determine the set of GNSS satellites based at least in part on reducing or minimizing a dilution of precision.

10. The system of claim 1, wherein the chip transition time information further comprises a quality indicator for the at least some of the GNSS satellites in the set, the quality indicator associated with a quality of the GNSS signal received by the mobile GNSS receiver, wherein the quality indicator comprises information associated with one or more of a GNSS signal power, a width of a peak in a correlator output, or a signal-to-noise ratio.

11. The system of claim 1, further comprising a link repeater, wherein the mobile station and the base station are each configured to bidirectionally communicate over the RF link with the link repeater.

12. The system of claim 11, wherein the mobile station comprises a mobile station clock, the link repeater comprises a link repeater clock, and the base station comprises a base station clock that is representative of time for the GNSS satellites, and where the mobile station and the link repeater are configured to synchronize the mobile station clock with the link repeater clock, and the link repeater and the base station are configured to synchronize the link repeater clock with the base station clock.

13. The system of claim 1, further comprising a pseudolite configured to communicate a navigation signal to the mobile station, and wherein the mobile station is configured to:

acquire the navigation signal from the pseudolite;

determine a pseudolite chip transition time associated with the navigation signal; and

communicate, to the base station over the RF link, the pseudolite chip transition time.

14. The system of claim 13, wherein the base station is configured to determine the updated position of the mobile station based at least in part on the pseudolite chip transition time.

15. The system of claim 13, wherein the pseudolite is configured to communicate the navigation signal at a pseudolite carrier frequency within 100 MHz of a GNSS satellite signal carrier frequency.

16. The system of claim 15, wherein the pseudolite carrier frequency is in a range from 1626.5 MHz to 1645.5 MHz.

17. The system of claim 1, wherein the mobile station is configured to store sleep parameters that include a time or a condition when the mobile station is to wake up and begin to communicate to with the base station.

18. The system of claim 1, wherein the mobile station is configured to:

include an autonomous mode in which the mobile station computes its position using GNSS signals acquired from GNSS satellites; and

operate in the autonomous mode if the mobile station is unable to receive communications from the base station over the RF link.

19. The system of claim 1, wherein:

the base station is configured to obtain information relating to satellite acquisition by the mobile station, and

the system is configured to analyze the information relating to satellite acquisition by the mobile station using a machine learning technique to update a model of a tracking area in which the movable object moves, conditions associated with the mobile station, or the determination of the set of GNSS satellites predicted to be viewable at the estimated position of the mobile station.

20. The system of claim 1, wherein to determine the chip transition time information associated with the GNSS code phases for the at least some of the GNSS satellites in the set, the mobile station is configured to search for a chip transition within a shift window based at least partly on an estimate of an error in clock synchronization between the mobile station and the base station.

21. The system of claim 1, wherein the base station is configured to continuously synchronize the base station clock to a time representative of the set of GNSS satellites.

22. A method for locating a movable object, the method performed by a mobile station configured to be associated with the movable object and a base station located at a fixed position, the mobile station and the base station configured to bidirectionally communicate over a radio frequency (RF) link having an RF link frequency in an RF band that is not licensed for cellular communications, the method comprising:

determining, by the mobile station via a dead reckoning technique, an estimated position of the mobile station;

communicating, by the mobile station over the RF link, the estimated position of the mobile station;

receiving, by the base station over the RF link, the estimated position;

determining, by the base station, satellite acquisition information that includes a set of global navigation satellite system (GNSS) satellites predicted to be viewable at the estimated position of the mobile station and GNSS code phases associated with each GNSS satellite in the set, the set of GNSS satellites including at least a minimum number of GNSS satellites;

synchronizing, by the base station, a base station clock to a time representative of the set of GNSS satellites;

communicating, by the base station over the RF link, the satellite acquisition information to the mobile station;

exchanging, by the mobile station and the base station over the RF link, clock timing information;

synchronizing, by the mobile station based at least partly on the clock timing information, a mobile station clock to the base station clock that is representative of the time for the set of GNSS satellites;

waking up, by the mobile station, a mobile GNSS receiver in the mobile station;

acquiring, by the mobile GNSS receiver based on timing of a GNSS code phase transition, GNSS signals from at least some of the GNSS satellites in the set of GNSS satellites;

putting to sleep, by the mobile station, the mobile GNSS receiver;

determining, by the mobile station and from the acquired GNSS signals, chip transition time information associated with the GNSS code phases for the at least some of the GNSS satellites in the set;

communicating, by the mobile station over the RF link, the chip transition time information to the base station;

determining, by the base station based at least in part on the chip transition time information, an updated position for the mobile station; and

communicating, by the base station over the RF link, the updated position to the mobile station.

23. The method of claim 22, wherein determining, by the mobile station via a dead reckoning technique, an estimated position of the mobile station comprises using measurements from a magnetic heading sensor and a wheel rotation sensor to determine the estimated position.

24. The method of claim 22, wherein the movable object comprises a human or an animal, and wherein determining, by the mobile station via a dead reckoning technique, an estimated position of the mobile station comprises using at least an accelerometer to determine the estimated position.

25. The method of claim 22, wherein the RF link frequency is in a range from 426 MHz to 435 MHz, 779 MHz to 787 MHz, 863 MHz to 870 MHz, 900 MHz to 928 MHz, 2.400 GHz to 2.483 GHz, or 5.725 GHz to 5.875 GHz.

26. The method of claim 22, further comprising ranking, by the base station, the set of GNSS satellites according to one or more ranking criteria.

27. The method of claim 22, wherein determining, by the base station, satellite acquisition information that includes a set of GNSS satellites predicted to be viewable at the estimated position of the mobile station comprises determining the set of GNSS satellites based at least in part on reducing or minimizing a dilution of precision.

28. The method of claim 22, wherein determining, by the mobile station and from the acquired GNSS signals, chip transition time information associated with the GNSS code phases for the at least some of the GNSS satellites in the set comprises calculating a quality indicator for the at least some of the GNSS satellites in the set, the quality indicator associated with a quality of the GNSS signal received by the mobile station.

29. The method of claim 22, further comprising:

exchanging, between the mobile station and the base station, clock timing information over the RF link; and

synchronizing, by the mobile station, based at least partly on the timing information, a mobile station clock to a base station clock that is representative of time for the GNSS satellites.

30. The method of claim 22, wherein the synchronizing, by the base station, a base station clock to a time representative of the set of GNSS satellites is performed continuously.