LOCATION SYSTEM

• US 20180164398A1
• Filed: 04/21/2016
• Published: 06/14/2018
• Est. Priority Date: 04/28/2015
• Status: Active Grant

• Current Assignee: Sonitor Technologies AS
• Original Assignee: Sonitor Technologies AS
• Inventors: OLSEN, ystein, BOOIJ, Wilfred
• Granted Patent: US 10,459,064 B2
• Time in Patent Office: Days
• CPC Class Codes: G01S 5/0036 of measured values, i.e. measurement on mobile and position calculation on base station
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/30 Determining absolute distances from a plurality of spaced points of known location

Abstract

A system for determining the location of a mobile receiver unit includes static transmitter units, each including a respective clock which it uses to transmit a positioning signal according to a respective transmission schedule. The mobile receiver unit receives a positioning signal from any of the static transmitter units. A first processing means uses information relating to the received positioning signal to determine the location of the mobile receiver unit. A second processing means uses information relating to a respective drift and/or offset of each of the clocks of the static transmitter units to generate transmission schedules for the static transmitter units. Each transmission schedule instructs a respective static transmitter unit to transmit a positioning signal at one or more scheduled times according to the clock of the static transmitter unit.

Claims

1. A system for determining a location of a mobile receiver unit, the system comprising:

a plurality of static transmitter units, each comprising a respective clock and being configured to use the respective clock to transmit a positioning signal according to a respective transmission schedule;

a mobile receiver unit configured to receive a positioning signal from any of the static transmitter units;

first processing subsystem configured to use information derived from the received positioning signal to determine the location of the mobile receiver unit; and

a second processing subsystem configured to use information representing a respective drift or offset of each of the clocks of the static transmitter units to generate transmission schedules for the static transmitter units, each transmission schedule instructing a respective static transmitter unit to transmit a positioning signal at one or more scheduled times according to the clock of the static transmitter unit.

2. The system of claim 1, wherein the generated transmission schedules instruct the static transmitter units to transmit positioning signals in different respective time slots.

3. The system of claim 1, wherein the generated transmission schedules instruct the static transmitter units to transit positioning signals substantially simultaneously.

4. The system of claim 1, wherein the first processing subsystem is remote from the mobile receiver unit, and wherein the mobile receiver unit is configured to send information derived from the received positioning signal to the first processing subsystem over one or more wired or wireless links.

5. The system of claim 1, wherein the second processing subsystem is remote from the static transmitter units and is configured to send the transmission schedules to the static transmitter units over one or more wired or wireless links.

6. The system of claim 1, wherein the second processing subsystem uses information representative of both the drift and the offset of each of the clocks of the static transmitter units to generate transmission schedules for the static transmitter units.

7. The system of claim 1, wherein the static transmitter units are configured to transmit discrete positioning signals at intervals.

8. The system of claim 1, wherein the positioning signals are ultrasonic signals.

9. The system of claim 1, wherein at least some of the positioning signals encode respective identifiers associated with the respective static transmitter units that transmitted the respective positioning signals.

10. The system of claim 1, wherein each transmission schedule comprises one or more values that determines a set of one or more clock values at which the static transmitter unit should transmit a positioning signal according to the clock of the static transmitter unit.

11. The system of claim 1, wherein each transmission schedule communicates a clock value and a period to a respective static transmitter unit, and wherein each static transmitter unit is configured to transmit a positioning signal when the clock of the static transmitter unit equals the respective communicated clock value and to transmit further positioning signals at intervals defined by the respective period.

12. The system of claim 1, wherein the first processing subsystem is configured to determine the location of the mobile receiver unit from any one or more of the group consisting of:

information identifying a static transmitter unit that transmitted the received positioning signal;

information representative of a timing of the received positioning signal;

information representative of a received signal strength of the received positioning signal;

information representative of a frequency of the received positioning signal;

information representative of a frequency shift of the received positioning signal; and

information representative of an angle-of-arrival of the received positioning signal.

13. The system of claim 1, wherein the second processing subsystem is configured to send an updated transmission schedule to a static transmitter unit, of the plurality of static transmitter units, when the clock on the static transmitter unit is determined by the second processing subsystem to have deviated from an expected time by more than a threshold level.

14. The system of claim 1, wherein the information representative of a respective drift or offset of each of the clocks of the static transmitter units is stored as data representing relative offsets or drifts between pairs of devices in the system, wherein the devices comprise clocks and include the plurality of static transmitter units.

15. The system of claim 1, wherein the second processing subsystem is configured to use relative offsets or drifts between pairs of devices in the system to derive offset or drift information for each static transmitter unit relative to a common reference clock.

16. The system of claim 1, wherein:

each of the static transmitter units comprises a respective radio transmitter;

the system comprises one or more radio gateways for communicating with the static transmitter units by radio, each radio gateway comprising a respective clock; and

the one or more radio gateways are coupled to the second processing subsystem by a network.

17. The system of claim 16, wherein each static transmitter unit is configured to broadcast transmitter-unit messages, by radio, at intervals, and wherein each radio gateway is configured to forward transmitter-unit messages that the radio gateway receives from the static transmitter units to the second processing subsystem.

18. The system of claim 16, wherein each transmitter-unit message includes information representing a time, according to the clock of the static transmitter unit, at which the respective static transmitter unit transmitted a most-recent positioning signal, and wherein the second processing subsystem is configured to use said information when generating an updated transmission schedule for the static transmitter unit.

19. The system of claim 16, wherein each radio gateway is configured, when forwarding a transmitter-unit message received from a static transmitter unit to the second processing subsystem, to send a reception timestamp to the second processing subsystem representing a time that the radio gateway received the transmitter-unit message from the static transmitter unit, according to the clock of the radio gateway.

20. The system of claim 19, wherein each static transmitter unit is configured to send a transmission timestamp to the second processing subsystem representing a time that the static transmitter unit transmitted a transmitter-unit message, according to the clock of the static transmitter unit, and wherein the second processing subsystem is configured to use transmission timestamps for transmitter-unit messages, and respective reception timestamps from one or more radio gateways, to determine information representative of drift or offset for the clocks of the static transmitter units.

21. The system of claim 20, wherein the second processing subsystem is configured, for a pairing of a radio gateway and a static transmitter unit, to store, in a buffer, information representative of a plurality of transmission timestamps from the static transmitter unit and corresponding reception timestamps from the radio gateway, and to use the buffered information to estimate a relative drift between the clock of the radio gateway and the clock of the static transmitter unit.

22. The system of claim 19, wherein the second processing subsystem is configured to use reception timestamps from two or more radio gateways, relating to a single transmitter-unit message from a static transmitter unit that is received by all of the two or more radio gateways, to determine a relative offset or drift between the clocks of the two or more radio gateways.

23. The system of claim 22, wherein the second processing subsystem is configured, for a pairing of two radio gateways, to store, in a buffer, information representative of a plurality of corresponding reception timestamps from the radio gateways, and to use the buffered information to estimate a relative drift between the clocks of the radio gateways.

24. The system of claim 16, wherein the second processing subsystem is configured to select one of the radio gateways to be a reference radio gateway for the system, and to determine offset or drift information for each static transmitter unit relative to the clock of the reference radio gateway.

25. The system of claim 24, wherein the second processing subsystem is configured to:

determine, for each pairing of a plurality of pairings formed of two radio gateways or of one radio gateway and one static transmitter unit, whether the second processing subsystem has received sufficient information to map time accurately between the clocks of the pairing, according to one or more quality criteria;

determine information representing a device graph comprising the reference radio gateway and a set of the radio gateways and static transmitter units that have clocks between which the second processing subsystem can map time accurately; and

generate a transmission schedule for a static transmitter unit by searching the device graph for a shortest path between the reference radio gateway and the static transmitter unit, and composing relative offset or drift information for devices along the shortest path in order to map a time or time period from the clock of the reference radio gateway to the clock of the static transmitter unit.

26. A method of determining a location of a mobile receiver unit using a plurality of static transmitter units, each comprising a respective clock, the method comprising:

using information representative of a respective drift or offset of each of the clocks of the static transmitter units to generate transmission schedules for the static transmitter units, each transmission schedule instructing a respective static transmitter unit to transmit a positioning signal at one or more scheduled times according to the clock of the static transmitter unit;

each of the static transmitters units using its clock to transmit a respective positioning signal according to a respective transmission schedule for the static transmitter unit;

receiving one of the positioning signals at the mobile receiver unit; and

using information derived from the received positioning signal to determine the location of the mobile receiver unit.

27. A server for use in a system for determining a location of a mobile receiver unit, the system comprising a plurality of static transmitter units, each comprising a respective clock and being configured to use the respective clock to transmit a positioning signal according to a respective transmission schedule, wherein the server is configured to:

use information representative of a respective drift or offset of each of the clocks of the static transmitter units to generate transmission schedules for the static transmitter units, each transmission schedule instructing a respective static transmitter unit to transmit a positioning signal at one or more scheduled times according to the clock of the static transmitter unit; and

receive information, from the mobile receiver unit, derived from a positioning signal received by the mobile receiver unit from one of the static transmitter units, and to use the information to determine the location of the mobile receiver unit.