Positioning of mobile objects based on mutually transmitted signals

• US 8,456,364 B2
• Filed: 04/02/2008
• Issued: 06/04/2013
• Est. Priority Date: 04/02/2008
• Status: Active Grant

• Current Assignee: Airwave Location Technologies, LLC, ONA Patents SL
• Original Assignee: Ekahau Oy
• Inventors: Misikangas, Pauli, Vasko, Kari, Koutaniemi, Arsi
• Primary Examiner(s): Issing, Gregory C
• Application Number:
  US12/933,544
• Publication Number:
  US 20110018769A1
• Time in Patent Office: 1,889 Days
• Field of Search: 342/451
• US Class Current: 342/451
• CPC Class Codes: G01S 5/0072 Transmission between mobile stations, e.g. anti-collision systems
• CPC Class Codes: G01S 5/02525 Gathering the radio frequency fingerprints
• CPC Class Codes: G01S 5/0284 Relative positioning
• CPC Class Codes: G01S 5/16 using electromagnetic waves other than radio waves

Abstract

Location estimation for a first target object assisted by a second target object, which have co-located signalling devices is provided. A positioning engine employs a data model of a location-dependent physical quantity and determines location probability distributions for the target objects. One signalling device sends positioning-assisting signals to the other which makes observations from it. The positioning engine uses observations on the physical quantity and the positioning-assisting signals to make a quantity observation set, and determines location probability distributions for the target objects. The positioning engine determines an updated first location probability distribution based on the location probability distributions and the positioning-assisting observation set. The positioning engine determines the location estimate for the first target object based on the updated first location probability distribution and triggers a physical action based on the location estimate for the first target object.

Claims

1. A method for determining a location estimate for a first target object in an environment which also comprises a second target object, the method comprising:

maintaining a positioning engine which is operable to model at least one location-dependent physical quantity with a data model of the environment, wherein the at least one location-dependent physical quantity is influenced by the location of the second target object, and wherein the positioning engine is operable to determine location probability distributions for the first and second target object;

associating the first and second target object respectively with a co-located first and second signalling device, wherein at least one signalling device comprises means for sending a positioning-assisting signal and another signalling device comprises means for receiving the positioning-assisting signal and means for making observations from the positioning-assisting signal;

the positioning engine receiving observations on the at least one location-dependent physical quantity;

at least one of the signalling devices sending a positioning-assisting signal, wherein the positioning-assisting signal is received by another signalling device which makes a positioning-assisting observation set from it and sends the positioning-assisting observation set to the positioning engine, wherein said at least one of the signaling devices and said other signaling device are associated and co-located with different target objects;

the positioning engine making a quantity observation set based on the received observations on the at least one location-dependent physical quantity;

the positioning engine determining a respective first and a second location probability distribution for the first and second target object, wherein at least the second location probability distribution is based on the data model and the quantity observation set;

the positioning engine determining an updated first location probability distribution based on the first location probability distribution, the second location probability distribution and the positioning-assisting observation set;

the positioning engine determining the location estimate for the first target object based on the updated first location probability distribution; and

the positioning engine triggering a physical action based on the location estimate for the first target object.

2. The method according to claim 1, wherein the physical action comprises outputting the location estimate for the first target object to a physical output device and/or physical storage.

3. The method according to claim 1, wherein the positioning-assisting signal is sent by the first signalling device and the positioning-assisting observation set is made and sent to the positioning engine by the second signalling device.

4. The method according to claim 1, wherein the positioning-assisting signal is sent by the second signalling device and the positioning-assisting observation set is made and sent to the positioning engine by the first signalling device.

5. The method according to claim 4, wherein the positioning assisting signal is sent as a response to a preceding positioning-assisting signal sent by the first signalling device.

6. The method according to claim 5, wherein a controller defines an operation logic for sending the preceding positioning-assisting signal and the preceding positioning-assisting signal is sent in response to a transmission request from the controller.

7. The method according to claim 6, wherein a controller adjusts the operation logic based on the positioning-adjusting observation set, wherein adjusting the operation logic comprises adjusting a time interval between consecutive transmission requests.

8. The method according to claim 7, wherein the second signalling device responds to the preceding positioning-assisting signal by sending the positioning signal only when there is an indicated need to assist positioning of the first target object.

9. The method according to claim 1, wherein the data model is a probabilistic data model which indicates a probability distribution for the at least one location-dependent physical quantity for each of several locations in the environment, and wherein the step of determining the location probability distribution for a target object comprises:

the positioning engine determines a probability for an observation of the at least one location-dependent physical quantity at a hypothetical location of the target object, based on the probability distribution for the at least one location-dependent physical quantity indicated by the data model at the target object'"'"'s hypothetical location; and

the positioning engine determines a density of the location probability distribution at the target object'"'"'s hypothetical location based on the probability for the observation of the at least one location-dependent physical quantity at the target object'"'"'s hypothetical location.

10. The method according to claim 9, wherein the estimating the updated first location probability distribution comprises:

estimating an additional location probability distribution for the first target object based on the second location probability distribution and the positioning-assisting observation set;

estimating the updated first location probability distribution by combining the first location probability distribution and the additional location probability distribution.

11. The method according to claim 10, wherein the estimating the additional location probability distribution comprises using a signal propagation model, wherein the signal propagation model is operable to estimate the likelihood of the positioning-assisting observation set for hypothetical locations of the target objects.

12. The method according claim 11, wherein the signal propagation model comprises taking into account obstacles within the environment affecting the positioning-assisting signal.

13. The method according to claim 1, wherein the positioning engine monitors a location estimate for one or more second target objects and progress of the positioning-assisting observation set as a function of the location estimate for the one or more second target objects and wherein the positioning engine further sends the one or more second target objects instructions for changing location based on the progress of the positioning-assisting observation set.

14. A positioning engine for determining a location estimate for a first target object in an environment which also comprises a second target object and wherein at least one location-dependent physical quantity is influenced by the location of the second target object, the positioning engine comprising:

a data model which models the at least one location-dependent physical quantity with of the environment,

means for receiving observations on the at least one location-dependent physical quantity;

means for associating the first and second target objects respectively with a co-located first and second signalling device;

means for receiving observations on the at least one location-dependent physical quantity reflecting the location of the second target object;

means for receiving a positioning-assisting observation set made from a positioning-assisting signal which is sent by at least one of the signalling devices and received by another one of the signalling devices, wherein said at least one of the signaling devices and said other signaling device are associated an co-located with different target objects;

means for making a quantity observation set based on the received observations on the at least one location-dependent physical quantity;

means for determining a respective first and a second location probability distribution for the first and second target object, wherein at least the second location probability distribution is based on the data model and the quantity observation set;

means for determining an updated first location probability distribution based on the first location probability distribution, the second location probability distribution and the positioning-assisting observation set;

means for determining the location estimate for the first target object based on the updated first location probability distribution; and

means for triggering a physical action based on the location estimate for the first target object.

15. A non-transitory and tangible computer-readable program carrier comprising a computer program product, wherein execution of the computer program product in a data processing system causes the data processing system to implement the positioning engine according to claim 14.