System and methods for determining the location dynamics of a portable computing device

• US 7,199,754 B2
• Filed: 07/25/2005
• Issued: 04/03/2007
• Est. Priority Date: 06/30/2003
• Status: Expired due to Fees

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Horvitz, Eric J., Krumm, John C.
• Primary Examiner(s): Issing; Gregory C.
• Application Number:
  US11/188,438
• Publication Number:
  US 20050270236A1
• Time in Patent Office: 617 Days
• Field of Search: 342/451, 342/464
• US Class Current: 342/451
• CPC Class Codes: G01C 21/206 specially adapted for indoor navigation
• CPC Class Codes: G01S 5/02524 Creating or updating the radio-map
• CPC Class Codes: H04L 9/40 Network security protocols
• CPC Class Codes: Y10S 707/99937 Sorting

Abstract

A location system for locating and determining the motion and velocity of a wireless device. The methods include direct inferences about whether a device is in motion versus static based on a statistical analysis of the variation of radio signal strengths over time. The system is trained according to a sparse set of identified locations from which signal strengths are measured. The system uses the signal properties of the identified locations to interpolate for a new location of the wireless device. The system uses a probabilistic graph where the identified locations of the floor plan, expected walking speeds of pedestrians, and independent inference of whether or not the device is in motion are used to determine the new location of the device.

Claims

1. A location system that facilitates locating a wireless device, comprising:

a computer-based mapping component that maps identified locations in a particular area to one or more location nodes, and displays a graphical representation of the particular area in a graphical user interface;

a measuring component that measures a signal strength and stores signal strength data related to the one or more location nodes; and

a probability processing component that

automatically generates transition probabilities associated with the wireless device, as a function of at least in part path constraints associated with the particular area, between a given pair of location nodes, and

determines at least one of motion of the wireless device at least in part by measuring variations of the signal strength data over a particular interval of time and the location of the wireless device using a regression function that is based at least in part upon the signal strength data, the regression function estimating new locations based upon the signal strength data.

2. The system of claim 1, the mapping component provides a representation of possible paths that the wireless device may traverse to the identified locations.

3. The system of claim 1, the mapping component provides a graphical representation of all of the identified locations to which the wireless device may travel, and possible paths that the wireless device may traverse to the identified locations.

4. The system of claim 1, the mapping component provides the capability of assigning edge weights to adjacent and non-adjacent location nodes.

5. The system of claim 1, the mapping component represents pathways to the identified locations and automatically converts the endpoint of each pathway to an end node, which is one type of location node.

6. The system of claim 5, the mapping component automatically distributes one or more intermediate location nodes among previously positioned location nodes according to predetermined spatial criteria.

7. The system of claim 1, the expected velocity of the wireless device is computed based upon consideration of a probability distribution of human pedestrian speeds and an inference of whether or not the wireless device is moving.

8. The system of claim 1, the mapping component derives a shortest path between two of the location nodes based upon a constraint-sensitive path-planning algorithm that considers physical barriers between the two corresponding identified locations.

9. The system of claim 1, the measuring component measures the signal strengths of networked transmitting devices displaced throughout an area that includes the identified locations.

10. The system of claim 1, the probability processing component generating an observation probability for each of the location nodes based on signal strengths received at that respective location node.

11. The system of claim 1, the probability processing component automatically generates and associates transition probability data with the location nodes using path constraints, moving probability data, and speed distribution data.

12. The system of claim 1, the probability processing component uses a Viterbi algorithm to generate a probability distribution over all location nodes for every set of observed signal strengths.

13. The system of claim 1, the regression function is an interpolation function that extends probability distributions of the location nodes to the new locations.

14. The system of claim 1, the probability processing component using a maximum-likelihood decoding algorithm to optimize over all possible paths between the identified locations with respect to a history of the measured signal properties.

15. The system of claim 1, the probability processing component capturing quantitatively a variation in signal strength of a wireless transmitter by sensing the wireless transmitter with the strongest signal, and calculating a variance of that strongest signal over time.

16. A wireless device location system, comprising:

means for displaying a graphical representation of a particular area in a graphical user interface;

means for measuring signal properties associated with a wireless device and relating to identified locations located in the particular area;

means for determining an inference of motion of the wireless device; and

means for approximating a location of the wireless device based at least in part on transitional probabilities as a function of path constraints associated with the particular area, the inference of motion, and the signal properties associated with the wireless device.

17. A method of determining the location dynamics of a mobile device, comprising:

providing a graphical representation of an area in a graphical user interface;

evaluating signal properties associated with a mobile device and relating to identified locations;

utilizing probability data, based upon a variation of the signal properties over time, for calculating an inference of motion of the mobile device; and

estimating a location of the mobile device based at least in part on transitional probabilities as a function of path constraints associated with the area, the inference of motion, and the signal properties, associated with the mobile device.