Mobile device and method for determining location of mobile device

• US 7,042,391 B2
• Filed: 12/12/2003
• Issued: 05/09/2006
• Est. Priority Date: 09/15/1997
• Status: Active Grant

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Meunier, Jean-Luc, Snowdon, Dave
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): BALAOING, ARIEL A
• Application Number:
  US10/735,554
• Publication Number:
  US 20050130677A1
• Time in Patent Office: 879 Days
• Field of Search: 4554561-4566, 455/414.2, 342/357.01, 342/357.02, 701/207
• US Class Current: 342/464
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/0252 Radio frequency fingerprinting
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

A mobile device, for determining location in a wireless network, includes a motion detector for detecting motion of the mobile device; a memory for storing wireless signal strength calibration data comprising a list of wireless signal strengths and known locations; a location detection module for measuring a wireless signal strength of any received network radio signals and for determining the location of the mobile device with reference to the wireless signal strength calibration data; and a location correction module, for applying a statistical correction to the measured wireless signal strength determined by the location detection module when the motion detector detects that the mobile device is moving less than a threshold amount. The mobile device may further include an orientation detector for detecting the orientation of the mobile device, which can be compared with orientation data stored in the calibration data.

Claims

1. A mobile device, comprising:

a motion detector for detecting motion of the mobile device, wherein the motion detector generates a Boolean value indicating the mobile device is moving if the detected motion is greater than a threshold amount;

an orientation detector for determining orientation of the mobile device;

a memory storing wireless signal strength calibration data comprising a list of wireless signal strength, orientations and known locations;

an antenna for receiving network radio signals from wireless base stations transmitting in an area;

a location detection module for measuring a wireless signal strength of any received network radio signals from the antenna and for determining the location of the mobile device using measured wireless signal strength with reference to the wireless signal strength calibration data, motion detection data and orientation data, wherein if the mobile device is moving, the location detection module determines location of the mobile device with reference to instantaneous wireless signal strength; and

wherein if the mobile device is not moving, the location detection module determines location of the mobile device with reference to statistically corrected measured wireless signal strength received from a location correction module, for applying a statistical correction to the measured wireless signal strength received by the location detection module;

wherein the location module first considers measured wireless signal strengths taking at the same orientation as determined by the orientation detector for determining location of the mobile device and if no location is determined considers measured wireless signal strengths at other orientations.

2. The mobile device of claim 1, wherein the statistical correction comprises calculating from a moving window of N signal strength samples, wherein M samples of the N samples have a measured signal strength above a predetermined value, from a minimum of X wireless base stations, an average value and standard deviation of the signal strength for each of the X wireless base stations.

3. The mobile device of claim 1, wherein the motion detector detects direction of motion;

and

wherein the location detection module, responsive to the detected direction of motion, predicts the mobile device'"'"'s next location.

4. The mobile device of claim 3, wherein the motion detector detects velocity of the mobile device;

and

wherein the location detection module, responsive to the detected velocity of motion, predicts the mobile device'"'"'s next location.

5. The mobile device of claim 3, wherein the location detection module rejects locations not in the direction of motion.

6. A method for determining a location of a mobile device, comprising:

storing wireless signal strength calibration data comprising a list of wireless signal strengths, orientations and known locations;

receiving network radio signals from wireless base stations transmitting in an area;

measuring a wireless signal strength of any received network radio signals;

detecting motion of the mobile device, wherein a Boolean value indicating the mobile device is moving is generated if the detected motion is greater than a threshold amount;

determining orientation of the mobile device;

determining the location of the mobile device using measured wireless signal strength with reference to the wireless signal strength calibration data, motion detection data and orientation data;

wherein if the mobile device is moving, determining location of the mobile device with reference to instantaneous wireless signal strength; and

wherein if the mobile device is not moving, applying a statistical correction to the measured wireless signal strength and determining location of the mobile device with reference to statistically corrected measured wireless signal strength;

considering measured wireless signal strengths taken at the same orientation as the determined orientation and if no location is determined considering measured wireless signal strengths at other orientations.

7. The method of claim 6, wherein the step of applying a statistical correction comprises calculating from a moving window of N signal strength samples, wherein M samples of the N samples have a measured signal strength above a predetermined value, from a minimum of X wireless base stations, an average value and standard deviation of the signal strength for each of the X wireless base stations.

8. The method of claim 6, further comprising detecting direction of motion of the mobile device;

and

responsive to the detected direction of motion, predicting the mobile device'"'"'s next location.

9. The method of claim 8, further comprising detecting velocity of the mobile device;

and

responsive to the detected velocity of motion, predicting the mobile device'"'"'s next location.

10. The method of claim 8, further comprising rejecting locations not in the direction of motion.