Mapping wireless signals with motion sensors

• US 8,633,817 B2
• Filed: 08/05/2010
• Issued: 01/21/2014
• Est. Priority Date: 10/21/2009
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Khorashadi, Behrooz, Das, Saumitra Mohan, Sridhara, Vinay, Aggarwal, Alok, Brunner, Christopher
• Primary Examiner(s): Wu, Daniel
• Assistant Examiner(s): Tang, Son M
• Application Number:
  US12/851,458
• Publication Number:
  US 20110090081A1
• Time in Patent Office: 1,265 Days
• Field of Search: 340/539.13, 340/572.1, 340988-9951, 3405733-5734, 3405392-53921, 701/200, 705/10
• US Class Current: 340/539.13
• CPC Class Codes: G01S 5/0249 Determining position using measurements made by a non-stationary device other than the device whose position is being determined
• CPC Class Codes: G01S 5/02525 Gathering the radio frequency fingerprints

Abstract

A displacement device for mapping wireless signal fingerprints includes motion sensors and at least one of a received signal strength indicator (RSSI) sensor and a round trip time (RTT) sensor. The motion sensors may include a pedometer and one or more sensors to receive turn information. The start position of the displacement device is initialized and as the displacement device is moved through an environment, the position of each measurement location is determined using the initialized position and data from the motion sensors. The measurement position along with the RSSI and/or RTT measurement is stored in a database, from which a map can be generated. The position of the access point may be determined using the RSSI measurement or RTT measurement. Additionally, accumulated errors in the measurement position may be monitored and when greater than a threshold, a user may be prompted to reinitialize the position of the displacement device.

Claims

1. A method comprising:

generating an initialized position, using a satellite positioning system (SPS), of a displacement device having motion sensors and at least one of a received signal strength indicator (RSSI) sensor and a round trip time (RTT) sensor;

moving the displacement device within an environment to a plurality of measurement locations;

determining at least one of a received signal strength and a round trip time for wireless signals at each of the plurality of measurement locations;

determining a position corresponding to each of the plurality of measurement locations based on the initialized position and data from the motion sensors, wherein the data from the motion sensors comprises a vector displacement estimation, and wherein accuracy of the vector displacement estimation is increased by obtaining an additional SPS fix; and

storing in a database the at least one of the received signal strength and the round trip time for wireless signals and the corresponding position for each of the plurality of measurement locations.

2. The method of claim 1, wherein the displacement device moves automatically through the environment.

3. The method of claim 1, wherein the displacement device is manually moved.

4. The method of claim 1, further comprising generating a map of the environment using the corresponding position for each of the measurement locations stored in the database.

5. The method of claim 1, further comprising determining the position of an access point using the determined at least one of the received signal strength and round trip time.

6. The method of claim 5, wherein the position of the access point is determined by determining a measurement location with at least one of a maximum value of a received signal strength measurement and a minimum value of a round trip time measurement for the access point and using the corresponding position as the position of the access point.

7. The method of claim 5, wherein the position of the access point is determined by translating a plurality of at least one of the received signal strengths and round trip times to distance estimates for the plurality of measurement locations and using corresponding positions for the plurality of measurement locations and the distance estimates to determine the position of the access point.

8. The method of claim 1, wherein generating the initialized position of the displacement device comprises designating a start location of the displacement device as an origin in an arbitrary coordinate system, the method further comprising translating the arbitrary coordinate system to another coordinate system.

9. The method of claim 1, wherein the motion sensors comprise a pedometer driven by a 3 axis accelerometer.

10. The method of claim 1, wherein the data from the motion sensors further comprises user provided turning information.

11. The method of claim 10, wherein the user provided turning information comprises a user designated 90 degrees left turn, 90 degrees right turn, and non 90 degrees turn.

12. The method of claim 1, wherein the data from the motion sensors further comprises data from at least one of a gyroscope, accelerometer and magnetometer to provide turning information.

13. The method of claim 1, further comprising recognizing loop closures to compensate for pedometer drift to increase accuracy of the vector displacement estimation.

14. The method of claim 1, wherein generating the initialized position of a displacement device is performed using a satellite positioning system (SPS) and moving in a first direction from an initial location outside the environment until a first good SPS fix is obtained, returning in a second direction opposite the first direction until a second good SPS fix is obtained, and returning to the initial location and fusing data from the first good SPS fix and the second good SPS fix with the pedometer based distance estimation.

15. The method of claim 1, wherein the position of each of the plurality of measurement locations is further determined based on a vertical vector displacement provided by a user as a building floor number.

16. The method of claim 1, wherein motion sensors comprise wheel displacement sensors and at least one of an accelerometer, gyroscope, magnetometer, and compass.

17. The method of claim 1, the method further comprising estimating accumulated errors from the motion sensors and reinitializing a position of the displacement device after accumulated errors have exceeded a predetermined threshold.

18. The method of claim 17, wherein generating the initialized position of the displacement device comprises designating a start location of the displacement device in a coordinate system, and reinitializing the position of the displacement by designating a current position of the displacement device in the coordinate system.

19. The method of claim 18, further comprising providing an indication that the accumulated errors have exceeded the predetermined threshold and reinitializing the position of the displacement device in response to the indication.

20. The method of claim 17, wherein initializing the position of the displacement device comprises entering the position in a digital map.

21. An apparatus comprising:

at least one of a received signal strength indicator (RSSI) sensor and a round trip time (RTT) sensor that determine at least one of RSSI measurements and RTT measurements for wireless signals within an environment;

motion sensors that provide data related to direction and magnitude of movement of the at least one of the RSSI sensor and the RTT sensor;

a processor connected to the motion sensors and at least the RSSI sensor and the RTT sensor;

memory connected to the processor; and

software held in the memory and run in the processor to cause the processor to use an initialized position, generated using a satellite positioning system (SPS), and the data from the motion sensors, wherein the data from the motion sensors comprises a vector displacement estimation, and wherein the accuracy of the vector displacement estimation is increased by obtaining an additional SPS fix, to determine measurement locations when the at least one of the RSSI measurements and the RTT measurements are made and to store the determined at least one of RSSI measurements and RTT measurements with corresponding measurement locations in the memory.

22. The apparatus of claim 21, wherein the motions sensors comprise a 3-axis accelerometer driven pedometer.

23. The apparatus of claim 22, wherein the motions sensors further comprise a sensor for receiving user provided turning information.

24. The apparatus of claim 23, wherein the user provided turning information comprises a user designated 90 degrees left turn, 90 degrees right turn, and non 90 degrees turn.

25. The apparatus of claim 22, wherein the motions sensors further comprise at least one of a gyroscope, accelerometer, and magnetometer.

26. The apparatus of claim 21, further comprising wheels and a motor coupled to the wheels.

27. The apparatus of claim 21, wherein software held in the memory and run in the processor causes the processor to generate a map using corresponding measurement locations.

28. The apparatus of claim 21, wherein software held in the memory and run in the processor causes the processor to determine a position of an access point using the at least one of the RSSI measurements and the RTT measurements.

29. The apparatus of claim 28, wherein the software held in the memory and run in the processor causes the processor to determine the position of the access point by determining a measurement location with at least one of a maximum value of a RSSI measurement and a minimum value of a RTT measurement for the access point and to store the corresponding measurement location as the position of the access point.

30. The apparatus of claim 28, wherein the software held in the memory and run in the processor causes the processor to determine the position of the access point by translating a plurality of the at least one of the RSSI measurements and the RTT measurements to distance estimates and using the corresponding measurement locations and the distance estimates to determine the position of the access point.

31. The apparatus of claim 21, wherein motion sensors comprise wheel displacement sensors and at least one of a gyroscope, accelerometer, magnetometer, and compass.

32. The apparatus of claim 21, wherein software held in the memory and run in the processor causes the processor to estimate accumulated errors from the motion sensors and to prompt reinitializing a position after the accumulated errors have exceeded a predetermined threshold.

33. The apparatus of claim 32, further comprising a display coupled to the processor and memory, wherein a digital map is displayed on the display and reinitializing the position is performed using the digital map.

34. A system for mapping wireless signal parameters within an environment, the system comprising:

means for generating an initialized position, using a satellite positioning system (SPS),

means for measuring wireless signal parameters including at least one of received signal strength (RSSI) and round trip time (RTT);

means for moving the means for measuring wireless signal parameters within the environment;

means for determining a position of the means for measuring wireless signal parameters based on direction and magnitude of movement from an initialized position within the environment, wherein the data from the means for determining a position of the means for measuring wireless signal parameters comprises a vector displacement estimation, and wherein accuracy of the vector displacement estimation is increased by obtaining an additional SPS fix; and

means for storing wireless signal parameters with corresponding positions of the means for measuring wireless signal parameters when the wireless signal parameters were measured.

35. The system of claim 34, further comprising means for determining a position of an access point using the wireless signal parameters.

36. The system of claim 35, wherein the means for determining the position of the access point determines a maximum value of a wireless signal parameter for the access point, wherein a corresponding position of the means for measuring wireless signal parameters when the wireless signal parameter with the maximum value was measured is stored as the position of the access point.

37. The system of claim 35, wherein the means for determining the position of the access point translates a plurality of at least one of the received signal strengths and round trip times to distance estimates and using the corresponding positions and the distance estimates to determine the position of the access point.

38. The system of claim 34, wherein the means for determining a position comprises wheel displacement sensors and at least one of a gyroscope, accelerometer, magnetometer, and compass.

39. The system of claim 34, wherein the means for determining a position comprises a 3-axis accelerometer driven pedometer.

40. The system of claim 39, wherein the means for determining a position further comprises a sensor for receiving user provided turning information.

41. The system of claim 39, wherein the means for determining a position further comprises at least one of a gyroscope, accelerometer and magnetometer.

42. The system of claim 34, further comprising means for estimating accumulated errors from means for determining the position and a means for prompting reinitializing a position after the accumulated errors have exceeded a predetermined threshold.

43. A computer-readable medium including program code stored thereon, comprising:

program code to determine at least one of received signal strength and round trip time for wireless signals from data provided by a received signal strength indicator (RSSI) sensor and a round trip time (RTT) sensor;

program code to determine a measurement position based on an initialized position and data from motion sensors when the at least one of received signal strength and round trip time is measured; and

program code to store the determined at least one of a received signal strength and round trip time in a database with a corresponding measurement position.

47. The computer-readable medium of claim 43, further comprising program code to estimate accumulated errors in the measurement position and to prompt the reinitializing of a position after the accumulated errors have exceeded a predetermined threshold.

44. A non-transitory computer-readable medium including program code stored thereon, comprising:

program code to determine at least one of received signal strength and round trip time for wireless signals from data provided by a received signal strength indicator (RSSI) sensor and a round trip time (RTT) sensor;

program code to determine a measurement position based on an initialized position, said initialized position generated using a satellite positioning system (SPS), and data from motion sensors, wherein the data from the motion sensors comprises a vector displacement estimation, and wherein the accuracy of the vector displacement estimation is increased by obtaining an additional SPS fix, when the at least one of received signal strength and round trip time is measured; and

program code to store the determined at least one of a received signal strength and round trip time in a database with a corresponding measurement position.

45. The computer-readable medium of claim 44, further comprising program code to determine the position of the access point by detecting at least one of a maximum value of a RSSI measurement and a minimum value of a RTT measurement for the access point and to store the corresponding measurement position as the position of the access point.

46. The computer-readable medium of claim 44, further comprising program code to determine the position of the access point by translating the at least one of the received signal strength and round trip time for a plurality of measurement positions to distance estimates and using the corresponding stored position for the plurality of measurement positions and the distance estimates to determine the position of the access point.