Area based position determination for terminals in a wireless network

• US 20040203880A1
• Filed: 10/24/2002
• Published: 10/14/2004
• Est. Priority Date: 08/08/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Riley, Wyatt
• Granted Patent: US 6,865,395 B2
• Time in Patent Office: Days
• US Class Current: 455/456.1
• CPC Class Codes: G01S 5/0252 Radio frequency fingerprinting
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

Techniques to estimate the position of a wireless terminal. In a method, the identities of a number of transmitters (e.g., BTSs) to be used to estimate the position are initially received. Expected areas for these transmitters are then determined. The expected area associated with each transmitter is indicative of an area where the terminal is likely to be located given that the signal from the transmitter is received by the terminal. Each expected area may comprise a location (e.g., the expected area center) to be used as an estimated position of the terminal and an uncertainty (or error estimate) associated with that estimated position. The expected areas for the transmitters are then combined (e.g., based on a weighted average) to determine a combined expected area, which is then provided as the estimate of the position of the terminal.

Claims

1. A method of estimating the position of a wireless terminal, comprising:

determining an expected area associated with a transmitter used to determine the approximate position estimate for the terminal;

adjusting the expected area based on at least one scale factor to determine an adjusted expected area; and

providing the adjusted expected area as the estimate position of the terminal.

2. The method of claim 1, wherein at least one scale factor is determined based on a received signal strength for the transmitter as measured at the terminal.

3. The method of claim 1, wherein at least one scale factor is determined based on a received power for the transmitter as measured at the terminal.

4. The method of claim 1, further comprising:

combining the estimate of the position with a second estimate of the position to estimate a final position for the terminal.

5. A method of estimating the position of a wireless terminal, comprising:

receiving identities of a plurality of transmitters to be used to estimate the position of the terminal;

determining a plurality of expected areas for the plurality of transmitters; and

combining the plurality of expected areas for the plurality of transmitters to estimate the position for the terminal.

6. The method of claim 5, wherein the approximate position estimate further comprises an uncertainty in the estimated position.

7. The method of claim 6, wherein the uncertainty is provided by an area within which the terminal is likely to be located.

8. The method of claim 5, further comprising:

combining the approximate position estimate with a second position estimate to estimate a final position for the terminal.

9. The method of claim 5, wherein the expected area associated with each transmitter comprises an estimated position of the terminal and an area within which the terminal is likely to be located, given only that the signal from the transmitter is received by the terminal.

10. The method of claim 5, further comprising:

adjusting the expected area associated with each transmitter based on at least one assigned scale factor to determine an adjusted expected area associated with the transmitter.

11. The method of claim 10, wherein the adjusting the expected area associated with each transmitter includes

moving a center of the expected area based on a first assigned scale factor.

12. The method of claim 11, wherein the adjusting the expected area associated with each transmitter further includes

scaling a size of the expected area based on the first assigned scale factor.

13. The method of claim 10, wherein adjusting the expected area associated with each transmitter further includes

scaling a size of the expected area based on a first assigned scale factor, and

moving a center of the expected area based on a second assigned scale factor.

14. The method of claim 10, wherein the adjusting the expected area associated with each transmitter includes

moving a center of the expected area based on a predicted power and a received power for the transmitter.

15. The method of claim 14, wherein the predicted power is determined based on a path loss prediction model.

16. The method of claim 10, wherein at least one scale factor for each transmitter is determined based on received signal strength for the transmitter as measured at the terminal.

17. The method of claim 10, wherein at least one scale factor for each transmitter is determined based on received power for the transmitter as measured at the terminal.

18. The method of claim 10, wherein at least one scale factor for each transmitter is determined based on transmit power of the transmitter.

19. The method of claim 10, wherein at least one scale factor for each transmitter is determined based on a round trip delay (RTD) measurement made by the transmitter.

20. The method of claim 5, wherein the plurality of expected areas are combined to determine a combined expected area that is provided as the estimate of the position of the terminal.

21. The method of claim 20, wherein the combining the plurality of expected areas includes

combining centers of the plurality of expected areas to determine a center for the combined expected area.

22. The method of claim 20, wherein the combining the plurality of expected areas includes

combining centers of the plurality of expected areas, based on a predicted power and a received power for each transmitter, to determine a center for the combined expected area.

23. The method of claim 22, wherein the center for the combined expected area is determined such that a root mean square difference between predicted powers and received powers for the plurality of transmitters is minimized.

24. The method of claim 20, wherein the combining the plurality of expected areas includes

determining a unit fault for the combined expected area, and

scaling the combined expected area based on the unit fault.

25. The method of claim 24, wherein the unit fault is determined based on a normalized average separation-sigma between the combined expected area and each of the plurality of expected areas.

26. The method of claim 5, wherein the combining the plurality of expected areas includes

determining a plurality of weights for the plurality of expected areas, and wherein the plurality of expected areas are combined based on the plurality of weights.

27. The method of claim 26, wherein the weight for each expected area is determined based on an uncertainty associated with the expected area.

28. The method of claim 27, wherein the uncertainty associated with each expected area is expressed as a horizontal estimated position error (HEPE).

29. The method of claim 5, wherein the combining the plurality of expected areas includes

determining a plurality of weights for the plurality of expected areas,

scaling the plurality of expected areas based on the associated weights,

combining the scaled expected areas to determine a combined expected area,

scaling centers of the plurality of expected areas based on the associated weights,

combining the scaled centers of the plurality of expected areas to determine a center for the combined expected area, and wherein the combined expected area and the combined expected area center are provided as the estimate of the position of the terminal.

30. The method of claim 5, wherein the expected area associated with each transmitter is determined based on a maximum antenna range associated with the transmitter.

31. The method of claim 5, wherein the expected area associated with each transmitter is determined based on antenna location and orientation for the transmitter.

32. The method of claim 5, wherein the expected area associated with each transmitter comprises a location to be used as an estimated position of a terminal and an area within which the terminal is likely to be located.

33. A method of estimating the position for a terminal in a wireless communication network, comprising:

receiving identities of a plurality of transmitters to be used to estimate the position of the terminal;

determining an expected area and a scale factor for each of the plurality of transmitters;

adjusting each expected area based on the associated scale factor to provide an adjusted expected area;

determining a plurality of weights for the plurality of transmitters;

combining the plurality of adjusted expected areas based on the plurality of weights to determine a combined expected area to be provided as the estimated position of the terminal.

34. The method of claim 33, wherein the scale factor for each transmitter is determined based on received signal strength or received power for the transmitter as measured at the terminal.

35. The method of claim 33, wherein the weight for each expected area is determined based on an uncertainty associated with the expected area.

36. The method of claim 33, wherein the combining the plurality of expected areas includes

weighting centers of the plurality of expected areas based on the associated weights,

combining the weighted centers of the expected areas to determine the center of the combined expected area,

scaling the plurality of expected areas based on the associated weights, and

combining the scaled expected areas to determine the combined expected area.

37. The method of claim 33, wherein the wireless communication network is a CDMA network.

38. A memory communicatively coupled to a digital signal processing device (DSPD) capable of interpreting digital information to:

receive identities of a plurality of transmitters to be used to estimate the position of the terminal;

determine a plurality of expected areas for the plurality of transmitters; and

combine the plurality of expected areas for the plurality of transmitters to estimate the position of the terminal.

39. An apparatus in a wireless communication network, comprising:

means for receiving identities of a plurality of transmitters to be used to estimate the position of the terminal;

means for determining a plurality of expected areas for the plurality of transmitters; and

means for combining the plurality of expected areas for the plurality of transmitters to estimate the position of the terminal.

40. The apparatus of claim 39, further comprising:

means for weighting centers of the plurality of expected areas based on the associated weights,

means for combining the weighted centers of the expected areas to determine the center of the combined expected area,

means for scaling the plurality of expected areas based on the associated weights, and

means for combining the scaled expected areas to determine the combined expected area.

41. A terminal comprising the apparatus of claim 39.

42. A position determining entity (PDE) comprising the apparatus of claim 39.