PAIRWISE MEASUREMENTS FOR IMPROVED POSITION DETERMINATION

• US 20140179340A1
• Filed: 12/21/2012
• Published: 06/26/2014
• Est. Priority Date: 12/21/2012
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Do, Ju-Yong, Venkatraman, Sai Pradeep
• Granted Patent: US 9,213,093 B2
• Time in Patent Office: Days
• US Class Current: 455/456.1
• CPC Class Codes: G01S 13/765 with exchange of information between interrogator and responder
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence

Abstract

Approaches for enhancing range-based position determination using pairwise error detection and compensation are provided. One method for enhancing a position estimate of a first node may include performing measurements at the first node using a signal received from a second node, and receiving measurements from the second node. The received measurements may be performed at the second node using a signal provided by the first node. The method may further include determining pairwise comparisons of the performed measurements and the received measurements, and compensating the measurements performed at the first node, based on the pairwise comparisons, for estimating the position of the first node. Systems and apparatuses for performing the various position determination methods are further presented.

Claims

1. A method for enhancing a position estimate of a first node, comprising:

performing measurements at the first node using a signal received from a second node;

receiving measurements from the second node, wherein the received measurements are performed at the second node using a signal provided by the first node;

determining pairwise comparisons of the performed measurements and the received measurements; and

compensating the measurements performed at the first node, based on the pairwise comparisons, for estimating a position of the first node.

2. The method of claim 1, further comprising:

measuring a Received Signal Strength Indicator (RSSI) at the first node, based on the signal from the second node;

comparing the RSSI at the first node to an RSSI determined at the second node for a same wireless channel;

measuring a Round Trip Time (RTT) between the first node and the second node;

comparing the RTT measured at the first node to an RTT measurement determined at the second node;

determining if an RTT bias exists; and

compensating the RTT to remove the RTT bias and provide a compensated RTT measurement.

3. The method of claim 2, further comprising:

determining if an RSSI bias exists; and

compensating the RSSI to remove the RSSI bias and provide a compensated RSSI measurement.

4. The method of claim 2, further comprising:

determining the position of the first node based on the compensated RTT measurement.

5. The method of claim 2, wherein at least one of the first node or the second node is a calibrated device.

6. The method of claim 2, wherein the first node is a first access point (AP) and the second node is a second AP.

7. The method of claim 2, wherein the first node is an access point (AP) and the second node is a mobile station.

8. The method of claim 2, wherein the first node is a first mobile station and the second node is a second mobile station.

9. The method of claim 2, further comprising:

determining a measurement error threshold;

discarding measurements that exceed the measurement error threshold; and

adjusting the RTT bias based on remaining measurements.

10. The method of claim 3, wherein the second node is calibrated and the first node is not calibrated, further comprising:

receiving calibration information from the second node; and

compensating the RTT measurement based only on the calibration information from the second node.

11. The method of claim 10, further comprising:

storing the RTT bias and/or the RSSI bias; and

using the RTT bias and/or the RSSI bias in subsequent measurement determinations with other nodes.

12. The method of claim 2, wherein the first node and second node have calibration information, further comprising:

determining a confidence level of the calibration information for each node; and

weighting the RTT bias based on the confidence level of each node.

13. A first node which determines an enhanced position estimate using pairwise measurements, comprising:

a wireless transceiver;

a processor coupled to the wireless transceiver; and

a memory coupled to the processor, wherein the memory stores executable instructions and data for causing the processor to;

perform measurements at the first node using a signal received from a second node,

receive measurements from the second node, wherein the received measurements are performed at the second node using a signal provided by the first node,

determine pairwise comparisons of the performed measurements and the received measurements, and

compensate the measurements performed at the first node, based on the pairwise comparisons, for estimating a position of the first node.

14. The first node of claim 13, wherein the memory comprises further instructions which cause the processor to:

measure a Received Signal Strength Indicator (RSSI) at the first node, based on the signal from the second node,

compare the RSSI at the first node to an RSSI determined at the second node for a same wireless channel,

measure a Round Trip Time (RTT) between the first node and the second node,

compare the RTT measured at the first node to an RTT measurement determined at the second node,

determine if an RTT bias exists, and

compensate the RTT to remove the RTT bias and provide a compensated RTT measurement.

15. The first node of claim 14, wherein the memory comprises further instructions which cause the processor to:

determine if an RSSI bias exists; and

compensate the RSSI to remove the RSSI bias and provide a compensated RSSI measurement.

16. The first node of claim 14, wherein the memory comprises further instructions which cause the processor to:

determine the position of the first node based on the compensated RTT measurement.

17. The first node of claim 14, wherein at least one of the first node or the second node is a calibrated device.

18. The first node of claim 14, wherein the first node is a first access point (AP) and the second node is a second AP.

19. The first node of claim 14, wherein the first node is an access point (AP) and the second node is a mobile station.

20. The first node of claim 14, wherein the first node is a first mobile station and the second node is a second mobile station.

21. The first node of claim 14, wherein the memory comprises further instructions which cause the processor to:

determine a measurement error threshold,

discard RTT measurements that exceed the measurement error threshold, and

adjust the RTT bias based on remaining measurements.

22. The first node of claim 15, wherein the second node is calibrated and the first node is not calibrated, and further wherein the memory comprises further instructions which cause the processor to:

receive calibration information from the second node, and

compensate the RTT measurement based only on the information from the second node.

23. The first node of claim 22, wherein the memory comprises further instructions which cause the processor to:

store the RTT bias and/or the RSSI bias, and

use the RTT bias and/or the RSSI bias in subsequent measurement determinations with other nodes.

24. The first node of claim 14, wherein the first node and second node have calibration information, further wherein the memory comprises further instructions which cause the processor to:

determine a confidence level of the calibration information for each node, and

weight the RTT bias based on the confidence level of each node.

25. An apparatus for enhancing a position estimate, comprising:

means for performing measurements at a first node using a signal received from a second node;

means for receiving measurements from the second node, wherein the received measurements are performed at the second node using a signal provided by the first node;

means for determining pairwise comparisons of the performed measurements and the received measurements; and

means for compensating the measurements performed at the first node, based on the pairwise comparisons, for estimating a position of the first node.

26. The apparatus of claim 25, further comprising:

means for measuring a Received Signal Strength Indicator (RSSI) at the first node, based on the signal from the second node;

means for comparing the RSSI at the first node to an RSSI determined at the second node for a same wireless channel;

means for measuring a Round Trip Time (RTT) between the first node and the second node;

means for comparing the RTT measured at the first node to an RTT measurement determined at the second node;

means for determining if an RTT bias exists; and

means for compensating the RTT to remove the RTT bias and provide a compensated RTT measurement.

27. The apparatus of claim 26, further comprising:

means for determining a measurement error threshold;

means for discarding measurements that exceed the measurement error threshold; and

means for adjusting the RTT bias based on remaining measurements.

28. The apparatus of claim 26, wherein the second node is calibrated and the first node is not calibrated, further comprising:

means for receiving calibration information from the second node; and

means for compensating the RTT measurement based only on the information from the second node.

29. A non-transitory computer-readable medium comprising instructions, which, when executed by a processor, cause the computer to perform operations, the instructions comprising:

instructions to perform measurements at the first node using a signal received from a second node;

instructions to receive measurements from the second node, wherein the received measurements are performed at the second node using a signal provided by the first node;

instructions to determine pairwise comparisons of the performed measurements and the received measurements; and

instructions to compensate the measurements performed at the first node, based on the pairwise comparisons, for estimating a position of the first node.

30. The non-transitory computer-readable medium of claim 29, further comprising:

instructions to measure a Received Signal Strength Indicator (RSSI) at the first node, based on the signal from the second node;

instructions to compare the RSSI at the first node to an RSSI determined at the second node for a same wireless channel;

instructions to measure a Round Trip Time (RTT) between the first node and the second node;

instructions to compare the RTT measured at the first node to an RTT measurement determined at the second node;

instructions to determine if an RTT bias exists; and

instructions to compensate the RTT to remove the RTT bias and provide a compensated RTT measurement.

31. A method for triggering an enhanced a position estimate of a first node using pairwise measurements, comprising:

receiving Round Trip Time (RTT) and Received Signal Strength Indicator (RSSI) measurements from a plurality of neighboring nodes, wherein the RTT and RSSI measurements are performed at the neighboring nodes using a signal provided by the first node;

evaluating a quality of the RTT and RSSI measurements received from the neighboring nodes, and performing pairwise comparison and compensation with each neighboring node associated with the RTT and/or RSSI measurements which fail the evaluating;

determining a position estimate of the first node based on the RTT measurements and RSSI measurements which pass the evaluating; and

comparing information based on the RTT measurements and/or the RSSI measurements with information derived from the position estimate, and performing pairwise comparison and compensation with each neighboring node associated with RTT measurements and/or RSSI measurements which compare unfavorably.

32. The method of claim 31, wherein the evaluating the RTT and RSSI measurements further comprises:

calculating variations of the RTT measurements for a given neighboring node;

determining whether variations in the RTT measurements are within an RTT threshold; and

determining whether variations in the RSSI measurements are within an RSSI threshold.

33. The method of claim 31, wherein the evaluating the RTT and RSSI measurements further comprises:

determining whether the RTT measurements are consistent with the RSSI measurements.

34. The method of claim 33, further comprising:

determining a range corresponding to an RTT measurement associated with a given neighboring node;

determining an expected RSSI value based on the range;

comparing, based on an RSSI threshold, the expected RSSI value with the RSSI measurement associated with the given neighboring node; and

indicating that the RSSI measurement is inconsistent with the RTT measurement when the comparing exceeds the RSSI threshold.

35. The method of claim 31, wherein the comparing information further comprises:

calculating a first range to a given neighboring node having a known position using the position estimate of the first node;

determining a second range to the given neighboring node based on the RTT measurement associated with the given node;

comparing, based on an RTT-range threshold, the first range and the second range; and

indicating that the RTT measurement associated with the given neighboring node compares unfavorably when the comparing exceeds the RTT-range threshold.

36. The method of claim 31, wherein the comparing information further comprises:

calculating a first range to a given neighboring node having a known position using the position estimate of the first node;

determining a second range to the given neighboring node based on the RSSI measurement associated with the given node;

comparing, based on an RSSI-range threshold, the first range and the second range; and

indicating that the RSSI measurement associated with the given neighboring node compares unfavorably when the comparing exceeds the RSSI-range threshold.

40. The first node of claim 33, further comprising instructions which cause the processor to:

determine a range corresponding to an RTT measurement associated with a given neighboring node,

determine an expected RSSI value based on the range,

compare, based on an RSSI threshold, the expected RSSI value with the RSSI measurement associated with the given neighboring node, and

indicate that the RSSI measurement is inconsistent with the RTT measurement when the compare exceeds the RSSI threshold.

41. The first node of claim 31, wherein the instructions to compare information further cause the processor to:

calculate a first range to a given neighboring node having a known position using the position estimate of the first node,

determine a second range to the given neighboring node based on the RTT measurement associated with the given node,

compare, based on an RTT-range threshold, the first range and the second range, and

indicate that the RTT measurement associated with the given neighboring node compares unfavorably when the comparing exceeds the RTT-range threshold.

42. The first node of claim 31, wherein the instructions to compare information further cause the processor to:

calculate a first range to a given neighboring node having a known position using the position estimate of the first node,

determine a second range to the given neighboring node based on the RSSI measurement associated with the given node,

compare, based on an RSSI-range threshold, the first range and the second range, and

indicate that the RSSI measurement associated with the given neighboring node compares unfavorably when the comparing exceeds the RSSI-range threshold.

37. A first node which triggers an enhanced position estimate using pairwise measurements, comprising:

a wireless transceiver;

a processor coupled to the wireless transceiver; and

a memory coupled to the processor, wherein the memory stores executable instructions and data for causing the processor to

receive Round Trip Time (RTT) and Received Signal Strength Indicator (RSSI) measurements from a plurality of neighboring nodes, wherein the RTT and RSSI measurements are performed at the neighboring nodes using a signal provided by the first node,

evaluate a quality of the RTT and RSSI measurements received from the neighboring nodes, and performing pairwise comparison and compensation with each neighboring node associated with the RTT and/or RSSI measurements which fail the evaluating,

determine a position estimate of the first node based on the RTT measurements and RSSI measurements which pass the evaluating, and

compare information based on the RTT measurements and/or the RSSI measurements with information derived from the position estimate, and performing pairwise comparison and compensation with each neighboring node associated with RTT measurements and/or RSSI measurements which compare unfavorably.

38. The first node of claim 37, wherein the instructions to evaluate the RTT and RSSI measurements further cause the processor to:

calculate variations of the RTT measurements for a given neighboring node,

determine whether variations in the RTT measurements are within an RTT threshold, and

determine whether variations in the RSSI measurements are within an RSSI threshold.

39. The first node of claim 37, wherein the instructions to evaluate the RTT and RSSI measurements cause the processor to:

determine whether the RTT measurements are consistent with the RSSI measurements.

43. An apparatus for triggering an enhanced position estimate of a first node using pairwise measurements, comprising:

means for receiving Round Trip Time (RTT) and Received Signal Strength Indicator (RSSI) measurements from a plurality of neighboring nodes, wherein the RTT and RSSI measurements are performed at the neighboring nodes using a signal provided by the first node;

means for evaluating a quality of the RTT and RSSI measurements received from the neighboring nodes, and performing pairwise comparison and compensation with each neighboring node associated with the RTT and/or RSSI measurements which fail the evaluating;

means for determining a position estimate of the first node based on the RTT measurements and RSSI measurements which pass the evaluating; and

means for comparing information based on the RTT measurements and/or the RSSI measurements with information derived from the position estimate, and performing pairwise comparison and compensation with each neighboring node associated with RTT measurements and/or RSSI measurements which compare unfavorably.

44. The apparatus of claim 43, wherein the means for evaluating the RTT and RSSI measurements further comprises:

means for calculating variations of the RTT measurements for a given neighboring node;

means for determining whether variations in the RTT measurements are within an RTT threshold; and

means for determining whether variations in the RSSI measurements are within an RSSI threshold.

45. The apparatus of claim 43, wherein the means for evaluating the RTT and RSSI measurements further comprises:

means for determining whether the RTT measurements are consistent with the RSSI measurements.

46. The apparatus of claim 45, further comprising:

means for determining a range corresponding to an RTT measurement associated with a given neighboring node;

means for determining an expected RSSI value based on the range;

means for comparing, based on an RSSI threshold, the expected RSSI value with the RSSI measurement associated with the given neighboring node; and

means for indicating that the RSSI measurement is inconsistent with the RTT measurement when the comparing exceeds the RSSI threshold.

47. A non-transitory computer-readable medium comprising instructions, which, when executed by a processor, cause the computer to perform operations, the instructions comprising:

instructions to receive Round Trip Time (RTT) and Received Signal Strength Indicator (RSSI) measurements from a plurality of neighboring nodes, wherein the RTT and RSSI measurements are performed at the neighboring nodes using a signal provided by the first node;

instructions to evaluate a quality of the RTT and RSSI measurements received from the neighboring nodes, and performing pairwise comparison and compensation with each neighboring node associated with the RTT and/or RSSI measurements which fail the evaluating;

instructions to determine a position estimate of the first node based on the RTT measurements and RSSI measurements which pass the evaluating; and

instructions to compare information based on the RTT measurements and/or the RSSI measurements with information derived from the position estimate, and performing pairwise comparison and compensation with each neighboring node associated with RTT measurements and/or RSSI measurements which compare unfavorably.

48. The non-transitory computer-readable medium of claim 47, further comprising:

instructions to calculate variations of the RTT measurements for a given neighboring node;

instructions to determine whether variations in the RTT measurements are within an RTT threshold; and

instructions to determine whether variations in the RSSI measurements are within an RSSI threshold.

49. The non-transitory computer-readable medium of claim 47, further comprising:

instructions to determine whether the RTT measurements are consistent with the RSSI measurements.

50. The non-transitory computer-readable medium of claim 49, further comprising:

instructions to determine a range corresponding to an RTT measurement associated with a given neighboring node;

instructions to determine an expected RSSI value based on the range;

instructions to compare, based on an RSSI threshold, the expected RSSI value with the RSSI measurement associated with the given neighboring node; and

instructions to indicate that the RSSI measurement is inconsistent with the RTT measurement when the compare exceeds the RSSI threshold.

51. A method for enhancing a position determination performed by a server, comprising:

receiving measurements from a node based on signals received from a plurality of neighboring nodes;

receiving signal measurements from a plurality of neighboring nodes based on signals received from the node;

determining a pairwise comparison of the measurements from the node and the measurements from each neighboring node;

compensating the measurements received from the node based on the pairwise comparisons; and

determining a position estimate of the node using the measurements that were compensated.

52. The method of claim 51, wherein the pairwise comparison further comprises:

receiving Round Trip Time (RTT) measurements from the node based on signals received from the plurality of neighboring nodes;

receiving RTT measurements from the plurality of neighboring nodes based on signals received from the node; and

determining pairwise RTT differences by subtracting the RTT measurements, received from each of the plurality of neighboring nodes, from the RTT measurements received from the node, wherein each pairwise RTT difference is based on the RTT measurements having a common wireless channel.

53. The method of claim 52, wherein the pairwise comparison further comprises:

receiving Received Signal Strength Indicator (RSSI) measurements from the node based on signals received from the plurality of neighboring nodes;

receiving RSSI measurements from the plurality of neighboring nodes based on signals received from the node; and

determining pairwise RSSI differences by subtracting the RSSI measurements, received from each of the plurality of neighboring nodes, from the RSSI measurements received from the node, wherein each pairwise RSSI difference is based on the RSSI measurements having a common wireless channel.

54. The method of claim 53, wherein the pairwise comparison further comprises

calculating statistics of the RSSI measurements;

calculating statistics of the RTT measurements;

determining uncertainties for each wireless channel based on the statistics of the RTT and RSSI measurements; and

removing outliers of the pairwise RSSI differences and the pairwise RTT differences based upon uncertainties of the wireless channel associated with the pairwise RSSI differences and the pairwise RTT differences.

55. The method of claim 54, wherein the compensating the measurements received from the node further comprises:

determining RSSI bias values based on a weighted average of the pairwise RSSI differences having the outliers removed; and

generating compensated RSSI measurements by removing RSSI bias values from the RSSI measurements.

56. The method of claim 55, wherein the compensating the measurements received from the node further comprises:

determining RTT bias values based on a weighted average of the pairwise RTT differences having the outliers removed; and

generating compensated RTT measurements by removing RTT bias values from the RTT measurements.

57. The method of claim 56, wherein the determining the position estimate of the node further comprises:

determining position of the node using the compensated RTT measurements, the compensated RSSI measurements, and uncertainties of the wireless channel.

58. A server which enhances a position determination of a node using pairwise measurements, comprising:

a network interface;

a processor coupled to the network interface; and

a memory coupled to the processor, wherein the memory stores executable instructions and data for causing the processor to

receive measurements from a node based on signals received from a plurality of neighboring nodes,

receive signal measurements from a plurality of neighboring nodes based on signals received from the node,

determine a pairwise comparison of the measurements from the node and the measurements from each neighboring node,

compensate the measurements received from the node based on the pairwise comparisons, and

determine a position estimate of the node using the compensated measurements.

59. The server of claim 58, wherein the memory comprises further instructions which cause the processor to:

receive Round Trip Time (RTT) measurements from the node based on signals received from the plurality of neighboring nodes,

receive RTT measurements from the plurality of neighboring nodes based on signals received from the node, and

determine pairwise RTT differences by subtracting the RTT measurements, received from each of the plurality of neighboring nodes, from the RTT measurements received from the node, wherein each pairwise RTT difference is based on the RTT measurements having a common wireless channel.

60. The server of claim 59, wherein the memory comprises further instructions which cause the processor to:

receive Received Signal Strength Indicator (RSSI) measurements from the node based on signals received from the plurality of neighboring nodes,

receive RSSI measurements from the plurality of neighboring nodes based on signals received from the node, and

determine pairwise RSSI differences by subtracting the RSSI measurements, received from each of the plurality of neighboring nodes, from the RSSI measurements received from the node, wherein each pairwise RSSI difference is based on the RSSI measurements having a common wireless channel.

61. The server of claim 60, wherein the memory comprises further instructions which cause the processor to:

calculate statistics of the RSSI measurements,

calculate statistics of the RTT measurements,

determine uncertainties for each wireless channel based on the statistics of the RTT measurements and the RSSI measurements, and

remove outliers of the pairwise RSSI differences and the pairwise RTT differences based upon uncertainties of the wireless channel associated with the pairwise RSSI differences and the pairwise RTT differences.

62. The server of claim 61, wherein the memory comprises further instructions which cause the processor to:

determine RSSI bias values based on a weighted average of the pairwise RSSI differences having the outliers removed, and

generate compensated RSSI measurements by removing RSSI bias values from the RSSI measurements.

63. The server of claim 62, wherein the memory comprises further instructions which cause the processor to:

determine RTT bias values based on a weighted average of the pairwise RTT differences having the outliers removed, and

generate compensated RTT measurements by removing RTT bias values from the RTT measurements.

64. The server of claim 63, wherein the memory comprises further instructions which cause the processor to:

determine position of the node using the compensated RTT measurements, the compensated RSSI measurements, and uncertainties of the wireless channel.

65. A server which enhances a position determination of a node using pairwise measurements, comprising:

means for receiving measurements from a node based on signals received from a plurality of neighboring nodes;

means for receiving signal measurements from a plurality of neighboring nodes based on signals received from the node;

means for determining a pairwise comparison of the measurements from the node and the measurements from each neighboring node;

means for compensating the measurements received from the node based on the pairwise comparisons; and

means for determining a position estimate of the node using the measurements that are compensated.

66. The server of claim 65, further comprising:

means for receiving Round Trip Time (RTT) measurements from the node based on signals received from the plurality of neighboring nodes;

means for receiving RTT measurements from the plurality of neighboring nodes based on signals received from the node; and

means for determining pairwise RTT differences by subtracting the RTT measurements, received from each of the plurality of neighboring nodes, from the RTT measurements received from the node, wherein each pairwise RTT difference is based on the RTT measurements having a common wireless channel.

67. The server of claim 66, further comprising:

means for receiving Received Signal Strength Indicator (RSSI) measurements from the node based on signals received from the plurality of neighboring nodes;

means for receiving RSSI measurements from the plurality of neighboring nodes based on signals received from the node; and

means for determining pairwise RSSI differences by subtracting the RSSI measurements, received from each of the plurality of neighboring nodes, from the RSSI measurements received from the node, wherein each pairwise RSSI difference is based on the RSSI measurements having a common wireless channel.

68. A non-transitory computer-readable medium comprising instructions, which, when executed by a processor, cause the computer to perform operations, the instructions comprising:

instructions to receive measurements from a node based on signals received from a plurality of neighboring nodes;

instructions to receive signal measurements from a plurality of neighboring nodes based on signals received from the node;

instructions to determine a pairwise comparison of the measurements from the node and the measurements from each neighboring node;

instructions to compensate the measurements received from the node based on the pairwise comparisons; and

instructions to determine a position estimate of the node using the measurements that are compensated.

69. The non-transitory computer-readable medium of claim 68, further comprising:

instructions to receive Round Trip Time (RTT) measurements from the node based on signals received from the plurality of neighboring nodes;

instructions to receive RTT measurements from the plurality of neighboring nodes based on signals received from the node; and

instructions to determine pairwise RTT differences by subtracting the RTT measurements, received from each of the plurality of neighboring nodes, from the RTT measurements received from the node, wherein each pairwise RTT difference is based on the RTT measurements having a common wireless channel.

70. The non-transitory computer-readable medium of claim 69, further comprising:

instructions to receive Received Signal Strength Indicator (RSSI) measurements from the node based on signals received from the plurality of neighboring nodes;

instructions to receive RSSI measurements from the plurality of neighboring nodes based on signals received from the node; and

instructions to determine pairwise RSSI differences by subtracting the RSSI measurements, received from each of the plurality of neighboring nodes, from the RSSI measurements received from the node, wherein each pairwise RSSI difference is based on the RSSI measurements having a common wireless channel.