Signal Waveform Construction for Position Determination by Scrambled Conical

• US 20090023462A1
• Filed: 07/17/2007
• Published: 01/22/2009
• Est. Priority Date: 07/17/2007
• Status: Abandoned Application

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Dent, Paul Wilkinson
• Application Number:
  US11/778,728
• Publication Number:
  US 20090023462A1
• Time in Patent Office: Days
• US Class Current: 455/456.500
• CPC Class Codes: G01S 1/42 Conical-scan beacons transmitting signals which indicate at a mobile receiver any displacement of the receiver from the conical-scan axis, e.g. for "beam-riding" missile control
• CPC Class Codes: G01S 3/56 Conical-scan beam systems using signals indicative of the deviation of the direction of reception from the scan axis

Abstract

A method and apparatus for determining a mobile station'"'"'s location using an antenna beam that traverses a scan pattern is described herein. In one embodiment, a device transmits/receives a signal as a position of a transmission/reception antenna beam traverses the scan pattern in a non-sequential order. A strength of the received signal is measured at a plurality of the beam positions. After reordering the signal strength measurements, the mobile station location relative to a nominal center of the beam is determined based on the reordered signal strength measurements. Another embodiment uses signals having different frequency components that are transmitted or received in beams executed in different scan patterns. In this embodiment, signal strength measurements associated with different frequency components are jointly processed to determine a combined correlation. The relative mobile station location is determined based on the combined correlation.

Claims

1. A method for determining a location of a mobile station comprising:

receiving a signal from a remote station within an antenna beam, wherein a position of the beam traverses a scan pattern in a non-sequential order;

making a signal strength measurement of said signal at a plurality of the beam positions;

spreading a noise component of said signal strength measurements; and

after spreading the noise component, determining a location of the mobile station based on the signal strength measurements.

2. The method of claim 1 wherein spreading the noise component comprises reordering the signal strength measurements to correspond to sequentially ordered beam positions of the scan pattern.

3. The method of claim 2 wherein determining the location of the mobile station comprises:

correlating the reordered signal strength measurements with a reference signal; and

determining the location of the mobile station based on the correlation.

4. The method of claim 3 wherein correlating comprises performing a Fourier transform on the reordered signal strength measurements.

5. The method of claim 3 wherein determining the location comprises:

determining an amplitude and a phase of the signal strength measurements based on the correlation; and

determining the location of the mobile station relative to a nominal center of the beam based on the amplitude and phase.

6. The method of claim 5 wherein determining the location based on the amplitude and phase comprises:

determining a distance between the mobile station and the nominal center of the beam based on the amplitude; and

determining a direction of the mobile station relative to the nominal center of the beam based on the phase.

7. The method of claim 1 further comprising varying the beam position between time slots or traffic frames of the signal.

8. The method of claim 1 wherein the remote station comprises the mobile station, wherein the beam comprises a reception beam configured to receive the signal from the mobile station at a network device, and wherein the network device determines the location of the mobile station based on the signal strength measurements.

9. The method of claim 1 wherein the remote station comprises a network device, and wherein the beam comprises a transmission beam configured to transmit the signal from the network device to the mobile station.

10. The method of claim 9 wherein determining the location comprises determining the location based on the signal strength measurements at the mobile station.

11. The method of claim 9 further comprising transmitting the signal strength measurements from the mobile station to the network device, wherein determining the location comprises determining the location at the network device based on the signal strength measurements received at the network device.

12. The method of claim 9 further comprising maintaining the transmitted signal at a generally constant mean transmission power for the plurality of the beam positions.

13. The method of claim 9 further comprising:

maintaining the transmission beam at a generally constant position during a timeslot or traffic frame of the signal; and

varying the position of the transmission beam between transmitted timeslots or traffic frames of the signal.

14. The method of claim 9 further comprising synchronizing the step of receiving the signal at the mobile station with one or more features of the signal.

15. A location processor to determine the location of a mobile station based on a signal received from a remote station within an antenna beam, wherein a position of the beam traverses a scan pattern in a non-sequential order, the location processor comprising:

a measurement unit configured to make a signal strength measurement of said received signal at a plurality of the beam positions;

a noise unit connected to an output of the measurement unit and configured to spread a noise component of the signal strength measurements; and

a location unit configured to determine the location of the mobile station based on the signal strength measurements output by the noise unit.

16. The location processor of claim 15 wherein the noise unit is configured to reorder the signal strength measurements.

17. The location processor of claim 16 wherein the location unit comprises:

a correlator to correlate the reordered signal strength measurements with a reference signal; and

a location calculator to determine the location of the mobile station based on the correlation.

18. The location processor of claim 16 wherein the correlator is configured to perform a Fourier transform on the reordered signal strength measurements.

19. The location processor of claim 16 wherein the location calculator is configured to:

determine an amplitude and a phase of the signal strength measurements relative to a nominal center of the beam based on the correlation; and

determine the location of the mobile station based on the amplitude and phase.

20. The location processor of claim 19 wherein the location calculator determines the location based on the amplitude and phase by:

determining a distance between the mobile station and the nominal center of the beam based on the amplitude; and

determining a direction of the mobile station relative to the nominal center of the beam based on the phase.

21. The location processor of claim 15 wherein the beam position varies between time slots or traffic frames of the received signal.

22. The location processor of claim 15 wherein the remote station comprises the mobile station, wherein the location processor is disposed in a network device, and wherein the beam comprises a reception beam configured to receive the signal from the mobile station at the network device.

23. The location processor of claim 15 wherein the remote station comprises a network device, and wherein the beam comprises a transmission beam configured to transmit the signal from the network device to the mobile station.

24. The location processor of claim 23 wherein at least a portion of the location processor is disposed in the mobile station.

25. The location processor of claim 23 wherein a mean transmission power associated with the signal transmitted by the transmission beam is kept the same for two or more of the plurality of beam positions.

26. The location processor of claim 23 wherein the position of the transmission beam is generally constant during a timeslot or traffic frame of the signal, and wherein the position of the transmission beam changes between the timeslots or traffic frames.

27. The location processor of claim 23 wherein the measurement unit is further configured to synchronize the step of receiving the signal with one or more features of the signal.

28. A method for transmitting a signal comprising:

generating a signal;

determining a scan pattern for an antenna beam, said scan pattern having a plurality of sequentially spaced beam positions; and

transmitting the signal to a mobile station within the antenna beam as the beam position traverses the scan pattern in a non-sequential order.

29. The method of claim 28 wherein a mean transmission power associated with the signal is kept the same at the plurality of beam positions.

30. The method of claim 28 wherein the beam position is generally constant during a timeslot or traffic frame of the signal, and wherein the beam position changes between the timeslots or traffic frames.

31. A transmitter for transmitting a signal comprising:

a processor to generate a signal and to determine a scan pattern for an antenna beam, said scan pattern comprising a plurality of sequentially spaced beam positions;

a beamformer to generate the antenna beam at a plurality of the beam positions; and

an antenna array configured to transmit the signal within the antenna beam as the beam position traverses the scan pattern in a non-sequential order.

32. The transmitter of claim 31 wherein a transmission power associated with the signal is generally constant at the beam positions.

33. The transmitter of claim 31 wherein the beam position is generally constant during a timeslot or traffic frame of the signal, and wherein the beam position changes between the timeslots or traffic frames.

34. A method for determining a location of a mobile station comprising:

generating a signal;

determining a scan pattern for an antenna beam, said scan pattern having a plurality of sequentially spaced beam positions;

transmitting the signal to a mobile station within the antenna beam as the beam position traverses the scan pattern in a non-sequential order;

receiving the signal at the mobile station;

making a signal strength measurement of the received signal at a plurality of the beam positions of the scan pattern;

reordering the signal strength measurements to spread a noise component in the received signal; and

determining a location of the mobile station based on the reordered signal strength measurements.

35. The method of claim 34 wherein determining the location comprises determining the location of the mobile station at the mobile station based on the reordered signal strength measurements.

36. The method of claim 34 further comprising transmitting the signal strength measurements to the network device, wherein reordering the signal strength measurements comprises reordering the received signal strength measurements at the network device, and wherein determining the location comprises determining the location of the mobile station at the network device based on the reordered signal strength measurements.

37. A wireless network comprising:

a network device comprising;

a processor to generate a signal and to determine a scan pattern for an antenna beam, said scan pattern comprising a plurality of sequentially spaced beam positions;

a beamformer to generate the antenna beam at a plurality of the beam positions; and

an antenna array configured to transmit the signal within the antenna beam as the beam position traverses the scan pattern in a non-sequential order; and

a mobile station comprising;

a receiver to receive the signal;

a measurement unit to make a signal strength measurement of the received signal at a plurality of the beam positions of the scan pattern;

a noise unit to reorder the signal strength measurements to spread a noise component in the received signal; and

a location unit to determine a location of the mobile station based on the reordered signal strength measurements.

38. A method for determining a location of a mobile station, the method comprising:

determining a first scan pattern comprising a plurality of sequentially ordered beam positions arranged about a first nominal center;

determining a second scan pattern comprising a plurality of sequentially ordered beam positions arranged about a second nominal center;

receiving a first signal associated with a first frequency from a remote station within a first beam, wherein a position of the first beam traverses the first scan pattern;

receiving a second signal associated with a second frequency from a remote station within a second beam, wherein a position of the second beam traverses the second scan pattern;

making a first signal strength measurement of said first signal and a second signal strength measurement of said second signal at a plurality of the beam positions of the first and second scan patterns;

jointly processing the signal strength measurements made on two or more of the beam positions on said first and second frequencies to determine a combined correlation with said scan patterns; and

determining the location of the mobile station based on the combined correlation.

39. The method of claim 38 wherein the first and second scan patterns are mutually orthogonal.

40. The method of claim 38 wherein the first and second scan patterns comprise a common scan pattern executed at different scan frequencies.

41. The method of claim 38 wherein the first and second scan patterns comprise a common scan pattern executed in first and second orders, respectively.

42. The method of claim 41 wherein the second order is offset from the first order by a predetermined phase or time.

43. The method of claim 41 wherein the first order comprises a non-sequential order.

44. The method of claim 43 further comprising spreading a noise component of the first signal by reordering the first signal strength measurements.

45. The method of claim 38 wherein determining the location comprises determining the location of the mobile station based on a Fourier transform of the signal strength measurements.

46. The method of claim 38 wherein jointly processing comprises, for each of the two or more beam positions in the scan patterns, adding the corresponding first and second signal strength measurements to reduce a noise component common to the first and second signal strength measurements.

47. The method of claim 38 wherein determining the location comprises:

determining an amplitude and a phase of the combined correlation; and

determining the location of the mobile station relative to a nominal center of the beam based on the amplitude and phase.

48. The method of claim 47 wherein determining the location based on the amplitude and phase comprises:

determining a distance between the mobile station and the nominal center of the beam based on the amplitude; and

determining a direction of the mobile station relative to the nominal center of the beam based on the phase.

49. The method of claim 38 further comprising changing a position of the first and second beams between time slots or traffic frames of the respective first and second signals.

50. The method of claim 38 wherein the remote station comprises the mobile station, wherein the first and second beams comprise respective first and second reception beams configured to receive the respective first and second signals from the mobile station at a network device, and wherein the network device determines the location of the mobile station based on the combined correlation.

51. The method of claim 38 wherein the remote station comprises a network device, wherein the first and second beams comprise respective first and second transmission beams configured to transmit the respective first and second signals from the network device to the mobile station.

52. The method of claim 38 wherein the first and second signals comprise first and second subcarriers of an orthogonal frequency division multiplexing signal.

53. A location processor to determine the location of a mobile station based on first and second signals received from a remote station within respective first and second beams, wherein a position of the first beam traverses a first scan pattern, and wherein a position of the second beam traverses a second scan pattern, the location processor comprising:

a measurement unit configured to make a first signal strength measurement of said first signal and a second signal strength measurement of said second signal at a plurality of the beam positions of said first and second scan patterns;

a noise unit configured to jointly process said first and second signal strength measurements made on two or more of the beam positions to determine a combined correlation with said scan patterns; and

a location unit configured to determine the location of the mobile station based on the combined correlation output by the noise unit.

54. The location processor of claim 53 wherein the first and second scan patterns are mutually orthogonal.

55. The location processor of claim 53 wherein the first and second scan patterns comprise a common scan pattern executed at different scan frequencies.

56. The location processor of claim 53 wherein the first and second scan patterns comprise a common scan pattern executed in first and second orders, respectively.

57. The location processor of claim 56 wherein the second order is offset from the first order by a predetermined phase or time.

58. The location processor of claim 56 wherein the first order comprises a non-sequential order.

59. The location processor of claim 58 wherein the noise unit is further configured to spread a noise component of the first signal by reordering the first signal strength measurements.

60. The location processor of claim 53 wherein the noise unit performs a Fourier transform of said signal strength measurements to determine a combine correlation, and wherein the location unit determines the location of the mobile station based on the combined correlation.

61. The location processor of claim 53 wherein the noise unit adds, for each of the two or more beam positions in the scan patterns, the corresponding first and second signal strength measurements to reduce a noise component common to the first and second signal strength measurements.

62. The location processor of claim 53 wherein the location unit determines the location by:

determining an amplitude and a phase of the combined correlation; and

determining the location of the mobile station relative to a nominal center of the beam based on the amplitude and phase.

63. The location processor of claim 62 wherein the location unit determines the location based on the amplitude and phase by:

determining a distance between the mobile station and the nominal center of the beam based on the amplitude; and

determining a direction of the mobile station relative to the nominal center of the beam based on the phase.

64. The location processor of claim 53 wherein the position for the first and second beams changes between time slots or traffic frames of the respective first and second signals.

65. The location processor of claim 53 wherein the location processor is disposed in a network device and the remote station comprises the mobile station, and wherein the first and second beams comprise first and second reception beams configured to receive the respective first and second signals from the mobile station at a network device.

66. The location processor of claim 53 wherein the remote station comprises a network device, wherein the first and second beams comprise first and second transmission beams configured to transmit the respective first and second signals from the network device to the mobile station.

67. The location processor of claim 53 wherein the first and second signals comprise first and second subcarriers of an orthogonal frequency division multiplexing signal.

68. A method for transmitting a signal comprising:

generating a first signal associated with a first frequency;

generating a second signal associated with a second frequency;

determining first and second scan patterns comprising a plurality of sequentially spaced beam positions;

transmitting the first signal to a mobile station within a first beam as the position of the first beam traverses the first scan pattern; and

transmitting the second signal to a mobile station within a second beam as the position of the second beam traverses the second scan pattern.

69. The method of claim 68 wherein the first and second scan patterns are mutually orthogonal.

70. The method of claim 68 wherein the first and second scan patterns comprise a common scan pattern executed in first and second orders, respectively.

71. The method of claim 68 wherein the second order is offset from the first order by a predetermined phase or time.

72. The method of claim 68 wherein at least one of the first and second orders comprises a non-sequential order.

73. The method of claim 68 wherein the first and second signals comprise first and second subcarriers of an orthogonal frequency division multiplexing signal.

74. A transmitter for transmitting a signal comprising:

a processor configured to;

generate a first signal associated with a first frequency;

generate a second signal associated with a second frequency; and

determine first and second scan patterns comprising a plurality of sequentially spaced beam positions;

a beamformer to generate first and second beams at two or more of the beam positions in the first and second scan patterns, respectively; and

an antenna array configured to;

transmit the first signal within the first beam as the position of the first beam traverses the first scan pattern; and

transmit the second signal within the second beam as the position of the second beam traverses the second scan pattern.

75. The transmitter of claim 74 wherein the first and second scan patterns are mutually orthogonal.

76. The transmitter of claim 74 wherein the first and second scan patterns comprise a common scan pattern executed in first and second orders, respectively.

77. The transmitter of claim 76 wherein the second order is offset from the first order by a predetermined phase or time.

78. The transmitter of claim 76 wherein at least one of the first and second orders comprises a non-sequential order.

79. The transmitter of claim 74 wherein the first and second signals comprise first and second subcarriers of an orthogonal frequency division multiplexing signal.

80. A method for determining a location of a mobile station comprising:

generating a first signal associated with a first frequency;

generating a second signal associated with a second frequency;

determining first and second scan patterns comprising a plurality of sequentially spaced beam positions;

transmitting the first signal to the mobile station within a first beam as the position of the first beam traverses the first scan pattern;

transmitting the second signal to the mobile station within a second beam as the position of the second beam traverses the second scan pattern;

receiving the first and second signals at the mobile station;

making a first signal strength measurement of said first signal and a second signal strength measurement of said second signal at two or more of the beam positions of the first and second scan patterns;

jointly processing said first and second signal strength measurements made on two or more of said beam positions to determine a combined correlation of the signal strength measurements with said scan patterns; and

determining a location of the mobile station based on the combined correlation.

81. The method of claim 80 further comprising transmitting said signal strength measurements to the network device, wherein determining the location comprises determining said combined correlation at the network and determining the location of the mobile station at the network device based on the combined correlation.

82. The method of claim 80 wherein the first and second signals comprise first and second subcarriers of an orthogonal frequency division multiplexing signal.

83. A wireless network comprising:

a network device comprising;

a processor to generate first and second signals associated with respective first and second frequencies, and to determine first and second scan patterns comprising a plurality of sequentially spaced beam positions;

a beamformer to generate first and second beams at two or more of the beam positions in the first and second scan patterns; and

an antenna array to transmit the first signal within the first beam as the position of the first beam traverses the first scan pattern, and to transmit the second signal within the second beam as the position of the second beam traverses the second scan pattern; and

a mobile station comprising;

a receiver to receive the first and second signals;

a measurement unit to make a first signal strength measurement of the first signal and a second signal strength measurement of said second signal at two or more of the beam positions of the first and second scan patterns, respectively;

a noise unit configured to jointly process said first and second signal strength measurements made on two or more of the beam positions to determine a combined correlation with said scan patterns; and

a location unit to determine a location of the mobile station based on the combined correlation.

84. The wireless network of claim 83 wherein the first and second signals comprise first and second subcarriers of an orthogonal frequency division multiplexing signal.