Interference detection, characterization and location in a wireless communications or broadcast system

• US 8,138,975 B2
• Filed: 12/30/2008
• Issued: 03/20/2012
• Est. Priority Date: 12/30/2008
• Status: Active Grant

• Current Assignee: Skyhook Holding, Inc. (Liberty Broadband Corp.)
• Original Assignee: TruePosition Incorporated
• Inventors: Bull, Jeffrey F., Ward, Matthew L.
• Primary Examiner(s): Phan, Dao
• Application Number:
  US12/346,598
• Publication Number:
  US 20120032854A1
• Time in Patent Office: 1,176 Days
• Field of Search: 342/357.25, 342/357.47, 342/437, 342/442, 342/450, 342/457, 342/465
• US Class Current: 342/450
• CPC Class Codes: G01S 19/21 Interference related issues ; Issues related to cross-correlation, spoofing or other methods of denial of service
• CPC Class Codes: G01S 19/215 issues related to spoofing
• CPC Class Codes: G01S 5/0215 Interference
• CPC Class Codes: G01S 5/02526 using non-dedicated equipment, e.g. user equipment or crowd-sourcing
• CPC Class Codes: H04K 2203/18 for wireless local area networks or WLAN
• CPC Class Codes: H04K 3/224 with countermeasures at transmission and/or reception of the jammed signal, e.g. stopping operation of transmitter or receiver, nulling or enhancing transmitted power in direction of or at frequency of jammer
• CPC Class Codes: H04K 3/228 Elimination in the received signal of jamming or of data corrupted by jamming interference suppression in receivers H04B1/10
• CPC Class Codes: H04W 12/122 Counter-measures against attacks; Protection against rogue devices
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 28/04 Error control
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

A Wide Area Sensor Network (WASN) is disclosed that utilizes wideband software defined radios (SDRs) to monitor RF energy over a wide frequency range, detect when critical frequencies are being jammed or otherwise interfered with, and locate the source of the interference so that the interference can be eliminated. The WASN may use one or more geolocation techniques In addition, the WASN may detect and locate unauthorized transmitters as well as estimate the transmitted power of authorized transmitters to assure they are not transmitting more power than authorized.

Claims

1. A method for detecting, classifying and locating radio frequency (RF) emitters in a wide area wireless communications network comprising one or more software defined radios, comprising:

maintaining a historical database of RF signal information, the RF signal information representing RF signals received by said one or more software defined radios for a predetermined duration over a predetermined bandwidth at a plurality of locations within said wide area wireless communications network;

detecting a presence of an interfering RF signal;

characterizing a received power of said interfering RF signal;

determining a bandwidth of said interfering RF signal; and

locating the source of said interfering RF signal via a network-based wireless location technique.

2. The method of claim 1, wherein said network-based wireless location technique is time-difference-of-arrival (TDOA).

3. The method of claim 1, wherein said network-based wireless location technique is a combination of TDOA and Angle of Arrival (AOA).

4. The method of claim 1, wherein said network comprises a single software defined radio, further comprising moving said software defined radio to multiple locations in a serial fashion over a geographic area to be monitored.

5. The method of claim 1, further comprising synchronizing time and frequency between software defined radios.

6. The method of claim 5, wherein said synchronizing is performed using a GPS timing receiver.

7. The method of claim 1, wherein said characterizing comprises estimating an absolute power transmitted by the interfering RF signal by using propagation models of a local environment.

8. The method of claim 1, wherein the software defined radios are calibrated in power to measure absolute power of the received RF signals.

9. The method of claim 7, wherein said locating comprises estimating radiated power of the source of said interfering RF signal by determining the source'"'"'s power and determining a location as a function of characteristics of the one or more software defined radios'"'"' receive antennae and an RF propagation model.

10. A method for detecting, classifying and locating radio frequency (RF) emitters, comprising:

receiving time domain RF data corresponding to a signal to be monitored, said RF data representing said signal during a predetermined duration and over a predetermined bandwidth;

associating the received time domain RF data with a plurality of equal time intervals spanning said predetermined duration;

converting the time domain RF data associated with said equal time intervals into frequency domain data corresponding to a plurality of frequency bins;

determining at least one power characteristic for each of said frequency bins and for said signal to be monitored;

for each of said frequency bins, determining that a source of interference is present when the at least one power characteristic for the frequency bin substantially differs from the at least one power characteristic of said signal to be monitored; and

locating the source of interference using a geolocation determination algorithm.

11. The method of claim 10, further comprising receiving information for the signal to be monitored, wherein said information comprises at least one of frequency channels occupied by said signal and a spectral density function.

12. The method of claim 10, further comprising passing the time domain RF data through digital downconverters to perform I/Q detection, bandlimiting, increasing bit resolution, and reducing a sample rate of the time domain RF data.

13. The method of claim 12, wherein said digital downconverters are implemented in programmable logic in the software defined radios.

14. The method of claim 10, wherein said locating is performed using at least one of Time of Arrival (TOA), Time Difference of Arrival (TDOA), Angle of Arrival (AOA), Power of Arrival (POA), Power Difference of Arrival (PDOA), and Frequency Difference of Arrival (FDOA) techniques.

15. The method of claim 10, wherein the method is performed on a continuous basis.

16. The method of claim 10, wherein the method is performed upon receiving an indication to initiate a search for interference.

17. The method of claim 10, wherein said locating further comprises using an additive probability of a plurality of geolocation techniques to render a best location estimate.

18. The method of claim 10, further comprising determining an effective utilization of RF channels by measuring RF power versus frequency and time.

19. The method of claim 10, wherein said network comprises a single software defined radio, further comprising moving said software defined radio to multiple locations in a serial fashion over a geographic area to be monitored.

20. The method of claim 10, further comprising synchronizing time and frequency between software defined radios.

21. The method of claim 20, wherein said synchronizing is performed using a GPS timing receiver.

22. The method of claim 20, wherein said synchronizing is performed using a plurality of signals and synchronizing techniques.

23. The method of claim 10, further comprising estimating an absolute power transmitted by the source of interference by using propagation models of a local environment.

24. The method of claim 10, wherein said locating further comprises determining velocity and heading of the source of interference using a Frequency Difference of Arrival (FDOA) technique.

25. The method of claim 10, wherein the software defined radios are calibrated in power to measure absolute power of the received time domain RF data.

26. The method of claim 10, further comprising time stamping data representing located sources of interference and storing the time stamped data in a database.

27. The method of claim 23, wherein said locating comprises estimating radiated power of the source of interference by determining the source'"'"'s power and determining a location as a function of characteristics of the one or more software defined radios'"'"' receive antennae and an RF propagation model.

28. The method of claim 10, further comprising generating an alert when unauthorized signals are detected and located.

29. The method of claim 10, further comprising determining a percentage occupancy metric over a predetermined geographic area as a function of a percentage of time during a predetermined time period that the signal is transmitted.

30. The method of claim 10, wherein the source of interference is a spoof signal.

31. The method of claim 30, wherein the signal to be monitored is a Global Navigation Satellite System (GNSS) signal.

32. The method of claim 31, wherein said determining at least one power characteristic comprises determining an absolute power level and said determining that a source of interference is present comprises determining that the absolute power level exceeds an absolute power level of the signal to be monitored.

33. The method of claim 32, wherein said determining that a source of interference is present comprises determining that a satellite associated with the at least one power characteristic is over the horizon.

34. A method for detecting, classifying and locating radio frequency (RF) signals in a wide area wireless communications network comprising one or more software defined radios, comprising:

receiving time domain RF data corresponding to a signal to be monitored, said RF data representing said signal during a predetermined duration and over a predetermined bandwidth;

associating the received time domain RF data with a plurality of equal time intervals spanning said predetermined duration;

converting the time domain RF data associated with said equal time intervals into frequency domain data corresponding to a plurality of frequency bins;

determining at least one power characteristic for each of said frequency bins and for said signal to be monitored;

identifying frequency bins with at least one power characteristic above a noise floor;

for each of the identified frequency bins with at least one power characteristic above said noise floor, characterizing signals in the frequency bin; and

locating the characterized signals using a geolocation determination algorithm.

35. The method of claim 34, further comprising receiving information for the signal to be monitored, wherein said information comprises at least one of frequency channels occupied by said signal and a spectral density function.

36. The method of claim 34, further comprising passing the time domain RF data through digital downconverters to perform I/Q detection, bandlimiting, increasing bit resolution, and reducing a sample rate of the time domain RF data.

37. The method of claim 36, wherein said digital downconverters are implemented in programmable logic in the software defined radios.

38. The method of claim 34, wherein said locating is performed using at least one of Time of Arrival (TOA), Time Difference of Arrival (TDOA), Angle of Arrival (AOA), Power of Arrival (POA), Power Difference of Arrival (PDOA), and Frequency Difference of Arrival (FDOA) techniques.

39. The method of claim 34, wherein the method is performed on a continuous basis.

40. The method of claim 34, wherein the method is performed upon receiving an indication to initiate a signal search.

41. The method of claim 34, wherein said locating further comprises using an additive probability of a plurality of geolocation techniques to render a best location estimate.

42. The method of claim 34, further comprising determining an effective utilization of RF channels by measuring RF power versus frequency and time.

43. The method of claim 34, further comprising determining a location of an unlicensed white space transmitter and a maximum power that the white space transmitter can transmit without interfering with digital over-the-air television service.

44. The method of claim 34, wherein said network comprises a single software defined radio, further comprising moving said software defined radio to multiple locations in a serial fashion over a geographic area to be monitored.

45. The method of claim 34, further comprising synchronizing time and frequency between software defined radios.

46. The method of claim 45, wherein said synchronizing is performed using a GPS timing receiver.

47. The method of claim 45, wherein said synchronizing is performed using a plurality of signals and synchronizing techniques.

48. The method of claim 34, further comprising estimating an absolute power transmitted by a source of interference by using propagation models of a local environment.

49. The method of claim 35, wherein said information comprises a catalog of legitimate signals.

50. The method of claim 49, further comprising comparing the characterized signals with said legitimate signals to identify illegitimate signals.

51. The method of claim 34, wherein the software defined radios are calibrated in power to measure absolute power of the received time domain RF data.

52. The method of claim 34, further comprising time stamping data representing characterized signals and storing the time stamped data in a database.

53. The method of claim 48, wherein said locating comprises estimating radiated power of the source of interference by determining the source'"'"'s power and determining a location as a function of characteristics of the one or more software defined radios'"'"' receive antennae and an RF propagation model.

54. The method of claim 50, further comprising generating an alert when illegitimate signals are identified.

55. The method of claim 34, further comprising determining a percentage occupancy metric over a predetermined geographic area as a function of a percentage of time during a predetermined time period that the characterized signals are transmitted.

56. A system for detecting, classifying and locating radio frequency (RF) emitters in a wide area wireless communications network, the system comprising one or more software defined radios with a wide instantaneous bandwidth and tuning range, at least one processor communicatively coupled to the one or more software defined radios, and at least one memory communicatively coupled to said at least one processor, the at least one memory storing therein computer readable instructions capable of configuring the system to perform the following method:

receiving time domain RF data corresponding to a signal to be monitored, said RF data representing said signal during a predetermined duration and over a predetermined bandwidth;

associating the received time domain RF data with a plurality of equal time intervals spanning said predetermined duration;

converting the time domain RF data associated with said equal time intervals into frequency domain data corresponding to a plurality of frequency bins;

determining at least one power characteristic for each of said frequency bins and for said signal to be monitored;

for each of said frequency bins, determining that a source of interference is present when the at least one power characteristic for the frequency bin substantially differs from the at least one power characteristic of said signal to be monitored; and

locating the source of interference using a geolocation determination algorithm.

57. The system of claim 56, further comprising receiving information for the signal to be monitored, wherein said information comprises at least one of frequency channels occupied by said signal and a spectral density function.

58. The system of claim 56, further comprising passing the time domain RF data through digital downconverters to perform I/Q detection, bandlimiting, increasing bit resolution, and reducing a sample rate of the time domain RF data.

59. The system of claim 58, wherein said digital downconverters are implemented in programmable logic in the software defined radios.

60. The system of claim 56, wherein said locating is performed using at least one of Time of Arrival (TOA), Time Difference of Arrival (TDOA), Angle of Arrival (AOA), Power of Arrival (POA), Power Difference of Arrival (PDOA), and Frequency Difference of Arrival (FDOA) techniques.

61. The system of claim 56, wherein the method is performed on a continuous basis.

62. The system of claim 56, wherein the method is performed upon receiving an indication to initiate a search for interference.

63. The system of claim 56, wherein said locating further comprises using an additive probability of a plurality of location techniques to render a best location estimate.

64. The system of claim 56, further comprising determining an effective utilization of RF channels by measuring RF power versus frequency and time.

65. The system of claim 56, wherein said network comprises a single software defined radio, further comprising moving said software defined radio to multiple locations in a serial fashion over a geographic area to be monitored.

66. The system of claim 56, further comprising synchronizing time and frequency between software defined radios.

67. The system of claim 66, wherein said synchronizing is performed using a GPS timing receiver.

68. The system of claim 66, wherein said synchronizing is performed a plurality of multiple signals and synchronizing techniques.

69. The system of claim 56, further comprising estimating an absolute power transmitted by the source of interference by using propagation models of a local environment.

70. The system of claim 56, wherein the software defined radios are controlled by a central controller.

71. The system of claim 56, wherein said locating further comprises determining velocity and heading of the source of interference using a Frequency Difference of Arrival (FDOA) technique.

72. The system of claim 56, wherein the software defined radios are calibrated in power to measure absolute power of the received time domain RF data.

73. The system of claim 56, further comprising time stamping data representing located sources of interference and storing the time stamped data in a database.

74. The system of claim 56, wherein said locating comprises estimating radiated power of the source of interference by determining the source'"'"'s power and determining a location as a function of characteristics of the one or more software defined radios'"'"' receive antennae and an RF propagation model.

75. The system of claim 56, further comprising generating an alert when unauthorized signals are detected and located.

76. The system of claim 56, further comprising determining a percentage occupancy metric over a predetermined geographic area as a function of a percentage of time during a predetermined time period that the signal is transmitted.

77. The system of claim 56, wherein the source of interference is a spoof signal.

78. The system of claim 77, wherein the signal to be monitored is a Global Navigation Satellite System (GNSS) signal.

79. The system of claim 78, wherein said determining at least one power characteristic comprises determining an absolute power level and said determining that a source of interference is present comprises determining that the absolute power level exceeds an absolute power level of the signal to be monitored.

80. The system of claim 78, wherein said determining that a source of interference is present comprises determining that a satellite associated with the at least one power characteristic is over the horizon.

81. A system for detecting, classifying and locating radio frequency (RF) signals in a wide area wireless communications network the system comprising one or more software defined radios with a wide instantaneous bandwidth and tuning range, at least one processor communicatively coupled to the one or more software defined radios, and at least one memory communicatively coupled to said at least one processor, the at least one memory storing therein computer readable instructions capable of configuring the system to perform the following method:

receiving time domain RF data corresponding to a signal to be monitored, said RF data representing said signal during a predetermined duration and over a predetermined bandwidth;

associating the received time domain RF data with a plurality of equal time intervals spanning said predetermined duration;

converting the time domain RF data associated with said equal time intervals into frequency domain data corresponding to a plurality of frequency bins;

determining at least one power characteristic for each of said frequency bins and for said signal to be monitored;

identifying frequency bins with at least one power characteristic above a noise floor;

for each of the identified frequency bins with at least one power characteristic above said noise floor, characterizing signals in the frequency bin; and

locating the characterized signals using a geolocation determination algorithm.

82. The system of claim 81, further comprising receiving information for the signal to be monitored, wherein said information comprises at least one of frequency channels occupied by said signal and a spectral density function.

83. The system of claim 81, further comprising passing the time domain RF data through digital downconverters to perform I/Q detection, bandlimiting, increasing bit resolution, and reducing a sample rate of the time domain RF data.

84. The system of claim 83, wherein said digital downconverters are implemented in programmable logic in the software defined radios.

85. The system of claim 81, wherein said locating is performed using at least one of Time Difference of Arrival (TDOA) techniques, Angle of Arrival (AoA) techniques, and Power Difference of Arrival (PDOA) techniques.

86. The system of claim 81, wherein the method is implemented on a continuous basis.

87. The system of claim 81, wherein the method is implemented upon receiving an indication to initiate a signal search.

88. The system of claim 81, wherein said locating further comprises using an additive probability of a plurality of geolocation techniques to render a best location estimate.

89. The system of claim 81, further comprising determining an effective utilization of RF channels by measuring RF power versus frequency and time.

90. The system of claim 81, further comprising determining a location of an unlicensed white space transmitter and a maximum power that the white space transmitter can transmit without interfering with digital over-the-air television service.

91. The system of claim 81, wherein said network comprises a single software defined radio, further comprising moving said software defined radio to multiple locations in a serial fashion over a geographic area to be monitored.

92. The system of claim 81, further comprising synchronizing time and frequency between software defined radios.

93. The system of claim 92, wherein said synchronizing is performed using a GPS timing receiver.

94. The system of claim 92, wherein said synchronizing is performed using a plurality of signals and synchronizing techniques.

95. The system of claim 81, further comprising estimating an absolute power transmitted by a source of interference by using propagation models of a local environment.

96. The system of claim 82, wherein said information comprises a catalog of legitimate signals.

97. The system of claim 96, further comprising comparing the characterized signals with said legitimate signals to identify illegitimate signals.

98. The system of claim 81, wherein the software defined radios are calibrated in power to measure absolute power of the received time domain RF data.

99. The system of claim 81, further comprising time stamping data representing characterized signals and storing the time stamped data in a database.

100. The system of claim 95, wherein said locating comprises estimating radiated power of the source of interference by determining the source'"'"'s power and determining a location as a function of characteristics of the one or more software defined radios'"'"' receive antennae and an RF propagation model.

101. The system of claim 97, further comprising generating an alert when illegitimate signals are identified.

102. The system of claim 81, further comprising determining a percentage occupancy metric over a predetermined geographic area as a function of a percentage of time during a predetermined time period that the characterized signals are transmitted.