Wide area positioning system

• US 8,130,141 B2
• Filed: 09/10/2009
• Issued: 03/06/2012
• Est. Priority Date: 09/10/2008
• Status: Active Grant

• Current Assignee: NextNav, LLC
• Original Assignee: Commlabs, Inc.
• Inventors: Pattabiraman, Ganesh, Meiyappan, Subramanian, Raghupathy, Arun, Sankar, Hari
• Primary Examiner(s): Liu, Harry
• Application Number:
  US12/557,479
• Publication Number:
  US 20100073229A1
• Time in Patent Office: 908 Days
• Field of Search: 342/357.42, 342/357.43, 342/357.62, 342/357.64, 342/357.76, 342/450, 342/458, 342/463, 342/464, 342/357.29, 455/456.1, 455/456.5, 455/456.6
• US Class Current: 342/357.29
• CPC Class Codes: G01S 1/08 Systems for determining direction or position line
• CPC Class Codes: G01S 19/11 wherein the cooperating elements are pseudolites or satellite radio beacon positioning system signal repeaters
• CPC Class Codes: G01S 19/24 Acquisition or tracking or demodulation of signals transmitted by the system synchronisation aspects of direct sequence spread spectrum modulation H04B1/7073
• CPC Class Codes: G01S 19/42 Determining position
• CPC Class Codes: G01S 19/46 the supplementary measurement being of a radio-wave signal type
• CPC Class Codes: G01S 5/10 Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements , e.g. omega or decca systemsG01S5/12 takes precedence ; beacons and receivers cooperating therewith G01S1/306, G01S1/308
• CPC Class Codes: H04B 1/7087 Carrier synchronisation aspects
• CPC Class Codes: H04B 1/709 Correlator structure
• CPC Class Codes: H04B 2201/7073 Direct sequence modulation synchronisation
• CPC Class Codes: H04B 7/2618 using hybrid code-time division multiple access [CDMA-TDMA]
• CPC Class Codes: H04W 4/02 Services making use of location information
• CPC Class Codes: H04W 56/005 compensating for timing error by adjustment in the receiver
• CPC Class Codes: H04W 72/0446 Resources in time domain, e.g. slots or frames
• CPC Class Codes: H04W 72/30 Resource management for broadcast services
• CPC Class Codes: H04W 72/51 based on terminal or device properties

Abstract

Systems and methods are described for determining position of a receiver. The positioning system comprises a transmitter network including transmitters that broadcast positioning signals. The positioning system comprises a remote receiver that acquires and tracks the positioning signals and/or satellite signals. The satellite signals are signals of a satellite-based positioning system. A first mode of the remote receiver uses terminal-based positioning in which the remote receiver computes a position using the positioning signals and/or the satellite signals. The positioning system comprises a server coupled to the remote receiver. A second operating mode of the remote receiver comprises network-based positioning in which the server computes a position of the remote receiver from the positioning signals and/or satellite signals, where the remote receiver receives and transfers to the server the positioning signals and/or satellite signals.

Claims

1. A positioning system comprising:

a terrestrial transmitter network comprising a plurality of transmitters that broadcast positioning signals comprising at least ranging signals and positioning system information, wherein a ranging signal comprises information used to measure a distance to a transmitter broadcasting the ranging signal;

a remote receiver that acquires at least one of the positioning signals and satellite signals, wherein the satellite signals are signals of a satellite-based positioning system, wherein a first operating mode of the remote receiver comprises terminal-based positioning in which the remote receiver computes a position of the remote receiver from at least one of the positioning signals and the satellite signals; and

a server coupled to the remote receiver, wherein a second operating mode of the remote receiver comprises network-based positioning in which the server computes a position of the remote receiver from information derived from at least one of the positioning signals and the satellite signals, wherein the remote receiver receives and transfers to the server information derived from at least one of the positioning signals and the satellite signals, wherein the remote receiver identifies multipath components of the positioning signals by generating a cross-correlation function by cross-correlating received samples with a reference sequence, and extracting from the cross-correlation function a vector that is derived from a first number of samples left of a peak of the cross-correlation function and a second number of samples right of the peak.

2. The positioning system of claim 1, comprising a communication system coupled to at least one of the remote receiver and the plurality of transmitters, wherein the communication system is a cellular communication system.

3. The positioning system of claim 1, wherein the plurality of transmitters are synchronized.

4. The positioning system of claim 3, wherein each transmitter of the plurality of transmitters transmits a signal including a pseudorandom number sequence and assistance data.

5. The positioning system of claim 4, wherein the signal transmitted by the plurality of transmitters comprises a preamble for at least one of frequency acquisition and timing alignment.

6. The positioning system of claim 4, wherein the pseudorandom number sequence includes relatively low autocorrelation values to facilitate detection of an earliest arriving path in a presence of multipath.

7. The positioning system of claim 4, wherein the plurality of transmitters form a CDMA network in which each transmitter of the plurality of transmitters transmits the sequence in a same time slot.

8. The positioning system of claim 4, wherein the plurality of transmitters form a TDMA network in which each transmitter of the plurality of transmitters transmits the sequence staggered in time in a separate time slot than other transmitters of the plurality of transmitters.

9. The positioning system of claim 8, wherein a frame duration of the TDMA network is determined by a product of frame duration and a number of transmitter slots used for positioning in a coverage area.

10. The positioning system of claim 4, wherein each transmitter in a first set of transmitters of the plurality of transmitters transmits the sequence in a common time slot staggered in time from time slots of other transmitters of the plurality of transmitters.

11. The positioning system of claim 10, wherein the separate time slot for transmission changes in a pseudorandom manner.

12. The positioning system of claim 10, wherein each transmitter in a second set of transmitters of the plurality of transmitters transmits the sequence in a same time slot and the sequence includes a different pseudorandom number than the first set of transmitters.

13. The positioning system of claim 12, wherein the same time slot for transmission changes in a pseudorandom manner.

14. The positioning system of claim 10, wherein a carrier signal of each transmitter is offset from the carrier signal of other transmitters of the plurality of transmitters.

15. The positioning system of claim 4, wherein the assistance data comprises at least one of system time at a rising edge of a pulse of a waveform, system time at a falling edge of a pulse of a waveform, geocode data of the plurality of transmitters, geocode data of adjacent transmitters adjacent to the plurality of transmitters, index of a sequence used by at least one transmitter in proximity of the plurality of transmitters, clock timing corrections for at least one transmitter, local atmospheric corrections, relationship of WAPS timing to GNSS time, indication of local environment to aid the remote receiver in pseudorange resolution, and at least one of an offset from base index of a set of pseudorandom sequences, a list of pseudorandom number sequences from a set of transmitters, and a list of transmitters that utilize a particular pseudorandom number sequence.

16. The positioning system of claim 4, wherein the assistance data includes data bits having an assigned priority.

17. The positioning system of claim 16, wherein the data bits having a higher priority are transmitted more often than data bits having a lower priority.

18. The positioning system of claim 1, wherein a timing difference between transmissions from different transmitters is transmitted to the remote receiver.

19. The positioning system of claim 1, wherein the plurality of transmitters are positioned so that the remote receiver receives signals from at least three transmitters and a geometric dilution of precision in each position is less than a threshold value.

20. The positioning system of claim 19, comprising determining position of each of the plurality of transmitters by minimizing a function that is a volume integration of a square of the geometric dilution of precision over a coverage volume.

21. The positioning system of claim 20, wherein the volume integration is with respect to coordinates of a position of the remote receiver.

22. The positioning system of claim 21, wherein the minimizing of the function is with respect to transmitter position coordinates of transmitters of the plurality of transmitters in a specified coverage area in the coverage volume.

23. The positioning system of claim 22, comprising weighting the function according to performance quality of a coverage region.

24. The positioning system of claim 1, wherein the plurality of transmitters are positioned at a plurality of heights.

25. The positioning system of claim 1, wherein a set of transmitters of the plurality of transmitters includes at least two transmitters both positioned at a same latitude and longitude and at least two different heights.

26. The positioning system of claim 25, wherein the set of transmitters in combination with the satellite signals are used to improve the quality of height estimate by providing improved Vertical Dilution of Precision (VDOP).

27. The positioning system of claim 1, wherein the plurality of transmitters include at least one transmitter that includes a repeater-receiver that receives and repeats a signal of the at least one transmitter.

28. The positioning system of claim 27, wherein the repeater-receiver extracts from the at least one transmitter extracted data that includes at least one of data of the positioning signals and system timing information.

29. The positioning system of claim 28, wherein the repeater-receiver retransmits the extracted data to at least one other repeater-transmitter.

30. The positioning system of claim 29, wherein the retransmission includes supplemental data along with the extracted data.

31. The positioning system of claim 30, wherein the supplemental data comprises at least one of latitude of a local antenna of the repeater-receiver, a longitude of the local antenna, and an altitude of the local antenna.

32. The positioning system of claim 1, wherein each transmitter of the plurality of transmitters are synchronized to a time reference, and a timing correction of each transmitter is provided to the remote receiver.

33. The positioning system of claim 32, wherein the time reference is a common time reference to which at least a set of transmitters of the plurality of transmitters are synchronized.

34. The positioning system of claim 32, wherein the time reference is at least one other transmitter in proximity to the transmitter.

35. The positioning system of claim 34, wherein the transmitter is synchronized with the at least one other transmitter via a pulse transmitted by the at least one other transmitter, wherein the transmitter is synchronized to an edge of the pulse.

36. The positioning system of claim 32, wherein the local time reference is at least one of a positioning system signal, a Global Navigation Satellite System (GNSS) signal, a Global Positioning System (GPS) signal, a differential positioning system signal, an atomic clock, a satellite radio signal, a cellular communications signal, and a television signal.

37. The positioning system of claim 32, comprising at least one reference receiver, wherein the at least one reference receiver receives a signal waveform from each transmitter, and time-tags pseudorange measurements for each transmitter using the signal waveform received.

38. The positioning system of claim 37, comprising generating timing difference corrections using the timing correction and pseudorange measurements of each transmitter.

39. The positioning system of claim 38, comprising applying the timing difference corrections to signals of the plurality of transmitters.

40. The positioning system of claim 32, comprising a GNSS timing receiver located with each transmitter in a set of transmitters in a geographical area, wherein the GNSS timing receiver receives differential corrections from a reference receiver in the geographical area and uses the differential corrections to generate timing difference corrections for the set of transmitters.

41. The positioning system of claim 32, wherein a set of transmitters use time transfer with a GNSS satellite in common view of the set of transmitters to generate timing difference corrections for the set of transmitters.

42. The positioning system of claim 32, comprising a set of GNSS receivers that each serve as the local time reference to a corresponding transmitter of a set of transmitters, wherein the set of GNSS receivers use at least one common GNSS satellite in deriving their timing pulse.

43. The positioning system of claim 32, wherein each transmitter of the plurality of transmitters transmits an offset relative to GNSS time, wherein the remote receiver generates the timing correction using the offset and the GNSS time.

44. The positioning system of claim 1, wherein a set of transmitters of the plurality of transmitters is employed ad hoc for localized position determination.

45. The positioning system of claim 1, wherein the remote receiver shares a clock source reference with a first system, wherein a host system includes the remote receiver and the first system.

46. The positioning system of claim 1, wherein the positioning signals are within operating parameters of a GNSS receiver.

47. The positioning system of claim 46, wherein the remote receiver comprises a GNSS receiver that includes components that are used for processing of the positioning signals received from the terrestrial transmitter network.

48. The positioning system of claim 47, wherein the remote receiver comprises a signal conditioner that conditions the positioning signals received from the terrestrial transmitter network as input signals to the GNSS receiver.

49. The positioning system of claim 48, wherein the conditioning comprises at least one of noise filtering and interference filtering.

50. The positioning system of claim 48, wherein the conditioning comprises translating at least one of intermediate frequencies and baseband frequencies of the positioning signals received from the terrestrial transmitter network to input frequencies of the GNSS receiver.

51. The positioning system of claim 48, wherein the conditioning comprises adjusting signal strength of the positioning signals received from the terrestrial transmitter network to a signal strength input of the GNSS receiver.

52. The positioning system of claim 48, wherein the conditioning comprises automatic gain control.

53. The positioning system of claim 48, wherein the remote receiver comprises a radio frequency (RF) front end that tunes to the frequency of transmission of the terrestrial positioning signal and is used to perform the signal conditioning.

54. The positioning system of claim 1, comprising determining a position of the remote receiver using at least one of the positioning signals and a GNSS signal, based on signal availability.

55. The positioning system of claim 54, wherein the positioning signals use gold codes and data transmitted on top of gold codes includes assistance data for a receiver of the GNSS signal.

56. The positioning system of claim 54, wherein timing information of associated with the plurality of transmitters is used as fine time aiding for a receiver of the GNSS signal.

57. The positioning system of claim 54, wherein a clock frequency estimate of the remote receiver is used for frequency aiding for a receiver of the GNSS signal.

58. The positioning system of claim 54, wherein a location estimate of the remote receiver is provided to a receiver of the GNSS signal.

59. The positioning system of claim 1, wherein a location estimate of a GNSS receiver and a quality metric of the location estimate is provided to the remote receiver.

60. The positioning system of claim 1, wherein a frequency estimate of a GNSS receiver and a confidence metric corresponding to the frequency estimate is provided to the remote receiver.

61. The positioning system of claim 1, wherein a time estimate of a GNSS receiver and an offset of the time estimate relative to GNSS time is provided to the remote receiver.

62. The positioning system of claim 1, wherein the remote receiver identifies multipath components of the positioning signals using high resolution earliest time of arrival estimates that include an estimated reference correlation function.

63. The positioning system of claim 1, wherein the remote receiver identifies multipath components of the positioning signals using high resolution earliest time of arrival estimates that include a partitioning of signal and noise subspaces.

64. The positioning system of claim 1, wherein the remote receiver identifies multipath components of the positioning signals by generating a reference vector from a correlation function measured in a channel environment that has low noise and at least one of easily separable multipath and no-multipath components.

65. The positioning system of claim 64, wherein the remote receiver identifies multipath components of the positioning signals by improving a signal-to-noise ratio in the vector by coherently averaging across at least one of a plurality of pseudorandom code frames and a plurality of bits.

66. The positioning system of claim 65, wherein the remote receiver identifies multipath components of the positioning signals by calculating a Fourier Transform of the vector.

67. The positioning system of claim 66, wherein the remote receiver identifies multipath components of the positioning signals by generating a frequency domain estimate of a channel corresponding to the transmitted sequence using the Fourier Transform of a measured vector and the Fourier Transform of the reference vector.

68. The positioning system of claim 67, wherein the remote receiver identifies multipath components of the positioning signals by generating a reduced channel estimate vector from the frequency domain estimate of the channel.

69. The positioning system of claim 68, wherein the remote receiver identifies multipath components of the positioning signals by defining an estimated covariance matrix of the reduced channel estimate vector.

70. The positioning system of claim 69, wherein the remote receiver identifies multipath components of the positioning signals by performing singular value decomposition on the estimated covariance matrix.

71. The positioning system of claim 70, wherein the remote receiver identifies multipath components of the positioning signals by generating a vector of sorted singular values.

72. The positioning system of claim 71, wherein the remote receiver identifies multipath components of the positioning signals by using the vector of sorted singular values to separate signal and noise subspaces.

73. The positioning system of claim 72, wherein the remote receiver identifies multipath components of the positioning signals by generating a noise subspace matrix.

74. The positioning system of claim 73, wherein the remote receiver identifies multipath components of the positioning signals by estimating time of arrival of a first path using the noise subspace matrix.

75. The positioning system of claim 1, wherein the plurality of transmitters detect unused electromagnetic spectrum and broadcast the positioning signals using a frequency of the unused electromagnetic spectrum.

76. The positioning system of claim 75, wherein the remote receiver comprises a spectrum sensor that listens for broadcasts from the plurality of transmitters in order to determine the frequency of the broadcast.

77. The positioning system of claim 75, wherein the plurality of transmitters notify the remote receiver of the frequency of the broadcast.

78. The positioning system of claim 1, wherein the broadcast of the positioning signals comprises segmenting a message over a plurality of frames, wherein each frame comprises a frame type and frame data.

79. The positioning system of claim 1, wherein the remote receiver receives assistance data, wherein the assistance data comprises at least one of system time at a rising edge of a pulse of a waveform, system time at a falling edge of a pulse of a waveform, geocode data of the plurality of transmitters, geocode data of transmitters adjacent to the plurality of transmitters, index of a sequence used by at least one transmitter in proximity of the plurality of transmitters, clock timing corrections for at least one transmitter, local atmospheric corrections, relationship of WAPS timing to GNSS time, indication of local environment to aid the remote receiver in pseudorange resolution, and at least one of an offset from base index of a set of pseudorandom sequences, a list of pseudorandom number sequences from a set of transmitters, and a list of transmitters that utilize a particular pseudorandom number sequence.

80. The positioning system of claim 79, wherein the assistance data is transferred to the remote receiver from at least one of the server, a communication system, a cellular communication system, and a broadcast system.

81. The positioning system of claim 1, wherein at least one of the remote receiver and the server compute a position of the receiver by formulating a set of equations as a non-linear objective function and generating a best estimate of the position as a set of position parameters that minimize the objective function.

82. The positioning system of claim 1, wherein at least one of the remote receiver and the server compute a position of the receiver by formulating a set of linearized equations and solving the set of linearized equations using least squares.

83. The positioning system of claim 1, wherein at least one of the remote receiver and the server compute a position of the receiver using an approximate location of a set of transmitters of the plurality of transmitters and received signal strength (RSS) data of the set of transmitters.

84. The positioning system of claim 1, wherein at least one of the remote receiver and the server compute a position of the receiver by storing sample segments of the positioning signal in the remote receiver, and subsequently processing the sample segments to search, acquire, and compute range to the plurality of transmitters.

85. The positioning system of claim 84, comprising storing at least one of an approximate position and a time tag, and subsequently processing the sample segments along with the at least one of the approximate position and the time tag.

86. The positioning system of claim 1, wherein at least one of the remote receiver and the server provides, along with a position of the receiver, a position quality metric that is a function of at least one of pseudo-range measurement equation residuals, quality of measurements, and geometry of the plurality of transmitters relative to the position.

87. The positioning system of claim 1, wherein at least one of the remote receiver and the server compute a position of the receiver using received signal strength data of the remote receiver.

88. The positioning system of claim 1, wherein at least one of the remote receiver and the server compute a position of the receiver using at least one of carrier phase data and code phase data of the positioning signals.

89. The positioning system of claim 1, wherein at least one of the remote receiver and the server compute a position of the receiver using differential positioning relative to at least one reference receiver.

90. The positioning system of claim 1, comprising an atmospheric data sensor as a component of the remote receiver, wherein at least one of the remote receiver and the server compute a position of the receiver using data of the atmospheric data sensor.

91. The positioning system of claim 90, wherein the data of the atmospheric data sensor includes at least one of pressure data, temperature data, and humidity data.

92. The positioning system of claim 1, wherein at least one of the remote receiver and the server compute a position of the receiver using at least one of a range measurement and a proxy for a range measurement from a signal of opportunity.

93. The positioning system of claim 92, wherein the signal of opportunity is received from a positioning system, a Global Navigation Satellite System (GNSS), a Global Positioning System (GPS), a differential positioning system, a radio signal, a television signal, a wireless network system, a WiFi system, a cellular system, and a Bluetooth system.

94. The positioning system of claim 1, wherein at least one of the remote receiver and the server compute a final position of the remote receiver using a range measurement from at least one additional signal source combined with a range measurement determined using the positioning signals, wherein the final position comprises at least one of latitude, longitude and height.

95. The positioning system of claim 1, wherein at least one of the remote receiver and the server compute an optimized location solution of the remote receiver using a position measurement from at least one additional signal source combined with a position measurement determined using the positioning signals and a position quality metric from the at least one additional signal source.

96. The positioning system of claim 1, wherein at least one of the remote receiver and the server compute a position of the receiver using hybrid positioning, the hybrid positioning comprising a measurement from the positioning signals and a measurement from at least one additional source.

97. The positioning system of claim 96, wherein the at least one additional source comprises at least one of an inertial navigation sensor, an accelerometer, a gyroscope, a magnetic sensor, a pressure sensor, and an atmospheric sensor.

98. The positioning system of claim 96, wherein the at least one additional source comprises an accelerometer, wherein at least one of the remote receiver and the server uses data of the accelerometer to determine a frequency for updating the position.

99. The positioning system of claim 98, wherein at least one of the remote receiver and the server uses a combination of sequence of position solutions and accelerometer measurements to detect at least one of static position and constant velocity.

100. The positioning system of claim 96, wherein at least one of the remote receiver and the server includes a position filter, wherein the position filter combines data of a plurality of signal sources to generate the position of the remote receiver.

101. The positioning system of claim 100, wherein at least one of the remote receiver and the server uses at least one of a position estimate and a velocity estimate to calibrate drift bias of the at least one additional source.

102. The positioning system of claim 100, wherein at least one of the remote receiver and the server estimates sensor parameters as a component of at least one of a position determination and a velocity determination.

103. The positioning system of claim 102, wherein at least one of the remote receiver and the server uses the estimated sensor parameters in a state vector of the position filter.

104. The positioning system of claim 102, wherein the sensor parameters estimated include at least one of bias, scale, and drift.

105. The positioning system of claim 1, comprising encrypted communication between at least one of the plurality of transmitters, the remote receiver and the server, wherein the encrypted communication includes at least one of data security and authentication.

106. The positioning system of claim 105, wherein at least one of symmetric key cryptography and asymmetric key cryptography are used to perform at least one of authentication and encryption of signal transmissions, wherein the remote receiver comprises a device identification and device key, wherein the server includes a database of pairings of the device identification and the device key.

107. The positioning system of claim 105, comprising transmitter authentication that rejects malicious transmitters.

108. The positioning system of claim 105, comprising receiver authorization that allows only authentic receivers to use information from the plurality of transmitters and the server.

109. The positioning system of claim 1, wherein the positioning system information comprises timing synchronization and corresponding correction information.

110. The positioning system of claim 1, wherein the server comprises a billing interface.

111. The positioning system of claim 1, wherein the remote receiver exchanges at least one of a location estimate, a frequency estimate, and a time estimate with at least one other system in order to aid performance of the at least one other system.

112. The positioning system of claim 111, wherein a host system integrates the remote receiver and the at least one other system.

113. The positioning system of claim 112, wherein the at least one other system comprises at least one of a Bluetooth transceiver, a wireless local area network transceiver, a Frequency Modulation (FM) transceiver, a television system, a cellular communication system, a satellite communication system, and a communication system.