Wide area positioning system

• US 8,643,540 B2
• Filed: 03/05/2012
• Issued: 02/04/2014
• Est. Priority Date: 09/10/2008
• Status: Active Grant

• Current Assignee: NextNav, LLC
• Original Assignee: NextNav, LLC
• Inventors: Pattabiraman, Ganesh, Meiyappan, Subramanian, Raghupathy, Arun, Sankar, Hari
• Primary Examiner(s): Liu, Harry
• Application Number:
  US13/412,508
• Publication Number:
  US 20130063301A1
• Time in Patent Office: 701 Days
• Field of Search: 342/357.29
• 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 1/04 Circuits
• CPC Class Codes: H04B 1/16 Circuits
• 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 system for determining a position of a receiver, comprising one or more processors that are operable to:

compute the position of the receiver based on positioning data that includes ranging information from each of a plurality of terrestrial transmitters of a terrestrial transmitter network, wherein the ranging information relates to a distance between the receiver and the respective transmitter;

identify multipath components of the positioning data 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 set of samples left of a peak of the cross-correlation function, a second set of samples right of the peak of the cross-correlation function, and a sample at the peak of the cross-correlation function; and

identify multipath components of the positioning data using a high resolution time of arrival measurement method.

2. The system of claim 1, wherein the high resolution time of arrival measurement method includes at least one of a MUSIC algorithm, an ESPRIT algorithm, an Eigen-space decomposition method, a signal space and noise space separation method, a singular value decomposition method, and a covariance estimation method.

3. The system of claim 1, wherein the system identifies multipath components of the positioning data by generating a reference vector from a correlation function determined by at least one of a calculated function and a measurement in a channel environment that has low noise and at least one of easily separable multipath and no-multipath components.

4. The system of claim 3, wherein the system identifies multipath components of the positioning data 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.

5. The system of claim 4, wherein the system identifies multipath components of the positioning data by calculating a Fourier Transform of the vector.

6. The system of claim 5, wherein the system identifies multipath components of the positioning data by generating a frequency domain estimate of a channel using the Fourier Transform of a measured vector and the Fourier Transform of the reference vector.

7. The system of claim 6, wherein the system identifies multipath components of the positioning data by generating a reduced channel estimate vector from the frequency domain estimate of the channel.

8. The system of claim 7, wherein the system identifies multipath components of the positioning data by defining an estimated covariance matrix of the reduced channel estimate vector.

9. The system of claim 8, wherein the system identifies multipath components of the positioning data by performing singular value decomposition on the estimated covariance matrix.

10. The system of claim 9, wherein the system identifies multipath components of the positioning data by generating a vector of sorted singular values.

11. The system of claim 10, wherein the system identifies multipath components of the positioning data by using the vector of sorted singular values to separate signal and noise subspaces.

12. The system of claim 11, wherein the system identifies multipath components of the positioning data by generating a noise subspace matrix.

13. The system of claim 12, wherein the system identifies multipath components of the positioning data by estimating time of arrival of a first path using the noise subspace matrix.

14. The system of claim 1, wherein computing of the position comprises 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.

15. The system of claim 1, wherein computing of the position comprises formulating a set of linearized equations and solving the set of linearized equations using least squares.

16. The system of claim 1, wherein computing of the position comprises use of an approximate location of a set of transmitters of the plurality of transmitters and received signal strength (RSS) data of the set of transmitters.

17. The system of claim 1, wherein computing of the position comprises storing sample segments of the positioning signals and subsequently processing the sample segments to search, acquire, and compute range to the plurality of transmitters.

18. The system of claim 1, comprising computing 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, wherein the position quality metric is provided along with a position of the receiver.

19. The system of claim 1, wherein computing of the position comprises use of received signal strength data of the remote receiver.

20. The system of claim 1, wherein computing of the position comprises use of at least one of carrier phase data and code phase data of the positioning data.

21. The system of claim 1, wherein computing of the position comprises use of differential positioning relative to at least one reference receiver.

22. The system of claim 1, wherein the system comprises an atmospheric data sensor, and computing of the position comprises use of data of the atmospheric data sensor.

23. The system of claim 1, wherein computing of the position comprises use of at least one of a range measurement and a proxy for a range measurement from a signal of opportunity received from one or more of a positioning system, a Global Navigation Satellite System (GNSS), a differential positioning system, a radio signal, a television signal, a wireless network system, a WiFi system, a cellular system, and a Bluetooth system.

24. The system of claim 1, wherein computing of the position comprises use of a range measurement from at least one additional signal source combined with a range measurement determined using the positioning data, wherein the final position comprises at least one of latitude, longitude and height.

25. The system of claim 1, wherein computing of the position comprises hybrid positioning, the hybrid positioning comprising a measurement from the positioning data and a measurement from at least one additional source that includes one or more of an inertial navigation sensor, an accelerometer, a gyroscope, a magnetic sensor, a pressure sensor, and an atmospheric sensor.

26. The system of claim 1, wherein the one or more processors are further operable to:

generate a position estimate and a velocity estimate of the receiver using a measurement from the positioning data and a measurement from an additional signal source, wherein at least one of the position estimate and the velocity estimate are used to calibrate drift bias of the additional source.

27. The system of claim 1, wherein the one or more processors are further operable to:

generate a position estimate and a velocity estimate of the receiver using a measurement from the positioning data and a measurement from an additional signal source, wherein sensor parameters are estimated from at least one of the position estimate and the velocity estimate.

28. The system of claim 27, wherein the sensor parameters estimated include at least one of bias, scale, and drift, wherein the sensor parameters estimated are used in a state vector of the position filter.

29. The system of claim 1, wherein computing of the position comprises determining 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 data and a position quality metric from the at least one additional signal source.

30. The system of claim 1, wherein the positioning data are determined by an entity operating within parameters of a GNSS receiver, and wherein a correlator of said entity is used for processing the positioning data.

31. The system of claim 1, wherein computing of the position comprises determining the position using the positioning data and data from a GNSS signal.

32. The system of claim 31, wherein the positioning data use gold codes, and data that modulates the gold codes includes assistance data for a receiver of the GNSS signal.

33. The system of claim 31, wherein timing information associated with the plurality of transmitters is used as fine time aiding for a receiver of the GNSS signal.

34. The system of claim 31, wherein a clock frequency estimate of the remote receiver is used for frequency aiding for a receiver of the GNSS signal.

35. The system of claim 31, wherein a location estimate of the remote receiver is provided to a receiver of the GNSS signal.

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

37. The 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 one or more processors.

38. The system of claim 1, wherein the system receives information of a time estimate of a GNSS receiver and an offset of the time estimate relative to GNSS time.

39. The system of claim 1, wherein the system receives, and transfers to the one or more processors, information derived from the positioning data and satellite signals originating from a satellite positioning system.

40. The system of claim 1, comprising a communication system coupled to the receiver, wherein the communication system is a cellular communication system.

41. The system of claim 1, wherein the positioning data comprises a pseudorandom number sequence and assistance data.

42. The system of claim 41, wherein the positioning data comprises a preamble for at least one of frequency acquisition and timing alignment.

43. The system of claim 41, wherein the pseudorandom number sequence is chosen to have low autocorrelation sidelobe values for detection of an earliest arriving path in a presence of multipath.

44. The system of claim 41, wherein the positioning data from a first transmitter conveys the pseudorandom number sequence in a first time slot staggered in time from that of at least one other transmitter.

45. The system of claim 44, wherein positioning data from a second transmitter conveys another pseudorandom number sequence in the first time slot, wherein the other pseudorandom number sequence conveyed by the second transmitter is different from the pseudorandom number sequence conveyed by the first transmitter.

46. The system of claim 44, wherein the positioning data from a second transmitter conveys the same pseudorandom number sequence as that of the first transmitter in another time slot different from the first time slot.

47. The system of claim 44, wherein a carrier signal of each positioning signal is offset from the carrier signal of at least one other positioning signal.

48. The system of claim 41, 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 corresponding to set of transmitters, and a list of transmitters that utilize a particular pseudorandom number sequence.

49. The system of claim 41, wherein the assistance data includes data bits having an assigned priority.

50. The system of claim 49, wherein the data bits having a higher priority are transmitted more often than data bits having a lower priority.

51. The system of claim 41, wherein the plurality of transmitters form a CDMA network in which each transmitter of the plurality of transmitters transmit different pseudorandom sequences in a same time slot.

52. The system of claim 41, wherein the plurality of transmitters form a TDMA network in which each transmitter of the plurality of transmitters transmits the sequence in a different time slot.

53. The system of claim 52, wherein a frame duration of the TDMA network is determined by a product of slot duration and a number of transmitter slots used for positioning in a coverage area.

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

55. The system of claim 1, wherein the system receives information of a timing difference between transmissions from different ones of the transmitters.

56. The system of claim 1, wherein the position is computed using an angle of arrival and a received signal strength indicator measurement for each of the positioning signals.

57. The system of claim 1, wherein the system receives information of a timing correction of each transmitter.

58. The system of claim 1, wherein each transmitter of the plurality of transmitters is synchronized to a time reference.

59. The system of claim 58, wherein the time reference is a common time reference to which the transmitters are synchronized.

60. The system of claim 58, wherein the 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 precision oscillator, a satellite radio signal, a cellular communications signal, and a television signal.

61. The system of claim 1, wherein the system includes a position filter that combines data of a plurality of signal sources to generate the position of the remote receiver.

62. The system of claim 1, wherein the system comprises a spectrum sensor that listens for broadcasts from the plurality of transmitters in order to determine a frequency of the broadcast.

63. The system of claim 1, wherein a host system integrates the receiver and at least one other system.

64. The system of claim 63, wherein the system shares a clock source reference with at least one of the host system and the at least one other system.

65. The system of claim 63, 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.

66. The system of claim 1, wherein the system 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.

67. The system of claim 1, wherein communication between the receiver, the terrestrial transmitter network and a server is encrypted, wherein the encrypted communication includes at least one of data security and authentication, 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 system comprises a device identification and device key, wherein the server includes a database of pairings of the device identification and the device key.

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

69. The system of claim 1, wherein the plurality of terrestrial transmitters includes time synchronized transmitters.

70. The system of claim 1, wherein the one or more processors are further operable to:

determine precision time bias information using a first set of positioning data from three or more terrestrial transmitters, wherein the precision time bias information is used to synchronize operation of at least one processor to a time scale associated with the positioning signals.

71. The system of claim 70, wherein the one or more processors are further operable to:

compute the position based on the precision time bias information.

72. The system of claim 70, wherein a first processor uses a precision time epoch.

73. The system of claim 1, wherein the one or more processors are further operable to:

compute the position using a measurement from an accelerometer;

determine a position update frequency using data from the accelerometer; and

compute an updated position of the receiver in accordance with the update frequency.

74. The system of claim 73, wherein the one or more processors are further operable to:

determine position and velocity of the receiver using a sequence of position solutions and measurements from the accelerometer.

75. The system of claim 1, wherein the positioning signals are synchronized to a common source of time and the positioning signals include at least some of the positioning data, and wherein the positioning data further includes time correction data that comprise time corrections to epochs of the positioning signals.

76. The system of claim 1, wherein the position is computed using each of the positioning signals and at least one of an angle of arrival and a received signal strength indicator measurement corresponding to each of the positioning signals.

77. The system of claim 76, wherein the system further comprises:

a database that stores transmitter information that includes angle of arrival information, transmit power and location information for each of the transmitters.

78. The system of claim 77, wherein the one or more processors are further operable to:

determine received signal strength indicator levels of the positioning signals;

identify a first portion of the transmitter information in the database corresponding to the received signal strength indicator levels of the positioning signals;

compute the position based on the first portion of the transmitter information.

79. The system of claim 77, wherein the one or more processors are further operable to:

determine angle of arrivals of the positioning signals;

identify a first portion of the transmitter information in the database corresponding to the angle of arrivals of the positioning signals;

compute the position based on the first portion of the transmitter information.

80. The system of claim 1, wherein the one or more processors are further operable to:

estimate sensor parameters from at least one sensor;

compute the position and a velocity based on the position data and the sensor parameters.

81. The system of claim 80, wherein the sensor parameters include at least one of bias, scale, and drift of the at least one sensor, and wherein the at least one sensor comprises at least one of an inertial navigation sensor, an accelerometer, a gyroscope, a magnetic sensor, a pressure sensor, and an atmospheric sensor.

82. The system of claim 81, wherein the one or more processors are further operable to:

use the sensor parameters in a state vector of a position filter of receiver positions.

83. The system of claim 82, wherein a first operating mode of the system comprises receiver-based positioning in which the one or more processors are located at the receiver, and wherein a second operating mode of the system comprises network-based positioning in which the one or more processors are included in a server that is located in a geographically remote location from the receiver.

84. The system of claim 1, wherein the one or more processors are further operable to:

cause segments of the positioning data to be stored; and

compute respective ranges to each of the plurality of transmitters using the sample segments.

85. The system of claim 84, wherein the one or more processors are further operable to:

cause an approximate position and time tags to be stored; and

compute the position using the sample segments, the approximate position, and the time tags.