Coding in a wide area positioning system (WAPS)

• US 9,119,165 B2
• Filed: 06/28/2012
• Issued: 08/25/2015
• Est. Priority Date: 09/10/2009
• Status: Active Grant

• Current Assignee: NextNav, LLC
• Original Assignee: NextNav, LLC
• Inventors: Krasner, Norman, Raghupathy, Arun
• Primary Examiner(s): LIU, HARRY K
• Application Number:
  US13/535,626
• Publication Number:
  US 20130057436A1
• Time in Patent Office: 1,153 Days
• Field of Search: 342/386, 342/357.77
• US Class Current: 1/1
• CPC Class Codes: G01S 19/11 wherein the cooperating elements are pseudolites or satellite radio beacon positioning system signal repeaters
• CPC Class Codes: G01S 19/45 by combining measurements of signals from the satellite radio beacon positioning system with a supplementary measurement
• CPC Class Codes: H04B 1/709 Correlator structure
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

Embodiments describe determining position by selecting a set of digital pseudorandom sequences. The magnitudes of the cross-correlation between any two sequences of the chosen set are below a specified threshold. A subset of digital pseudorandom sequences are selected from the set such that the magnitudes of the autocorrelation function of each member of the subset, within a specified region adjacent to the peak of the autocorrelation function, are equal to or less than a prescribed value. Each transmitter transmits a positioning signal, and at least a portion of the positioning signal is modulated with at least one member of the subset. At least two transmitters of the plurality of transmitters modulate respective positioning signals with different members of the subset of digital pseudorandom sequences.

Claims

1. A method for transmitting position location signals from a plurality of transmitters, comprising:

identifying a set of pseudorandom sequences, wherein a maximum magnitude of a cross-correlation function between any two pseudorandom sequences of the set of pseudorandom sequences is below a specified threshold;

identifying, from the set of pseudorandom sequences, a subset of at least three pseudorandom sequences,

wherein all magnitudes of an autocorrelation function corresponding to the pseudorandom sequences of the subset, within a specified region adjacent to a peak of the autocorrelation function, are equal to or less than a prescribed value, and

wherein two or more magnitudes of the autocorrelation function, outside of the specified region, exceed the prescribed value;

transmitting a first positioning signal from a first transmitter, wherein at least a portion of the first positioning signal is modulated in accordance with a first pseudorandom sequence of the subset of pseudorandom sequences; and

transmitting a second positioning signal from a second transmitter, wherein at least a portion of the second positioning signal is modulated in accordance with a second pseudorandom sequence of the subset of pseudorandom sequences.

2. The method of claim 1, wherein the prescribed value is less than or equal to the maximum magnitude of the cross-correlation function between any two pseudorandom sequences of the set of pseudorandom sequences.

3. The method of claim 2, wherein the prescribed value is the peak value of the autocorrelation function divided by a non-repeating length of the pseudorandom sequences.

4. The method of claim 1, wherein the specified region adjacent to the peak of the autocorrelation function includes at least five (5) pseudorandom sequence symbols.

5. The method of claim 1, wherein the specified region adjacent to the peak of the autocorrelation function includes at least ten (10) pseudorandom sequence symbols.

6. The method of claim 2, wherein the set of pseudorandom sequences comprises a set of binary pseudorandom sequences selected from one of Kasami codes, Bent codes, and Gold codes.

7. The method of claim 1, wherein at least one pseudorandom sequence of the set of pseudorandom sequences has a truncated sequence length, wherein the truncated sequence length is shorter than a standard sequence length.

8. The method of claim 1, wherein at least one pseudorandom sequence of the set of pseudorandom sequences has an extended sequence length, wherein the extended sequence length is longer than a standard sequence length.

11. The method of claim 1, wherein the set of pseudorandom sequences has an alphabet size greater than two (2).

12. The method of claim 11, wherein the set of pseudorandom sequences is a set of quaternary sequences.

13. The method of claim 11, wherein the alphabet size is a power of two (2).

35. The method of claim 1, wherein the method comprises:

synchronizing a plurality of transmitters to a time reference.

36. The method of claim 35, wherein the method comprises:

transmitting assistance data using the plurality of transmitters.

37. The method of claim 35, wherein the plurality of transmitters are located at respective positions so that a remote receiver receives signals from at least three transmitters, wherein a geometric dilution of precision in each of the respective positions is less than a threshold value, wherein the respective position of each of the plurality of transmitters is determined by minimizing a function that is a volume integration of a square of the geometric dilution of precision over a coverage volume, wherein the volume integration is with respect to coordinates of a position of the remote receiver, 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, wherein the function is weighted according to performance quality of a coverage region.

38. The method of claim 35, wherein a carrier signal of at least one of the plurality of transmitters is offset in frequency from the carrier signal of at least one other transmitter of the plurality of transmitters.

39. The method of claim 36, 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 each of 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, and indication of local environment.

9. A method for transmitting position location signals, comprising:

identifying a set of pseudorandom sequences, wherein a maximum magnitude of a cross-correlation function between any two pseudorandom sequences of the set of pseudorandom sequences is below a specified threshold;

identifying, from the set of pseudorandom sequences, a subset of at least three pseudorandom sequences,

wherein all magnitudes of an autocorrelation function corresponding to the pseudorandom sequences of the subset, within a specified region adjacent to a peak of the autocorrelation function, are equal to or less than a prescribed value, and

wherein two or more magnitudes of the autocorrelation function, outside of the specified region, exceed the prescribed value;

transmitting a positioning signal during a first period of time from a first transmitter, wherein a first portion of the positioning signal is modulated with a first pseudorandom sequence of the subset of pseudorandom sequences, wherein the first pseudorandom sequence has a first length; and

transmitting the positioning signal during a second period of time from the first transmitter, wherein a second portion of the positioning signal is modulated with a second pseudorandom sequence of the subset of pseudorandom sequences, wherein the second pseudorandom sequence pseudorandom sequence has a second length.

10. The method of claim 9, wherein the first length and the second length are different.

14. The method of claim 9, wherein the second portion consists of the first portion.

15. A positioning system comprising at least one processor that:

identifies a set of pseudorandom sequences, wherein a maximum magnitude of a cross-correlation function between any two pseudorandom sequences of the set of pseudorandom sequences is below a specified threshold;

identifies, from the set of pseudorandom sequences, a subset of at least three pseudorandom sequences,

wherein all magnitudes of an autocorrelation function corresponding to the pseudorandom sequences of the subset, within a specified region adjacent to a peak of the autocorrelation function, are equal to or less than a prescribed value, and

wherein two or more magnitudes of the autocorrelation function, outside of the specified region, exceed the prescribed value;

causes a first transmitter of a plurality of transmitters to transmit a first positioning signal, wherein at least a portion of the first positioning signal is modulated in accordance with a first pseudorandom sequence of the subset of pseudorandom sequences; and

causes a second transmitter of the plurality of transmitters to transmit a second positioning signal, wherein at least a portion of the second positioning signal is modulated in accordance with a second pseudorandom sequence of the subset of pseudorandom sequences.

16. The system of claim 15, wherein the prescribed value is less than or equal to the maximum magnitude of the cross-correlation function between any two pseudorandom sequences of the set of pseudorandom sequences.

17. The system of claim 16, wherein the prescribed value is the peak value of the autocorrelation function divided by a non-repeating length of the pseudorandom sequences.

18. The system of claim 15, wherein the specified region adjacent to the peak of the autocorrelation function includes at least five (5) pseudorandom sequence symbols.

19. The system of claim 15, wherein the specified region adjacent to the peak of the autocorrelation function includes at least ten (10) pseudorandom sequence symbols.

20. The system of claim 16, wherein the set of pseudorandom sequences comprises a set of binary pseudorandom sequences selected from one of Kasami codes, Bent codes, and Gold codes.

21. The system of claim 15, wherein at least one pseudorandom sequence of the set of pseudorandom sequences has a truncated sequence length, wherein the truncated sequence length is shorter than a standard sequence length.

22. The system of claim 15, wherein at least one pseudorandom sequence of the set of pseudorandom sequences has an extended sequence length, wherein the extended sequence length is longer than a standard sequence length.

29. The system of claim 15, wherein the system comprises a plurality of transmitters that are synchronized to a time reference.

30. The system of claim 29, wherein the plurality of transmitters transmit assistance data.

31. The system of claim 29, wherein the plurality of transmitters form at least one of a CDMA network and a TDMA network.

32. The system of claim 29, wherein the plurality of transmitters are located at respective positions so that a remote receiver receives signals from at least three transmitters, wherein a geometric dilution of precision in each of the respective positions is less than a threshold value, wherein the respective position of each of the plurality of transmitters is determined by minimizing a function that is a volume integration of a square of the geometric dilution of precision over a coverage volume, wherein the volume integration is with respect to coordinates of a position of the remote receiver, 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, wherein the function is weighted according to performance quality of a coverage region.

33. The system of claim 29, wherein a carrier signal of at least one of the plurality of transmitters is offset in frequency from the carrier signal of at least one other transmitter of the plurality of transmitters.

34. The system of claim 30, 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 each of 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, and indication of local environment.

59. The system of claim 15, wherein the at least one processor computes a position of a receiver based on a first signal modulated with a first pseudorandom sequence from the subset and a second signal modulated with a second pseudorandom sequence from the subset.

23. A positioning system comprising at least one processor that:

identifies a set of pseudorandom sequences, wherein a maximum magnitude of a cross-correlation function between any two pseudorandom sequences of the set of pseudorandom sequences is below a specified threshold;

identifies, from the set of pseudorandom sequences, a subset of at least three pseudorandom sequences,

wherein all magnitudes of an autocorrelation function corresponding to the pseudorandom sequences of the subset, within a specified region adjacent to a peak of the autocorrelation function, are equal to or less than a prescribed value, and

wherein two or more magnitudes of the autocorrelation function, outside of the specified region, exceed the prescribed value;

causes transmission of a positioning signal during a first period of time from a first transmitter, wherein a first portion of the positioning signal is modulated with a first pseudorandom sequence of the subset of pseudorandom sequences, wherein the first pseudorandom sequence has a first length; and

causes transmission of the positioning signal during a second period of time from the first transmitter, wherein a second portion of the positioning signal is modulated with a second pseudorandom sequence of the subset of pseudorandom sequences, wherein the second pseudorandom sequence pseudorandom sequence has a second length.

24. The system of claim 23, wherein the first length and the second length are different.

25. The system of claim 23, wherein the set of pseudorandom sequences has an alphabet size greater than two (2).

26. The system of claim 23, wherein the set of pseudorandom sequences is a set of quaternary sequences.

27. The system of claim 25, wherein the alphabet size is a power of two (2).

28. The system of claim 23, wherein the second portion consists of the first portion.

40. A device embodying program instructions adapted to be executed by at least one processor to implement a method for transmitting position location signals from a plurality of transmitters, the method comprising:

identifying a set of pseudorandom sequences, wherein a maximum magnitude of a cross-correlation function between any two pseudorandom sequences of the set of pseudorandom sequences is below a specified threshold;

identifying, from the set of pseudorandom sequences, a subset of at least three pseudorandom sequences,

wherein all magnitudes of an autocorrelation function corresponding to the pseudorandom sequences of the subset, within a specified region adjacent to a peak of the autocorrelation function, are equal to or less than a prescribed value, and

wherein two or more magnitudes of the autocorrelation function, outside of the specified region, exceed the prescribed value;

causing transmission of a first positioning signal from a first transmitter of the plurality of transmitters, wherein at least a portion of the first positioning signal is modulated in accordance with a first pseudorandom sequence of the subset of pseudorandom sequences; and

causing transmission of a second positioning signal from a second transmitter of the plurality of transmitters, wherein at least a portion of the second positioning signal is modulated in accordance with a second pseudorandom sequence of the subset of pseudorandom sequences.

41. The device of claim 40, wherein the prescribed value is less than or equal to the maximum magnitude of the cross-correlation function between any two pseudorandom sequences of the set of pseudorandom sequences.

42. The device of claim 41, wherein the prescribed value is the peak value of the autocorrelation function divided by a non-repeating length of the pseudorandom sequences.

43. The device of claim 40, wherein the specified region adjacent to the peak of the autocorrelation function includes at least five (5) pseudorandom sequence symbols.

44. The device of claim 40, wherein the specified region adjacent to the peak of the autocorrelation function includes at least ten (10) pseudorandom sequence symbols.

45. The device of claim 41, wherein the set of pseudorandom sequences comprises a set of binary pseudorandom sequences selected from one of Kasami codes, Bent codes, and Gold codes.

46. The device of claim 40, wherein at least one pseudorandom sequence of the set of pseudorandom sequences has a truncated sequence length, wherein the truncated sequence length is shorter than a standard sequence length.

47. The device of claim 40, wherein at least one pseudorandom sequence of the set of pseudorandom sequences has an extended sequence length, wherein the extended sequence length is longer than a standard sequence length.

50. The device of claim 40, wherein the set of pseudorandom sequences has an alphabet size greater than two (2).

51. The device of claim 50, wherein the set of pseudorandom sequences is a set of quaternary sequences.

52. The device of claim 50, wherein the alphabet size is a power of two (2).

54. The device of claim 40, wherein the method comprises:

synchronizing a plurality of transmitters to a time reference.

55. The device of claim 54, wherein the method comprises:

transmitting assistance data using the plurality of transmitters.

56. The device of claim 54, wherein the plurality of transmitters are located at respective positions so that a remote receiver receives signals from at least three transmitters, wherein a geometric dilution of precision in each of the respective positions is less than a threshold value, wherein the respective position of each of the plurality of transmitters is determined by minimizing a function that is a volume integration of a square of the geometric dilution of precision over a coverage volume, wherein the volume integration is with respect to coordinates of a position of the remote receiver, 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, wherein the function is weighted according to performance quality of a coverage region.

57. The device of claim 54, wherein a carrier signal of at least one of the plurality of transmitters is offset in frequency from the carrier signal of at least one other transmitter of the plurality of transmitters.

58. The device of claim 55, 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 each of 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, and indication of local environment.

48. A device embodying program instructions adapted to be executed by at least one processor to implement a method for transmitting position location signals, the method comprising:

identifying a set of pseudorandom sequences, wherein a maximum magnitude of a cross-correlation function between any two pseudorandom sequences of the set of pseudorandom sequences is below a specified threshold;

identifying, from the set of pseudorandom sequences, a subset of at least three pseudorandom sequences,

wherein all magnitudes of an autocorrelation function corresponding to the pseudorandom sequences of the subset, within a specified region adjacent to a peak of the autocorrelation function, are equal to or less than a prescribed value, and

wherein two or more magnitudes of the autocorrelation function, outside of the specified region, exceed the prescribed value;

causing transmission of a positioning signal during a first period of time from a first transmitter, wherein a first portion of the positioning signal is modulated with a first pseudorandom sequence of the subset of pseudorandom sequences, wherein the first pseudorandom sequence has a first length; and

causing transmission of the positioning signal during a second period of time from the first transmitter, wherein a second portion of the positioning signal is modulated with a second pseudorandom sequence of the subset of pseudorandom sequences, wherein the second pseudorandom sequence pseudorandom sequence has a second length.

49. The device of claim 48, wherein the first length and the second length are different.

53. The device of claim 48, wherein the second portion consists of the first portion.