Method and system for determining the position of a mobile receiver

• US 5,600,706 A
• Filed: 05/09/1994
• Issued: 02/04/1997
• Est. Priority Date: 04/08/1992
• Status: Expired due to Term

• Current Assignee: Comcast MO Group Incorporated (Comcast Corporation)
• Original Assignee: U S West Inc.
• Inventors: Dunn, Michael J., Feuerstein, Martin J., Chuang, Ching, Reudink, Douglas O. J., Foerster, Ronald E., Atherly, Don H., Vendetti, Dino J.
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): Shankar, Vijay
• Application Number:
  US08/240,070
• Time in Patent Office: 1,002 Days
• Field of Search: 379/59, 379/60, 455/33.1, 455/33.4, 455/54.1, 455/56.1, 342/450, 342/457, 342/357, 342/463
• US Class Current: 455/456.2
• 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: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04M 15/8033 location-dependent, e.g. business or home
• CPC Class Codes: H04M 15/8083 involving reduced rates or discounts, e.g. time-of-day reductions or volume discounts
• CPC Class Codes: H04M 2215/0184 involving reduced rates or discounts, e.g. time-of-day reductions, volume discounts, cell discounts, group billing, frequent calling destination(s) or user history list
• CPC Class Codes: H04M 2215/32 Involving wireless systems
• CPC Class Codes: H04M 2215/7435 Location dependent, e.g. Bussiness or home
• CPC Class Codes: H04W 4/02 Services making use of location information
• CPC Class Codes: H04W 4/24 Accounting or billing
• CPC Class Codes: H04W 60/00 Affiliation to network, e.g. registration; Terminating affiliation with the network, e.g. de-registration
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

A position system and method utilizes a plurality of range transceivers located at known fixed locations and which are adapted to transmit approximately synchronized digital range signals for receipt by both a primary receiver and a supplemental receiver, the former disposed at a known location and the latter disposed at an unknown location. The range transceivers are adapted to transmit pulse sequences which include an error portion corresponding to the approximate synchronization error of each range signal. This error portion is constantly updated in accordance with the last determined synchronization errors of the corresponding range signals received by a secondary transceiver. In an alternative embodiment employing Code Division Multiple Access (CDMA) technology, the range transceiver time stamp on transmitted range signals may be adjusted to account for the measured timing error for a given range transceiver. The supplemental receiver receives the range signals and uses the same in accordance with known time of arrival or time difference of arrival calculation techniques to determine the position of the supplemental receiver.

Claims

1. A positioning system, comprising:

a plurality of range transceivers at known fixed locations each having a time reference base for transmitting approximately synchronized digital range signals having a signal energy;

at least one primary receiver each disposed at a known location relative to the locations of said plurality of range transceivers which (a) receives the digital range signals, (b) determines a deviation representing the amount that each digital range signal deviates from system synchronization, and (c) sends corresponding error signals to said plurality of range transceivers so as to more closely bring said digital range signals into synchronization;

a supplemental receiver at an unknown location which receives said synchronized digital range signals; and

computation means, in communication with the supplemental receiver, for computing, based on the time difference of arrival of the received synchronized digital range signals, coordinate values defining the position of said supplemental receiver.

2. A positioning system as in claim 1 wherein said digital range signals are pulse sequences.

3. A positioning system as in claim 2 wherein said pulse sequences are multiple sequential or interleaved "Barker Codes."

4. A positioning system as in claim 2 wherein said pulse sequences are Pseudo Random Noise (PN) sequences.

5. A positioning system as in claim 4 wherein said PN sequences have a unique code phase offset used to identify the range transceiver.

6. A positioning system as in claim 1 wherein said primary receiver is adapted to send said error signals via RF communication link.

7. A positioning system as in claim 1 wherein said primary receiver is adapted to send said error signals via direct electrical communication.

8. A positioning system as in claim 1 wherein each of said at least one primary receiver further comprises:

a time detection device which detects and decodes said digital range signals;

a precision time reference generated locally or received from a central source, said precision time reference having a selected accuracy sufficient for desired system tolerances; and

a controller in electrical communication with said time detection device and said precision time reference which compares said decoded digital range signals with said precision time reference to determine the deviation from the system synchronization.

9. A positioning system as in claim 1 wherein the plurality of range transceivers are adapted to transmit said digital range signals sequentially in time using a time slotted protocol.

10. A positioning system as in claim 5 wherein the plurality of range transceivers transmit said digital range signals simultaneously.

11. A positioning system as in claim 10 wherein said supplemental receiver is adapted to compare said received digital range signals having known code phase offsets with a predetermined list of valid offsets.

12. A positioning system as in claim 1 wherein said supplemental receiver ranks said digital range signals based on a weighted combination of the signal energy of said digital range signal and the location of said range transceivers.

13. A positioning system as in claim 10 wherein the plurality of said range transceivers are further adapted to transmit said digital range signals on the same frequency so as to conserve bandwidth.

14. A positioning system as in claim 13 wherein said supplemental receiver receives said digital range signals over an interval of time sufficient to overcome a degradation in signal to interference ratio on signals from distant range transceivers.

15. A positioning system as in claim 13 wherein said supplemental receiver receives said digital range signals having code phase offsets selected to provide low autocorrelation sufficient to overcome a degradation in signal to interference ratio on said digital range signals received from distant range transceivers.

16. A positioning system as in claim 13 wherein said supplemental receiver has a dynamic range sufficient to overcome a degradation in signal to interference ratio on said digital range signals received from distant range transceivers.

17. A positioning system as in claim 13 wherein said supplemental receiver receives said digital range signals during a gated scanning period.

18. A positioning system as in claim 17 wherein said gated scanning period includes a narrow rotating null beam.

19. A positioning system as in claim 17 wherein said gated scanning period includes a narrow rotating fan beam.

20. A positioning system as in claim 13 wherein said plurality of range transceivers are each adapted to transmit a time stamp within said digital range signal, said time stamp adjusted by said range transceiver to simulate synchronization.

21. A positioning system as in claim 20 wherein said adjustments to said time stamps correspond to the last determined deviation from the system synchronization of the corresponding digital range signals received by said at least one primary receiver.

22. A positioning system as in claim 1 wherein said plurality of range transceivers are further adapted to receive said error signals and correspondingly adjust the output of the next transmitted digital range signal so as to drive the detected synchronization error to approximately zero.

23. A positioning system as in claim 1 wherein said plurality of range transceivers are each adapted to transmit multiple pulse sequences, said pulse sequences including an error portion corresponding to the approximate synchronization error of each digital range signal.

24. A positioning system as in claim 23 wherein the error portions of said pulse sequences generated by said plurality of range transceivers correspond to the last determined synchronization errors of the corresponding digital range signals received by said at least one primary receiver.

25. A positioning system as in claim 1 wherein said computation means is adapted to determine the time difference of arrival of said digital range signals in accordance with hyperbolic multilateration techniques.

26. A positioning system as in claim 1 wherein said computation means is adapted to determine the absolute time of arrival of said digital range signals in accordance with range-range techniques.

27. A positioning system as in claim 1 which is further adapted for use in a wireless telephone system operative in the microwave band from approximately 800 MHz to 2.5 GHz.

28. A positioning system as in claim 1 wherein said supplemental receiver comprises a wireless telephone.

29. A positioning system as in claim 1 wherein said supplemental receiver is a Personal Digital Assistant (PDA).

58. A positioning system as in claim 9 wherein the plurality of said range transceivers are further adapted to transmit said digital range signals on the same frequency so as to conserve bandwidth.

59. A positioning system as in claim 1 wherein said computation means is adapted to determine the time difference of arrival of said digital range signals in accordance with trilateration techniques.

30. A positioning system for use in a wireless telephone system that includes a cell site transceiver that transmits and receives voice signals and control signals to and from a mobile telephone unit over one or more respective voice and primary control channels in order to provide wireless telephone service within a cell site coverage area, the positioning system comprising:

a plurality of range transceivers at known fixed locations, each of which include a time reference base for transmitting an approximately synchronized digital range signal having a signal energy over one or more secondary control channels;

at least one primary receiver at a known location relative to the locations of said range transceivers, which (a) receives the digital range signals, (b) determines a deviation representing the amount that each digital range signal deviates from system synchronization, and (c) sends corresponding error signals to said plurality of range transceivers over said secondary control channels so as to more closely bring said digital range signals into synchronization; and

a mobile receiver at an unknown location which (a) receives said synchronized digital range signals over said secondary control channels, and (b) determines coordinate values defining its position based on the time difference of arrival of the received synchronized digital range signals.

31. A positioning system as in claim 30 wherein said mobile receiver is further adapted to (a) compare said determined coordinate values to a stored set of coordinates corresponding to a predetermined zone of operation, (b) determine the position of the mobile receiver relative to the predetermined zone, and (c) transmit an electrical signal indicating whether said mobile unit is in or out of said zone over said primary control channel for receipt by said transceiver.

32. A positioning system as in claim 31 wherein said mobile receiver further comprises display means for displaying whether said mobile receiver is within said predetermined zone.

33. A positioning system as in claim 32 wherein said display means comprises a Light Emitting Diode (LED).

34. A positioning system as in claim 30 wherein said at least one primary receiver further comprises:

a time detection device which detects and decodes said digital range signals;

a precision time reference generated locally or received from a central source, said precision time reference having a selected accuracy sufficient for desired system tolerances; and

a controller in electrical communication with said time detection device and said precision time reference which compares said decoded digital range signals with said reference signal to determine the deviation from the system synchronization.

35. A positioning system as in claim 30 wherein the plurality of said plurality of range transceivers are adapted to transmit said digital range signals sequentially in time using a time slotted protocol.

36. A positioning system as in claim 31 wherein the plurality of said plurality of range transceivers transmit said digital range signals simultaneously, each digital range signal having a unique code phase offset.

37. A positioning system as in claim 36 wherein said mobile receiver is adapted to compare said received digital range signals having known code phase offsets with a predetermined list of valid offsets.

38. A positioning system as in claim 30 wherein said mobile receiver ranks said digital range signals based on a weighted combination of the signal energy of said digital range signal and the location of said plurality of range transceivers.

39. A positioning system as in claim 36 wherein the plurality of range transceivers are further adapted to transmit said digital range signals on the same frequency so as to conserve bandwidth.

40. A positioning system as in claim 39 wherein said mobile receiver receives said digital range signals over an interval of time sufficient to overcome a degradation in signal to interference ratio on signals from distant range transceivers.

41. A positioning system as in claim 39 wherein said mobile receiver receives said digital range signals having code phase offsets selected to provide low autocorrelation sufficient to overcome a degradation in signal to interference ratio on said digital range signals received from distant range transceivers.

42. A positioning system as in claim 39 wherein said mobile receiver has a dynamic range sufficient to overcome a degradation in signal to interference ratio on said digital range signals received from distant range transceivers.

43. A positioning system as in claim 39 wherein said mobile receiver receives said digital range signals during a gated scanning period.

44. A positioning system as in claim 43 wherein said gated scanning period includes a narrow rotating null beam.

45. A positioning system as in claim 43 wherein said gated scanning period includes a narrow rotating fan beam.

46. A positioning system as in claim 39 wherein said plurality of range transceivers are each adapted to transmit a time stamp within said digital range signal, said time stamp adjusted by said range transceiver to simulate synchronization.

47. A positioning system as in claim 46 wherein said adjustments to said time stamps correspond to the last determined synchronization error of the corresponding digital range signals received by said at least one primary receiver.

48. A positioning system as in claim 30 wherein said plurality of range transceivers are further adapted to receive said error signals and correspondingly adjust the output of the next transmitted digital range signal so as to drive the detected synchronization error to approximately zero.

49. A positioning system as in claim 30 wherein said plurality of range transceivers are each adapted to transmit multiple pulse sequences, said pulse sequences including an error portion corresponding to the approximate synchronization error of each digital range signal.

50. A positioning system as in claim 49 wherein the error portions of said pulse sequences generated by said plurality of range transceivers correspond to the last determined synchronization errors of the corresponding digital range signals received by said at least one primary receiver.

60. A positioning system as in claim 35 wherein the plurality of said range transceivers are further adapted to transmit said digital range signals on the same frequency so as to conserve bandwidth.

51. A method for determining the position of a mobile unit with respect to the positions of a plurality of range transceivers that are positioned at known fixed locations, wherein each transceiver transmits an approximately synchronized digital range signal, comprising:

at a known location relative to the locations of said range transceivers, receiving the digital range signals by at least one primary receiver, determining a deviation representing the amount that each digital range signal deviates from system synchronization, and sending corresponding error signals to said primary range transceivers so as to more closely bring said digital range signals into synchronization;

at a mobile unit'"'"'s location, receiving said synchronized digital range signals; and

computing, based on the time difference of arrival of the received synchronized digital range signals, coordinate values defining the position of said mobile unit.

52. The method of claim 51 wherein the step of determining the deviation from the system synchronization comprises:

detecting and decoding said digital range signals;

generating or receiving a reference signal having a selected accuracy sufficient for system tolerances; and

comparing said decoded digital range signals with said reference signal.

53. The method of claim 51 wherein the digital range signal includes a time stamp and the method further comprising adjusting the time stamp of the next transmitted digital range signal of each of said plurality of range transceivers in accordance with said determined deviation from the system synchronization so as to simulate synchronization.

54. The method of claim 53 further comprising the step of adjusting the time stamp of the next range signal generated by each of said plurality of range transceivers in accordance with the last determined deviation from the system synchronization of the corresponding digital range signals received by said at least one primary receiver.

55. The method of claim 53 further comprising adjusting the output of the next transmitted digital range signal of each of said plurality of range transceivers in accordance with said determined deviation from the system synchronization so as to drive said corresponding error signals to approximately zero.

56. The method of claim 51 wherein said plurality of range transceivers are each adapted to transmit multiple pulse sequences, said pulse sequences including an error portion corresponding to the approximate synchronization error of each range signals.

57. The method of claim 56 further comprising the step of adjusting the error portion of the next digital range signal generated by each of said plurality of range transceivers in accordance with the last determined deviation from the system synchronization of the corresponding digital range signals received by said at least one primary receiver.