System and method for positioning a mobile station in a CDMA cellular system

• US 6,157,842 A
• Filed: 10/16/1997
• Issued: 12/05/2000
• Est. Priority Date: 10/16/1997
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Karlsson, Jonas, Ovesjo, Fredrik
• Primary Examiner(s): VO, NGUYEN THANH
• Application Number:
  US08/951,345
• Time in Patent Office: 1,146 Days
• Field of Search: 455/456, 455/457, 455/59, 455/522, 455/524, 455/502, 342/450, 342/463, 370/342
• US Class Current: 455/456.2
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

A system and method for improving the accuracy of a location estimation measurement within a telecommunication system is disclosed. During a cessation of transmissions by a local base transceiver system in communication with the mobile station, the mobile station communicates with other, more remote base transceiver systems and trilateration and other distance measuring techniques are employed to calculate the position of the mobile station in relation to those remote base transceiver systems. In another embodiment of the present invention, the local base transceiver system is also used to calculate the position. In still another embodiment, during a cessation of transmissions by the mobile stations in communication with a local base transceiver system, the local base transceiver system is better able to use remote mobile stations for trilateration.

Claims

1. A radiocommunication system for determining a location position of a mobile station therein, said radiocommunication system comprising:

a local base transceiver system in communication with said mobile station, said local base transceiver system ceasing transmissions for a given time interval;

distance detection means for detecting and measuring, during said given time interval, a multiplicity of distance measurements to a corresponding multiplicity of remote base transceiver systems;

calculation means for calculating said location position of said mobile station within said radiocommunication system using said remote base transceiver system distance measurements; and

conflict detection means for detecting a time interval conflict between said local base transceiver system and at least one of said remote base transceiver systems, wherein said given time interval of transmission cessation of said local base transceiver system substantially overlaps another time interval of transmission cessation of said at least one remote base transceiver system, wherein upon detecting said time interval conflict said local base transceiver system transmits a time interval adjustment signal.

2. The system according to claim 1, wherein said calculation means uses at least two remote base transceiver system distance measurements.

3. The system according to claim 2, wherein said calculation means uses at least three remote base transceiver system distance measurements.

4. The system according to claim 1, wherein said distance detection means is within said mobile station, said distance detection means further detecting and measuring a local distance measurement for said local base transceiver system, and wherein said calculation means uses said local distance measurement in calculating the location position of said mobile station.

5. The system according to claim 1, wherein said conflict detection means is within said mobile station.

6. The system according to claim 1, further comprising:

conflict resolution means, wherein upon detection of said time interval conflict by said conflict detection means, said conflict resolution means transmits said time interval adjustment signal.

7. The system according to claim 6, wherein said conflict resolution means is attached to said local base transceiver system.

8. The system according to claim 1, wherein successive cessations of transmission by said local base receiver system are separated by random time intervals.

9. The system according to claim 8, wherein said random time intervals are determined by an identifier associated with said local base transceiver system.

10. The system according to claim 9, wherein said identifier is a PN-sequence offset.

11. The system according to claim 1, wherein successive cessations of transmission by said local base transceiver system are separated by periodic time intervals.

12. The system according to claim 11, wherein said periodic time intervals are determined by an identifier associated with said local base transceiver system.

13. The system according to claim 1, wherein said local base transceiver system transmits an idle period alert prior to ceasing said transmissions.

14. The system according to claim 1, wherein the communications between said local base station and said mobile station during said given time interval are masked.

15. The system according to claim 14, wherein a plurality of other communications between said local base transceiver station and a corresponding plurality of other mobile stations during said given time interval are masked.

16. The system according to claim 1, wherein said radiocommunication system is a code division multiple access system.

17. The system according to claim 1, wherein said distance detection means is within said mobile station, said mobile station forwarding said multiplicity of distance measurements to said local base transceiver system.

18. The system according to claim 1, wherein said distance detection means is within said local base transceiver system.

19. The system according to claim 18, wherein said distance detection means within said local base transceiver system, during said given time interval, detects and measures a mobile distance measurement to a remote mobile station, said remote mobile station being in communication with said local base transceiver system and at least one of said remote base transceiver systems.

20. The system according to claim 18, wherein said distance detection means within said local base transceiver system, during said given time interval, detects and measures respective mobile distance measurements to said mobile station from a respective plurality of said remote base transceiver systems.

21. The system according to claim to claim 1, wherein said calculation means is attached to said local base transceiver system, said distance measurements being forwarded to said calculation means via said local base transceiver system.

22. The system according to claim 1, wherein said local base transceiver system is in communication with at least one other mobile station, said local base transceiver system comprising alignment means to coordinate said given time interval transmission cessation with said mobile stations.

23. The system according to claim 22, wherein said alignment means aligns respective CDMA frames for said mobile stations and said local base transceiver system.

24. The system according to claim 1, wherein said local base transceiver system ceases all transmissions during said given time interval but for a pilot signal.

25. The system according to claim 1, wherein said distance detection means is within said mobile station, said mobile station, during said given time interval, detecting and measuring respective mobile distance measurements thereto from a respective plurality of said remote base transceiver systems.

26. A method for determining a location position of a mobile station communicating with a local base transceiver system within a radiocommunication system, said method comprising the steps of:

ceasing transmissions by said local base transceiver system for a given time interval;

detecting, during said given time interval, a multiplicity of distance measurements to a corresponding multiplicity of remote base transceiver systems;

forwarding said multiplicity of distance measurements of said remote base transceiver systems to a calculator means;

calculating, within said calculation means, said location position of said mobile station within said radiocommunication system using said remote base transceiver system distance measurements;

detecting a time interval conflict between said local base transceiver system and at least one of said remote base transceiver systems, wherein said given time interval of transmission cessation of said local base transceiver system substantially overlaps another time interval of transmission cessation of said at least one remote base transceiver system; and

upon detecting said interval conflict, transmitting a time interval adjustment signal.

27. The method according to claim 26, wherein at least two said remote base transceiver systems are used for said distance measurements.

28. The method according to claim 27, wherein at least three said remote base transceiver systems are used for said distance measurements.

29. The method according to claim 26, further comprising the step of:

detecting, by said mobile station, a local distance measurement for said local base transceiver system, said local distance measurement being one of said multiplicity of distance measurements used in said step of calculating the location position of said mobile station.

30. The method according to claim 26, wherein successive cessations of transmission by said local base receiver system are separated by random time intervals.

31. The method according to claim 26, wherein successive cessations of transmission by said local base transceiver system are separated by periodic time intervals.

32. The method according to claim 26, further comprising the step of:

transmitting, by said local base transceiver system prior to said transmission cessation, an idle period alert signal.

33. The method according to claim 26, further comprising the step of:

masking, during said transmission cessation, the communications between said local base station and said mobile station.

34. The method according to claim 33, wherein said step of masking further comprises masking a plurality of other communications between said local base transceiver system and a corresponding plurality of other mobile stations.

35. The method according to claim 26, wherein said radiocommunication system is a code division multiple access system.

36. The method according to claim 26, wherein said mobile station, in said step of detecting, detects said given time interval, said mobile station forwarding said multiplicity of distance measurements to said local base transceiver system.

37. The method according to claim 26, wherein said local base transceiver system, in said step of detecting, detects said given time interval.

38. The method according to claim 37, wherein said step of detecting further comprises detecting a mobile distance measurement to a remote mobile station being in communication with said local base transceiver system and at least one of said remote base transceiver systems.

39. The method according to claim 26, wherein in said step of calculation, said calculation means is attached to said local base transceiver system, said distance measurements being forwarded to said calculation means via said local base transceiver system.

40. The method according to claim 26, further comprising the step of:

aligning, by said local base transceiver system, said mobile station and at least one other mobile station with said given time interval.

41. The method according to claim 40, wherein said step of aligning aligns respective CDMA frames for said mobile stations and said local base transceiver system.

42. The method according to claim 26, wherein said local base transceiver system ceases all transmissions during said given time interval but for a pilot signal.

43. A radiocommunication system having a plurality of mobile stations, comprising:

a local base transceiver system in communication with said mobile stations;

transmission cessation means, within said local base transceiver system, for ceasing the communications from said local base transceiver system to said mobile stations for a given time interval; and

conflict detection means for detecting a time interval conflict, between said local base transceiver system and at least one remote base transceiver system, wherein when said given time interval of transmission cessation of said local base transceiver system substantially overlaps another time interval of transmission cessation of said at least one remote base transceiver system, upon detecting said time interval conflict said local base transceiver system transmits a time interval adjustment signal.

44. The system according to claim 43, further comprising:

distance detection means for detecting and measuring, during said given time interval, a multiplicity of distance measurements to a corresponding multiplicity of remote base transceiver systems; and

calculation means for calculating a location position of said mobile station within said radiocommunications system using said remote base transceiver system distance measurements.

45. The system according to claim 43, wherein successive cessations of transmission by said local base transceiver system are separated by random time intervals.

46. The system according to claim 43, wherein successive cessations of transmission by said local base transceiver system are separated by periodic time intervals.

47. The system according to claim 43, wherein said local base transceiver system transmits an idle period alert prior to ceasing said transmission.

48. The system according to claim 43, wherein said radiocommunication system is a code division multiple access system.

49. The system according to claim 43, wherein said local base transceiver system is in communication with at least two mobile stations, said local base transceiver system comprising alignment means to coordinate said given time interval transmission cessation with said at least two mobile stations.

50. The system according to claim 49, wherein said alignment means aligns respective CDMA frames for said mobile stations and said local base transceiver system.

51. The system according to claim 43, wherein said local base transceiver system ceases all transmissions during said given time interval but for a pilot signal.

52. The method according to claim 43, wherein said local base transceiver system ceases all transmissions during said given time interval but for a pilot signal.

53. A method for ceasing transmissions from a local base transceiver system to a plurality of mobile stations in a radiocommunication system, said method comprising the steps of:

determining, within said local base transceiver system, a given time interval in which to cease said transmissions to said mobile stations;

ceasing said transmissions during said given time interval, at least one of said mobile stations during said time interval communicating with at least one remote base station transceiver system;

detecting a time interval conflict between said local base transceiver system and at least one of said remote base transceiver systems, wherein said given time interval of transmission cessation of said local base transceiver system substantially overlaps another time interval of transmission cessation of said at least one remote base transceiver system; and

upon detecting said interval conflict, transmitting a time interval adjustment signal.

54. The method according to claim 53, wherein said communicating by said mobile stations with said at least one remote base transceiver system further comprises the steps of:

detecting, during said given time interval, a multiplicity of distance measurements to a corresponding multiplicity of remote base transceiver systems;

forwarding said multiplicity of distance measurements of said remote base transceiver systems to a calculator means; and

calculating, within said calculation means, a location position of said mobile station within said radiocommunication system using said remote base transceiver system distance measurements.

55. The method according to claim 53, wherein successive cessations of transmission by said local base receiver system are separated by random time intervals.

56. The method according to claim 53, wherein successive cessations of transmission by said local base transceiver system are separated by periodic time intervals.

57. The method according to claim 53, further comprising the step of:

transmitting, by said local base transceiver system prior to said transmission cessation, an idle period alert signal.

58. The method according to claim 53, further comprising the step of:

masking, during said transmission cessation, the communications between said local base station and said mobile stations.

59. The method according to claim 53, wherein said radiocommunication system is a code division multiple access system.

60. The method according to claim 53, further comprising the step of:

aligning, by said local base transceiver system, a multiplicity of mobile stations with said given time interval.

61. The method according to claim 60, wherein said aligning aligns respective CDMA frames for said mobile stations and said local base transceiver system.

62. The method according to claim 53, wherein said local base transceiver system ceases all transmissions during said given time interval but for a pilot signal.