Mobile location estimation in a wireless system using designated time intervals of suspended communication

• US 6,021,330 A
• Filed: 07/22/1997
• Issued: 02/01/2000
• Est. Priority Date: 07/22/1997
• Status: Expired due to Term

• Current Assignee: Alcatel-Lucent USA, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Vannucci, Giovanni
• Primary Examiner(s): Urban, Edward F.
• Assistant Examiner(s): Gesesse, Tilahun
• Application Number:
  US08/898,440
• Time in Patent Office: 924 Days
• Field of Search: 455/456, 455/457, 455/440, 455/67.4, 455/67.6, 342/450, 342/457, 342/464
• 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

Methods and apparatus for estimating mobile location in a wireless communication system including a plurality of base stations. In a base-to-mobile embodiment, the system base stations periodically transmit location signals to mobile stations during a system-wide blank-and-burst interval during which normal wireless communications are suspended. The interval is made sufficiently short that disruption to normal operation is negligible. Each base station transmits a distinct location signal which can be identified by a mobile station as associated with a particular base station. A given mobile station for which a location estimate is to be generated detects location signals from at least three of the system base stations. The detected location signals are used to generate differential path delay measurements which may be further processed in accordance with a triangulation technique to generate an estimate of mobile location. The suspension of normal wireless communications permits the location signals to occupy a broad bandwidth corresponding to multiple voice data channels, such that high resolution differential path delay measurements can be generated. The location signals from adjacent or neighboring base stations may also be configured to appear mutually orthogonal at a receiving mobile station, such that location signals from base stations close to a mobile will not interfere with detection of a location signal from a more distant base station. For example, the location signals may be selected to have waveforms which exhibit substantially non-overlapping comb-like frequency spectra. The invention may also be implemented in partial system blanking embodiments and mobile-to-base embodiments.

Claims

1. A method of estimating mobile station location in a wireless communication system, the method comprising the steps of:

transmitting during a particular time interval a location signal from a base station of the system, wherein the base station and at least one additional base station of the system at least partially suspend wireless communications for the particular time interval during which the location signal is transmitted, such that the at least partial suspension of wireless communications makes available additional system bandwidth at least a portion of which is utilized for transmission of the location signal; and

detecting the location signal in a mobile station of the wireless system to generate information for estimating the location of the mobile station.

2. The method of claim 1 wherein the transmitting step includes transmitting during the particular time interval a first location signal from a first base station, a second location signal from a second base station and a third location signal from a third base station, such that the first, second and third location signals each include a distinct characteristic identifying the corresponding base station, wherein each of the first, second and third base stations at least partially suspend wireless communications for the particular time interval during which the location signals are transmitted.

3. The method of claim 2 wherein the first, second and third base stations suspend all wireless communications with mobile stations of the system for the time interval during which the location signals are transmitted.

4. The method of claim 2 wherein the first, second and third location signals have substantially non-overlapping comb-like frequency spectra.

5. The method of claim 1 wherein the location signal is configured to appear mutually orthogonal to at least one other location signal from one other base station, as observed at the mobile station.

6. The method of claim 1 wherein the location signal is a pilot signal transmitted by the base station.

7. The method of claim 1 wherein the particular time interval during which the location signal is transmitted has a duration of about 1 ms to about 100 ms.

8. The method of claim 1 wherein the location signal includes a predetermined waveform carrying no additional information other than that provided by the waveform itself.

9. The method of claim 1 wherein the location signal includes a waveform which carries additional information.

10. The method of claim 1 wherein the location signal has a comb-like frequency spectrum.

11. The method of claim 1 wherein the location signal occupies a bandwidth normally occupied by multiple channels of the wireless system.

12. A base station for use in estimating mobile station location in a wireless communication system, the base station comprising:

a location signal generator for generating a location signal; and

a base station transmitter for transmitting the location signal during a particular time interval for which the corresponding base station and at least one additional base station of the system at least partially suspend wireless communications with mobile stations of the system, such that the at least partial suspension of wireless communications makes available additional system bandwidth at least a portion of which is utilized for transmission of the location signal, and such that a particular mobile station can detect the location signal to generate information for estimating the location of the mobile station.

13. The base station of claim 12 wherein during the particular time interval a first location signal is transmitted from a first base station, a second location signal is transmitted from a second base station and a third location signal is transmitted from a third base station, such that the first, second and third location signals each include a distinct characteristic identifying the corresponding base station, wherein each of the first, second and third base stations at least partially suspend wireless communications for the particular time interval during which the location signals are transmitted.

14. The base station of claim 12 wherein the location signal is configured to appear mutually orthogonal to at least one other location signal from one other base station, as observed at the mobile station.

15. The base station of claim 12 wherein the location signal is a pilot signal transmitted by the base station.

16. The base station of claim 12 wherein the particular time interval during which the location signal is transmitted has a duration of about 1 ms to about 100 ms.

17. The base station of claim 12 wherein the location signal includes a predetermined waveform carrying no additional information other than that provided by the waveform itself.

18. The base station of claim 12 wherein the location signal includes a waveform which carries additional information.

19. The base station of claim 12 wherein the location signal has a comb-like frequency spectrum.

20. The base station of claim 13 wherein the first, second and third location signals have substantially non-overlapping comb-like frequency spectra.

21. The base station of claim 12 wherein the location signal occupies a bandwidth normally occupied by multiple channels of the wireless system.

22. A mobile station for use in estimating mobile station location in a wireless communication system, the mobile station comprising:

a receiver for detecting a location signal transmitted by a base station of the wireless system during a particular time interval for which the base station and at least one other base station of the system at least partially suspend wireless communications with mobile stations of the system, such that the at least partial suspension of wireless communications makes available additional system bandwidth at least a portion of which is utilized for transmission of the location signal; and

a processor having an input coupled to an output of the receiver for receiving a detected location signal therefrom, and for processing the detected signal to generate information for estimating the location of the mobile station.

23. The mobile station of claim 22 wherein during the particular time interval a first location signal is transmitted from a first base station, a second location signal is transmitted from a second base station and a third location signal is transmitted from a third base station, such that the first, second and third location signals each include a distinct characteristic identifying the corresponding base station, wherein each of the first, second and third base stations at least partially suspend wireless communications for the particular time interval during which the location signals are transmitted.

24. The mobile station of claim 23 wherein the first, second and third location signals are configured to appear mutually orthogonal at the mobile station.

25. The mobile station of claim 23 wherein the first, second and third location signals have substantially non-overlapping comb-like frequency spectra.

26. The mobile station of claim 22 wherein the particular time interval during which the location signals is transmitted has a duration of about 1 ms to about 100 ms.

27. The mobile station of claim 22 wherein the location signal includes a predetermined waveform carrying no additional information other than that provided by the waveform itself.

28. The mobile station of claim 22 wherein the location signal has a comb-like frequency spectrum.

29. The mobile station of claim 22 wherein the location signal occupies a bandwidth normally occupied by multiple channels of the wireless system.

30. A wireless communication system comprising:

at least one mobile station; and

a plurality of base stations, including at least one base station for transmitting a location signal, wherein the location signal is transmitted during a particular time interval for which the at least one base station and at least one other of the plurality of base stations at least partially suspend wireless communications, such that the at least partial suspension of wireless communications makes available additional system bandwidth at least a portion of which is utilized for transmission of the location signal and such that the mobile station can detect the location signal to generate information for estimating the location of the mobile station.

31. The system of claim 30 wherein during the particular time interval a first location signal is transmitted from a first base station, a second location signal is transmitted from a second base station and a third location signal is transmitted from a third base station, such that the first, second and third location signals each include a distinct characteristic identifying the corresponding base station, wherein each of the first, second and third base stations at least partially suspend wireless communications for the particular time interval during which the location signals are transmitted.

32. The system of claim 31 wherein the first, second and third location signals are configured to appear mutually orthogonal at the mobile station.

33. The system of claim 31 wherein the first, second and third base stations suspend all wireless communications with mobile stations of the system for the time interval during which the location signals are transmitted.

34. The system of claim 31 wherein the first, second and third location signals have substantially non-overlapping comb-like frequency spectra.

35. The system of claim 30 wherein the particular time interval during which the location signal is transmitted has a duration of about 1 ms to about 100 ms.

36. The system of claim 30 wherein the location signal includes a predetermined waveform carrying no additional information other than that provided by the waveform itself.

37. The system of claim 30 wherein the location signal has a comb-like frequency spectrum.

38. The system of claim 30 wherein the location signal occupies a bandwidth normally occupied by multiple channels of the wireless system.

39. A method of estimating mobile station location in a wireless communication system, the method comprising the steps of:

transmitting during a particular time interval a location signal from a mobile station of the system, wherein the mobile station and at least one other mobile station of the system at least partially suspend wireless communications for the particular time interval during which the location signal is transmitted, such that the at least partial suspension of wireless communications makes available additional system bandwidth at least a portion of which is utilized for transmission of the location signal; and

detecting the location signal in one or more base stations of the wireless system to generate information for estimating the location of the mobile station.

40. The method of claim 39 wherein the particular time interval during which the location signal is transmitted has a duration of about 1 ms to about 100 ms.

41. The method of claim 39 wherein the location signal has a comb-like frequency spectrum.

42. A mobile station for use in estimating mobile station location in a wireless communication system, the mobile station comprising:

a transmitter for transmitting during a particular time interval a location signal from the mobile station, wherein the mobile station and at least one other mobile station of the system at least partially suspend wireless communications for the particular time interval during which the location signal is transmitted, such that the at least partial suspension of wireless communications makes available additional system bandwidth at least a portion of which is utilized for transmission of the location signal; and

a processor having an output coupled to an input of the transmitter for directing the transmitter to transmit the location signal during the interval, such that the location signal may be detected in one or more base stations of the wireless system in order to generate information for estimating the location of the mobile station.

43. The mobile station of claim 42 wherein the particular time interval during which the location signal is transmitted has a duration of about 1 ms to about 100 ms.

44. The mobile station of claim 42 wherein the location signal has a comb-like frequency spectrum.

45. A wireless communication system comprising:

a plurality of mobile stations, a particular one of the mobile stations operative to transmit a location signal during a particular time interval, wherein the particular mobile station and at least a subset of the other mobile stations of the system at least partially suspend wireless communications for the particular time interval during which the location signal is transmitted, such that the at least partial suspension of wireless communications makes available additional system bandwidth at least a portion of which is utilized for transmission of the location signal; and

a plurality of base stations, including one or more base stations for detecting the location signal in order to generate information for estimating the location of the particular mobile station.

46. The system of claim 45 wherein the particular time interval during which the location signal is transmitted has a duration of about 1 ms to about 100 ms.

47. The system of claim 45 wherein the location signal has a comb-like frequency spectrum.