System for robust location of a mobile-transmitter

• US 6,438,380 B1
• Filed: 02/28/1997
• Issued: 08/20/2002
• Est. Priority Date: 02/28/1997
• Status: Expired due to Term

• Current Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Tekinay, Sirin, Bi, Qi, Kuo, Wen-Yi
• Primary Examiner(s): Kincaid, Lester G.
• Application Number:
  US08/808,693
• Time in Patent Office: 1,999 Days
• Field of Search: 455/422, 455/432, 455/433, 455/456, 455/435, 455/440, 455/517, 455/524, 455/67.1, 455/404, 455/95, 342/357-1-3, 342/357.17, 342/450, 342/453, 342/457, 342/465
• US Class Current: 455/456.1
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

The present invention is a more accurate system for estimating the location of a mobile-telephone without significantly increasing the interference level for other mobile-telephones in the same or neighboring cells. In one embodiment, the present invention uses a plurality of location terminals deployed throughout a cell to increase the chances of detecting line-of-sight signals and the signal-to-noise ratio at the location terminals. In this embodiment, a wireless communication network transmits receive information to the plurality of location terminals instructing each of the location terminals to receive a signal from a particular mobile-telephone. Specifically, the location terminal is instructed to monitor a specific communication channel during a specific time interval. Upon receiving the signal, each of the location terminals produces detection information that is used by a location processor to estimate a location for the mobile-telephone, wherein the detection information includes times-of-arrival of the signal at each of the location terminals. In one embodiment, the location processor uses well-known location techniques, such as time difference of arrival, ranging, etc., to estimate the location for the mobile-telephone.

Claims

1. A method for locating a mobile-transmitter using a plurality of location terminals within a cell comprising the steps of:

transmitting receive information to the plurality of location terminals instructing each of the location terminals to receive a first signal from a particular mobile-transmitter in communication with a base station within the cell, wherein the location terminal transmits to the base station and not to the mobile-terminal;

receiving the first signal transmitted from the mobile-transmitter using the receive information at each of the plurality of location terminals to produce detection information; and

estimating a location for the mobile-transmitter using the detection information,

said transmitting step being automatically performed in response to expiration of a time interval.

2. The method of claim 1, wherein the receive information includes communication channel information specifying a particular communication channel for the plurality of location terminals to monitor.

3. The method of claim 2, wherein the receive information includes a search window indicating a time interval for monitoring the communication channel.

4. The method of claim 3, wherein the communication channel information and the search window are transmitted via a paging channel.

5. The method of claim 3, wherein the communication channel information and the search window are transmitted via a wireline connection.

6. The method of claim 3, wherein the step of receiving the first signal includes the step of:

monitoring the communication channel for the time interval specified by the search interval.

7. The method of claim 2, wherein the receive information includes timing information for synchronizing the plurality of location terminals using a common time reference.

8. The method of claim 7, wherein the timing information is transmitted via a pilot channel.

9. The method of claim 1, wherein the detection information includes times-of-arrival for the signal at each of the plurality of location terminals.

10. The method of claim 9, wherein the detection information includes signal strength measurements at each of the plurality of location terminals.

11. The method of claim 1, wherein the step of estimating the location includes the step of:

transmitting the detection information via an access channel to a wireless communication network.

12. The method of claim 1 comprising the additional step of:

transmitting a second signal to the mobile-transmitter to cause the mobile-transmitter to cease transmitting the first signal.

13. The method of claim 12, wherein the second signal is transmitted to the mobile-transmitter when the first signal is at a particular power level.

14. The method of claim 12, wherein the second signal is transmitted via a paging channel.

15. The method of claim 1 comprising the additional step of:

transmitting a second signal to the mobile-transmitter to cause the mobile-transmitter to transmit the first signal.

16. The method of claim 15, wherein the second signal instructs the mobile-transmitter to transmit the first signal using a particular communication channel.

17. The method of claim 15, wherein the second signal instructs the mobile-transmitter to transmit the first signal at a particular power level using a particular communication channel.

18. The method of claim 17, comprising the additional step of:

transmitting a third signal to the mobile-transmitter to cause the mobile-transmitter to lower the power level at which the first signal is being transmitted.

19. The method of claim 15, wherein the second signal is transmitted via a paging channel.

20. The method of claim 1, wherein the step of receiving the first signal includes the step of:

determining a time-of-arrival for a known data sequence at each of the plurality of location terminals.

21. A method for locating a mobile-transmitter comprising the steps of:

receiving at a location terminal receive information specifying a particular communication channel to monitor from a base station located within a same cell as the location terminal, wherein the location terminal transmits to the base station and not to the mobile-terminal, and wherein said receive information is automatically transmitted in response to expiration of a time interval;

monitoring the communication channel;

recording a time-of-arrival corresponding to a time when a signal is received at the location terminal via the communication channel; and

transmitting the time-of-arrival to a location processor.

22. The method of claim 21, wherein the communication channel is monitored for a time interval specified by a search window included in the receive information.

23. The method of claim 21 further comprising the step of:

time synchronizing the location terminal to a time reference using a time indicated by the receive information.

24. The method of claim 21, wherein the step of recording the time-of-arrival includes the step of:

examining the received signal for a known data sequence.

25. The method of claim 21, wherein the step of recording the time-of-arrival includes the step of:

measuring a signal strength for the received signal.

26. A system for locating a mobile-telephone within a geographical area covered by a plurality of cells in a wireless network, comprising:

a base station within each cell, including

a processor,

a detection device for detecting a telephone number dialed by said mobile-telephone, and

a transmission device for automatically broadcasting information identifying a communication channel in response to said detection of said telephone number being dialed; and

a plurality of location terminals within each cell, each location terminal including

a reception device for receiving said channel-identifying information from said base station,

a reception device for receiving a signal transmitted from said mobile-telephone over said channel identified by said received channel-identifying information to produce detection information,

wherein said processor determines a location of said mobile-telephone using detection information transmitted from one or more of said plurality of location terminals to said base station.

27. The system of claim 26, wherein each of said plurality of location terminals within a cell transmits to the base station within said cell and not to the mobile-telephone.

28. A system for locating a mobile-telephone within a geographical area covered by a plurality of cells in a wireless network, comprising:

a base station within each cell, including

a processor,

a request receiving device for receiving a request transmitted from said mobile-telephone, and

a transmission device for automatically broadcasting information identifying a communication channel in response said request received from said mobile-telephone; and

a plurality of location terminals within each cell which transmit to the base station of said cell and not to said mobile-telephone, each location terminal including

a reception device for receiving said channel-identifying information from said base station,

a detection device for receiving a signal transmitted from said mobile-telephone over said channel identified by said received channel-identifying information to produce detection information,

wherein said processor determines a location of said mobile-telephone using detection information transmitted from one or more of said plurality of location terminals to said base station.

29. A method for locating a mobile-telephone using a plurality of location terminals within a cell, comprising:

at a base station within the cell, transmitting channel-identifying information to the plurality of location terminals in response to a first signal transmitted from said mobile-telephone;

at each location terminal within the cell,

receiving a second signal transmitted from said mobile-telephone over a channel identified by said channel-identifying information to produce detection information, and

transmitting said detection information to said base station, such that said detection information is not transmitted to said mobile-telephone; and

at said base station, estimating a location for the mobile-telephone using said detection information.

30. The method of claim 29, wherein the first signal includes at least one of a dialed telephone number and a location determination request.

31. A system for locating a mobile transmitter within a cell, comprising:

a base station within said cell, including

a processor, and

a transmission device for automatically transmitting information identifying a communication channel to said plurality of location terminals in response to expiration of a time interval; and

a plurality of location terminals within said cell which transmit to the base station and not to said mobile-telephone, each location terminal including

a reception device for receiving said channel-identifying information from said base station,

a detection device for receiving a signal transmitted from said mobile transmitter over said channel identified by said received channel-identifying information to produce detection information,

wherein said processor determines a location of said mobile-telephone using detection information transmitted from one or more of said plurality of location terminals to said base station.

32. The system of claim 31, wherein said information transmitted by said base station includes a search window indicating a time interval for receiving said signal transmitted from said mobile transmitter.