Method and apparatus for locating and tracking cellular telephones in a CDMA cellular communication network

• US 6,097,958 A
• Filed: 10/10/1997
• Issued: 08/01/2000
• Est. Priority Date: 10/10/1997
• Status: Expired due to Fees

• Current Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Original Assignee: Northern Telecom Limited (Nortel Networks Corporation)
• Inventors: Bergen, Scott
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Bhattacharya, Sam
• Application Number:
  US08/949,063
• Time in Patent Office: 1,026 Days
• Field of Search: 455/432, 455/433, 455/435, 455/456, 455/457, 455/560, 455/410, 455/411, 455/517, 455/524
• US Class Current: 455/456.2
• CPC Class Codes: H04W 4/02 Services making use of location information
• 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 initially locating and subsequently tracking the location of one or more mobile phones in a cellular communication network are disclosed. Software for implementing a scheduling and tracking system ("STS") is incorporated into the base station controller ("BSC") of a cellular communication network for performing scheduling and tracking functions with respect to mobile phone location. In one aspect of the invention, time difference of arrival ("TDOA") techniques are used to determine a location of each of a number of designated mobile phones active in the network. In another aspect of the invention, a scheduling portion of the STS originates and maintains a schedule of time measurement updates with reference to the previous location of the mobile phone. In yet another aspect of the invention, a tracking portion of the STS keeps track of the location of each of the designated mobile phones over time.

Claims

1. A method of tracking a plurality of cellular telephones in a cellular telephone network, the method comprising:

selecting a plurality of cellular telephones to be tracked;

scheduling time measurements for each of said selected cellular telephones, wherein said scheduling comprises assigning update times to said selected cellular telephones to achieve maximum possible separation between said update times across said cellular telephone network both temporally and geographically;

for each of said selected cellular telephones;

performing said time measurements according to said assigned update time;

determining a location of said selected cellular telephone using said time measurements; and

adding said determined location to a tracking log for said selected cellular telephone.

2. The method of claim 1 wherein said assigning update times to said selected cellular telephones is based on a last update time, a cluster, and a current primary BTS active sector of each of said selected cellular telephones.

3. The method of claim 1 further comprising outputting information contained in one or more of said tracking logs in a manner designated by a user.

4. The method of claim 1 wherein said selecting comprises designating a class of service, wherein all cellular telephones of said designated class of service are selected to be tracked.

5. The method of claim 1 wherein said selecting comprises designating a geographic area of said cellular telephone network, wherein all cellular telephones active within said designated geographic area are selected to be tracked.

6. The method of claim 1 wherein said selecting comprises selecting all cellular telephones active within said cellular telephone network.

7. The method of claim 1 wherein said cellular telephone network is a CDMA network.

8. In a cellular communication network comprising a base station controller ("BSC") and a plurality of base station transceiver subsystems ("BTSes"), a method of locating and tracking a location of a plurality of cellular telephones comprising:

identifying at least one cellular telephone to be located and tracked;

for each of said identified cellular telephones, determining a primary BTS ("PBTS") and at least two secondary BTSes ("SBTSes") for said identified cellular telephone;

scheduling a time for performing time measurements for each of said identified cellular telephones, wherein said scheduling comprises assigning update times to said selected cellular telephones to achieve maximum possible separation between said update times across said cellular telephone network both temporally and geographically;

for each of said identified cellular telephones;

immediately prior to said scheduled time, sending setup information to each of said PBTS and SBTSes;

subsequent to said sending setup information, said PBTS ramping up the power of said identified cellular telephone;

at said scheduled time, said PBTS and said SBTS performing said time measurements and forwarding said time measurements to said BSC; and

said BSC determining a location of said cellular telephone using said time measurements and adding said location to a tracking log for said cellular telephone.

9. The method of claim 8 wherein said assigning update times to said selected cellular telephones is based on a last update time, a cluster, and a current primary BTS active sector of each of said selected cellular telephones.

10. The method of claim 8 further comprising outputting information contained in one or more of said tracking logs in a manner designated by a user.

11. The method of claim 8 wherein said selecting comprises designating a class of service, wherein all cellular telephones of said designated class of service are selected to be tracked.

12. The method of claim 8 wherein said selecting comprises designating a geographic area of said cellular telephone network, wherein all cellular telephones active within said designated geographic area are selected to be tracked.

13. The method of claim 8 wherein said selecting comprises selecting all cellular telephones active within said cellular telephone network.

14. The method of claim 8 wherein said cellular telephone network is a CDMA network.

15. A method of updating a schedule of time measurements to be performed for a plurality of cellular telephones in a cellular telephone network, said time measurements for use in determining and tracking a location of said cellular telephones, the method comprising:

sorting said current cellular telephones by cluster;

assigning an update time slot to each of said current cellular telephones based on a last update time, a cluster, and a current primary BTS active sector of said current cellular telephone to achieve maximum possible separation between said update times across said cellular telephone network both temporally and geographically;

adding additional cellular telephones to said schedule, each of said additional cellular telephones being added to said schedule based on a primary BTS active sector of said additional cellular telephone to achieve maximum possible separation between said update times across said cellular telephone network both temporally and geographically;

identifying scheduling conflicts between at least two cellular telephones; and

resolving scheduling conflicts by moving a higher priority one of said at least two cellular telephones up on said schedule, moving a lower priority one of said at least two cellular telephones down on said schedule, or both until said conflict is resolved.

16. The method of claim 15 further comprising preempting one or more lower priority ones of said at least two cellular telephones if said conflict cannot be resolved.

17. The method of claim 15 wherein said assigning is performed such that time measurements are not performed simultaneously for more than one current cellular telephone in a single cluster.

18. The method of claim 15 wherein said assigning is performed such that time measurements may be performed simultaneously for more than one current cellular telephone in different clusters.

19. The method of claim 15 wherein said cellular telephone network is a CDMA network.

20. The method of claim 15 wherein each said cluster comprises at least one sector.

21. The method of claim 15 wherein said network is a multiple carrier frequency network, the method further comprising designating separate clusters for said multiple carrier frequency network.

22. Apparatus for tracking a plurality of cellular telephones in a cellular telephone network, the apparatus comprising:

means for scheduling time measurements for each of a plurality of selected cellular telephones, wherein said scheduling comprises assigning update times to said selected cellular telephones to achieve maximum possible separation between said update times across said cellular telephone network both temporally and geographically;

means for, with respect to each of said selected cellular telephones, performing said time measurements according to said scheduling, determining a location of said selected cellular telephone using said time measurements, and adding said determined location to a tracking log for said selected cellular telephone.

23. The apparatus of claim 22 wherein said means for scheduling comprises means for assigning update times to said selected cellular telephones based on a last update time, a cluster, and a current primary BTS active sector of each of said selected cellular telephones.

24. The apparatus of claim 22 further comprising means for outputting information contained in one or more of said tracking logs in a manner designated by a user.

25. The apparatus of claim 22 wherein said selecting comprises designating a class of service, wherein all cellular telephones of said designated class of service are selected to be tracked.

26. The apparatus of claim 22 wherein said selecting comprises designating a geographic area of said cellular telephone network, wherein all cellular telephones active within said designated geographic area are selected to be tracked.

27. The apparatus of claim 22 wherein said selecting comprises selecting all cellular telephones active within said cellular telephone network.

28. The apparatus of claim 22 wherein said cellular telephone network is a CDMA network.