Method and system for providing location information for emergency services

• US 7,844,281 B2
• Filed: 10/01/2007
• Issued: 11/30/2010
• Est. Priority Date: 11/17/2004
• Status: Active Grant

• Current Assignee: AT&T Mobility II LLC (AT&T, Inc.)
• Original Assignee: AT&T Mobility II LLC (AT&T, Inc.)
• Inventors: Burke, Scott B.
• Primary Examiner(s): Feild, Joseph H
• Assistant Examiner(s): Nguyen, Huy D
• Application Number:
  US11/865,707
• Publication Number:
  US 20080064414A1
• Time in Patent Office: 1,156 Days
• Field of Search: 455/456.1, 455/456.2, 455/456.3, 455/456.5, 455/456.6, 455/422.1, 455/426.1
• US Class Current: 455/456.1
• CPC Class Codes: G01S 5/0009 Transmission of position information to remote stations involving assistance data G01S5/0236
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/04 Position of source determined by a plurality of spaced direction-finders
• 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

Emergency Services architecture for determining the location of a wireless caller. The architecture leverages a synchronization feature of GSM networks of the Base Station Subsystem (BSS) to enable employment of sparse networks by removing WLS (Wireless Location Sensor) equipment from selected cell sites. Thus, the location of a wireless caller within a sparse site can be determined. Sparse network location services can be provided further utilizing Time Difference of Arrival (TDOA) technology, and other network-based location technologies such as Enhanced Observed Time Difference (EOTD) and Angle of Arrival (AOA). Hybrid network-based/handset-based location technologies may also be used with the disclosed invention.

Claims

1. A system that facilitates locating a mobile station, comprising:

a wireless communication network comprising one or more cell groups, the one or more cell groups respectively comprising at least one sparse cell and one or more non-sparse cells to which the at least one sparse cell is synchronized;

a geolocation control system (GCS) that obtains timing information from at least one non-sparse cell in the wireless communication network in response to radio signal information transmitted by a mobile station from a sparse cell in the wireless communication network; and

an offset table implemented by the GCS that contains information relating to timing offsets between respective cell groups in the wireless communication network and identities of cells that comprise the respective cell groups, the GCS determines a location of the mobile station based at least in part on the timing information obtained from the non-sparse cells and the information contained in the offset table.

2. The system of claim 1, wherein the non-sparse cells in the wireless communication network comprise respective wireless location sensors that provide timing information to the GCS.

3. The system of claim 2, wherein at least one sparse cell in a cell group is synchronized to one or more non-sparse cells in the cell group based at least in part on the timing information provided by the respective wireless location sensors at the one or more non-sparse cells.

4. The system of claim 2, wherein the respective wireless location sensors at the one or more non-sparse cells utilize global positioning system (GPS) technology as a reference for the timing information provided by the respective wireless location sensors to the GCS.

5. The system of claim 1, wherein the information relating to timing offsets contained in the offset table comprises respective offsets of one or more slave timing references relative to a master timing reference, the slave timing references correspond to one or more first cell groups and the master timing reference corresponds to one or more second cell groups.

6. The system of claim 5, wherein the master timing reference is a timing reference provided by GPS technology.

7. The system of claim 5, wherein the one or more slave timing references comprise at least one of a timing reference provided by an atomic clock or a timing reference provided by an oven-controlled crystal oscillator (OCXO).

8. The system of claim 5, wherein a cell group operating according to a slave timing reference periodically synchronizes with a cell group operating according to a master timing reference.

9. The system of claim 1, wherein the GCS determines at least one of a latitude or a longitude associated with the location of the mobile station based at least in part on the timing information obtained from the non-sparse cells and the information contained in the offset table.

10. The system of claim 1, wherein the sparse cells in the wireless communication network lack respective wireless location sensors.

11. The system of claim 1, wherein the GCS communicates with a GPS system to determine at least one of a latitude or a longitude that represents the location of the mobile station.

12. The system of claim 1, wherein the timing information provided by the non-sparse cells to the GCS is based on time difference of arrival (TDOA) technology.

13. The system of claim 1, wherein the timing information provided by the non-sparse cells to the GCS is based on enhanced observed time difference (EOTD) technology.

14. The system of claim 1, wherein the timing information provided by the non-sparse cells to the GCS is based on angle of arrival (AOA) technology.

15. The system of claim 1, wherein the radio signal information transmitted by the mobile station corresponds to an emergency call and the GCS provides the location of the mobile station to a public service access point (PSAP).

16. A system that facilitates locating a mobile terminal, comprising:

a sparse site synchronized with a first non-sparse site from which a mobile station conducts a transmission; and

a geolocation control system (GCS) that receives timing information corresponding to the transmission conducted by the mobile terminal from at least the first non-sparse site, a second non-sparse site, and a third non-sparse site, the GCS computes a location of the mobile terminal at least in part by applying timing offsets between the non-sparse sites to the timing information received from the non-sparse sites and computing the location of the mobile terminal based on the offset timing information, wherein the GCS computes at least one of a latitude or a longitude associated with the location of the mobile terminal based on the offset timing information.

17. The system of claim 16, wherein the GCS stores the timing offsets in an offset table.

18. The system of claim 16, wherein the GCS utilizes global positioning system (GPS) technology to facilitate calculation of the at least one of a latitude or a longitude associated with the location of the mobile terminal.

19. The system of claim 16, wherein the transmission by the mobile station is an emergency call and the GCS provides the location of the mobile station to a public service access point (PSAP).

20. A method for locating a mobile station, comprising:

synchronizing at least one sparse cell with one or more non-sparse cells in a wireless communication network;

receiving timing information from at least one of the one or more non-sparse cells in response to radio signal information transmitted by a mobile station from the at least one sparse cell in the wireless communication network;

storing offset information relating to timing offsets between respective cell groups in the wireless communication network and identities of cells that comprise the respective cell groups; and

determining a location of the mobile station based at least in part on the timing information obtained from the least one of the one or more non-sparse cells and the offset information.