System and method for locating mobile units operating within a wireless communication system

• US 6,330,454 B1
• Filed: 03/29/1999
• Issued: 12/11/2001
• Est. Priority Date: 12/31/1998
• Status: Expired due to Fees

• Current Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Verdonk, Timothy C.
• Primary Examiner(s): Bost, Dwayne
• Assistant Examiner(s): WEST, LEWIS G
• Application Number:
  US09/280,263
• Time in Patent Office: 988 Days
• Field of Search: 455/404, 455/456, 455/422, 455/435, 455/461, 455/457, 455/458, 701/207, 701/209, 342/357.08, 342/450, 342/451
• 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 wireless communication system constructed according to the present invention interfaces with a Service Control Point (SCP) to provide location information for a serviced mobile unit. The SCP sends a locate request to a Home Location Register (HLR) of the wireless communication system, requesting the location of the serviced mobile unit. The HLR then accesses a serving Mobile Switching Center (MSC), the serving MSC being identified by the HLR as currently servicing the mobile unit. Depending upon the particular constraints of the requested operation by the SCP (e.g., immediate locate request or most recent locate request), the serving MSC either retrieves location information for the mobile unit from its Visitor Location Register (VLR) or sends a page to the mobile unit. The mobile unit responds to the page and, based upon the cell/sector from which the mobile unit responded, the serving MSC determines an approximate location of the mobile unit. With the location information retrieved, the serving MSC then converts the cell/sector identification to longitude and latitude information. The serving MSC may also convert a time-stamp associated with the location information (when the location information was recorded) to a normalized time standard such as Greenwich Standard Time. With this location information determined, the serving MSC provides the information to the requesting SCP. This information may be provided either directly by the serving MSC to the requesting SCP or may be provided via the HLR that receive the request. In converting the cell/sector identification in which the mobile unit was last located, the serving MSC (or other element of the wireless communication system that performs the conversion) provides the most likely location of the mobile unit within the cell/sector.

Claims

1. A method of providing location information for a mobile unit operating in a wireless communication system, the method comprising:

receiving a locate request for the mobile unit, wherein the locate request includes parameters indicating whether to return a current location of the mobile unit or to return a last known location of the mobile unit;

forward the locate request to a mobile switching center serving the mobile unit;

when the locate request includes a request for a last known location of the mobile unit, retrieving a cell/sector identification of the last known location of the mobile unit;

when the locate request includes a request for a current location of the mobile unit, paging the mobile unit and receiving a page response from the mobile unit, the page response indicating a cell/sector identification in which the mobile unit currently operates;

converting the cell/sector identification into a longitude and a latitude; and

returning the longitude and the latitude in response to the locate request.

2. The method of claim 1, wherein the locate request is received from a service control point.

3. The method of claim 2, wherein the service control point receives the locate request from a subscriber computer via a coupled network.

4. The method of claim 1, further comprising:

determining a time stamp that corresponds to the location of the mobile unit; and

returning the time stamp with the longitude and latitude.

5. The method of claim 4, wherein the time stamp is converted to standard time.

6. The method of claim 1, wherein in converting the cell/sector identification into a longitude and a latitude, a center of area for the corresponding cell/sector is assumed to be the location of the mobile unit.

7. The method of claim 1, wherein in converting the cell/sector identification into a longitude and a latitude, a physical feature located within the corresponding cell/sector is assumed to be the location of the mobile unit.

8. A wireless communication system comprising:

a home location register that receives a locate request for a mobile unit;

a serving mobile switching center that receives the locate request from the home location register;

a visitor location register coupled to the serving mobile switching center that contains a last known cell/sector identification for a cell/sector serving the mobile unit;

when the locate request includes a request for a last known location of the mobile unit, the serving mobile switching center retrieving a cell/sector identification of the last known location of the mobile unit;

when the locate request includes a request for a current location of the mobile unit, the serving mobile switching center paging the mobile unit and receiving a page response from the mobile unit, the page response indicating a cell/sector identification in which the mobile unit currently operates;

the serving mobile switching center converting the cell/sector identification into a longitude and a latitude; and

the serving mobile switching center returning the longitude and the latitude to the home location register.

9. The wireless communication system of claim 8, further comprising a service control point that interfaces with a subscriber computer, that receives the locate request from the subscriber computer and forwards the locate request to the home location register, and that receives the longitude and latitude from the home location register and returns the longitude and latitude to the subscriber computer.

10. The wireless communication system of claim 9, wherein the service control point receives the locate request from the subscriber computer via a coupled network.

11. The wireless communication system of claim 8, wherein:

the serving mobile switching center determines a time stamp that is associated with the cell/sector; and

the serving mobile switching center returns the time stamp with the longitude and latitude.

12. The wireless communication system of claim 11, wherein the time stamp is converted to standard time.

13. The wireless communication system of claim 8, wherein in converting the cell/sector identification into a longitude and a latitude, a center of area for the cell/sector is assumed to be the location of the mobile unit.

14. The wireless communication system of claim 8, wherein in converting the cell/sector identification into a longitude and a latitude, a physical feature located within the cell/sector is assumed to be the location of the mobile unit.

15. The wireless communication system of claim 8, wherein the locate request includes parameters indicating whether to return a current location of the mobile unit or to return a last known location of the mobile unit.