System and method for determining absolute time based upon air interface timing in time of arrival based positioning

• US 6,385,452 B1
• Filed: 07/28/1999
• Issued: 05/07/2002
• Est. Priority Date: 07/28/1999
• Status: Expired due to Term

• Current Assignee: Unwired Planet LLC (JP Morgan Chase & Co)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Zadeh, Bagher R., Lindqvist, Dan
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): Nguyen, Simon
• Application Number:
  US09/362,777
• Time in Patent Office: 1,014 Days
• Field of Search: 455/440, 455/439, 455/432-433, 455/436, 455/442, 455/456, 342/126, 342/146, 342/357.1, 370/331, 370/337
• US Class Current: 455/440
• CPC Class Codes: G01S 2205/008 using a mobile telephone network
• CPC Class Codes: G01S 5/02 using radio waves using satellite radio beacon systems for determining position G01S19/00
• CPC Class Codes: H04W 36/06 Reselecting a communication resource in the serving access point
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

A telecommunications system and method is disclosed for reducing the signaling load on the network by instructing a Location Measurement Unit (LMU) to measure the relation between the absolute time and air interface timing, e.g., TDMA frame number, only when a positioning request has been received. Prior to configuring the LMU for time of arrival (TOA)-based positioning of a particular mobile station, the Serving Mobile Location Center (SMLC) can request an LMU associated with a particular cell to perform an asynchronous handover within the same cell. During this asynchronous handover, the LMU measures the relation between the absolute time and the TDMA frame number, and sends this relation information to the SMLC. The SMLC uses this relation information in configuring the LMU for TOA-based positioning of the particular mobile station.

Claims

1. A telecommunications system for determining update relation information corresponding to a current absolute time and an associated current time division multiple access frame number, comprising:

a serving mobile location center for receiving a positioning request and sending a request for said update relation information in response to receiving said positioning request;

a base station controller for receiving said request for said update relation information from said serving mobile location center and generating an asynchronous intra-cell handover command in response thereto; and

at least one location measurement unit in communication with said base station controller for receiving said asynchronous intra-cell handover command from said base station controller, performing an asynchronous intra-cell handover, obtaining said update relation information during said handover and transmitting said update relation information to said serving mobile location center for use by said serving mobile location center in a subsequent time of arrival based positioning of a mobile station.

2. The telecommunications system of claim 1, wherein said request for update relation information is included within a Mobile Application Part Channel Information message.

3. The telecommunications system of claim 2, further comprising:

a mobile switching center connected to said base station controller for receiving said Mobile Application Part Channel Information message, converting said Mobile Application Part Channel Information message into a Base Station Subsystem Mobile Application Part Channel Information message and transmitting said Base Station Subsystem Mobile Application Part Channel Information message to said base station controller.

4. The telecommunications system of claim 1, further comprising:

a base transceiver station connected to said base station controller and in wireless communication with said at least one location measurement unit, said asynchronous intra-cell handover being performed to said base transceiver station.

5. The telecommunications system of claim 4, wherein said base transceiver station sends information to said at least one location measurement unit during said asynchronous intra-cell handover.

6. The telecommunications system of claim 1, wherein said asynchronous intra-cell handover command includes said current time division multiple access frame number.

7. The telecommunications system of claim 6, wherein said at least one location measurement unit correlates said current absolute time value within said at least one location measurement unit with said received current time division multiple access frame number to determine said update relation information.

8. The telecommunications system of claim 1, further comprising:

a timer within said serving mobile location center, said serving mobile location center initiating said timer upon receipt of previous update relation information.

9. The telecommunications system of claim 8, wherein said serving mobile location center determines whether said timer has expired upon receipt of said positioning request, said request for update relation information being sent only when said timer has expired.

10. The telecommunications system of claim 1, further comprising:

a database within said serving mobile location center for storing said update relation information.

11. A method for determining update relation information corresponding to a current absolute time and an associated current time division multiple access frame number, comprising the steps of:

receiving at a serving mobile location center a positioning request;

sending a request for said update relation information for at least one location measurement unit in response to receiving said positioning request; and

receiving said update relation information from said at least one location measurement unit at said serving mobile location center for use in a subsequent time of arrival based positioning of a mobile station.

12. The method of claim 11, wherein said step of sending further comprises the step of:

sending said request for update relation information within a Mobile Application Part Channel Information message.

13. The method of claim 11, wherein said step of receiving said update relation information further comprises the step of:

receiving at said serving mobile location center said current absolute time value associated with said at least one location measurement unit and said associated current time division multiple access frame number.

14. The method of claim 11, further comprising the step of:

initiating a timer within said serving mobile location center upon receipt of previous update relation information.

15. The method of claim 14, wherein said step of sending further comprises the steps of:

determining whether said timer has expired upon receipt of said positioning request; and

if said timer has expired, sending said request for update relation information.

16. The method of claim 11, further comprising the step of:

storing said update relation information within a database within said serving mobile location center.

17. A method for determining update relation information corresponding to a current absolute time and an associated current time division multiple access frame number, comprising the steps of:

receiving an asynchronous intra-cell handover command at a location measurement unit from a said base station controller in communication with said location measurement unit;

performing an asynchronous intra-cell handover by said location measurement unit;

obtaining update relation information during said handover; and

transmitting said update relation information to a serving mobile location center connected to said base station controller for use in a subsequent time of arrival based positioning of a mobile station.

18. The method of claim 17, wherein said asynchronous intra-cell handover command includes said current time division multiple access frame number.

19. The method of claim 18, wherein said step of obtaining further comprises the step of:

correlating said current absolute time value within said at least one location measurement unit with said received current time division multiple access frame number to determine said update relation information.

20. The method of claim 17, wherein said step of performing further comprises the step of:

receiving, at said at least one location measurement unit, information from a base transceiver station in communication with said at least one location measurement unit during said asynchronous intra-cell handover.

21. A method for positioning a mobile station within a cellular network, comprising the steps of:

receiving at a serving mobile location center a positioning request;

sending a request for update relation information corresponding to a current absolute time and an associated current time division multiple access frame number for at least one location measurement unit to a base station controller in response to receiving said positioning request;

receiving, by said at least one location measurement unit, an asynchronous intra-cell handover command from said base station controller;

obtaining, by said at least one location measurement unit, said update relation information during an asynchronous intra-cell handover; and

transmitting said update relation information from said at least one location measurement unit to said serving mobile location center via said base station controller for use in a subsequent time of arrival based positioning of said mobile station.

22. The method of claim 21, wherein said asynchronous intra-cell handover command includes said current time division multiple access frame number.

23. The method of claim 22, wherein said step of obtaining further comprises the step of:

correlating said current absolute time value within said at least one location measurement unit with said received current time division multiple access frame number to determine said update relation information.

24. The method of claim 21, further comprising the step of:

initiating a timer within said serving mobile location center upon receipt of previous update relation information.

25. The method of claim 24, wherein said step of sending said request further comprises the step of:

determining, by said serving mobile location center, whether said timer has expired upon receipt of said positioning request;

if said timer has expired, sending said request for update relation information.

26. The method of claim 21, further comprising the step of:

storing, within a database within said serving mobile location center, said update relation information.

27. The method of claim 21, further comprising the step of:

configuring, by said serving mobile location center, said at least one location measurement unit using said received update relation information.

28. The method of claim 27, wherein said step of configuring further comprises the step of:

transmitting a Location Services Information Request message from said serving mobile location center to said at least one location measurement unit.

29. The method of claim 28, further comprising the steps of:

obtaining, by said at least one location measurement unit, positioning measurements in response to said Location Services Information Request message; and

transmitting said positioning measurements to said serving mobile location center.

30. The method of claim 29, further comprising the step of:

calculating, by said serving mobile location unit, a location of said mobile station using said positioning measurements.

31. The method of claim 21, wherein said step of performing further comprises the step of:

receiving, at said at least one location measurement unit, information from a base transceiver station in communication with said at least one location measurement unit during said asynchronous intra-cell handover.