Selection of positioning handover candidates based on angle

• US 6,047,183 A
• Filed: 10/30/1997
• Issued: 04/04/2000
• Est. Priority Date: 10/30/1997
• Status: Expired due to Term

• Current Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Kingdon, Christopher H., Zadeh, Bagher R.
• Primary Examiner(s): Bost, Dwayne D.
• Assistant Examiner(s): Gary, Erika A.
• Application Number:
  US08/960,720
• Time in Patent Office: 887 Days
• Field of Search: 455/440, 455/525, 455/456, 455/436, 455/437, 455/438, 455/439, 342/450, 342/359
• US Class Current: 455/440
• CPC Class Codes: H04W 36/32 by location or mobility data, e.g. speed data
• CPC Class Codes: H04W 36/322 by location data
• 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 for determining optimal target Base Transceiver Stations (BTSs) to perform positioning handovers and obtain positioning data is disclose. When a positioning request is received by a Base Station Controller (BSC) serving the Mobile Station (MS) to be positioned, the serving BSC accesses a database within the BSC, which contains a list of cells belonging to candidate target BTSs. Based on this information, and the main antenna direction of the serving BTS, two candidates for positioning handovers are selected from the list such that the angle between the main direction of two adjacent BTSs is nearly equivalent to the angle between the main direction of two additional adjacent BTSs. By selecting the target BTSs in this manner, it can be ensured that the target BTSs surround the MS, thus decreasing the error in the location calculations performed by a Positioning Center (PC).

Claims

1. A telecommunications system for determining first and second optimal target base transceiver stations to be utilized for triangulation to determine the location of a mobile terminal, said telecommunications system comprising:

a serving base transceiver station in wireless communication with said mobile terminal, said serving base transceiver station having a main antenna direction associated therewith; and

a controlling node connected to said serving base transceiver station, said controlling node being adapted to select said first and second optimal target base transceiver stations from a candidate list of potential target base transceiver stations based on the calculation of first angles between an antenna direction of each of said potential target base transceiver stations and said main direction and second angles between each said respective antenna direction of each of said potential target base transceiver stations;

wherein said first and second optimal target base transceiver stations have the minimum difference between said respective first angles and between each of said respective first angles and said respective second angle associated with said first and second optimal target base transceiver stations.

2. The telecommunications system of claim 1, wherein said controlling node is a base station controller.

3. The telecommunications system of claim 1, wherein said controlling node is within a mobile switching center.

4. The telecommunications system of claim 1, further comprising a database within said controlling node containing a list of cells and said associated potential target base transceiver stations.

5. The telecommunications system of claim 1, wherein positioning handovers are performed to said first and second optimal target base transceiver stations for triangulation to determine the location of said mobile terminal, said positioning handovers being performed by said mobile terminal sending respective messages to said first and second optimal target base transceiver stations instructing said first and second optimal base transceiver stations to obtain positioning data.

6. The telecommunications system of claim 5, wherein said positioning data are Timing Advance values.

7. The telecommunications system of claim 5, wherein the location of said mobile terminal is determined by a positioning center in communication with said controlling node, said positioning center using said positioning data to determine the location of said mobile terminal.

8. The telecommunications system of claim 7, wherein the location of said mobile terminal is sent from said positioning center to a requesting node in communication with said positioning center.

9. A method for determining first and second optimal target base transceiver stations to be utilized for triangulation to determine the location of a mobile terminal, said mobile terminal being in wireless communication with a serving base transceiver station having a main antenna direction associated therewith, said method comprising the steps of:

determining a candidate list of potential target base transceiver stations by a controlling node connected to said serving base transceiver station;

calculating first angles between an antenna direction of each of said potential target base transceiver stations and said main antenna direction;

calculating second angles between each said respective antenna direction of each of said potential target base transceiver stations;

selecting said first and second optimal target base transceiver stations having the minimum difference between said respective first angles and between each of said respective first angles and said respective second angle associated with said first and second optimal target base transceiver stations.

10. The method of claim 9, wherein said controlling node is a base station controller.

11. The method of claim 9, wherein said step of determining is performed by said mobile terminal measuring the signal strength associated with a plurality of cells associated with said potential target base transceiver stations and forwarding the signal strength of each of said cells to said controlling node.

12. The method of claim 9, further comprising, after said step of selecting, the step of:

performing positioning handovers to said first and second optimal target base transceiver stations for triangulation to determine the location of said mobile terminal, said step of performing said positioning handovers being performed by said mobile terminal sending respective messages to said first and second optimal target base transceiver stations instructing said first and second optimal base transceiver stations to obtain positioning data.

13. The method claim 12, wherein said positioning data are Timing Advance values.

14. The method of claim 12, further comprising, after said step of performing said positioning handovers, the step of:

determining, by a positioning center in communication with said controlling node, the location of said mobile terminal, using said positioning data.

15. The method of claim 14, further comprising, after said step of determining the location of said mobile terminal, the step of:

sending the location of said mobile terminal from said positioning center to a requesting node in communication with said positioning center.