Method and system for saving dropped calls

• US 6,445,918 B1
• Filed: 11/01/1999
• Issued: 09/03/2002
• Est. Priority Date: 11/01/1999
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Hellander, Bo
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): Ferguson, Keith
• Application Number:
  US09/431,671
• Time in Patent Office: 1,037 Days
• Field of Search: 455/422, 455/423, 455/424, 455/425, 455/432, 455/433, 455/434, 455/435, 455/436, 455/437, 455/438, 455/439, 455/440, 455/442, 455/443, 455/444, 455/445, 455/456, 455/457, 455/8, 455/500, 455/513, 455/514, 455/515, 455/517, 455/63, 455/67.1, 455/550, 455/555, 455/560, 370/331, 370/332, 370/333
• US Class Current: 455/423
• CPC Class Codes: H04W 36/12 Reselecting a serving backbone network switching or routing node
• CPC Class Codes: H04W 76/10 Connection setup

Abstract

A method and system for reconnecting dropped calls in a mobile telecommunications network. Upon detecting a call drop of an ongoing call, a mobile station involved in the call transmits a call reconnect request to a target cell in the network. The target cell can be selected from a neighboring cell list received from a serving cell during the call. In response to the call reconnect request, a target switching node associated with the target cell locates the call and reconnects the mobile station to the call using a traffic channel in the target cell.

Claims

1. A method for reconnecting dropped calls in a mobile telecommunications network, comprising the steps of:

receiving a neighboring cell list identifying a plurality of cells at a mobile station;

measuring a signal quality of at least one signal transmitted from at least one of the cells identified in the neighboring cell list;

detecting at the mobile station a radio path loss of a call involving the mobile station;

selecting a target cell based on said signal quality measurement;

transmitting a call reconnect request from the mobile station to the target cell;

requesting an identification of a serving switching node involved in the call from a remote database in response to the call reconnect request; and

reconnecting the mobile station to the call in response to the call reconnect request.

2. The method of claim 1, further comprising the step of assigning a traffic channel in the target cell, said assigned traffic channel used to reconnect the mobile station to the call.

3. The method of claim 2, wherein the call uses a traffic channel in a serving cell prior to the radio path loss.

4. The method of claim 3, wherein the serving cell and the target cell are associated with the serving switching node.

5. The method of claim 4, wherein the serving switching node controls assignments of traffic channels in the serving cell and the target cell.

6. The method of claim 3, wherein the radio path loss results from a radio path failure for the call in the serving cell.

7. The method of claim 3, wherein the serving cell is associated with the serving switching node through which the call is routed prior to the radio path loss and the target cell is associated with a target switching node, said method further comprising the step of requesting a handoff of the call from the serving switching node to the target switching node in response to the call reconnect request.

8. The method of claim 7, further comprising the step of retrieving an identification of the serving switching node in response to the call reconnect request, said identification used to request the handoff.

9. The method of claim 7, further comprising the step of requesting a handoff of the call from each of at least one border switching node in response to the call reconnect request, the at least one border switching node including the serving switching node.

10. The method of claim 1, wherein the neighboring cell list identifies a control channel in the target cell, said call reconnect request transmitted on said control channel.

11. A cellular telecommunications system, comprising:

a serving switching node through which a call involving a mobile station is routed;

a serving base station associated with the serving switching node, said first base station in radio contact with a mobile station prior to a loss of said radio contact;

a target base station receiving a call re-connection request from the mobile station after said loss of radio contact; and

a target switching node controlling said target base station, said target switching node assigning a traffic channel in the target base station for use by the mobile station and requesting an identification of the switching node involved in the call from a remote database in response to the call reconnect request, and wherein the target switching node establishes a radio connection on said traffic channel between said call and said mobile station in response to the call re-connection.

12. The system of claim 11, wherein the target switching node further locates said call at the serving switching node and requests a handoff of said call from the serving switching node, the serving switching node handing off control of said call to the target switching node in response to the handoff request.

13. The system of claim 12, wherein said remote database is a home location register.

14. The system of claim 13, wherein the switching node identified by said remote database is an anchor switching node, said target switching node requesting from said anchor switching node an identification of the serving switching node, the anchor switching node sending an identification of the serving switching node in response to the serving switching node identification request.

15. The system of claim 11, wherein the target switching node requests a handoff of said call from at least one border switching node, the at least one border switching node including the serving switching node, the serving switching node handing off control of said call to the target switching node in response to the handoff request.

16. The system of claim 15, further comprising a home location register, wherein the target switching node requests the handoff from the at least one border switching node in response to an indication received from the home location register that current location data for the mobile station is unavailable.

17. The system of claim 15, further comprising an anchor switching node, wherein the target switching node requests the handoff from the at least one border switching node in response to an indication received from the anchor switching node that current location data for the mobile station is unavailable.

18. A method for reconnecting dropped calls in a mobile telecommunications system, comprising the steps of:

detecting at a mobile station a call drop of a call involving the mobile station, said call drop including a loss of a radio link between the mobile station and a serving communication station;

transmitting a call reconnect request from the mobile station to a target communication station associated with a target switching node in response to the detection of the call drop;

requesting an identification of the switching node involved in the call from a remote database in response to the call reconnect request;

locating the call, in response to the call reconnect request, at a switching node involved in the call, wherein said switching node involved in the call differs from the target switching node; and

reconnecting the mobile station to the call using a radio link between the mobile station and the target communication station.

19. The method of claim 18, further comprising the step of selecting the target communication station from a neighboring cell list transmitted to the mobile station from the serving communication station during the call.

20. The method of claim 18, further comprising the steps of:

requesting, in response to the call reconnect request, a handoff of the call from the switching node involved in the call to the target switching node; and

handing off the call from the switching node involved in the call to the target switching node in response to the handoff request.

21. The method of claim 18, wherein the remote database comprises a home location register.

22. The method of claim 18, wherein the remote database is associated with an anchor switching node.

23. The method of claim 18, wherein the switching node involved in the call comprises a serving switching node associated with the serving communication station.

24. The method of claim 18, further comprising the steps of:

requesting, in response to the call reconnect request, a handoff of the call from at least one border switching node to the target switching node, wherein the at least one border includes the switching node involved in the call; and

handing off the call from the switching node involved in the call to the target switching node in response to the handoff request.