REESTABLISHMENT OF AN RRC CONNECTION FOR AN EMERGENCY CALL IN AN LTE NETWORK

• US 20110105074A1
• Filed: 11/05/2010
• Published: 05/05/2011
• Est. Priority Date: 11/05/2009
• Status: Abandoned Application

• Current Assignee: HTC Corporation
• Original Assignee: HTC Corporation
• Inventors: Wu, Chih-Hsiang
• Application Number:
  US12/940,988
• Publication Number:
  US 20110105074A1
• Time in Patent Office: Days
• US Class Current: 455/404.1
• CPC Class Codes: H04W 4/90 Services for handling of emergency or hazardous situations, e.g. earthquake and tsunami warning systems [ETWS]
• CPC Class Codes: H04W 76/19 Connection re-establishment
• CPC Class Codes: H04W 76/50 for emergency connections

Abstract

A mobile device initiates an RRC connection reestablishment procedure or a cell update procedure for an emergency call after experiencing a failure condition in an LTE network environment. The mobile device establishes an RRC connection with an acceptable cell to originate an emergency call. The mobile device detects a failure condition, such as a radio link failure, which disrupts the RRC connection. The mobile device searches for available cells that it may reestablish the RRC connection with, but can only find acceptable cells. The mobile device may initiate an RRC connection reestablishment procedure with an acceptable cell. The mobile device may also only attempt to reestablish the RRC connection with a cell that is part of a PLMN that the original acceptable cell was also a part of. The mobile device may also enter an RRC_IDLE mode upon detecting a failure condition.

Claims

1. A method of reestablishing a radio resource control (RRC) connection, the method performed by a wireless mobile device configured to communicate wirelessly with a Long Term Evolution (LTE) or a Universal Mobile Telecommunications System (UMTS) network employing a wireless communications protocol, the wireless mobile device comprising a processor, a radio, and a memory, the method comprising:

establishing an RRC connection with a first acceptable cell of an LTE or UMTS network, wherein the first acceptable cell supports emergency calls;

establishing an emergency call via the RRC connection;

detecting a failure condition in the RRC connection, wherein the failure condition is one of a radio link failure, a handover failure, a mobility from Evolved Universal Terrestrial Radio Access (E-UTRA) failure, an integrity check failure, or an RRC connection reconfiguration failure;

detecting a second acceptable cell, wherein the second acceptable cell is either the first acceptable cell or another acceptable cell; and

sending a request to the second acceptable cell to reestablish the RRC connection without considering sending the request to a suitable cell.

2. The method of claim 1, wherein the request to the second acceptable cell to reestablish the RRC connection commences an RRC connection reestablishment procedure or a cell update procedure.

3. The method of claim 1, further comprising detecting a suitable cell, wherein the suitable cell supports emergency calls.

4. The method of claim 1, wherein the second acceptable cell and the first acceptable cell are different cells, and wherein the first acceptable cell belongs to a public land mobile network (PLMN) and the second acceptable cell also belongs to the PLMN.

5. The method of claim 1, further comprising receiving an indication from the second acceptable cell that it supports emergency calls.

6. A method of establishing an RRC connection, the method performed by a wireless mobile device configured to communicate wirelessly with an LTE or a UMTS network employing a wireless communications protocol, the wireless mobile device comprising a processor, a radio, and a memory, the method comprising:

establishing a first RRC connection with a first acceptable cell of an LTE or UMTS network, wherein the first acceptable cell supports emergency calls;

establishing a first emergency call via the first RRC connection;

detecting a failure condition in the first RRC connection, wherein the failure condition is one of a radio link failure, a handover failure, a mobility from E-UTRA failure, an integrity check failure, or an RRC connection reconfiguration failure;

entering an RRC_IDLE mode upon detecting the failure condition without waiting for a timer to expire, wherein the timer is associated with a procedure for reestablishing the RRC connection;

establishing a second RRC connection with a second cell; and

establishing a second emergency call via the second RRC connection.

7. The method of claim 6, wherein the timer is timer T311 or timer T305.

8. The method of claim 6, wherein the second emergency call is established automatically upon establishing the second RRC connection with the second cell.

9. A method of reestablishing an RRC connection, the method performed by a wireless mobile device configured to communicate wirelessly with an LTE or UMTS network employing a wireless communications protocol, the wireless mobile device comprising a processor, a radio, and a memory, the method comprising:

establishing an RRC connection with a first cell of an LTE or UMTS network, wherein the first cell supports emergency calls;

establishing an emergency call via the RRC connection;

detecting a failure condition in the RRC connection, wherein the failure condition is one of a radio link failure, a handover failure, a mobility from E-UTRA failure, an integrity check failure, or an RRC connection reconfiguration failure;

searching for a second cell that either;

(i) belongs to a PLMN that the first cell also belongs to, or

(ii) is identified as able to supports emergency calls; and

in response to finding the second cell, sending a request to reestablish the RRC connection to the second cell.

10. The method of claim 9, further comprising entering an RRC_IDLE mode when a second cell that belongs to a PLMN that the first cell also belongs to or that supports emergency calls is not found, but a suitable cell is found.

11. The method of claim 9, wherein the request to reestablish the RRC connection commences an RRC connection reestablishment procedure or a cell update procedure.

12. The method of claim 9, wherein the second cell is either an acceptable cell or a suitable cell.

13. The method of claim 9, further comprising receiving an indication from the second cell that it supports emergency calls.

14. The method of claim 10, further comprising establishing a second RRC connection with the suitable cell and establishing a second emergency call via the suitable cell.

15. The method of claim 9, wherein the first cell is an acceptable cell.