Apparatus, system and method for VoLTE call continuity

1. A system, comprising:

a first user equipment (UE) configured to perform a Voice over Long Term Evolution (LIE) (VoLTE) call;

a second UE configured to perform the VoLTE call with the first UE;

wherein the first UE is configured to maintain continuity of the VoLTE call by:

determining when one of a first dedicated bearer linked to a first default bearer of the first UE or a second dedicated bearer linked to a second default bearer of the second UE is lost; and

transmitting a signal to an Internet Protocol (IP) Multimedia Subsystem (IMS) server that prevents release of the determined dedicated bearer, the signal further triggering a re-activation of the determined dedicated bearer.

2. A user equipment, comprising:

a transceiver configured to establish a connection with a Long Term Evolution (LTE) Network; and

a processor configured to execute a Voice over LTE (VoLTE) call application with a further user equipment,

wherein the transceiver and processor are configured to maintain continuity of the VoLTE call by:

determining when one of a first dedicated bearer linked to a first default bearer of the user equipment and a second dedicated bearer linked to a second default bearer of the further user equipment is lost; and

transmitting a signal to an Internet Protocol (IP) Multimedia Subsystem (IMS) server that holds the determined dedicated bearer from release, the signal further triggering a re-activation of the determined dedicated bearer.

3. The user equipment of claim 2 , wherein one of the first or second dedicated bearers are lost from a radio link failure (RLF).

4. The user equipment of claim 2 , wherein, when the first dedicated bearer is determined to be lost, the user equipment is further configured to perform a Radio Resource Control (RRC) reestablishment procedure.

5. The user equipment of claim 4 , wherein, when the RRC reestablishment procedure succeeds, the user equipment remains in a RRC connected state to transmit the signal to the IMS server.

6. The user equipment of claim 4 , wherein, when the RRC reestablishment procedure fails, the user equipment enters a RRC idle state and transmits the signal to the IMS server, the signal triggering a RRC connection request.

7. The user equipment of claim 4 , wherein the signal is a Session Initiation Protocol (SIP) message invite.

8. The user equipment of claim 2 , wherein, when the second dedicated bearer is determined to be lost, the user equipment is configured to determine whether downlink (DL) Real-time Transport Protocol (RTP) packets have been received within a predetermined timer.

9. The user equipment of claim 8 , wherein the predetermined timer is less than a RTP timer between six and ten seconds.

10. The user equipment of claim 8 , wherein the signal is a SIP message re-invite including proper parameter information associated with the VoLTE call, the signal triggering a dedicated bearer reestablishment procedure for the second UE.

11. A method comprising:

at a first user equipment (UE) configured to perform a Voice over Long Term Evolution (LTE) (VoLTE) call with a second UE:

determining when one of a first dedicated bearer linked to a first default bearer of the first UE or a second dedicated bearer linked to a second default bearer of the second UE is lost; and

transmitting a signal to an Internet Protocol (IP) Multimedia Subsystem (IMS) server that delays release of the determined dedicated bearer, the signal further triggering a re-activation of the determined dedicated bearer, the re-activation of the determined dedicated bearer maintaining continuity of the VoLTE call.

12. The method of claim 11 , wherein, when the first dedicated bearer is determined to be lost, the method further comprises:

performing a Radio Resource Control (RRC) reestablishment procedure.

13. The method of claim 12 , wherein, when the RRC reestablishment procedure succeeds, the first UE remains in a RRC connected state to transmit the signal to the IMS server.

14. The method of claim 12 , wherein, when the RRC reestablishment procedure fails, the first UE enters a RRC idle state and transmits the signal to the IMS server, the signal triggering a RRC connection request.

15. The method of claim 12 , wherein the signal is a Session Initiation Protocol (SIP) message invite.

16. The method of claim 11 , wherein, when the second dedicated bearer is determined to be lost, the method further comprises:

determining whether downlink (DL) Real-time Transport Protocol (RTP) packets have been received within a predetermined timer.

17. The method of claim 16 , wherein the predetermined timer is less than a RTP timer between six and ten seconds.

18. The method of claim 16 , wherein the signal is a SIP message re-invite including proper parameter information associated with the VoLTE call, the signal triggering a dedicated bearer reestablishment procedure for the second UE.

19. A method, comprising:

at a first user equipment (UE) configured to perform a Voice over Long Term Evolution (LTE) (VoLTE) call with a second UE:

performing the VoLTE call with the second UE using a first dedicated bearer linked to a first default bearer associated with a first evolved Node B (eNB) of the LTE network;

establishing a connection to the LTE network via a second eNB, the second eNB assigning a second default bearer to the first UE;

determining that the second eNB has not configured a second dedicated bearer linked to the second default bearer for the first UE;

transmitting a signal to an Internet Protocol (IP) Multimedia Subsystem (IMS) server that triggers a setup procedure for the second eNB to establish the second dedicated bearer for the first UE, the establishment of the second dedicated bearer maintaining a VoLTE call continuity.

20. The method of claim 19 , further comprising:

roaming to the second eNB of the LTE network.