Method and apparatus for resuming RRC connection in wireless communication system
A method for resuming an RRC connection performed by a UE in a wireless communication system may include entering an EMM-IDLE mode with a suspend indication as the RRC connection is suspended; generating an initial NAS message when a procedure using the initial NAS message is triggered; requesting a resume of the RRC connection from an upper layer of the UE to a lower layer; and switching from the EMM-IDLE mode with the suspend indication to an EMM-CONNECTED mode when the upper layer receives an indication that the RRC connection is resumed from the lower layer.
1. A method for resuming a radio resource control (RRC) connection performed by a user equipment (UE) in a wireless communication system, comprising:
entering an Evolved Packet System (EPS) Mobility Management (EMM)-IDLE mode with a suspend indication as the RRC connection is suspended; generating an initial Non-Access Stratum (NAS) message when a procedure using the initial NAS message is triggered; requesting a resume of the RRC connection from an upper layer of the UE to a lower layer; and switching from the EMM-IDLE mode with the suspend indication to an EMM-CONNECTED mode when the upper layer receives an indication that the RRC connection is resumed from the lower layer, when the initial NAS message is a first message type in which an accept response to be transmitted from a Mobility Management Entity (MME) is existed, wherein the initial NAS message is transmitted to the MME, and when the initial NAS message is a second message type in which an accept response to be transmitted from the MME is not existed, wherein the initial NAS message is not transmitted to the MME.
2. The method for resuming the RRC connection of claim 1 , wherein the procedure using the initial NAS message of the second message type is assumed to be accepted always by the MME.
3. The method for resuming the RRC connection of claim 1 , wherein the MME recognizes that the procedure using the initial NAS message of the second message type is triggered when the MME does not receive the initial NAS message within a preconfigured time from a time of recognizing that the RRC connection is resumed, and is a network entity that accept the procedure always.
4. The method for resuming the RRC connection of claim 3 , wherein the time of recognizing that the RRC connection is resumed by the MME corresponds to a time of receiving an S1-AP UE Context Resume Request message including an Evolved Packet System (EPS) bearer list for which the resume is requested from an evolved-NodeB (eNB).
5. The method for resuming the RRC connection of claim 4 , wherein the initial NAS message of the first message type is a TAU (Tracking Area Update) request message, an Attach request message, a Detach request message or an Extended Service Request message generated for CSFB (Circuit Switched Fallback) reason, and
wherein the initial NAS message of the second message type is a Service request message or an Extended Service Request message generated for non-CSFB reason.
6. The method for resuming the RRC connection of claim 5 , wherein a service type value of the Extended Service Request message generated for the non-CSFB reason is configured to be a value indicating ‘packet services via S1’.
7. The method for resuming the RRC connection of claim 5 , further comprising transmitting uplink data or uplink signaling, when the initial NAS message of the second message type is the Service request message and the UE is switched to the EMM-CONNECTED mode.
8. The method for resuming the RRC connection of claim 5 , further comprising maintaining the EMM-IDLE mode with the suspend indication, when the upper layer receives an indication that the RRC connection resume is failed and the RRC connection is suspended from the lower layer.
9. The method for resuming the RRC connection of claim 5 , further comprising switching from the EMM-IDLE mode with the suspend indication to the EMM-IDLE mode without the suspend indication, when the upper layer receives an indication that the RRC connection resume is failed and the RRC connection is not suspended from the lower layer.
10. The method for resuming the RRC connection of claim 5 , switching from the EMM-IDLE mode with the suspend indication to the EMM-IDLE mode without the suspend indication, transmitting the initial NAS message and proceeding the procedure using the initial NAS message, when upper layer receives an indication that the RRC connection resume is fallbacked.
11. A user equipment (UE) for resuming a radio resource control (RRC) connection in a wireless communication system, comprising: a communication module configured to transmit and receive a signal; and a processor configured to control the communication module, wherein the processor is configured to:
enter an Evolved Packet System (EPS) Mobility Management (EMM)-IDLE mode with a suspend indication as the RRC connection is suspended; generate an initial Non-Access Stratum (NAS) message when a procedure using the initial NAS message is triggered; request a resume of the RRC connection from an upper layer of the UE to a lower layer; and switch from the EMM-IDLE mode with the suspend indication to an EMM-CONNECTED mode when the upper layer receives an indication that the RRC connection is resumed from the lower layer, when the initial NAS message is a first message type in which an accept response to be transmitted from a Mobility Management Entity (MME) is existed, wherein the initial NAS message is transmitted to the MME, and when the initial NAS message is a second message type in which an accept response to be transmitted from the MME is not existed, wherein the initial NAS message is not transmitted to the MME.
12. The UE of claim 11 , wherein the procedure using the initial NAS message of the second message type is assumed to be accepted always by the MME.
13. The UE of claim 12 , wherein the MME recognizes that the procedure using the initial NAS message of the second message type is triggered when the MME does not receive the initial NAS message within a preconfigured time from a time of recognizing that the RRC connection is resumed and is a network entity that accept the procedure always.
14. The UE of claim 13 , wherein the time of recognizing that the RRC connection is resumed by the MME corresponds to a time of receiving an S1-AP UE Context Resume Request message including an Evolved Packet System (EPS) bearer list for which the resume is requested from an evolved-NodeB (eNB).
15. The UE of claim 14 , wherein the initial NAS message of the first message type is a TAU (Tracking Area Update) request message, an Attach request message, a Detach request message or an Extended Service Request message generated for CSFB (Circuit Switched Fallback) reason, and
wherein the initial NAS message of the second message type is a Service request message or an Extended Service Request message generated for non-CSFB reason.