Method and apparatus for handling handover procedure

1. A method for handling a handover procedure for a Radio Resource Control (RRC) layer in a user equipment (UE) of a wireless communication system, the method comprising:

indicating occurrence of a handover procedure to a Packet Data Convergence Protocol (PDCP) layer of the UE when receiving an RRC Connection Reconfiguration message for triggering the handover procedure;

applying a new security configuration to the PDCP layer if the RRC Connection Reconfiguration message comprises an information element (IE) for providing the security configuration after indicating occurrence of the handover procedure to the PDCP layer; and

requesting a Medium Access Control (MAC) layer of the UE to initiate a random access procedure for the handover procedure after applying the new security configuration to the PDCP layer.

2. The method of claim 1 further comprising:

re-establishing a Radio Link Control (RLC) layer of the UE after indicating the occurrence of the handover procedure to the PDCP layer and before applying the security configuration to the PDCP layer.

3. The method of claim 1 further comprising:

updating a radio resource configuration of the UE according to an IE “radioResourceConfiguration” included in the RRC Connection Reconfiguration message before requesting the MAC layer to initiate the random access procedure.

4. The method of claim 1 , wherein the RRC Connection Reconfiguration message comprises an IE “mobilityControlInformation” for triggering the handover procedure in the RRC layer of the UE.

5. The method of claim 1 , wherein the information element for providing the security configuration is an IE “securityConfiguration”.

6. A communication device for handling a handover procedure for a Radio Resource Control (RRC) layer in a user equipment (UE) of a wireless communication system, the communication device comprising:

a processor; and

a memory coupled to the processor;

wherein the processor is configured to execute a program code stored in the memory to

indicate occurrence of a handover procedure to a Packet Data Convergence Protocol (PDCP) layer of the UE when receiving an RRC Connection Reconfiguration message for triggering the handover procedure;

apply a new security configuration to the PDCP layer if the RRC Connection Reconfiguration message comprises an information clement (IE) for providing the security configuration after indicating occurrence of the handover procedure to the PDCP layer; and

request a Medium Access Control (MAC) layer of the UE to initiate a random access procedure for the handover procedure after applying the new security configuration to the PDCP layer.

7. The communication device of claim 6 , wherein the processor is further configured to execute the program code stored in the memory to:

re-establish a Radio Link Control (RLC) layer of the UE after indicating the occurrence of the handover procedure to the PDCP layer and before applying the security configuration to the PDCP layer.

8. The communication device of claim 6 , wherein the processor is further configured to execute the program code stored in the memory to:

update a radio resource configuration of the UE according to an IE “radioResourceConfiguration” included in the RRC Connection Reconfiguration message before requesting the MAC layer to initiate the random access procedure.

9. The communication device of claim 6 . wherein the RRC Connection Reconfiguration message comprises an 1 E “mobilityControlInformation” for triggering the handover procedure in the RRC layer of the UE.

10. The communication device of claim 6 , wherein the information element for providing the security configuration is an IE “securityConfiguration”.