Method of handling cell change and related apparatus

1. A method of handling cell change for a mobile device, the method comprising:

receiving a cell change order message from a source cell of a first radio access technology (RAT);

in response to the receiving, performing a cell change order procedure from the source cell of the a first RAT to a target cell of a second RAT;

performing a radio resource control (RRC) connection establishment procedure when selecting the target cell of the second RAT;

receiving system information including access barring information of the target cell of the second radio access technology, from the target cell of the second radio access technology, wherein the access barring information indicates that the RRC connection establishment procedure is barred;

determining access barring according to the access barring information;

determining that the cell change order procedure is failed when the target cell of the second RAT is selected and the RRC connection establishment procedure is failed due to the access barring;

selecting to the source cell after determining that the cell change order procedure is failed; and

sending a cell change order failure message to the source cell.

2. The method of claim 1 further comprising determining that the cell change order is failed when the RRC CONNECTION REJECT message of the RRC connection establishment procedure is received.

3. The method of claim 1 , wherein cell change order failure message includes failure information indicating that the failure of the cell change order procedure is caused by the access barring.

4. The method of claim 1 further comprising determining that the cell change order procedure is complete when a RRC CONNECTION SETUP message from the target cell is received.

5. A communication device for appropriately handling cell change, the communication device comprising:

a storage device for storing program code corresponding to a process; and

a processor coupled to the storage device, for processing the program code to execute the process;

wherein the process comprises:

receiving a cell change order message from a source cell of a first radio access technology (RAT);

in response to the receiving, performing a cell change order procedure from the source cell of the first RAT to a target cell of a second RAT;

performing a radio resource control (RRC) connection establishment procedure when selecting the target cell of the second RAT;

receiving system information including access barring information of the target cell of the second radio access technology, from the target cell of the second radio access technology, wherein the access barring information indicates that the RRC connection establishment procedure is barred;

determining access barring according to the access barring information;

determining that the cell change order procedure is failed when the target cell of the second RAT is selected and the RRC connection establishment procedure is failed due to the access barring;

selecting to the source cell after determining that the cell change order procedure is failed; and

sending a cell change order failure message to the source cell.

6. The communication device of claim 5 , wherein the process further comprises determining that the cell change order is failed when a RRC CONNECTION REJECT message of the RRC, an abbreviation of radio resource control, connection establishment procedure is received.

7. The communication device of claim 5 , wherein cell change order failure message includes failure information indicating that the failure of the cell change order procedure is caused by the access barring.

8. The communication device of claim 5 , wherein the process further comprises determining that the cell change order procedure is complete when a RRC CONNECTION SETUP message from the target cell is received.