Method of handling handover in dual connectivity

1. A network comprising a first base station (BS), a second BS and a third BS for handling a handover for a communication device in a dual connectivity, comprising:

at least one storage device; and

at least one processing circuit, coupled to the at least one storage device, wherein the at least one storage device stores, and the at least one processing circuit is configured to execute instructions of:

the first BS connecting to the communication device with a first signalling radio bearer (SRB);

the first BS transmitting a radio resource control (RRC) message to the communication device via the first SRB, wherein the RRC message comprises a first secondary cell group (SCG) configuration configuring the second BS as a secondary node (SN);

the second BS transmitting a first measurement configuration to the communication device via a second SRB;

the second BS receiving a first measurement report associated to the first measurement configuration from the communication device via the second SRB;

the first BS determining the handover from the first BS to the third BS;

the first BS transmitting a first interface message to the second BS in response to the determination;

the first BS receiving a second interface message in response to the first interface message from the second BS, wherein the second interface message comprises at least one of the first measurement configuration and a second SCG configuration;

the first BS transmitting a Handover Request message to the third BS, wherein the Handover Request message comprises the at least one of the first measurement configuration and the second SCG configuration;

the first BS receiving a Handover Request Acknowledge message in response to the Handover Request message from the third BS, wherein the Handover Request Acknowledge message comprises a Handover Command message; and

the first BS transmitting the Handover Command message to the communication device.

2. The network of claim 1 , wherein the instructions further comprise:

the third BS receiving a Handover Complete message in response to the Handover Command message from the communication device.

3. The network of claim 1 , wherein the Handover Command message releases the second BS, and does not configure a BS as the SN for the communication device.

4. The network of claim 1 , wherein the Handover Command message comprises a third SCG configuration configuring the second BS or a fourth BS as the SN for the communication device.

5. The network of claim 4 , wherein the instructions further comprise:

the third BS transmitting the at least one of the first measurement configuration and the second SCG configuration to the second BS or the fourth BS, when determining to configure the second BS or the fourth BS as the SN for the communication device.

6. The network of claim 5 , wherein the instructions further comprise:

the second BS determining whether to keep the first measurement configuration for the communication device; or

the second BS configuring a second measurement configuration to the communication device.

7. The network of claim 6 , wherein the second measurement configuration is comprised in the Handover Command message.

8. The network of claim 1 , wherein the instructions further comprise:

the second BS transmitting the first SCG configuration to the first BS.

9. The network of claim 1 , wherein the first interface message requests at least the second SCG configuration.

10. The network of claim 1 , wherein the instructions further comprise:

the second BS stopping updating the second SCG configuration via the second DRB, when receiving the first interface message from the first BS.

11. The network of claim 1 , wherein the instructions further comprise:

the first BS transmitting a third measurement configuration to the communication device via the first SRB; and

the first BS receiving a second measurement report associated to the third measurement configuration from the communication device via the first SRB.