Device and method of handling a radio network temporary identifier

1. A Distributed Unit (DU) for handling a Radio Network Temporary Identifier (RNTI), 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 instructions, and the at least one processing circuit is configured to execute the instructions of:

receiving a random access (RA) preamble from a communication device;

transmitting a RA response (RAR) including a first cell RNTI (C-RNTI) to the communication device, in response to the RA preamble;

receiving a radio resource control (RRC) Resume Request message from the communication device operating in an RRC_INACTIVE state;

transmitting an INITIAL uplink (UL) RRC MESSAGE TRANSFER message including the RRC Resume Request message to a Centralized Unit (CU), wherein the INITIAL UL RRC MESSAGE TRANSFER message includes the first C-RNTI;

receiving a UE CONTEXT SETUP REQUEST message for responding to the INITIAL UL RRC MESSAGE TRANSFER message for the communication device from the CU;

transmitting a UE CONTEXT SETUP RESPONSE message for responding to the UE CONTEXT SETUP REQUEST message, to the CU;

receiving a downlink (DL) RRC MESSAGE TRANSFER message from the CU, wherein the DL RRC MESSAGE TRANSFER message includes a RRC Resume message for responding to the RRC Resume Request message;

transmitting the RRC Resume message to the communication device, operating in the RRC_INACTIVE state, according to the first C-RNTI; and

communicating data with the communication device according to the first C-RNTI.

2. The DU of claim 1 , wherein the UE CONTEXT SETUP REQUEST message includes a second C-RNTI, and a first value of the first C-RNTI and a second value of the second C-RNTI are the same or different.

3. The DU of claim 1 , wherein the UE CONTEXT SETUP REQUEST message does not include a second C-RNTI.

4. A first Distributed Unit (DU) for handling a Radio Network Temporary Identifier (RNTI), 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 instructions, and the at least one processing circuit is configured to execute the instructions of:

receiving a random access (RA) preamble from a communication device;

transmitting a RA response (RAR) including a first cell RNTI (C-RNTI) to the communication device, in response to the RA preamble;

receiving a radio resource control (RRC) Resume Request message from the communication device operating in an RRC_INACTIVE state;

transmitting an INITIAL uplink (UL) RRC MESSAGE TRANSFER message including the RRC Resume Request message to a first Centralized Unit (CU);

receiving a UE CONTEXT SETUP REQUEST message for responding to the INITIAL UL RRC MESSAGE TRANSFER message for the communication device from the first CU;

transmitting a UE CONTEXT SETUP RESPONSE message for responding to the UE CONTEXT SETUP REQUEST message, to the first CU, wherein the UE CONTEXT SETUP RESPONSE message includes a second C-RNTI;

receiving a downlink (DL) RRC MESSAGE TRANSFER message from the first CU, wherein the DL RRC MESSAGE TRANSFER message includes a RRC Resume message for responding to the RRC Resume Request message and the RRC Resume message includes the second C-RNTI;

transmitting the RRC Resume message to the communication device operating in the RRC_INACTIVE state; and

communicating data with the communication device according to the second C-RNTI.

5. The first DU of claim 4 , wherein a first value of the first C-RNTI and a second value of the second C-RNTI are the same or different.

6. The first DU of claim 4 , wherein the instructions further comprise:

transmitting the RRC Resume message to the communication device according to the first C-RNTI.

7. The first DU of claim 4 , wherein the second C-RNTI is received by the first CU from a second DU, before the RRC Resume Request message is received by the first CU.

8. The first DU of claim 4 , wherein the second C-RNTI is received by the first CU from a second CU.

9. A Distributed Unit (DU) for handling a Radio Network Temporary Identifier (RNTI), 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 instructions, and the at least one processing circuit is configured to execute the instructions of:

receiving a random access (RA) preamble from a communication device;

transmitting a RA response (RAR) including a first cell RNTI (C-RNTI), to the communication device, in response to the RA preamble;

receiving a radio resource control (RRC) Resume Request message from the communication device operating in an RRC_INACTIVE state;

transmitting an INITIAL uplink (UL) RRC MESSAGE TRANSFER message including the RRC Resume Request message to a Centralized Unit (CU);

receiving a UE CONTEXT SETUP REQUEST message for responding to the INITIAL UL RRC MESSAGE TRANSFER message for the communication device from the CU, wherein the UE CONTEXT SETUP REQUEST message includes a second C-RNTI;

transmitting a UE CONTEXT SETUP RESPONSE message for responding to the UE CONTEXT SETUP REQUEST message, to the CU;

receiving a downlink (DL) RRC MESSAGE TRANSFER message from the CU, wherein the DL RRC MESSAGE TRANSFER message includes a RRC Resume message for responding to the RRC Resume Request message;

transmitting the RRC Resume message to the communication device operating in the RRC_INACTIVE state; and

communicating data with the communication device according to the second C-RNTI.

10. The DU of claim 9 , wherein the instructions further comprise:

transmitting the RRC Resume message to the communication device according to the first C-RNTI.