Device and Method of Handling a Radio Resource Control State Change

A network for handling a Radio Resource Control (RRC) state change, comprising:

• a storage unit, for storing instructions of:
• transmitting a RRC Connection Setup message to a communication device to establish a RRC connection between the communication device and a first base station (BS) of the network;
• transmitting a Security Mode Command message via the RRC connection to the communication device, to activate a security for a data communication between the communication device and the first BS;
• transmitting a RRC Connection Reconfiguration message configuring at least one radio bearer (RB) from the first BS, after activating the security;
• receiving a user equipment (UE) capability indicating that the communication device supports a RRC_Light_Connected state, from the communication device;
• transmitting a first RRC message configuring the RRC_Light_Connected state to the communication device according to the UE capability, when determining no data in a first BS buffer needs to be transmitted to the communication device and there is no data in a buffer of the communication device to be transmitted;
• receiving a RRC message requesting entering a RRC_Connected state from the communication device, after transmitting the first RRC message;
• and
• transmitting a second RRC message configuring the communication device to enter the RRC_Connected state to the communication device in response to the RRC message;
• and
• a processing circuit, coupled to the storage unit, configured to execute the instructions stored in the storage unit.