Base station for mobile communication system

A base station (BS) for a mobile communication system, the BS being a primary BS for a user equipment (UE), the BS comprising:

• a transceiver;
• a network interface, being configured to connect to a secondary BS;
• and
• a processor, being electrically connected to the transceiver and the network interface, and being configured to execute the following operations:
• calculating a first time synchronization error between the BS and the UE, the first time synchronization error being associated with a first subcarrier spacing (SCS) of the BS and comprising at least one of a first detection synchronization signal time error caused by the UE and a first propagation delay time estimation error, the first detection synchronization signal time error and the first propagation delay time estimation error being associated with the first SCS;
• calculating a second time synchronization error between the secondary BS and the UE, the second time synchronization error being associated with a second SCS of the secondary BS and comprising at least one of a second detection synchronization signal time error caused by the UE and a second propagation delay time estimation error, the second detection synchronization signal time error and the second propagation delay time estimation error being associated with the second SCS;
• determining a smaller time synchronization error between the first time synchronization error and the second time synchronization error, the smaller time synchronization error corresponding to a target BS, the target BS being one of the BS and the secondary BS;
• generating a synchronization indication message, the synchronization indication message indicating one of the BS and the secondary BS;
• and
• transmitting the synchronization indication message to the UE via the transceiver to make the UE to receive a piece of reference time information of the target BS from one of the BS and the secondary BS.