After receiving a packet data protocol (PDP) activation request signaling from a user equipment (UE), a base station checks whether to activate a local Internet protocol access (LIPA) function for the UE. If yes, the base station informs a core network (CN) for authentication and signaling control. If the user plane data from the UE is allowed to be transmitted via the LIPA, the base station assigns a private IP address to the UE; and the UE access internet via the base station. The base station determines whether user plane data from the UE passes through the CN; and the CN measures Internet service time provided to the UE. If all user plane data transmitted from the UE are allowed to be transmitted via the LIPA, the base station periodically transmits a data packet to the CN to maintain signaling link.