There is provided user equipment for communicating with a base station in a mobile communication system including the base station and the user equipment, the user equipment including a PDCP layer processor provided with a storage unit that receives and stores a plurality of acknowledgement signals to be transmitted to the base station; and an RLC layer processor that transmits, to the PDCP layer processor, a signal transmission grant signal that indicates that transmission of an uplink signal is allowed, wherein, upon receiving the signal transmission grant signal, the PDCP layer processor transmits, to the RLC layer processor, an acknowledgement signal that is received most recently among the plurality of acknowledgement signals.