A radio network controller (206, 208, 400) providing, at predetermined time intervals, a base station (210, 212, 214, 216) capable of communicating with a mobile terminal through a radio link with an original of data to be transmitted to the mobile terminal by the base station, the radio network controller comprising: division means for dividing the original of the data into a plurality of data portions of a predetermined data size; and means for providing the base station with the plurality of data portions a predetermined number at a time at the predetermined time intervals; characterized by further comprising means (410, 406) for reproviding the base station with said plurality of data portions for retransmitting all the plurality of data portions to the mobile terminal, in response to not receiving a response signal within a predetermined period due to an IP transmission line included in a communications channel between the radio network controller and the mobile terminal through the base station, the response signal being transmitted by the mobile terminal in response to data, in which a polling bit is set, contained in one of the plurality of data portions; measuring means (412, 406, 402, 414) for measuring a response period of a signal in the communications channel between the radio network controller and the mobile terminal through the base station by transmitting a time stamp request message to the mobile terminal, receiving a time stamp response message transmitted from the mobile terminal in response to reception of the time stamp request message, and determining a reception time of the time stamp response message on which the response period is based; and means for changing the predetermined number to a greater value in response to the response period measured by the measuring means being more than a threshold value. division means for dividing the original of the data into a plurality of data portions of a predetermined data size; and means for providing the base station with the plurality of data portions a predetermined number at a time at the predetermined time intervals; characterized by further comprising means (410, 406) for reproviding the base station with said plurality of data portions for retransmitting all the plurality of data portions to the mobile terminal, in response to not receiving a response signal within a predetermined period due to an IP transmission line included in a communications channel between the radio network controller and the mobile terminal through the base station, the response signal being transmitted by the mobile terminal in response to data, in which a polling bit is set, contained in one of the plurality of data portions; measuring means (412, 406, 402, 414) for measuring a response period of a signal in the communications channel between the radio network controller and the mobile terminal through the base station by transmitting a time stamp request message to the mobile terminal, receiving a time stamp response message transmitted from the mobile terminal in response to reception of the time stamp request message, and determining a reception time of the time stamp response message on which the response period is based; and means for changing the predetermined number to a greater value in response to the response period measured by the measuring means being more than a threshold value.