A base station of a mobile device's movement destination receives a diversity handover (DHO) start notification from a mobile station at the beginning of a DHO. This notifies a radio network control apparatus and an instruction is issued to the base station to add a radio link. The time for transmitting data to a mobile device is determined, the transmission timing is rounded up, and the data is transmitted from the base station to a mobile device. In this event, a search window's timing for receiving data from the mobile device is shifted with the round up of the transmission timing; and therefore the width of the search window is enlarged. The movement destination's base station also receives a DHO complete notification from a mobile device at the completion of the DHO. The movement destination's base station changes the width of the width-enlarged window back to the original width.