The present invention can improve a reception quality of mobile stations and utilize radio resources effectively, by resolving the problem caused when the conventional multicast communications system. The present invention relates to a radio communications system for transmitting same data to a plurality of cells via at least one base station and performing a soft combining or a selective combining on the same data received by a mobile station. The radio communications system includes a controlling unit configured to set up a cycle at which synchronization processing on transmission timing of the same data among the plurality of cells is performed, or an accuracy by which the synchronization processing is performed, for each control apparatus which performs the synchronization processing.