In a mobile communication system in which the same frequency channel f1 is used to perform communication of the same data between a moving mobile station 2 and a plurality of base stations 1a to 1d while sequentially establishing synchronization therebetween, subcarriers assigned to the base stations 1a to 1d are set so as to satisfy the following conditions. 1. The same frequency channel f1 is used for all the base stations. 2. Subcarriers do not overlap between adjacent base stations. 3. Adjacent subcarriers are not used in each subcarrier set. 4. All subcarriers within the frequency channel f1 (subcarriers having closest intervals which can hold an orthogonal relationship) are used.