A radio performs random access by receiving control information and grouping a predetermined number of sequences that are generated from a plurality of base sequences into a plurality of groups by partitioning the predetermined number of sequences. At least one of the groups is associated with a first respective range of data amounts and a first respective range of reception qualities. Sequences generated from a common base sequence are arranged in an increasing order of respective cyclic shifts associated with the sequences. A sequence is randomly selected from a plurality of sequences contained in one group of the plurality of groups. A position at which the predetermined number of sequences are partitioned is determined based on the control information. A number of sequences contained in each of the plurality of groups varies in accordance with the control information.