Terminal apparatus and sequence assigning method

A system comprising a base station and a mobile station, wherein

• the base station comprises:
• a transmitter, which, in operation, transmits, to the mobile station, control information related to a sequence, the sequence being within one of a first group or a second group, the first group being divided into first subgroups each including a first number of one or more first sequences, the second group being divided into second subgroups each including a second number of one or more second sequences, the first sequences and the second sequences having different lengths, and the first number being different from the second number;
• and
• a receiver, which, in operation, receives a reference signal, which is transmitted from the mobile station, and
• the mobile station comprises:
• a receiver, which, in operation, receives, from the base station, the control information;
• and
• a transmitter, which, in operation, transmits, to the base station, the reference signal using the sequence based on the control information.