Mobile station apparatuses are provided that receive downlink allocation information from a base station apparatus in a downlink control channel. Each mobile station apparatus performs demodulation, decoding, and cyclic redundancy check on the downlink shared channel in accordance with the downlink allocation information received. Each mobile station apparatus generates an acknowledgement or a non-acknowledgement in accordance with the result of the cyclic redundancy check. Each mobile station apparatus then selects the lowest number and the second lowest number of the numbers of the control channel elements in which the downlink allocation information is received. Based on the selected numbers, each mobile station apparatus 2 obtains a physical resource block (PRB), as well as a cyclic shift and an orthogonal code sequence in the time domain for each transmission antenna, and spreads the acknowledgement or the non-acknowledgement and the uplink pilot channel.