Data transmission system and data transmission method with retransmission of data

In a receiving side apparatus (150), reception quality of receive data is measured by a reception quality measurement section (157), receive data errors are detected by an error detection section (156), and when an error is detected a retransmission request signal and reception quality signal are transmitted multiplexed with transmit data by a transmit frame creation section (158). In a transmitting side apparatus (100), when a retransmission request signal is received a capacity necessary for demodulating data in a receiving side apparatus (150) is detected from a reception quality signal by a scheduling section (110), and data is retransmitted at that capacity. In a second embodiment, the receiving side apparatus determines a capacity necessary for demodulation and transmits a signal indicating said capacity to the transmitting side apparatus. By this means it is possible to reduce the number of data retransmissions during transmission and reception, and to improve transmission efficiency.