MULTICAST TRANSMISSION TERMINAL, MULTICAST RECEPTION TERMINAL, MULTICAST SYSTEM, PROGRAM, MULTICAST TRANSMISSION METHOD, AND MULTICAST RECEPTION METHOD

PROBLEM TO BE SOLVED: To enable acknowledgement with ensured real-timeness in multicasting to suppress the degradation of communication quality.SOLUTION: ACK receiving units 106-1 to 106-n receive at least one acknowledgment transmitted with a center frequency that is different from a center frequency for the multicast transmission and with a bandwidth that is narrower than the bandwidth for the multicast transmission. A discovery unit 108 finds receiving terminals that are destinations of the multicast transmission. An allocation unit 109 allocates a center frequency for each of the receiving terminals to use for transmission of its acknowledgment depending on the number of the receiving terminals found by the discovery unit 108 so that at least one receiving terminal is allocated a center frequency that is different from the center frequency for the multicast transmission, and generates an allocation list indicating these allocations. A notification control unit 1041 causes a data transmission unit 105 to multicast transmit the allocation list generated by the allocation unit 109.