A radio communication system comprising a reception device, a transmission device for transmitting a radio signal to the reception device and a relay station wherein the transmission device comprises: a generation unit (14, 15) configured to generate a plurality of data blocks, and a transmission unit configured to transmit the plurality of data blocks to the reception device through a radio transmission path (Link-2), and simultaneously transmit the plurality of data blocks to the relay station through a first radio transmission link (Link-1), the relay station is configured: to receive the plurality of data blocks transmitted through the first radio transmission link (Link-1) by the transmission device, to generate a grouped data block comprising an information bit of each of the plurality of data blocks and a generated parity bit, and to transmit the grouped data block to the reception device through a second radio transmission link (Link-3), and the reception device is configured to receive the plurality of data blocks transmitted through the radio transmission path (Link-2) from the transmission unit, and the grouped data block transmitted through the second radio transmission link (Link-3) from the relay station, wherein the reception device comprises a combination unit configured to combine corresponding data between the plurality of received data blocks and the grouped data block, and wherein, when the transmission device knows a transmission quality of the radio transmission path (Link-2) but does not know a transmission quality of the second radio transmission link (Link-3) and when the relay station knows the transmission quality of the radio transmission path (Link-2) and the second transmission link (Link-3), then: a rate of each data block in the grouped data block is determined by the relay station based on the channel quality of the radio transmission path (Link-2) and the second transmission link (Link-3) using mapping data that describes a relationship between a received block mutual information and a block error rate for each data block so that a highest block error rate in block error rates obtained after combining data by the combination unit on each data block is determined as a lowest rate, and a modulation and coding scheme for the grouped data block is determined so that a block error rate of a grouped data block can be equal to or smaller than a predetermined threshold. a generation unit (14, 15) configured to generate a plurality of data blocks, and a transmission unit configured to transmit the plurality of data blocks to the reception device through a radio transmission path (Link-2), and simultaneously transmit the plurality of data blocks to the relay station through a first radio transmission link (Link-1), to receive the plurality of data blocks transmitted through the first radio transmission link (Link-1) by the transmission device, to generate a grouped data block comprising an information bit of each of the plurality of data blocks and a generated parity bit, and to transmit the grouped data block to the reception device through a second radio transmission link (Link-3), and a rate of each data block in the grouped data block is determined by the relay station based on the channel quality of the radio transmission path (Link-2) and the second transmission link (Link-3) using mapping data that describes a relationship between a received block mutual information and a block error rate for each data block so that a highest block error rate in block error rates obtained after combining data by the combination unit on each data block is determined as a lowest rate, and a modulation and coding scheme for the grouped data block is determined so that a block error rate of a grouped data block can be equal to or smaller than a predetermined threshold.