A new-part acquiring unit acquires a part of a block generated by a block generating unit, as a new part to be contained in a packet. A retransmission-part acquiring unit acquires a part of a block corresponding to a NAK as a retransmission part to be contained in a packet among blocks held in a retransmission buffer unit. An encoding unit groups a new part acquired by the new-part acquiring unit and a retransmission part acquired by the retransmission-part acquiring unit, and generates a packet. A modulating unit modulates a packet output from the encoding unit. A wireless processing unit performs a predetermined wireless transmission process to a modulated packet, and transmits a processed modulated packet via an antenna.