Abstract: Nodes (N1 to N3) include MTU length calculation sections (31 to 33) which multiply baud rates (D21 to D23) of communication parameters (D11 to D13) set based on results of negotiation with other nodes (N1 to N3) by a communication regulated time used in timer control for transmission/reception, and which calculate MTU lengths as maximum packet lengths of the packets based on the multiplication results so that transmission times of the packets for the destination nodes are equal to each other, and also include communication control sections (21 to 23) which divide data to be transmitted to destination nodes into packets having the calculated MTU length to transmit the packets.

Abstract: Respective nodes N1 to N3 only detect a carrier, and the node N3 sets a random time between a time after a certain period of time t1 and a time until a certain period of time t2 after the carrier of data D11 is gone as a waiting time so as to transmit data within this waiting time. The node N1 transmits ACK data D12 with respect to the data D11 to the node N12 before the certain period of time t1 after the carrier of the data D11 is gone. The node N3 detects the carrier of the ACK data D12 and again sets a random time after the certain period of time t1 until the certain period of time t2 to transmit the data.