Communication system

To provide a communications system capable of resolving dropped data by achieving retransmission control without increasing the communications load, such as with ACK. Measurement data received by a transmitting station is stored in the form of a ring buffer after the assignment of a data number for each specific number of measurement data so as to enable the transmission as a packet, the packet is transmitted through one-way multicast communications to a receiving station, and when the existence of a dropped packet is detected by a receiving station that has received the transmission, a retransmission request is sent by retransmission requesting means to the transmitting station from the receiving station, and the transmitting station transmits to the receiving station, as a packet, the applicable data number and all of the measurement data for that data number.