Communication system

Abstract

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.

Description

technical field [0001] The present invention relates to a communication system capable of realizing retransmission control without increasing communication load and eliminating data shortage. Background technique [0002] Time-series data communication is performed by connecting temperature regulators, measuring instruments, control devices such as PLCs, and monitoring devices (PCs, servers), etc. via a network. This kind of data communication is to communicate various processing state quantities, but there are various forms in its manner. For example, when sending data measured by a measuring device to other devices, using a connection-type communication format such as TCP / IP allows sending without unexpected failure. This is a technique of adding a number to a packet to be sent (including measurement data for a certain period) and making the sending side resend the packet for which no ACK (Acknowledge: Receipt Acknowledgment) has been received from the receiving side so t...

AI Technical Summary

Problems solved by technology

[0004] When the measured data must be sent to the receiving side, the above-mentioned mechanism is necessary, but in the case of data (real-time data, etc.) that have passed a certain amount of time, there is the following problem: due to the old Data resending at the expense of the latest data transfer

[0013] However, since there are many recipients of data in multicast communication, bidirectional exchange cannot be performed, and it is not suitable for applications that require reliability in communication.

In addition, there is a problem that the communication load increases in so-called TCP / IP two-way communication.

Furthermore, when ACK is used as retransmission control for the same period, there is a problem that ACKs transmitted from multiple receiving sides are concentrated on the sending side (ACK-Implosion)

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