Communication apparatus, system control apparatus, train communication system, and communication method for controlling transmission of low latency frames and general frames

A communication method of a train communication system mounted on a train and including a system control apparatus that generates control frames and a communication apparatus that transfers the control frames, wherein

• the control frames include a general frame and a low latency frame that is required to be transferred with lower latency than the general frame, and when the communication apparatus preferentially transfers the low latency frame over the general frame, the communication method comprises:
• monitoring traffic of the low latency frame and, when the traffic is higher than or equal to a predetermined threshold, transmitting, to the system control apparatus, a first notification frame indicating that the traffic is higher than or equal to the predetermined threshold, wherein the monitoring the traffic of the low latency frame is performed by counting a number of low latency frames discarded due to an overflow of a buffer;
• transmitting, to the communication apparatus, a first priority setting frame that is a response to the first notification frame, the communication apparatus having a priority setting table set therein, the priority setting table indicating priority of the control frames and instructing a modification to the priority setting table such that a control frame having low priority among the control frames treated as the low latency frames is treated as the general frame;
• and
• modifying the priority setting table on the basis of the first priority setting frame such that a control frame having low priority among the control frames treated as the low latency frames is treated as the general frame.