Patent ID: 7586954

Claim:
A communication system in which a plurality of terminals are connected to each other through a transmission path so as to establish a network, each of the terminals comprising: a transmitting section for transmitting a frame; a receiving section for receiving the frame; clock means for generating a local time inherent to the terminal; clock synchronizing means for calculating a reception time of the frame, an estimated reception time of the frame, and an initial value of the local time, and for adjusting a clock; storing means for storing a communication schedule that defines a transmission and reception procedure of the frame within a communication cycle of a given period and setting information related to the communication schedule; and communication control means for controlling the communication operation of the terminal by the transmitting section and the receiving section on the basis of the local time and the communication schedule, wherein the communication control means in each of the terminals operates as a leading terminal that leads the communication schedule in a case where the terminal first starts the communication among the plurality of terminals, and operates as an integration terminal that conducts the integration into the network in other cases in a startup phase where the network is established, wherein in a case where the terminal is the leading terminal, the communication control means in each of the terminals transmits the sub-startup frame in the same communication cycle at a timing when the estimated reception time can be calculated due to the startup frame for the global time reference and the communication schedule stored in the integration terminal at a transmission timing defined by the communication schedule in advance, after starting the communication schedule with the local time as the global time used on the network, wherein in a case where the terminal is the integration terminal, the communication control means in each of the terminals receives the startup frame and the sub-startup frame, and starts the communication schedule by the local time according to an initial value of the local time calculated from the reception time of the startup frame, the reception time of the sub-startup frame, and the estimated reception time, and wherein the clock synchronizing means calculates the initial value of the local time according to the reception time of the startup frame, and the reception time and the estimated reception time of the sub-startup frame.