Patent ID: 7693173

Claim:
A communication system which performs data communication with a communication medium being shared among terminals for peer-to-peer communication, in a communication network comprising plural terminals, wherein no control station exists or, even when a control station exists, the control station does not control access to the communication medium, each of said terminals comprising: a time sync unit for establishing time synchronization with another terminal to which the terminal communicates, using time sync information for establishing time synchronization relating to an access timing to the communication medium; and a communication monitor unit for monitoring the time sync information that is transmitted and received in communication between other terminals; wherein the time sync information, which is obtained in the communication between other terminals by the communication monitor unit, is transmitted to a terminal different from said other terminals, in which no time synchronization has been established, wherein each terminal establishes time synchronization of the self-terminal on the basis of the time sync information obtained by the communication monitor unit, and wherein, when each terminal cannot obtain the time sync information which is exchanged in the communication between other terminals, the terminal transmits the time sync information to make a request of establishing time synchronization, when it starts transmission.