Patent ID: 8260134

Claim:
A synchronized code division multiplexing communication method that utilizes an access network system including, a common transmission line provided with an optical splitter that branches one input signal to N outputs, N being an integer of at least two, and combines N input signals and outputs one signal, a central office coupled to another end of the common transmission line, N branch transmission lines which are formed by branching by the optical splitter, and first to N-th optical network units that are coupled to the respective branch transmission lines, the access network system performing 1-to-N communication by code division multiplexing between the central office and the first to N-th optical network units, the synchronized code division multiplexing communication method comprising, at the central office: a presence check step of performing a check of device terminals that are connected to the central office and device terminals that are not connected, on the basis of whether or not the central office receives response signals returned from the first to N-th optical network units; a ranging processing step of performing a transmission timing adjustment for the optical network units that are connected, on the basis of response times determined by the times at which the response signals are received by the central office; a connection state acquisition step of performing a verification of whether or not all of the first to N-th optical network units are in the state of being connected with the central office and a verification of whether or not an optical network unit that was not connected at the presence check step has come into the state of being connected since completion of the presence check step; and a transmission frame switching step of, if all of the first to N-th optical network units are in the state of being connected with the central office, switching the network system to communicate with transmission frames that do not include a discovery time interval, if an optical network unit that has not been connected has come into the state of being connected since completion of the presence check step, performing communication with transmission frames that include the discovery time interval, and if it has not been verified that an optical network unit that was confirmed as not being connected in the presence check step has come into the state of being connected since completion of the presence check step, performing communication with transmission frames that do not include the discovery time interval.