COMMUNICATION SYSTEM TECHNICAL FIELD [0001] The present invention relates to a communication system equipped with a transmission device that transmits data and a reception device that receives the data. BACKGROUND ART [0002] A communication system equipped with a transmission device that transmits data and a reception device that receives the data is known. In a communication system described in Patent Document 1 as one of communication systems of this type, a transmission device is equipped with a plurality of radio communication devices and a data decomposition/composition converter. In a like manner, a reception device is equipped with a plurality of radio communication devices and a data decomposition/composition converter. That is to say, this communication system is equipped with plural pairs of radio communication devices. [0003] The data decomposition/composition converter of the transmission device divides inputted data into a plurality of unit data, and sends each of the unit data to the radio communication device corresponding to the unit data. The respective radio communication devices accept the unit data sent by the data decomposition/composition converter, and transmit the accepted unit data to the radio communication devices of the reception device. [0004] The data decomposition/composition converter of the reception device converts the unit data received by the respective radio communication device to restore the data inputted into the transmission device. With such a communication system, it is possible to make a communication bandwidth broader (a communication speed higher) than in the case of transmitting and receiving data by using only one pair of communication radio devices. [0005] [Patent Document 1] Japanese Unexamined Patent Application Publication No. JP-A 2002-191073 [0006] In the communication system described above, it is impossible to change a communication bandwidth without changing the configuration of the data decomposition/composition converter. That is to say, there is a problem that it is impossible to easily change a communication bandwidth. SUMMARY [0007] Accordingly, an object of the present invention is to provide a communication system capable of solving the aforementioned problem, "it is impossible to easily change a communication bandwidth." [0008] In order to achieve the object, a communication system of an embodiment of the present invention is equipped with a plurality of transceiver devices each composed of a transmission device that transmits unit data obtained by decomposing data by a predetermined unit in order to transmit and receive the data and a reception device that receives the unit data transmitted by the transmission device. The plurality of transmission devices are connected in series. [0009] Furthermore, the transmission device is equipped with: a transmission device identification information storing means configured to store transmission device identification information for identifying the device itself; a unit data accepting means configured to accept the unit data from a front stage side; a transmission device identification information generating means configured to generate transmission device identification information for identifying any one of the plurality of transmission devices from in-unit-data information included in the accepted unit data, in accordance with a predetermined generation process; a unit data transmitting means configured to, in a case that the generated transmission device identification information corresponds to the stored transmission device identification information, transmit the accepted unit data to the reception device configuring the transceiver device together with the transmission device; and a unit data sending means configured to, in a case that the generated transmission device identification information does not correspond to the stored transmission device identification information, send the accepted unit data to a transmission device connected to a back stage side. [0010] Further, a transmission device of another embodiment of the present invention is equipped with: a transmission device identification information storing means configured to store transmission device identification information for identifying the device itself; a unit data accepting means configured to accept unit data obtained by decomposing data by a predetermined unit in order to transmit and receive the data; a transmission device identification information generating means configured to generate transmission device identification information from in-unit-data information included in the accepted unit data, in accordance with a predetermined generation process; a unit data transmitting means configured to, in a case that the generated transmission device identification information corresponds to the stored transmission device identification information, transmit the accepted unit data to a reception device configuring a transceiver device together with the device itself; and a unit data sending means configured to, in a case that the generated transmission device identification information does not correspond to the stored transmission device identification information, send the accepted unit data. [0011] Further, a communication method of another embodiment of the present invention is applied to a communication system which is equipped with a plurality of transceiver devices each composed of a transmission device that transmits unit data obtained by decomposing data by a predetermined unit in order to transmit and receive the data and a reception device that receives the unit data transmitted by the transmission device, and in which the plurality of transmission devices are connected in series. [0012] Furthermore, the communication method including: accepting the unit data from a front stage side, by the transmission device; generating transmission device identification information for identifying any one of the plurality of transmission devices from in-unit-data information included in the accepted unit data, in accordance with a predetermined generation process, by the transmission device; in a case that transmission device identification information stored by the transmission device in order to identify the device itself corresponds to the transmission device identification information generated by the transmission device, transmitting the accepted unit data to the reception device configuring the transceiver device together with the transmission device, by the transmission device; and in a case that transmission device identification information stored by the transmission device in order to identify the device itself does not correspond to the transmission device identification information generated by the transmission device, sending the accepted unit data to a transmission device connected to a back stage side, by the transmission device. [0013] Further, a computer program of another embodiment of the present invention is a computer program for causing a transmission device to realize: a unit data accepting means configured to accept unit data obtained by decomposing data by a predetermined unit in order to transmit and receive the data, from a front stage side; a transmission device identification information generating means configured to generate transmission device identification information from in-unit-data information included in the accepted unit data in accordance with a predetermined generation process; a unit data transmitting means configured to, in a case that transmission device identification information stored by the transmission device in order to identify the device itself corresponds to the generated transmission device identification information, transmit the accepted unit data to a reception device configuring a transceiver device together with the device itself; and a unit data sending means configured to, in a case that transmission device identification information stored by the transmission device in order to identify the device itself does not correspond to the generated transmission device identification information, send the accepted unit data to a back stage side. [0014] With the configurations as described above, the present invention makes it possible to easily change a communication bandwidth. BRIEF DESCRIPTION OF DRAWINGS [0015] Fig. 1 is a diagram showing a schematic configuration of a communication system according to a first exemplary embodiment of the present invention; Fig. 2 is a diagram showing a schematic configuration of a transmission device shown in Fig. 1; Fig. 3 is an explanation view conceptually showing header information included in a frame; Fig. 4 is a sequence diagram showing an operation of the communication system according to the first exemplary embodiment of the present invention; Fig. 5 is a diagram showing a schematic configuration of a communication device according to a second exemplary embodiment of the present invention; Fig. 6 is a sequence diagram showing an operation of a communication system according to the second exemplary embodiment of the present invention; and Fig. 7 is a block diagram schematically showing a function of a communication device according to a third exemplary embodiment of the present invention. EMBODIMENT [0016] Below, the respective exemplary embodiments of a communication system, a transmission device, a communication method and a computer program according to the present invention will be described with reference to Figs. 1 to 7. [0017]