COMMUNICATION DEVICE, COMMUNICATION SYSTEM, AND COMMUNICATION METHOD

A communication device is provided that readily increases the communication capacity of communication data based on a given protocol, without increasing the number of wired connections. The communication device sends and receives communication data through a communication line (21). A transmitting section (60) sends a communication signal (TS1) of modulated communication data (S1) to the communication line (21). A receiving section (50) demodulates a communication signal (TR1) received from the communication line (21) to obtain communication data (R1). The transmitting section (60) modulates the communication data (S1) on the basis of a frequency that varies dynamically within a predetermined transmission frequency band (F1). The receiving section (50) demodulates the received modulated communication signal corresponding to the transmission frequency band (F1), to obtain the communication data (R1).