A first mobile device including a connection terminal configured to electrically connect to a second mobile device, a variable impedance device connected to the connection terminal, the variable impedance device configured to vary an impedance, processing circuitry configured to determine a power line communication (PLC) mode between the first mobile device and the second mobile device to be one of a low-speed PLC mode or a high-speed PLC mode, and control the impedance of the variable impedance device according to the determined PLC mode, and a PLC modem configured to receive power from the second mobile device or communicate data with the second mobile device based on the determined PLC mode.