Mobile devices, mobile systems and operating methods thereof

1. An operating method of a first mobile device, the operating method comprising:

receiving a host request from a second mobile device through a connection terminal in a first power line communication (PLC) mode, the first mobile device and the second mobile device respectively modulating signals according to different modulation schemes in the first PLC mode, the different modulation schemes including current modulation and voltage modulation;

changing a PLC mode between the first mobile device and the second mobile device from the first PLC mode to a second PLC mode including increasing an impedance of a signal line in response to the host request, the signal line being connected to the connection terminal, and the first mobile device and the second mobile device both modulating signals according to a common modulation scheme in the second PLC mode;

receiving data from the second mobile device in the second PLC mode; and

changing the PLC mode from the second PLC mode to the first PLC mode including decreasing the impedance of the signal line based on completion of the receiving the data.

2. The operating method of claim 1 , wherein the receiving data comprises:

receiving a current pulse toggling between a high current and a low current, through the connection terminal from the second mobile device.

3. The operating method of claim 1 , further comprising:

receiving power from the second mobile device in the first PLC mode.

4. The operating method of claim 3 , wherein the receiving power comprises:

maintaining a line current flowing through the signal line as a high current.

5. The operating method of claim 1 , further comprising:

receiving power from the second mobile device in the second PLC mode.

6. The operating method of claim 1 , wherein

the first PLC mode corresponds to a low speed PLC mode, and

the second PLC mode corresponds to a high speed PLC mode.

7. The operating method of claim 1 , wherein the host request is a voltage modulated signal.

8. The operating method of claim 1 , wherein the common modulation scheme is current modulation.

9. An operating method of a second mobile device, the operating method comprising:

transmitting a host request to a first mobile device through a connection terminal in a first power line communication (PLC) mode, the first mobile device and the second mobile device respectively modulating signals according to different modulation schemes in the first PLC mode, the different modulation schemes including current modulation and voltage modulation;

receiving a client response from the first mobile device as a response to the host request;

changing a PLC mode between the first mobile device and the second mobile device from the first PLC mode to a second PLC mode including increasing an impedance of a signal line based on the client response, the signal line being connected to the connection terminal, and the first mobile device and the second mobile device both modulating signals according to a common modulation scheme in the second PLC mode;

transmitting data to the first mobile device in the second PLC mode; and

changing the PLC mode from the second PLC mode to the first PLC mode including decreasing the impedance of the signal line based on completion of the transmitting the data.

10. The operating method of claim 9 , wherein the transmitting data comprises:

transmitting a current pulse toggling between a high current and a low current, through the connection terminal to the second mobile device.

11. The operating method of claim 9 , further comprising:

transmitting power to the first mobile device in the first PLC mode.

12. The operating method of claim 11 , wherein the transmitting power comprises:

maintaining a line current flowing through the signal line as a high current.

13. The operating method of claim 9 , further comprising:

transmitting power to the first mobile device in the second PLC mode.

14. The operating method of claim 9 , wherein

the first PLC mode corresponds to a low speed PLC mode, and

the second PLC mode corresponds to a high speed PLC mode.

15. A mobile system, comprising:

a first mobile device; and

a second mobile device, the first mobile device and the second mobile device being configured to transfer power and data with each other using power line communication (PLC), wherein

the first mobile device includes

a first connection terminal configured to electrically connect to the second mobile device,

a first variable impedance device connected to the first connection terminal, and

first processing circuitry configured to

send a client response to the second mobile device in response to receiving a host request from the second mobile device,

change a first PLC mode between the first mobile device and the second mobile device from a low-speed PLC mode to a high-speed PLC mode in response to sending the client response, the first mobile device and the second mobile device respectively modulating signals according to different modulation schemes in the low-speed PLC mode, the different modulation schemes including current modulation and voltage modulation, and the first mobile device and the second mobile device both modulating signals according to a common modulation scheme in the high-speed PLC mode, and

control an impedance of the first variable impedance device according to the first PLC mode, and

the second mobile device includes

a second connection terminal configured to electrically connect to the first mobile device,

a second variable impedance device connected to the second connection terminal, and

second processing circuitry configured to

receive the client response from the first mobile device in response to sending the host request,

change a second PLC mode from the low-speed PLC mode to the high-speed PLC mode in response to receiving the client response, and

control an impedance of the second variable impedance device according to the second PLC mode.

16. A first mobile device comprising:

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

send a client response to the second mobile device in response to receiving a host request from the second mobile device,

change a power line communication (PLC) mode between the first mobile device and the second mobile device from a first PLC mode to a second PLC mode in response to sending the client response, the first mobile device and the second mobile device respectively modulating signals according to different modulation schemes in the first PLC mode, the different modulation schemes including current modulation and voltage modulation, and the first mobile device and the second mobile device both modulating signals according to a common modulation scheme in the second PLC mode, and

control the impedance of the variable impedance device according to the 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 PLC mode.

17. The first mobile device of claim 16 , wherein

the first PLC mode corresponds to a low speed PLC mode, and

the second PLC mode corresponds to a high speed PLC mode.

18. The first mobile device of claim 16 , wherein

the PLC modem is configured to receive the power from the second mobile device in the first PLC mode; and

the impedance of the variable impedance device corresponds to a first impedance in the first PLC mode.

19. The first mobile device of claim 18 , wherein

the PLC modem is configured to communicate the data with the second mobile device in the second PLC mode; and

the impedance of the variable impedance device corresponds to a second impedance in the second PLC mode, the second impedance being higher than the first impedance.