Method for transmitting and receiving control information and apparatus for same

1. A method for a first user equipment to control a transmission power in a wireless communication system supporting a direct communication between the first user equipment and a second user equipment, the method comprising:

receiving, by the first user equipment, a 2-bit power control command from a base station through a physical downlink control channel,

wherein, when the first user equipment is configured to perform the direct communication with the second user equipment, the 2-bit power control command indicates a value from among a first set of power control values, the first set of power control values consisting of {−3 dB, −1 dB, 0 dB, 1 dB}, and

wherein, when the first user equipment is configured to perform a communication with the base station, the 2-bit power control command indicates a value from among a second set of power control values, the second set of power control values consisting of {−1 dB, 0 dB, 1 dB, 3 dB}; and

adjusting, by the first user equipment, a transmission power using the value indicated by the 2-bit power control command,

wherein a mapping relationship between a value of the 2-bit power control command and the first and second sets of power control values is defined according to the following table:

the value of the power

the first set of power

the second set of power

control command

control values

control values

0

−3 dB

−1 dB  

1

−1 dB

0 dB

2

  0 dB

1 dB

3

  1 dB

 3 dB.

2. The method of claim 1 , wherein the adjusting of the transmission power includes:

adding the value indicated by the 2-bit power control command from among the first set of power control values or the second set of power control values to a preamble power.

3. The method of claim 1 , wherein the 2-bit power control command is received through a 2-bit TPC (transmit power control) field of downlink control information.

4. A first user equipment configured to control a transmission power in a wireless communication system supporting a direct communication between the first user equipment and a second user equipment, the first user equipment comprising:

a RF (Radio Frequency) module; and

a processor operably coupled with the RF module,

wherein the processor is configured to:

receive a 2-bit power control command from a base station through a control channel,

wherein, when the first user equipment is configured to perform the direct communication with the second user equipment, the 2-bit power control command indicates a value from among a first set of power control values, the first set of power control values consisting of {−3 dB, −1 dB, 0 dB, 1 dB}, and

wherein, when the first user equipment is configured to perform a communication with the base station, the 2-bit power control command indicates a value from among a second set of power control values, the second set of power control values consisting of {−1 dB, 0 dB, 1 dB, 3 dB}, and

adjust a transmission power using the value indicated by the 2-bit power control command,

wherein a mapping relationship between a value of the 2-bit power control command and the first and second sets of power control values is defined according to the following table:

the value of the power

the first set of power

the second set of power

control command

control values

control values

0

−3 dB

−1 dB  

1

−1 dB

0 dB

2

  0 dB

1 dB

3

  1 dB

 3 dB.

5. The first user equipment of claim 4 , wherein the adjusting of the transmission power includes adding the value indicated by the 2-bit power control command from among the first set of power control values or the second set of power control values to a preamble power.

6. The first user equipment of claim 4 , wherein the 2-bit power control command is received through a 2-bit TPC (transmit power control) field of downlink control information.

7. A method for a base station to transmit control information in a wireless communication system supporting a direct communication between a first user equipment and a second user equipment, the method comprising:

receiving channel status information from the first user equipment; and

transmitting a 2-bit power control command to the second user equipment through a control channel, the 2-bit power control command being decided based upon the channel status information,

wherein, when the first user equipment and the second user equipment are different from each other, the 2-bit power control command indicates a value from among a first set of power control values, the first set of power control values consisting of {−3 dB, −1 dB, 0 dB, 1 dB},

wherein, when the first user equipment and the second user equipment are the same, the 2-bit power control command indicates a value from among a second set of power control values, the second set of power control values consisting of {−1 dB, 0 dB, 1 dB, 3 dB}, and

wherein a mapping relationship between a value of the 2-bit power control command and the first and second sets of power control values is defined according to the following table:

the value of the power

the first set of power

the second set of power

control command

control values

control values

0

−3 dB

−1 dB  

1

−1 dB

0 dB

2

  0 dB

1 dB

3

  1 dB

 3 dB.

8. The method of claim 7 , wherein the channel status information includes at least one of reception power information of a reference signal, SINR (Signal to Interference plus Noise Ratio) information, and MCS (modulation and coding scheme) level information.

9. The method of claim 8 , wherein the SINR information includes at least one of difference information between a received SINR level and a target SINR of the first user equipment, a margin value for a minimum SINR level at which an MCS level is normally operated, the MCS level being currently used by the first user equipment, and a margin value for a minimum SINR level allowing a higher MCS level to be operated, the higher MCS level being higher than the MCS level currently used by the first user equipment.

10. The method of claim 8 , wherein the MCS level information includes target MCS level information, the target MCS level information being decided by a received SINR level of the first user equipment.

11. A base station configured to transmit control information to a first user equipment in a wireless communication system supporting a direct communication between the first user equipment and a second user equipment, the base station comprising:

a RF (Radio Frequency) module; and

a processor operably coupled with the RF module,

wherein the processor is configured to:

receive channel status information from the first user equipment; and

transmit a 2-bit power control command to the second user equipment through a control channel, the 2-bit power control command being decided based upon the channel status information,

wherein, when the first user equipment and the second user equipment are different from each other, the 2-bit power control command indicates a value from among a first set of power control values, the first set of power control values consisting of {−3 dB, −1 dB, 0 dB, 1 dB},

wherein, when the first user equipment and the second user equipment are the same, the 2-bit power control command indicates a value from among a second set of power control values, the second set of power control values consisting of {−1 dB, 0 dB, 1 dB, 3 dB}, and

wherein a mapping relationship between a value of the 2-bit power control command and the first and second sets of power control values is defined according to the following table:

the value of the power

the first set of power

the second set of power

control command

control values

control values

0

−3 dB

−1 dB  

1

−1 dB

0 dB

2

  0 dB

1 dB

3

  1 dB

 3 dB.

12. The base station of claim 11 , wherein the channel status information includes at least one of reception power information of a reference signal, SINR (Signal to Interference plus Noise Ratio) information, and MCS (modulation and coding scheme) level information.

13. The base station of claim 12 , wherein the SINR information includes at least one of difference information between a received SINR level and a target SINR of the first user equipment, a margin value for a minimum SINR level at which an MCS level is normally operated, the MCS level being currently used by the first user equipment, and a margin value for a minimum SINR level allowing a higher MCS level to be operated, the higher MCS level being higher than the MCS level currently used by the first user equipment.

14. The base station of claim 12 , wherein the MCS level information includes target MCS level information, the target MCS level information being decided by a received SINR level of the first user equipment.

15. The method of claim 7 , wherein the 2-bit power control command is transmitted through a 2-bit TPC (transmit power control) field of downlink control information.

16. The base station of claim 11 , wherein the 2-bit power control command is transmitted through a 2-bit TPC (transmit power control) field of downlink control information.