Method and apparatus for transmitting aperiodic sounding reference signal in wireless communication system

1. A method for transmitting an aperiodic sounding reference signal (SRS) by a periodic SRS by a user equipment (UE) in a wireless communication system, the method comprising:

receiving information on a power offset for the aperiodic SRS and common power information which is common to both the aperiodic SRS and a periodic SRS from a base station (BS) through a radio resource control (RRC) signaling;

determining a transmission power of the aperiodic SRS based on the information on the power offset for the aperiodic SRS and the common power information; and

transmitting the aperiodic SRS to the BS based on the transmission power of the aperiodic SRS,

wherein the information on the power offset for the aperiodic SRS is non-common information used for transmitting the aperiodic SRS but not the periodic SRS.

2. The method of claim 1 , wherein the transmission of the aperiodic SRS is triggered by the BS.

3. The method of claim 1 , wherein the information on the power offset for the aperiodic SRS has a length of 4 bits.

4. The method of claim 1 , wherein the transmission power of the aperiodic SRS is determined by an Equation below:

P SRS,c ( i )=min{ P CMAX,c ( i ), P SRS _ OFFSET,c ( m )+10 log 10 ( M SRS,c )+ P O _ PUSCH,c ( j )+α c ( j )·PL c +f c ( i )},

wherein i is a subframe index, c is a serving cell, P CMAX,c (i) is a pre-set transmission power of the UE, P SRS _ OFFSET,c (m) denotes the information on the power offset for the aperiodic SRS when m=1, M SRS,c is a bandwidth of the SRS transmission indicated by a number of resource blocks, P O _ PUSCH,c (j) is a parameter configured by a sum of P O _ NOMINAL _ PUSCH (j), a cell-specific component given by an higher layer, and P O _ UE _ PUSCH (j), a UE-specific component also given by the higher layer, α c (j) is a cell-specific parameter given by the higher layer, PL c is an estimated value of pathloss calculated by the UE, and f(i) indicates a current power control adjustment state with respect to a physical uplink shared channel (PUSCH).

5. The method of claim 1 , wherein the information on the power offset for the aperiodic SRS is determined by a UE-specific parameter informing a compensation value having a size of a transport block in power controlling.

6. The method of claim 5 , wherein the information on the power offset for the aperiodic SRS is determined in units of 1 dB within a range of [−3, 12] dB, when the value of the UE-specific parameter is 1.25.

7. The method of claim 5 , wherein the information on the power offset for the aperiodic SRS is determined in units of 1.5 dB within a range of [−10.5, 12] dB, when the value of the UE-specific parameter is 0.

8. A user equipment (UE) in a wireless communication system, the UE comprising:

a memory;

a transceiver; and

a processor, that is coupled to the memory and the transceiver, and that:

controls the transceiver to receive information on a power offset for an aperiodic sounding reference signal (SRS) and common power information which is common to both the aperiodic SRS and a periodic SRS from a base station (BS) through a radio resource control (RRC) signaling,

determines a transmission power of the aperiodic SRS based on the information on the power offset for the aperiodic SRS and the common power information, and

controls the transceiver to transmit the aperiodic SRS to the BS based on the transmission power of the aperiodic SRS,

wherein the information on the power offset for the aperiodic SRS is non-common information used for transmitting the aperiodic SRS but not the periodic SRS.

9. The UE of claim 8 , wherein the transmission of the aperiodic SRS is triggered by the BS.

10. The UE of claim 8 , wherein the information on the power offset for the aperiodic SRS has a length of 4 bits.

11. The UE of claim 8 , wherein the transmission power of the aperiodic SRS is determined by an Equation below:

P SRS,c ( i )=min{ P CMAX,c ( i ), P SRS _ OFFSET,c ( m )+10 log 10 ( M SRS,c )+ P O _ PUSCH,c ( j )+α c ( j )·PL c +f c ( i )},

wherein i is a subframe index, c is a serving cell, P CMAX,c (i) is a pre-set transmission power of the UE, P SRS _ OFFSET,c (m) denotes the information on the power offset for the aperiodic SRS when m=1, M SRS,c is a bandwidth of the SRS transmission indicated by a number of resource blocks, P O _ PUSCH,c (j) is a parameter configured by a sum of P O _ NOMINAL _ PUSCH (j), a cell-specific component given by an higher layer, and P O _ UE _ PUSCH (j), a UE-specific component also given by the higher layer, α c (j) is a cell-specific parameter given by the higher layer, PL c is an estimated value of pathloss calculated by the UE, and f(i) indicates a current power control adjustment state with respect to a physical uplink shared channel (PUSCH).

12. The UE of claim 8 , wherein the information on the power offset for the aperiodic SRS is determined by a UE-specific parameter informing a compensation value having a size of a transport block in power controlling.

13. The UE of claim 12 , wherein the information on the power offset for the aperiodic SRS is determined in units of 1 dB within a range of [−3, 12] dB, when the value of the UE-specific parameter is 1.25.

14. The UE of claim 12 , wherein the information on the power offset for the aperiodic SRS is determined in units of 1.5 dB within a range of [−10.5, 12] dB, when the value of the UE-specific parameter is 0.