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 user equipment (UE) in a wireless communication system, the method comprising:

receiving separate periodic and aperiodic SRS power offset parameters for a periodic SRS and an aperiodic SRS, respectively, from a base station (BS) through a radio resource control (RRC) signaling;

receiving common parameters for both the periodic SRS and the aperiodic SRS from the BS through the RRC signaling;

setting transmission powers of the periodic SRS and the aperiodic SRS based on the periodic and aperiodic SRS power offset parameters, respectively, and the common parameters; and

transmitting the periodic SRS and the aperiodic SRS to the BS based on the transmission powers of the periodic SRS and the aperiodic SRS, respectively,

wherein the periodic SRS power offset parameters are non-common parameters used for transmitting the periodic SRS but not the aperiodic SRS, and the aperiodic SRS power offset parameters are non-common parameters used for transmitting the aperiodic SRS but not the periodic SRS.

2. The method of claim 1 , wherein at least one of the periodic SRS power offset parameters and at least one of the aperiodic SRS power offset parameters have a length of 4 bits, respectively.

3. The method of claim 1 , wherein the transmission power of the periodic SRS and the transmission power of the aperiodic SRS, are determined by 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 pre-set transmission power of the UE, P SRS _ OFFSET,c (m) denotes one of the periodic SRS power offset parameters when m=0 and P SRS _ OFFSET,c (m) denotes one of the aperiodic SRS power offset parameters when m=1, M SRS,c is a bandwidth of the SRS transmission indicated by the number of resource blocks, P O _ PUSCH,c (j) is a parameter configured by the 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).

4. The method of claim 1 , wherein at least one of the periodic SRS power offset parameters and at least one of the aperiodic SRS power offset parameters are determined by a UE-specified parameter indicating a compensation value having a size of a transport block in power controlling.

5. The method of claim 4 , wherein when the value of the UE-specific parameter is 1.25, the at least one of the periodic and aperiodic SRS power offset parameters is determined in units of 1 dB within the range of [−3, 12] dB.

6. The method of claim 4 , wherein when the value of the UE-specific parameter is 0, the periodic and aperiodic SRS power offset parameters is determined in units of 1.5 dB within the range of [−10.5, 12] dB.

7. The method of claim 1 , wherein the transmission of the aperiodic SRS is triggered by a triggering message transmitted from the BS.

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

a radio frequency (RF) unit; and

a processor, coupled to the RF unit, and configured to:

receive separate periodic and aperiodic sounding reference signal (SRS) power offset parameters for a periodic SRS and an aperiodic SRS, respectively, from a base station (BS) through a radio resource control (RRC) signaling;

receive common parameters for both the periodic SRS and the aperiodic SRS from the BS through the RRC signaling;

set transmission powers of the periodic SRS and the aperiodic SRS based on the periodic and aperiodic SRS power offset parameters, respectively, and the common parameters; and

transmit the periodic SRS and the aperiodic SRS to the BS based on the transmission powers of the periodic SRS and the aperiodic SRS, respectively,

wherein the periodic SRS power offset parameters are non-common parameters used for transmitting the periodic SRS but not the aperiodic SRS, and the aperiodic SRS power offset parameters are non-common parameters used for transmitting the aperiodic SRS but not the periodic SRS.

9. The UE of claim 8 , wherein at least one of the periodic SRS power offset parameters and at least one of the aperiodic SRS power offset parameters have a length of 4 bits, respectively.

10. The UE of claim 8 , wherein the transmission power of the periodic SRS and the transmission power of the aperiodic SRS are determined by 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 pre-set transmission power of the UE, P SRS _ OFFSET,c (m) denotes one of the periodic SRS power offset parameters when m=0 and P SRS _ OFFSET,c (m) denotes one of the aperiodic SRS power offset parameters when m=1, M SRS,c is a bandwidth of the SRS transmission indicated by the number of resource blocks, P O _ PUSCH,c (j) is a parameter configured by the 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 upper 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).

11. The UE of claim 8 , wherein at least one of the periodic SRS power offset parameters and at least one of the aperiodic SRS power offset parameters are determined by a UE-specified parameter indicating a compensation value having a size of a transport block in power controlling.

12. The UE of claim 11 , wherein when the value of the UE-specific parameter is 1.25, the at least one of the periodic and aperiodic SRS power offset parameters is determined in units of 1 dB within the range of [−3, 12] dB.

13. The UE of claim 11 , wherein when the value of the UE-specific parameter is 0, the at least one of the periodic and aperiodic SRS power offset parameters is determined in units of 1.5 dB within the range of [−10.5, 12] dB.