Method and apparatus of transmitting sounding reference signal in multiple antenna system

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

receiving, by the UE, a cyclic shift parameter and a transmission comb parameter via a higher layer from a base station;

determining, by the UE, four cyclic shift values for each of the four antennas according to the cyclic shift parameter, wherein the four cyclic shift values are separated from each other by a constant interval of 2 to be {0,2,4,6} or {1,3,5,7};

determining, by the UE, transmission combs for each of the four antennas according to the transmission comb parameter;

generating, by the UE, four SRS sequences, which correspond to the four antennas respectively, based on the four cyclic shift values, respectively;

mapping, by the UE, the four SRS sequences to subcarriers based on the transmission combs; and

transmitting, by the UE, the four SRS sequences via the four antennas, respectively, to the base station,

wherein each of the transmission combs has a value of either 0 or 1, and

wherein a number of antennas, among the four antennas, for which a transmission comb has a value of 0 and a number of antennas, among the four antennas, for which a transmission comb has a value of 1 is same.

2. The method of claim 1 , wherein the cyclic shift parameter indicates a cyclic shift value for one antenna among the four antennas, and

wherein cyclic shift values for the remaining three antennas are derived from the cyclic shift value for the one antenna.

3. The method of claim 1 , wherein cyclic shift values for the antennas for which the transmission comb has a value of 0 are separated from each other by a maximum interval of 4, and

wherein cyclic shift values for the antennas for which the transmission comb has a value of 1 are separated from each other by a maximum interval of 4.

4. The method of claim 1 , further comprising:

receiving a power control parameter from the base station; and

setting a transmission power according to the power control parameter.

5. The method of claim 4 , wherein the transmission power is equally divided for each of the four SRS sequences.

6. The method of claim 4 , wherein the transmission power is separately set for each of the four SRS sequences.

7. The method of claim 6 , wherein the power control parameter is received for each of the four SRS sequences, and

wherein the power control parameter for each the four SRS sequences is indicated by an offset.

8. The method of claim 1 , wherein the four SRS sequences are transmitted in different SRS periods from each other.

9. The method of claim 1 , wherein two SRS sequences among the four SRS sequences are transmitted in a first SRS period, and

wherein the remaining two SRS sequences among the four SRS sequences are transmitted in a second SRS period.

10. The method of claim 9 , wherein a pair of antennas corresponding to the two SRS sequences transmitted in the first SRS period and a pair of antennas corresponding to the remaining two SRS sequences transmitted in the second SRS period are indicated by the base station.

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

a transceiver; and

a processor, coupled to the transceiver, that:

controls the transceiver to receive a cyclic shift parameter and a transmission comb parameter via a higher layer from a base station,

determines four cyclic shift values for each of four antennas according to the cyclic shift parameter, wherein the four cyclic shift values are separated from each other by a constant interval of 2 to be {0,2,4,6} or {1,3,5,7},

determines transmission combs for each of the four antennas according to the transmission comb parameter,

generates four sounding reference signal (SRS) sequences, which correspond to the four antennas respectively, based on the four cyclic shift values, respectively,

maps the four SRS sequences to subcarriers based on the transmission combs, and

controls the transceiver to transmit the four SRS sequences via the four antennas, respectively, to the base station,

wherein each of the transmission combs has a value of either 0 or 1, and

wherein a number of antennas, among the four antennas, for which a transmission comb has a value of 0 and a number of antennas, among the four antennas, for which a transmission comb has a value of 1 is same.

12. The UE of claim 11 , wherein the cyclic shift parameter indicates a cyclic shift value for one antenna among the four antennas, and

wherein cyclic shift values for the remaining three antennas are derived from the cyclic shift value for the one antenna.

13. The UE of claim 11 , wherein cyclic shift values for the antennas for which the transmission comb has a value of 0 are separated from each other by a maximum interval of 4, and

wherein cyclic shift values for the antennas for which the transmission comb has a value of 1 are separated from each other by a maximum interval of 4.

14. The UE of claim 11 , wherein the processor further:

controls the transceiver to receive a power control parameter from the base station; and

sets a transmission power according to the power control parameter.

15. The UE of claim 14 , wherein the transmission power is equally divided for each of the four SRS sequences.

16. The UE of claim 14 , wherein the transmission power is separately set for each of the four SRS sequences.

17. The UE of claim 16 , wherein the power control parameter is received for each of the four SRS sequences, and

wherein the power control parameter for each the four SRS sequences is indicated by an offset.

18. The UE of claim 11 , wherein the four SRS sequences are transmitted in different SRS periods from each other.

19. The UE of claim 11 , wherein two SRS sequences among the four SRS sequences are transmitted in a first SRS period, and

wherein the remaining two SRS sequences among the four SRS sequences are transmitted in a second SRS period.

20. The UE of claim 19 , wherein a pair of antennas corresponding to the two SRS sequences transmitted in the first SRS period and a pair of antennas corresponding to the remaining two SRS sequences transmitted in the second SRS period are indicated by the base station.