Method and apparatus for weight factor matrix determination for beam forming

1. A weight factor matrix determining method for beamforming, comprising:

determining a first transmission power for a first terminal being a target terminal and a second transmission power for a plurality of second terminals other than the target terminal;

calculating an Eigen vector with an Eigen value for a ratio of the first and second transmission powers; and

determining a weight factor matrix in a serving base station, with the calculated Eigen vector,

wherein in the calculating of an Eigen vector, the Eigen vector is calculated according to a level of the Eigen value,

wherein the determining of the first transmission power sequentially determines the weight factor matrix according to a sequence of the Eigen vector, the sequence of the Eigen vector being a level sequence of the Eigen value.

2. The weight factor matrix determining method according to claim 1 ,

wherein the number of calculated Eigen vectors is determined as the number of streams transmitted from the serving base station.

3. The weight factor matrix determining method according to claim 1 , wherein the first transmission power is determined using the weight factor matrix and a first channel response matrix between the serving base station and first terminal.

4. The weight factor matrix determining method according to claim 3 , wherein the first channel response matrix is estimated using a sounding symbol shared by the serving base station and the first terminal.

5. The weight factor matrix determining method according to claim 3 , wherein the first channel response matrix is determined with a codeword corresponding to a codeword which is fed back from the first terminal among a plurality of codewords shared by the serving base station and the first terminal.

6. The weight factor matrix determining method according to claim 3 , wherein the first channel response matrix is determined and provided by the first terminal.

7. The weight factor matrix determining method according to claim 1 , wherein the first transmission power is determined using a trace value for multiplication of a conjugate transpose matrix of the weight factor matrix, a conjugate matrix of a first channel response matrix between the serving base station and first terminal, the first channel response matrix, and the weight factor matrix.

8. The weight factor matrix determining method according to claim 1 , wherein the second transmission power is determined using the weight factor matrix and a second channel response matrix between the serving base station and second terminal.

9. The weight factor matrix determining method according to claim 1 , wherein the second transmission power is determined using a trace value for multiplication of a conjugate transpose matrix of the weight factor matrix, a sum of results which are obtained by multiplying a conjugate matrix of a second channel response matrix between the serving base station and the second terminal and the second channel response matrix, and the weight factor matrix.

10. The weight factor matrix determining method according to claim 1 , wherein,

the second transmission power is determined using a sum of results which are obtained by multiplying a conjugate matrix of a second channel response matrix between the serving base station and second terminal and the second channel response matrix, and

the sum of results, which are obtained by multiplying the conjugate matrix of the second channel response matrix between the serving base station and the second terminal and the second channel response matrix, is defined as a value which is obtained by subtracting multiplication of a conjugate matrix of a first channel response matrix between the serving base station and first terminal and the first channel response matrix from a correlation matrix of uplink signals respectively received from the first and second terminals.

11. The weight factor matrix determining method according to claim 1 , wherein the Eigen value is calculated using the ratio of the first and second transmission powers and white noise in a downlink channel.

12. A weight factor matrix determining apparatus for beamforming, comprising:

a transmission power determiner configured to determine a plurality of transmission powers for respective terminals;

an Eigen value calculator configured to calculate an Eigen value, defined as a ratio of first and second transmission powers, by using the first transmission power for the first terminal being a target terminal and the second transmission power for the second terminal among the transmission powers, and calculating an Eigen vector corresponding to the Eigen value; and

a weight factor matrix determiner configured to determine a weight factor matrix with the calculated Eigen vector,

wherein the weight factor matrix determiner determines the number of calculated Eigen vectors, which will be used for the weight factor matrix, as the number of streams transmitted from the serving base station,

wherein when a plurality of Eigen vectors are calculated by the Eigen value calculator, the weight factor matrix determiner determines the weight factor matrix by sequentially using a certain number of Eigen vectors among the plurality of Eigen vectors in descending sequence of Eigen value.

13. The weight factor matrix determining apparatus according to claim 12 , wherein the transmission power determiner determines the first transmission power by using the weight factor matrix and a first channel response matrix between a serving base station and the first terminal.

14. The weight factor matrix determining apparatus according to claim 13 , wherein the first channel response matrix is determined and provided by the first terminal, estimated using a sounding symbol shared by the serving base station and the first terminal, or determined with a codeword corresponding to a codeword which is transmitted from the first terminal among a plurality of codewords shared by the serving base station and the first terminal.

15. The weight factor matrix determining apparatus according to claim 12 , wherein the transmission power determiner determines the first transmission power by using a trace value for multiplication of a conjugate transpose matrix of the weight factor matrix, a conjugate matrix of a first channel response matrix between the serving base station and first terminal, the first channel response matrix, and the weight factor matrix.

16. The weight factor matrix determining apparatus according to claim 12 , wherein the transmission power determiner determines the second transmission power by using the weight factor matrix and a second channel response matrix between the serving base station and second terminal.

17. The weight factor matrix determining apparatus according to claim 12 , wherein the transmission power determiner determines the second transmission power by using a trace value for multiplication of a conjugate transpose matrix of the weight factor matrix, a sum of results which are obtained by multiplying a conjugate matrix of a second channel response matrix between the serving base station and the second terminal and the second channel response matrix, and the weight factor matrix.

18. The weight factor matrix determining apparatus according to claim 12 , wherein,

the transmission power determiner determines the second transmission power by using a sum of results which are obtained by multiplying a conjugate matrix of a second channel response matrix between the serving base station and second terminal and the second channel response matrix, and

the sum of results, which are obtained by multiplying the conjugate matrix of the second channel response matrix between the serving base station and the second terminal and the second channel response matrix, is calculated using a value which is obtained by subtracting multiplication of a conjugate matrix of a first channel response matrix between the serving base station and first terminal and the first channel response matrix from a correlation matrix of uplink signals respectively transmitted from the first and second terminals.

19. The weight factor matrix determining apparatus according to claim 12 , wherein the Eigen value calculator calculates the Eigen value by using the ratio of the first and second transmission powers and white noise in a downlink channel.