Transmitter beamforming at base station with partial channel information and UE feedback

1. A method of obtaining a beamforming matrix, the method comprising:

inputting partial channel estimation derived from sounding reference signal (SRS) switching;

inputting precoding matrix indicator (PMI) feedback from a user equipment (UE); and

composing a beamforming matrix using the PMI feedback and partial channel estimation.

2. The method of claim 1 , wherein a first set of columns of the precoding matrix is obtained from the partial channel estimation and a second set of columns of the precoding matrix are obtained from the PMI feedback.

3. The method of claim 1 , wherein the PMI feedback is obtained by projecting a matrix indicated by the PMI feedback into a sub-space that is orthogonal to columns obtained from the partial channel estimation.

4. The method of claim 1 , comprising performing a singular value decomposition (SVD) for a channel matrix.

5. The method of claim 1 , comprising calculating a projection matrix using the PMI feedback.

6. The method of claim 1 , comprising calculating a residual matrix using the PMI feedback.

7. The method of claim 6 , comprising performing a singular value decomposition (SVD) for the residual matrix.

8. The method of claim 1 , comprising calculating a transformation matrix using of the PMI feedback.

9. The method of claim 1 , comprising selecting a first set of columns of a singular matrix in composing the precoding matrix.

10. A system for obtaining a beamforming matrix, the system comprising:

a processor; and

a memory storing non-transitory processor-executable instructions that, when executed by the processor, cause the processor to:

input partial channel estimation derived from sounding reference signal (SRS) switching;

input precoding matrix indicator (PMI) feedback;

compose a precoding matrix using the PMI feedback and partial channel estimation.

11. The system of claim 10 , wherein a first set of columns of the precoding matrix are obtained from the partial channel estimation and a second set of columns of the precoding matrix are obtained from the PMI feedback.

12. The system of claim 10 , wherein the PMI feedback is obtained by projecting a matrix indicated by the PMI feedback into a sub-space that is orthogonal to columns obtained from the partial channel estimation.

13. The system of claim 10 , comprising performing a singular value decomposition (SVD) for a channel matrix.

14. The system of claim 10 , comprising calculating a projection matrix using the PMI feedback.

15. The system of claim 10 , comprising calculating a residual matrix using the PMI feedback.

16. The system claim 15 , comprising performing a singular value decomposition (SVD) for the residual matrix.

17. The system of claim 10 , comprising calculating a transformation matrix using of the PMI feedback.

18. The system of claim 10 , comprising selecting a first set of columns of a singular matrix in composing the precoding matrix.

19. A method of composing a final beamforming matrix, the method comprising:

performing a first singular value decomposition (SVD) of a partial channel estimation matrix to obtain a first singular matrix, the partial channel estimation matrix being based on one or more uplink sounding reference signals (SRS) or one or more other reference signals;

obtaining a first beamforming matrix based on precoding matrix indicator (PMI) feedback;

calculating a projection of the first beamforming matrix to the first singular matrix;

performing, after removing the projection of the first beamforming matrix to the first singular matrix, a second SVD of a residual of the first beamforming matrix to obtain a second singular matrix; and

using, the first singular matrix and a first set of columns of the second singular matrix to compose the final beamforming matrix.

20. A non-transitory computer-readable medium comprising instructions for deriving a beamforming matrix, wherein execution of the instructions by one or more processors causes the one or more processors to carry out the steps of:

estimating a partial channel based on one or more received sounding reference signals (SRS);

deriving a first beamforming matrix based on a received precoding matrix indicator (PMI) feedback; and

deriving a second beamforming matrix based on the partial channel and the first beamforming matrix.