Frequency domain channel state information (CSI) compression

1. A base station (BS), comprising:

at least one processor configured to:

receiving a CSI report, wherein the CSI report includes a channel quality indicator (CQI), a rank indicator (RI), and a precoding matrix indicator (PMI);

constructing a precoding matrix based on a linear combination of a plurality of mutually orthogonal digital Fourier transformation (DFT) spatial beams;

determining a number of bits for the PMI of the precoding matrix;

determining a space frequency matrix based, at least in part, on the number of bits for the PMI and the precoding matrix;

compressing the space frequency matrix; and

determining a compressed PMI based, at least in part, on the space frequency matrix; and

radio front end circuitry configured to transmit the compressed PMI over a wireless network.

2. The BS of claim 1 , wherein the compressing the space frequency matrix includes using linear transformation.

3. The BS of claim 1 , wherein the compressing the space frequency matrix includes using frequency domain compression, wherein the frequency domain compression comprises multiplying the space frequency matrix with a complex number, the complex number having an arbitrary phase and unit amplitude.

4. The BS of claim 1 , wherein the compressing the space frequency matrix includes using time domain compression, wherein the time domain compression comprises deriving a first set of time domain coefficients from a second set of time domain coefficients.

5. The BS of claim 1 , wherein the radio front end circuitry includes a radio frequency integrated circuit (RFIC) configured to transmit the compressed PMI.

6. The BS of claim 1 , wherein the CSI report comprises a first part and a second part, the first part having a fixed payload size.

7. The BS of claim 6 , wherein a payload size of the second part depends on content of the first part.

8. A method of operating a base station (BS), comprising:

receiving a CSI report, wherein the CSI report includes a channel quality indicator (CQI), a rank indicator (RI), and a precoding matrix indicator (PMI);

constructing a precoding matrix based on a linear combination of a plurality of mutually orthogonal digital Fourier transformation (DFT) spatial beams;

determining a number of bits for the PMI of the precoding matrix;

determining a space frequency matrix based, at least in part, on the number of bits for the PMI and the precoding matrix;

compressing the space frequency matrix;

determining a compressed PMI based, at least in part, on the space frequency matrix; and

transmitting the compressed PMI over a wireless network.

9. The method of claim 8 , wherein the compressing the space frequency matrix includes using linear transformation.

10. The method of claim 8 , wherein the compressing the space frequency matrix includes using frequency domain compression, wherein the frequency domain compression comprises multiplying the space frequency matrix with a complex number, the complex number having an arbitrary phase and unit amplitude.

11. The method of claim 8 , wherein the compressing the space frequency matrix includes using time domain compression, wherein the time domain compression comprises deriving a first set of time domain coefficients from a second set of time domain coefficients.

12. The method of claim 8 , wherein the CSI report comprises a first part and a second part, the first part having a fixed payload size.

13. The method of claim 12 , wherein the first part reports indexes of basis vectors in linear combinations.

14. The method of claim 12 , wherein a payload size of the second part depends on content of the first part.

15. One or more non-transitory computer-readable media (CRM) having computer instructions stored thereon that, when executed by by one or more processors, cause the one or more processors to:

receive a CSI report, wherein the CSI report includes a channel quality indicator (CQI), a rank indicator (RI), and a precoding matrix indicator (PMI);

construct a precoding matrix based on a linear combination of a plurality of mutually orthogonal digital Fourier transformation (DFT) spatial beams;

determine a number of bits for the PMI of the precoding matrix;

determine a space frequency matrix based, at least in part, on the number of bits for the PMI and the precoding matrix;

compress the space frequency matrix;

determine a compressed PMI based, at least in part, on the space frequency matrix; and

transmit the compressed PMI over a wireless network.

16. The one or more non-transitory CRM of claim 15 , wherein the computer instructions further cause the one or more processors to compress the space frequency matrix, the compressing including using linear transformation.

17. The one or more non-transitory CRM of claim 15 , wherein the computer instructions further cause the one or more processors to compress the space frequency matrix, the compressing including using frequency domain compression, wherein the frequency domain compression comprises multiplying the space frequency matrix with a complex number, the complex number having an arbitrary phase and unit amplitude.

18. The one or more non-transitory CRM of claim 15 , wherein the computer instructions further cause the one or more processors to compress the space frequency matrix, the compressing including using time domain compression, wherein the time domain compression comprises deriving a first set of time domain coefficients from a second set of time domain coefficients.

19. The one or more non-transitory CRM of claim 15 , wherein the CSI report comprises a first part and a second part, the first part having a fixed payload size.

20. The one or more non-transitory CRM of claim 19 , wherein a payload size of the second part depends on content of the first part.