Elevation PMI reporting on PUCCH

1. A method of wireless communication at a user equipment (UE), comprising:

receiving reference signals (RSs) from a base station, the base station comprising an antenna array including a long axis;

determining, based on the RSs, a first channel state information (CSI) indicator indicating a first precoding configuration of the base station, the first precoding configuration optimized to at least one of improve transmitted signal power, improve received signal power, or reduce interference in an elevation dimension, wherein the elevation dimension is parallel to the long axis of the antenna array of the base station;

determining, based on the RSs, a second CSI indicator indicating a second precoding configuration of the base station, the second precoding configuration optimized to at least one of improve the transmitted signal power, improve the received signal power, or reduce interference in an azimuth dimension, wherein the azimuth dimension is perpendicular to the long axis of the antenna array of the base station;

transmitting, to the base station, a first CSI report including at least the first CSI indicator and a channel quality indicator (CQI), wherein the first CSI report includes an E-PMI indicator and a data unit, and wherein the E-PMI indicator indicates whether the data unit carries an E-PMI or a spatial differential channel quality indicator (CQI); and

transmitting, to the base station, a second CSI report including the second CSI indicator, wherein the first CSI report and the second CSI report are transmitted alternately.

2. The method of claim 1 , wherein the first CSI indicator includes at least an elevation precoding matrix indicator (E-PMI), and wherein the second CSI indicator includes at least an azimuth precoding matrix indicator (A-PMI).

3. The method of claim 1 , wherein the first CSI report is transmitted to the base station on a physical uplink control channel (PUCCH).

4. The method of claim 1 , wherein a payload size of the first CSI report is less than or equal to 11 information bits.

5. The method of claim 1 , wherein the first CSI report further includes a rank indicator (RI).

6. The method of claim 5 , wherein the first CSI indicator includes a first elevation precoding matrix indicator (E-PMI).

7. The method of claim 1 , wherein the first CSI indicator includes a first elevation precoding matrix indicator (E-PMI), wherein the second CSI indicator includes a first azimuth precoding matrix indicator (A-PMI).

8. The method of claim 1 , wherein the first CSI report includes a channel quality indicator (CQI) that is determined based on the second CSI indicator and the first CSI indicator.

9. The method of claim 1 , wherein the first CSI indicator and the second CSI indicator are determined based on the RSs received in a same subframe.

10. The method of claim 1 , wherein the first CSI indicator and the second CSI indicator are determined based on the RSs received in different subframes.

11. The method of claim 1 , wherein the first CSI indicator includes a second elevation precoding matrix indicator (E-PMI) and the second CSI indicator includes a second azimuth precoding matrix indicator (A-PMI).

12. The method of claim 1 , wherein a physical uplink control channel (PUCCH) established between the UE and the base station has a plurality of resources corresponding to a plurality of values, and wherein the first CSI report is transmitted on a resource of the plurality of resources corresponding to a value of the first CSI indicator.

13. The method of claim 1 , wherein a payload size of the first CSI report is up to 13 information bits, wherein the first CSI report is transmitted on a physical uplink control channel (PUCCH) using PUCCH format 2, wherein the first CSI report includes the first CSI indicator, the second CSI indicator, and a channel quality indicator (CQI).

14. The method of claim 1 , wherein a payload size of the first CSI report is up to 22 information bits, wherein the first CSI report is transmitted on a physical uplink control channel (PUCCH) using PUCCH format 3, and wherein the first CSI report includes the first CSI indicator, the second CSI indicator, and a channel quality indicator (CQI).

15. An apparatus for wireless communication, the apparatus being a user equipment (UE), comprising:

means for receiving reference signals (RSs) from a base station, the base station comprising an antenna array including a long axis;

means for determining, based on the RSs, a first channel state information (CSI) indicator indicating a first precoding configuration of the base station, the first precoding configuration optimized to at least one of improve transmitted signal power, improve received signal power, or reduce interference in an elevation dimension, wherein the elevation dimension is parallel to the long axis of the antenna array of the base station;

means for determining, based on the RSs, a second CSI indicator indicating a second precoding configuration of the base station, the second precoding configuration optimized to at least one of improve the transmitted signal power, improve the received signal power, or reduce interference in an azimuth dimension, wherein the azimuth dimension is perpendicular to the long axis of the antenna array of the base station;

means for transmitting, to the base station, a first CSI report including at least the first CSI indicator and a channel quality indicator (CQI)), wherein the first CSI report includes an E-PMI indicator and a data unit, and wherein the E-PMI indicator indicates whether the data unit carries an E-PMI or a spatial differential channel quality indicator (CQI); and

means for transmitting, to the base station, a second CSI report including the second CSI indicator, wherein the first CSI report and the second CSI report are transmitted alternately.

16. The apparatus of claim 15 , wherein the first CSI indicator includes at least an elevation precoding matrix indicator (E-PMI), and wherein the second CSI indicator includes at least an azimuth precoding matrix indicator (A-PMI).

17. The apparatus of claim 15 , wherein the first CSI report is transmitted to the base station on a physical uplink control channel (PUCCH).

18. The apparatus of claim 15 , wherein a payload size of the first CSI report is less than or equal to 11 information bits.

19. The apparatus of claim 15 , wherein the first CSI report further includes a rank indicator (RI).

20. The apparatus of claim 19 , wherein the first CSI indicator includes a first elevation precoding matrix indicator (E-PMI).

21. An apparatus for wireless communication, the apparatus being a user equipment (UE), comprising:

a memory; and

at least one processor coupled to the memory and configured to:

receive reference signals (RSs) from a base station, the base station comprising an antenna array including a long axis;

determine, based on the RSs, a first channel state information (CSI) indicator indicating a first precoding configuration of the base station, the first precoding configuration optimized to at least one of improve transmitted signal power, improve received signal power, or reduce interference in an elevation dimension, wherein the elevation dimension is parallel to the long axis of the antenna array of the base station;

determine, based on the RSs, a second CSI indicator indicating a second precoding configuration of the base station, the second precoding configuration optimized to at least one of improve the transmitted signal power, improve the received signal power, or reduce interference in an azimuth dimension, wherein the azimuth dimension is perpendicular to the long axis of the antenna array of the base station;

transmit, to the base station, a first CSI report including at least the first CSI indicator and a channel quality indicator (CQI)), wherein the first CSI report includes an E-PMI indicator and a data unit, and wherein the E-PMI indicator indicates whether the data unit carries an E-PMI or a spatial differential channel quality indicator (CQI); and

transmit, to the base station, a second CSI report including the second CSI indicator, wherein the first CSI report and the second CSI report are transmitted alternately.

22. A non-transitory computer-readable medium storing computer executable code for wireless communication at a user equipment (UE), comprising code for:

receiving reference signals (RSs) from a base station, the base station comprising an antenna array including a long axis;

determining, based on the RSs, a first channel state information (CSI) indicator indicating a first precoding configuration of the base station, the first precoding configuration optimized to at least one of improve transmitted signal power, improve received signal power, or reduce interference in an elevation dimension, wherein the elevation dimension is parallel to the long axis of the antenna array of the base station;

determining, based on the RSs, a second CSI indicator indicating a second precoding configuration of the base station, the second precoding configuration optimized to at least one of improve the signal power or reduce interference in an azimuth dimension, wherein the azimuth dimension is perpendicular to the long axis of the antenna array of the base station;

transmitting, to the base station, a first CSI report including at least the first CSI indicator and a channel quality indicator (CQI)), wherein the first CSI report includes an E-PMI indicator and a data unit, and wherein the E-PMI indicator indicates whether the data unit carries an E-PMI or a spatial differential channel quality indicator (CQI); and

transmitting, to the base station, a second CSI report including the second CSI indicator, wherein the first CSI report and the second CSI report are transmitted alternately.