Uplink transmit diversity and precoding

1. A method of wireless communications, comprising:

identifying, by a user equipment (UE) comprising at least two antennas, an uplink transmission of at least one stream as using one of cyclic prefix orthogonal frequency division multiplexing or discrete Fourier transform spread orthogonal frequency division multiplexing;

applying, by the UE, a precoding matrix to the at least one identified stream, wherein the precoding matrix changes over time according to a precoding cycling pattern, wherein applying the precoding matrix to the at least one identified stream comprises applying the precoding matrix to a sounding reference signal (SRS), wherein the precoding matrix for the SRS follows the precoding cycling pattern; and

transmitting, by the UE, the at least one identified stream from the at least two antennas according to the applied precoding matrix.

2. The method of claim 1 , wherein the precoding cycling pattern changes the precoding matrix on a symbol basis.

3. The method of claim 1 , wherein the precoding cycling pattern changes the precoding matrix on a subframe basis.

4. The method of claim 1 , further comprising receiving an indication from a base station indicating a preferred precoding matrix selected from the precoding cycling pattern.

5. The method of claim 4 , wherein applying the precoding matrix to the at least one identified stream comprises applying the preferred precoding matrix to the at least one identified stream.

6. The method of claim 1 , wherein applying the precoding matrix to the SRS comprises applying a first precoding matrix to a first SRS for a physical uplink shared channel (PUSCH) and applying a second precoding matrix to a second SRS for a physical uplink control channel (PUCCH).

7. A method of wireless communications, comprising:

identifying, by a user equipment (UE) comprising at least two antennas, an uplink transmission of at least one stream as using one of cyclic prefix orthogonal frequency division multiplexing or discrete Fourier transform spread orthogonal frequency division multiplexing;

applying, by the UE, a precoding matrix to the at least one identified stream, wherein the precoding matrix changes over time according to a precoding cycling pattern, wherein applying the precoding matrix to the at least one identified stream comprises precoding a demodulation reference signal (DMRS) and a data portion of the at least one identified stream with the same precoding matrix varying according to the precoding cycling pattern; and

transmitting, by the UE, the at least one identified stream from the at least two antennas according to the applied precoding matrix.

8. The method of claim 7 , further comprising:

receiving an indication from a base station indicating a preferred precoding matrix selected from the precoding cycling pattern; and

applying the preferred precoding matrix to the at least one identified stream without the precoding cycling pattern.

9. The method of claim 7 , wherein the precoding cycling pattern varies by subframe and one DMRS symbol is transmitted per subframe.

10. The method of claim 7 , wherein the precoding cycling pattern varies by symbol period and one DMRS symbol is transmitted per symbol period.

11. A method of wireless communications, comprising:

identifying, by a user equipment (UE) comprising at least two antennas, an uplink transmission of at least one stream as using one of cyclic prefix orthogonal frequency division multiplexing or discrete Fourier transform spread orthogonal frequency division multiplexing;

applying, by the UE, a precoding matrix to the at least one identified stream, wherein the precoding matrix changes over time according to a precoding cycling pattern, wherein applying the precoding matrix to the at least one identified stream comprises:

precoding a data portion of the at least one identified stream with the precoding matrix varying according to the precoding cycling pattern; and

applying no precoding matrix to a DMRS portion of the at least one identified stream; and

transmitting, by the UE, the at least one identified stream from the at least two antennas according to the applied precoding matrix.

12. A method of wireless communications, comprising:

identifying, by a user equipment (UE) comprising at least two antennas, an uplink transmission of at least one stream as using one of cyclic prefix orthogonal frequency division multiplexing or discrete Fourier transform spread orthogonal frequency division multiplexing;

applying, by the UE, a precoding matrix to the at least one identified stream, wherein the precoding matrix changes over time according to a precoding cycling pattern, wherein applying the precoding matrix to the at least one identified stream comprises:

determining a code division multiplexing (CDM) group of the UE; and

precoding the at least one identified stream with the precoding matrix selected based on the CDM group of the UE; and

transmitting, by the UE, the at least one identified stream from the at least two antennas according to the applied precoding matrix.

13. The method of claim 12 , wherein the at least one identified stream includes a non-coherent transmission on a PUCCH.

14. A user equipment (UE), comprising:

a memory;

at least two antennas;

a transceiver; and

a processor in communication with the memory and the transceiver, wherein the processor is configured to:

identify an uplink transmission of at least one stream as using one of cyclic prefix orthogonal frequency division multiplexing or discrete Fourier transform spread orthogonal frequency division multiplexing;

apply a precoding matrix to the at least one identified stream including a sounding reference signal (SRS), wherein the precoding matrix changes over time according to a precoding cycling pattern, wherein the precoding matrix for the SRS follows the precoding cycling pattern; and

transmit the at least one identified stream from the at least two antennas according to the applied precoding matrix.

15. The UE of claim 14 , wherein the precoding cycling pattern changes the precoding matrix on a symbol basis.

16. The UE of claim 14 , wherein the precoding cycling pattern changes the precoding matrix on a subframe basis.

17. The UE of claim 14 , wherein the processor is configured to receive an indication from a base station indicating a preferred precoding matrix selected from the precoding cycling pattern.

18. The UE of claim 17 , wherein the processor is configured to apply the preferred precoding matrix to the at least one identified stream.

19. The UE of claim 14 , wherein the processor is configured to apply a first precoding matrix to a first SRS for a physical uplink shared channel (PUSCH) and apply a second precoding matrix to a second SRS for a physical uplink control channel (PUCCH).

20. A user equipment (UE), comprising:

a memory;

at least two antennas;

a transceiver; and

a processor in communication with the memory and the transceiver, wherein the processor is configured to:

identify an uplink transmission of at least one stream as using one of cyclic prefix orthogonal frequency division multiplexing or discrete Fourier transform spread orthogonal frequency division multiplexing;

apply a precoding matrix to the at least one identified stream, wherein the precoding matrix changes over time according to a precoding cycling pattern;

precode a demodulation reference signal (DMRS) and a data portion of the at least one identified stream with the same precoding matrix varying according to the precoding cycling pattern; and

transmit the at least one identified stream from the at least two antennas according to the applied precoding matrix.

21. The UE of claim 20 , wherein the processor is configured to:

receive an indication from a base station indicating a preferred precoding matrix selected from the precoding cycling pattern; and

apply the preferred precoding matrix to the at least one identified stream without the precoding cycling pattern.

22. The UE of claim 20 , wherein the precoding cycling pattern varies by subframe and one DMRS symbol is transmitted per subframe.

23. The UE of claim 20 , wherein the precoding cycling pattern varies by symbol period and one DMRS symbol is transmitted per symbol period.

24. A user equipment (UE), comprising:

a memory;

at least two antennas;

a transceiver; and

a processor in communication with the memory and the transceiver, wherein the processor is configured to:

identify an uplink transmission of at least one stream as using one of cyclic prefix orthogonal frequency division multiplexing or discrete Fourier transform spread orthogonal frequency division multiplexing;

apply a precoding matrix to the at least one identified stream, wherein the precoding matrix changes over time according to a precoding cycling pattern;

precode a data portion of the at least one identified stream with the precoding matrix varying according to the precoding cycling pattern;

apply no precoding matrix to a DMRS portion of the at least one identified stream; and

transmit the at least one identified stream from the at least two antennas according to the applied precoding matrix.

25. A user equipment (UE), comprising:

a memory;

at least two antennas;

a transceiver; and

a processor in communication with the memory and the transceiver, wherein the processor is configured to:

identify an uplink transmission of at least one stream as using one of cyclic prefix orthogonal frequency division multiplexing or discrete Fourier transform spread orthogonal frequency division multiplexing;

determine a code division multiplexing (CDM) group of the UE;

apply a precoding matrix to the at least one identified stream, wherein the precoding matrix changes over time according to a precoding cycling pattern;

precode the at least one identified stream with the precoding matrix selected based on the CDM group of the UE; and

transmit the at least one identified stream from the at least two antennas according to the applied precoding matrix.

26. The UE of claim 25 , wherein the at least one identified stream includes a non-coherent transmission on a PUCCH.

27. A user equipment (UE), comprising:

at least two antennas;

means for identifying, by the UE, an uplink transmission of at least one stream as using one of cyclic prefix orthogonal frequency division multiplexing or discrete Fourier transform spread orthogonal frequency division multiplexing;

means for determining a code division multiplexing (CDM) group of the UE;

means for applying, by the UE, a precoding matrix to the at least one identified stream, wherein the precoding matrix changes over time according to a precoding cycling pattern, and the precoding matrix is selected based on the CDM group of the UE; and

means for transmitting, by the UE, the at least one identified stream from the at least two antennas according to the applied precoding matrix.

28. A non-transitory computer-readable medium storing computer code executable by a processor for wireless communications, comprising code to:

identify, by a UE comprising at least two antennas, an uplink transmission of at least one stream as using one of cyclic prefix orthogonal frequency division multiplexing or discrete Fourier transform spread orthogonal frequency division multiplexing;

apply, by the UE, a precoding matrix to the at least one identified stream, wherein the precoding matrix changes over time according to a precoding cycling pattern;

precode a data portion of the at least one identified stream with the precoding matrix varying according to the precoding cycling pattern; and

apply no precoding matrix to a DMRS portion of the at least one identified stream; and

transmit, by the UE, the at least one identified stream from the at least two antennas according to the applied precoding matrix.