Techniques for flexible duplexing

1. A method of wireless communications, comprising:

receiving a reconfiguration message indicating a change for a frequency division duplex (FDD) uplink band to a temporary time division duplex (TDD) band; and

determining a reference configuration for a pair of FDD bands including an FDD downlink band and the temporary TDD band, the reference configuration indicating a pattern of sub-frames associated with the pair of FDD bands.

2. The method of claim 1 , further comprising:

determining a hybrid automatic repeat request (HARQ) timing for the FDD downlink band based on the reference configuration; and

transmitting an acknowledgment status signal on the temporary TDD band in response to a transmission received on the FDD downlink band based on the HARQ timing, wherein the acknowledgment status signal is an acknowledgment (ACK) signal or a negative-acknowledgment (NACK).

3. The method of claim 2 , wherein determining the HARQ timing comprises determining an uplink sub-frame of the temporary TDD band in which to transmit the acknowledgment status signal based on the reference configuration.

4. The method of claim 3 , wherein the pair of FDD bands is aggregated and the FDD downlink band is associated with a primary cell.

5. The method of claim 1 , further comprising:

receiving a grant on a downlink sub-frame of the temporary TDD band, the grant scheduling an uplink transmission on the temporary TDD band; and

determining an uplink sub-frame for the uplink transmission based on an FDD uplink HARQ timing.

6. The method of claim 1 , further comprising:

receiving a grant on a downlink sub-frame of the temporary TDD band, the grant scheduling an uplink transmission on the temporary TDD band; and

determining an uplink sub-frame for the uplink transmission based on the reference configuration.

7. The method of claim 6 , further comprising:

determining an uplink HARQ process number for the uplink transmission based on a 3-bit HARQ process number included in the grant.

8. The method of claim 1 , further comprising:

determining that the pair of FDD bands is not aggregated with at least one second band;

identifying the FDD downlink band and the temporary TDD band as being associated with separate cells based on the determining that the pair of FDD bands are not aggregated with at least a second band;

allocating a soft buffer to each of the FDD downlink band and the temporary TDD band by equally dividing a total number of soft channel bits between the FDD downlink band and the temporary TDD band; and

determining a maximum number of HARQ processes for each of the FDD downlink band and the temporary TDD band based on the reference configuration, wherein the maximum number of HARQ processes is used for soft buffer management in each separate cell.

9. The method of claim 1 , further comprising:

determining that the pair of FDD bands is aggregated with at least one second band;

identifying the FDD downlink band and the temporary TDD band as being associated with a single cell in response to determining that the pair of FDD bands are aggregated with the at least one second band;

allocating a soft buffer to be shared between the FDD downlink band and the temporary TDD band; and

determining a maximum number of HARQ processes for the single cell of the FDD downlink band and the temporary TDD band based on the reference configuration, wherein the maximum number of HARQ processes is used for soft buffer management.

10. The method of claim 9 , further comprising:

receiving a downlink transmission either on the FDD downlink band or on the temporary TDD band but not simultaneously.

11. The method of claim 1 , further comprising:

determining a downlink control information (DCI) format, a HARQ timing, and a physical uplink control channel (PUCCH) resource mapping for an uplink sub-frame of the temporary TDD band based on a band used to receive a physical downlink control channel (PDCCH) and a search space used to receive the PDCCH.

12. The method of claim 11 , wherein the determining comprises determining the DCI format, the HARQ timing, and the PUCCH resource mapping based on an FDD format in response to the PDCCH being received on the FDD downlink band in a common search space.

13. The method of claim 11 , wherein the determining comprises determining the downlink control information (DCI) format, the HARQ timing, and the PUCCH resource mapping based on a TDD format applicable to the reference configuration in response to the PDCCH being received on the temporary TDD band or in a user equipment (UE) specific search space.

14. The method of claim 1 , further comprising:

determining a DCI format, a HARQ timing, and a PUCCH resource mapping for an uplink sub-frame of the temporary TDD band based on a downlink sub-frame used to receive a physical downlink control channel (PDCCH) and the reference configuration.

15. The method of claim 14 , wherein the downlink sub-frame has a sub-frame index a fixed number of sub-frames before the UL sub-frame based on the reference configuration, and an FDD formatting is used for the DCI format, the HARQ timing, and the PUCCH resource mapping.

16. The method of claim 14 , wherein the downlink sub-frame does not have a sub-frame index a fixed number of sub-frames before the UL sub-frame based on the reference configuration and a TDD formatting is used for the DCI format, the HARQ timing and the PUCCH resource mapping.

17. The method of claim 1 , further comprising:

transmitting an uplink sounding reference signal (SRS) in a special sub-frame of the temporary TDD band based on a TDD reporting format, wherein an uplink timing advance control and a power control for SRS transmission are based on an FDD format.

18. The method of claim 1 , further comprising:

determining whether the FDD downlink band is associated with a primary cell or a secondary cell;

determining a periodic channel state information (CSI) reporting format based on whether the FDD downlink band is associated with the primary cell or the secondary cell.

19. The method of claim 18 , further comprising:

transmitting a periodic CSI report based on a TDD reporting format in response to determining that the FDD downlink band is associated with the primary cell.

20. The method of claim 18 , further comprising:

transmitting a periodic CSI report based on a CSI reporting format of the primary cell in response to determining that the FDD downlink band is associated with the secondary cell.

21. An apparatus for wireless communications, comprising:

a transceiver configured to receive sub-frames of a downlink channel;

a memory; and

at least one processor communicatively coupled to the transceiver and to the memory via at least one bus, the at least one processor configured to:

receive a reconfiguration message indicating a change for a frequency division duplex (FDD) uplink band to a temporary time division duplex (TDD) band; and

determine a reference configuration for a pair of FDD bands including an FDD downlink band and the temporary TDD band, the reference configuration indicating a pattern of sub-frames associated with the pair of FDD bands.

22. The apparatus of claim 21 , wherein the at least one processor is configured to:

determine a hybrid automatic repeat request (HARQ) timing for the FDD downlink band based on the reference configuration; and

transmit an acknowledgment status signal on the temporary TDD band in response to a transmission received on the FDD downlink band based on the HARQ timing, wherein the acknowledgment status signal is an acknowledgment (ACK) signal or a negative-acknowledgment (NACK).

23. The apparatus of claim 21 , wherein the at least one processor is configured to:

receive a grant on a downlink sub-frame of the temporary TDD band, the grant scheduling an uplink transmission on the temporary TDD band; and

determine an uplink sub-frame for the uplink transmission based on an FDD uplink HARQ timing.

24. The apparatus of claim 21 , wherein the at least one processor is configured to:

receive a grant on a downlink sub-frame of the temporary TDD band, the grant scheduling an uplink transmission on the temporary TDD band; and

determine an uplink sub-frame for the uplink transmission based on the reference configuration.

25. The apparatus of claim 21 , wherein the at least one processor is configured to:

determine that the pair of FDD bands is not aggregated with at least one second band;

identify the FDD downlink band and the temporary TDD band as being associated with separate cells based on the determining that the pair of FDD bands are not aggregated with at least a second band;

allocate a soft buffer to each of the FDD downlink band and the temporary TDD band by equally dividing a total number of soft channel bits between the FDD downlink band and the temporary TDD band; and

determine a maximum number of HARQ processes for each of the FDD downlink band and the temporary TDD band based on the reference configuration, wherein the maximum number of HARQ processes is used for soft buffer management in each separate cell.

26. The apparatus of claim 21 , wherein the at least one processor is configured to:

determine that the pair of FDD bands is aggregated with at least one second band;

identify the FDD downlink band and the temporary TDD band as being associated with a single cell in response to determining that the pair of FDD bands are aggregated with the at least one second band;

allocate a soft buffer to be shared between the FDD downlink band and the temporary TDD band; and

determine a maximum number of HARQ processes for the single cell of the FDD downlink band and the temporary TDD band based on the reference configuration, wherein the maximum number of HARQ processes is used for soft buffer management.

27. The apparatus of claim 21 , wherein the at least one processor is configured to:

determine a downlink control information (DCI) format, a HARQ timing, and a physical uplink control channel (PUCCH) resource mapping for an uplink sub-frame of the temporary TDD band based on a band used to receive a physical downlink control channel (PDCCH) and a search space used to receive the PDCCH.

28. The apparatus of claim 21 , wherein the at least one processor is configured to:

transmit an uplink sounding reference signal (SRS) in a special sub-frame of the temporary TDD band based on a TDD reporting format, wherein an uplink timing advance control and a power control for SRS transmission are based on an FDD format.

29. An apparatus for wireless communications, comprising:

means for receiving a reconfiguration message indicating a change for a frequency division duplex (FDD) uplink band to a temporary time division duplex (TDD) band; and

means for determining a reference configuration for a pair of FDD bands including an FDD downlink band and the temporary TDD band, the reference configuration indicating a pattern of sub-frames associated with the pair of FDD bands.

30. A computer-readable medium storing computer executable code for wireless communications, comprising:

code for receiving a reconfiguration message indicating a change for a frequency division duplex (FDD) uplink band to a temporary time division duplex (TDD) band; and

code for determining a reference configuration for a pair of FDD bands including an FDD downlink band and the temporary TDD band, the reference configuration indicating a pattern of sub-frames associated with the pair of FDD bands.