Narrowband time-division duplex frame structure for narrowband communications

1. A method of wireless communication for a base station, comprising:

determining a bandwidth for narrowband communications;

determining a time-division duplex (TDD) frame structure from a plurality of TDD frame structures for the narrowband communications, the TDD frame structure including at least one of two or more contiguous downlink subframes, or one or more flexible subframes that can be configured as either a downlink subframe or an uplink subframe, the plurality of TDD frame structures includes a first set of TDD frame structures associated with a first switching periodicity, a second set of TDD frame structures associated with a second switching periodicity, and a third set of TDD frame structures associated with a third switching periodicity, each of the first switching periodicity, the second switching periodicity, and the third switching periodicity being different; and

communicating with a user equipment (UE) using the TDD frame structure determined for the narrowband communications.

2. The method of claim 1 , wherein the TDD frame structure for the narrowband communications is different than another TDD frame structure actively being used in an overlapping frequency region by a different radio access technology (RAT).

3. The method of claim 1 , wherein:

when a first duration is used by the UE to switch between monitoring a downlink subframe to sending a transmission using an uplink subframe, a special subframe is located in both half frames of the TDD frame structure;

when a second duration that is longer than the first duration is used by the UE to switch between monitoring the downlink subframe to sending the transmission using the uplink subframe, a special subframe may be located in a first half frame of the TDD frame structure but not a second half frame of the TDD frame structure; and

when a third duration that is longer than the second duration is used by the UE to switch between monitoring the downlink subframe to sending the transmission using the uplink subframe, no special subframes are present in the TDD frame structure.

4. The method of claim 1 , wherein the TDD frame structure has at least three contiguous downlink subframes.

5. The method of claim 4 , further comprising:

transmitting a system information block (SIB) in a first subframe of the TDD frame structure; and

transmitting a secondary synchronization signal (SSS) in a second subframe of the TDD frame structure, the second subframe being different than the first subframe.

6. The method of claim 1 , wherein the bandwidth used for the narrowband communications is smaller than cellular bandwidths available for different radio access technologies (RATs).

7. An apparatus for wireless communication for a base station, comprising:

means for determining a bandwidth for narrowband communications;

means for determining a time-division duplex (TDD) frame structure from a plurality of TDD frame structures for the narrowband communications, the TDD frame structure including at least one of two or more contiguous downlink subframes, or one or more flexible subframes that can be configured as either a downlink subframe or an uplink subframe, the plurality of TDD frame structures includes a first set of TDD frame structures associated with a first switching periodicity, a second set of TDD frame structures associated with a second switching periodicity, and a third set of TDD frame structures associated with a third switching periodicity, each of the first switching periodicity, the second switching periodicity, and the third switching periodicity being different; and

means for communicating with a user equipment (UE) using the TDD frame structure determined for the narrowband communications.

8. The apparatus of claim 7 , wherein the TDD frame structure for the narrowband communications is different than another TDD frame structure actively being used in an overlapping frequency region by a different radio access technology (RAT).

9. The apparatus of claim 7 , wherein:

when a first duration is used by the UE to switch between monitoring a downlink subframe to sending a transmission using an uplink subframe, a special subframe is located in both half frames of the TDD frame structure;

when a second duration that is longer than the first duration is used by the UE to switch between monitoring the downlink subframe to sending the transmission using the uplink subframe, a special subframe may be located in a first half frame of the TDD frame structure but not a second half frame of the TDD frame structure; and

when a third duration that is longer than the second duration is used by the UE to switch between monitoring the downlink subframe to sending the transmission using the uplink subframe, no special subframes are present in the TDD frame structure.

10. The apparatus of claim 7 , wherein the TDD frame structure has at least three contiguous downlink subframes.

11. The apparatus of claim 10 , further comprising:

means for transmitting a system information block (SIB) in a first subframe of the TDD frame structure; and

means for transmitting a secondary synchronization signal (SSS) in a second subframe of the TDD frame structure, the second subframe being different than the first subframe.

12. The apparatus of claim 7 , wherein the bandwidth used for the narrowband communications is smaller than cellular bandwidths available for different radio access technologies (RATs).

13. An apparatus for wireless communication for a base station, comprising:

a memory; and

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

determine a bandwidth for narrowband communications;

determine a time-division duplex (TDD) frame structure from a plurality of TDD frame structures for the narrowband communications, the TDD frame structure including at least one of two or more contiguous downlink subframes, or one or more flexible subframes that can be configured as either a downlink subframe or an uplink subframe, the plurality of TDD frame structures includes a first set of TDD frame structures associated with a first switching periodicity, a second set of TDD frame structures associated with a second switching periodicity, and a third set of TDD frame structures associated with a third switching periodicity, each of the first switching periodicity, the second switching periodicity, and the third switching periodicity being different; and

communicate with a user equipment (UE) using the TDD frame structure determined for the narrowband communications.

14. The apparatus of claim 13 , wherein the TDD frame structure for the narrowband communications is different than another TDD frame structure actively being used in an overlapping frequency region by a different radio access technology (RAT).

15. The apparatus of claim 13 , wherein:

when a first duration is used by the UE to switch between monitoring a downlink subframe to sending a transmission using an uplink subframe, a special subframe is located in both half frames of the TDD frame structure;

when a second duration that is longer than the first duration is used by the UE to switch between monitoring the downlink subframe to sending the transmission using the uplink subframe, a special subframe may be located in a first half frame of the TDD frame structure but not a second half frame of the TDD frame structure; and

when a third duration that is longer than the second duration is used by the UE to switch between monitoring the downlink subframe to sending the transmission using the uplink subframe, no special subframes are present in the TDD frame structure.

16. The apparatus of claim 13 , wherein the TDD frame structure has at least three contiguous downlink subframes.

17. The apparatus of claim 16 , wherein the at least one processor is further configured to:

transmit a system information block (SIB) in a first subframe of the TDD frame structure; and

transmit a secondary synchronization signal (SSS) in a second subframe of the TDD frame structure, the second subframe being different than the first subframe.

18. The apparatus of claim 13 , wherein the bandwidth used for the narrowband communications is smaller than cellular bandwidths available for different radio access technologies (RATs).

19. A non-transitory computer-readable medium storing computer executable code for a base station, comprising code to:

determine a bandwidth for narrowband communications;

determine a narrowband time-division duplex (TDD) frame structure from a plurality of TDD frame structures for the narrowband communications, the TDD frame structure including at least one of two or more contiguous downlink subframes, or one or more flexible subframes that can be configured as either a downlink subframe or an uplink subframe, the plurality of TDD frame structures includes a first set of TDD frame structures associated with a first switching periodicity, a second set of TDD frame structures associated with a second switching periodicity, and a third set of TDD frame structures associated with a third switching periodicity, each of the first switching periodicity, the second switching periodicity, and the third switching periodicity being different; and

communicate with a user equipment (UE) using the TDD frame structure determined for the narrowband communications.

20. The non-transitory computer-readable medium of claim 19 , wherein the TDD frame structure for the narrowband communications is different than another TDD frame structure actively being used in an overlapping frequency region by a different radio access technology (RAT).

21. The non-transitory computer-readable medium of claim 19 , wherein:

when a first duration is used by the UE to switch between monitoring a downlink subframe to sending a transmission using an uplink subframe, a special subframe is located in both half frames of the TDD frame structure;

when a second duration that is longer than the first duration is used by the UE to switch between monitoring the downlink subframe to sending the transmission using the uplink subframe, a special subframe may be located in a first half frame of the TDD frame structure but not a second half frame of the TDD frame structure; and

when a third duration that is longer than the second duration is used by the UE to switch between monitoring the downlink subframe to sending the transmission using the uplink subframe, no special subframes are present in the TDD frame structure.

22. The non-transitory computer-readable medium of claim 19 , wherein the TDD frame structure has at least three contiguous downlink subframes.

23. The non-transitory computer-readable medium of claim 22 , further comprising code to:

transmit a system information block (SIB) in a first subframe of the TDD frame structure; and

transmit a secondary synchronization signal (SSS) in a second subframe of the TDD frame structure, the second subframe being different than the first subframe.

24. The non-transitory computer-readable medium of claim 19 , wherein the bandwidth used for the narrowband communications is smaller than cellular bandwidths available for different radio access technologies (RATs).