Carrier-sensing techniques for LTE-based transmissions over unlicensed carriers

1. An apparatus, comprising:

at least one memory; and

logic for user equipment (UE), at least a portion of the logic comprised in circuitry coupled to the at least one memory, the logic to cause the UE to:

receive an uplink (UL) grant indicating a transmit subframe, the transmit subframe to comprise a subframe during which the UE is authorized to perform UL transmission via an unlicensed carrier;

determine whether the UL grant comprises a listen-before-talk (LBT)-contingent UL grant; and

in response to a determination that the UL grant comprises an LBT-contingent UL grant:

identify an LBT interval for the transmit subframe; and perform an LBT procedure during the LBT interval to determine whether the unlicensed carrier is idle, the LBT procedure to comprise performing multiple clear channel assessments (CCAs), wherein the LBT procedure comprises, prior to performing each CCA of the multiple CCAs:

determining whether sufficient time remains before a scheduled start time of the UL transmission; and

in response to a determination that sufficient time does not remain before the scheduled start time of the UL transmission, terminating the LBT procedure without performing the UL transmission.

2. The apparatus of claim 1 , the logic to cause the UE to perform UL transmission to an evolved node B (eNB) via the unlicensed carrier during the transmit subframe in response to a determination that the unlicensed carrier is idle.

3. The apparatus of claim 1 , the LBT procedure to comprise performing at least one enhanced CCA (eCCA).

4. The apparatus of claim 1 , the LBT interval to comprise one or more punctured orthogonal frequency-division multiplexing (OFDM) symbols.

5. The apparatus of claim 1 , the LBT interval to comprise an initial portion of the transmit subframe.

6. The apparatus of claim 1 , the LBT interval to comprise a concluding portion of a subframe immediately preceding the transmit subframe.

7. A system, comprising:

the apparatus of claim 1 ;

at least one radio frequency (RF) transceiver; and

at least one RF antenna.

8. At least one non-transitory computer-readable storage medium comprising a set of instructions that, in response to being executed at user equipment (UE), cause the UE to:

identify a transmit subframe based on a listen-before-talk (LBT)-contingent uplink grant received from an evolved node B (eNB);

perform an LBT procedure during an LBT interval for the transmit subframe to determine whether a Long Term Evolution in Unlicensed Spectrum (LTE-U) carrier is clear, the LBT procedure to comprise performing multiple clear channel assessments (CCAs), wherein the LBT procedure comprises, prior to performing each CCA of the multiple CCAs:

determining whether sufficient time remains before a scheduled start time of the transmit subframe; and

in response to a determination that sufficient time does not remain before the scheduled start time of the transmit subframe, terminating the LBT procedure without performing uplink transmission;

in response to a determination that the LTE-U carrier is clear, perform uplink transmission during the transmit subframe; and

in response to a determination that the LTE-U carrier is not clear, refrain from transmission during the transmit subframe.

9. The at least one computer-readable storage medium of claim 8 , the transmit subframe to comprise a subframe during which the UE is authorized to perform uplink transmission to the eNB pending the determination that the LTE-U carrier is clear.

10. The at least one computer-readable storage medium of claim 8 , the LBT procedure to comprise performing at least one enhanced CCA (eCCA).

11. The at least one computer-readable storage medium of claim 8 , the LBT interval to comprise one or more punctured orthogonal frequency-division multiplexing (OFDM) symbols.

12. The at least one computer-readable storage medium of claim 8 , the LBT interval to comprise an initial portion of the transmit subframe.

13. The at least one computer-readable storage medium of claim 8 , the LBT interval to comprise a concluding portion of a subframe immediately preceding the transmit subframe.

14. User equipment (UE), comprising:

a radio frequency (RF) antenna;

an RF transceiver; and

logic, at least a portion of which is in circuitry coupled to the RF transceiver, the logic to cause the UE to:

identify a listen-before-talk (LBT) interval based on an uplink (UL) grant received from an evolved node B (eNB);

perform an LBT procedure during the LBT interval to determine whether an unlicensed carrier is idle, the LBT procedure to comprise performing multiple clear channel assessments (CCAs), wherein the LBT procedure comprises, prior to performing each CCA of the multiple CCAs:

determining whether sufficient time remains before a scheduled start time of a UL transmission associated with the UL grant; and

in response to determining that sufficient time does not remain before the scheduled start time of the UL transmission, terminating the LBT procedure without performing the UL transmission; and

transmit data to the eNB over the unlicensed carrier during a transmit subframe indicated by the UL grant in response to a determination during the LBT procedure that the unlicensed carrier is idle.

15. The UE of claim 14 , the logic to cause the UE to refrain from transmission over the unlicensed carrier during the transmit subframe in response to a determination during the LBT procedure that the unlicensed carrier is not idle.

16. The UE of claim 14 , the LBT procedure to comprise performing at least one enhanced CCA (eCCA).

17. The UE of claim 14 , the LBT interval to comprise one or more punctured orthogonal frequency-division multiplexing (OFDM) symbols.

18. The UE of claim 14 , the LBT interval to comprise an initial portion of the transmit subframe.

19. The UE of claim 14 , the LBT interval to comprise a concluding portion of a subframe immediately preceding the transmit subframe.