Devices and methods for ELAA multi-carrier LBT

1. An apparatus of a user equipment for uplink channel access in license-assisted access (LAA), the apparatus comprising:

a memory; and

processing circuitry coupled to the memory and configured to:

process one or more uplink (UL) grants from a base station scheduling a plurality of physical uplink shared channel (PUSCH) transmissions on a plurality of unlicensed carriers at a first PUSCH starting position, the one or more UL grants indicating a first channel access procedure for the plurality of PUSCH transmissions, wherein the first PUSCH starting position is identified based on a grant timing association included in the one or more UL grants;

select a first unlicensed carrier of the plurality of unlicensed carriers for the first channel access procedure associated with the first PUSCH starting position, wherein the plurality of unlicensed carriers are identified in the one or more UL grants; and

select at least a second unlicensed carrier of the plurality of unlicensed carriers other than the first unlicensed carrier for a second channel access procedure associated with the first PUSCH starting position.

2. The apparatus of claim 1 wherein the memory is configured to store one or more channel access indications from the one or more uplink (UL) grants from the base station scheduling the plurality of PUSCH transmissions on the plurality of unlicensed carriers at the first PUSCH starting position.

3. The apparatus of claim 1 wherein the first channel access procedure comprises a category-4 listen-before-talk (LBT) procedure.

4. The apparatus of claim 1 wherein the first channel access procedure comprises a random backoff counter.

5. The apparatus of claim 1 wherein the second channel access procedure comprises a fixed LBT sensing interval.

6. The apparatus of claim 5 wherein the fixed LBT sensing interval is set to 25 microseconds.

7. The apparatus of claim 1 wherein the processing circuitry is further configured to initiate a first PUSCH transmission on the first unlicensed carrier following successful completion of the first channel access procedure.

8. The apparatus of claim 7 wherein the processing circuitry is further configured to initiate an additional PUSCH transmission on each of the remaining unlicensed carriers of the plurality of unlicensed carriers that has succeeded with the second channel access procedure immediately before the first PUSCH transmission on the first unlicensed carrier.

9. The apparatus of claim 2 wherein the processing circuitry is configured to select the first unlicensed carrier randomly from the plurality of unlicensed carriers.

10. The apparatus of claim 1 wherein the apparatus comprises an integrated circuit, wherein the processing circuitry comprises baseband circuitry disposed in the integrated circuit, and wherein the integrated circuit further comprises the memory.

11. The apparatus of claim 1 further comprising:

one or more antennas coupled to the processing circuitry via radio frequency front-end circuitry, wherein the one or more antennas are configured to transmit the plurality of PUSCH transmissions;

application circuitry coupled to the processing circuitry; and

a display coupled to the application circuitry.

12. A non-transitory computer-readable storage medium comprising instructions for license-assisted access (LAA) uplink communication operations that, when executed by processing circuitry of an apparatus, configure the apparatus to:

process one or more uplink (UL) grants from a base station scheduling a plurality of physical uplink shared channel (PUSCH) transmissions on a plurality of unlicensed carriers at a first PUSCH starting position, the one or more UL grants indicating a first channel access procedure for the plurality of PUSCH transmissions;

select a first unlicensed carrier of the plurality of unlicensed carriers for the first channel access procedure associated with the first PUSCH starting position, wherein a contention window size for the first channel access procedure is set in response to base station signaling; and

select remaining unlicensed carriers of the plurality of unlicensed carriers other than the first unlicensed carrier for a second channel access procedure associated with the first PUSCH starting position.

13. The computer-readable storage medium of claim 12 wherein the first channel access procedure comprises a listen-before-talk (LBT) procedure associated with a variable contention window (CW) updated based on hybrid automatic repeat request (HARQ) feedback for all carriers of the plurality of unlicensed carriers.

14. The computer-readable storage medium of claim 12 wherein the first channel access procedure comprises a random backoff counter.

15. The computer-readable storage medium of claim 12 wherein the second channel access procedure comprises a fixed LBT sensing interval.

16. The computer-readable storage medium of claim 15 wherein the fixed LBT sensing interval is set to 25 microseconds.

17. The computer-readable storage medium of claim 12 wherein the instructions further configure the apparatus to:

initiate a first PUSCH transmission on the first unlicensed carrier following successful completion of the first channel access procedure.

18. The computer-readable storage medium of claim 17 wherein the instructions further configure the apparatus to:

initiate an additional PUSCH transmission on each of the remaining unlicensed carriers of the plurality of unlicensed carriers that has succeeded with the second channel access procedure immediately before the first PUSCH transmission on the first unlicensed carrier.

19. The computer-readable storage medium of claim 13 wherein the instructions further configure the apparatus to:

select the first unlicensed carrier randomly from the plurality of unlicensed carriers.