Methods and apparatus for an autonomous downlink transmission

1. A method for wireless communication by a user equipment (UE) to enable an autonomous downlink transmission over a shared spectrum, comprising:

receiving a triggering event indicating that the UE has pending downlink (DL) data;

receiving a configuration command from a serving generic NodeB (gNB), in response to the triggering event, to enable an autonomous DL transmission (ADT) capability at the UE; and

upon receiving the configuration command, initiating a listen before talk (LBT) procedure of a first LBT type to obtain an uplink (UL) transmission opportunity (TxOP) after determining that the UE does not have any UL data to transmit.

2. The method of claim 1 , further comprising:

transmitting uplink control information (UCI) to request for allocating resources for the TxOP for the pending DL data.

3. The method of claim 2 , further comprising:

broadcasting a clear to send (CTS) signal in a separate signaling message or together with the UCI to reserve the UL TxOP.

4. The method of claim 2 , further comprising receiving the pending DL data using the UL TxOP, wherein allocated resources for receiving the pending DL data is dynamically configured via the UCI or semi-statically configured through a radio resource control (RRC) protocol message; and wherein radio frame structures of the allocated resources for the pending DL data are different than those for regular DL or UL data.

5. The method of claim 4 , wherein the radio frame structures are allocated via at least one of:

a semi-static configuration through an RRC message;

a dynamic configuration message; or

an indication in a received downlink control information (DCI).

6. The method of claim 1 , further comprising

initiating a second LBT procedure of a second LBT type for a secondary carrier for the TxOP for the pending DL data.

7. The method of claim 6 , wherein the first LBT type comprises a category (CAT)-4 LBT procedure and the second LBT type comprise a CAT-2 LBT procedure;

and wherein the CAT-4 LBT procedure or/and the CAT-2 LBT procedure is UE beam specific.

8. The method of claim 1 , further comprising

receiving a second configuration command from the serving gNB to disable the ADT capability.

9. The method of claim 1 , wherein the ADT capability is associated with a priority class and/or a plurality of time granularities.

10. The method of claim 1 , wherein the triggering event comprise one or more of:

a paging message,

an indication that the UE has a large number of unacknowledged downlink (DL) HARQ processes;

an indication from an upper layer indicating that there is a pending upper layer data; and

a number of bad channel state indicators that fall below a predetermined threshold.

11. A method for wireless communication by a generic node B (gNB) to enable an autonomous downlink transmission over a shared spectrum, comprising:

informing a user equipment (UE) via a triggering event that there is pending downlink (DL) data to be transmitted to the UE; and

transmitting a first configuration command to the UE, in response to the triggering event, to enable an autonomous DL transmission (ADT) capability at the UE; and

determining if an uplink (UL) transmission opportunity (TxOP) is available via a listen before talk (LBT) procedure of a first LBT type.

12. The method of claim 11 , further comprising:

receiving an uplink control information (UCI) message to request for allocating resources for autonomous DL transmissions of the pending DL data.

13. The method of claim 12 , further comprising transmitting the pending DL data on the allocated resource using the TxOP, wherein a radio frame structure of the allocated resources for the UL TxOP, is different than that for resources allocated for regular DL or UL data transmissions.

14. The method of claim 13 , wherein allocation of the radio frame structure is performed via one of:

a semi-static configuration through an RRC message;

a dynamic configuration message; or

an indication in a DCI message transmitted to the UE.

15. The method of claim 11 , further comprising

receiving a clear to send (CTS) indicator either by itself or together with the UCI message, in response to reserving the UL TxOP for the UE.

16. The method of claim 11 , further comprising

in response to a second LBT procedure of a second LBT type initiated by the UE, allocating a secondary carrier for the UL TxOP.

17. The method of claim 16 , wherein the first LBT type comprises a category (CAT)-4 LBT and the second LBT type comprise a CAT-2 LBT; and wherein the first LBT procedure or/and the second LBT procedure are UE beam specific.

18. The method of claim 16 , further comprising

transmitting a second configuration command to the UE to disable the ADT capability.

19. The method of claim 11 , wherein the ATD capability is associated with a plurality of time granularities and/or with a priority class.

20. The method of claim 11 , wherein the triggering event comprise one or more of:

transmitting a paging message to the UE; and

transmitting an indication that the UE has a large number of unacknowledged downlink (DL) HARQ processes.

21. An apparatus for wireless communication by a user equipment (UE) to enable an autonomous downlink transmission over a shared spectrum, comprising:

means for receiving a triggering event indicating that the UE has pending downlink (DL) data;

means for receiving a configuration command from a serving generic NodeB (gNB), in response to the triggering event, to enable an autonomous DL transmission (ADT) capability at the UE; and

means for upon receiving the configuration command, initiating a listen before talk (LBT) procedure of a first LBT type to obtain an uplink (UL) transmission opportunity (TxOP) after determining that the UE does not have any UL data to transmit.

22. The apparatus of claim 21 , further comprising:

means for transmitting uplink control information (UCI) to request for allocating resources for the TxOP for the pending DL data.

23. The apparatus of claim 22 , further comprising:

means for broadcasting a clear to send (CTS) signal in a separate signaling message or together with the UCI to reserve the UL TxOP.

24. The apparatus of claim 22 , further comprising

means for receiving the pending DL data using the UL TxOP, wherein allocated resources for receiving the pending DL data is dynamically configured via the UCI or semi-statically configured through a radio resource control (RRC) protocol message; and wherein radio frame structures of the allocated resources for the pending DL data are different than those for regular DL or UL data.

25. The apparatus of claim 21 , further comprising

means for initiating a second LBT procedure of a second LBT type for a secondary carrier for the TxOP for the pending DL data.

26. An apparatus for wireless communication by a user equipment (UE) to enable an autonomous downlink transmission over a shared spectrum, comprising:

a transceiver;

a memory; and

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

receive a triggering event indicating that the UE has pending downlink (DL) data;

receive a configuration command from a serving generic NodeB (gNB) to enable an autonomous DL transmission (ADT) capability at the UE, in response to the triggering event; and

upon receiving the configuration command, initiating a listen before talk (LBT) procedure of a first LBT type to obtain an uplink (UL) transmission opportunity (TxOP) after determining that the UE does not have any UL data to transmit.

27. The apparatus of claim 26 , wherein the at least one processor is further configured to transmit uplink control information (UCI) to request for allocating resources for the TxOP for the pending DL data.

28. The apparatus of claim 27 , wherein the at least one processor is further configured to broadcast a clear to send (CTS) signal in a separate signaling message or together with the UCI to reserve the UL TxOP.

29. The apparatus of claim 27 , wherein the at least one processor is further configured to receive the pending DL data using the UL TxOP, wherein allocated resources for receiving the pending DL data is dynamically configured via the UCI or semi-statically configured through a radio resource control (RRC) protocol message; and wherein radio frame structures of the allocated resources for the pending DL data are different than those for regular DL or UL data.

30. The apparatus of claim 29 , wherein the radio frame structures are allocated via one of:

a semi-static configuration through an RRC message;

a dynamic configuration message; or

an indication in a received downlink control information (DCI).