Network controlled sidelink off-loading over unlicensed carrier

1. A method of wireless communication performed by a first user equipment (UE), comprising:

receiving, by the UE from a base station (BS), a first downlink control information (DCI) associated with a first listen-before-talk (LBT) time, wherein the first DCI is associated with a cyclic prefix (CP) extension, and wherein the CP extension is associated with a traffic priority; and

determining, by the UE, a start time of a first sidelink transmission opportunity for communicating in an unlicensed frequency band at the first LBT time based on the traffic priority associated with the CP extension.

2. The method of claim 1 , wherein:

the receiving the first DCI comprises:

receiving the first DCI in a licensed frequency band;

the first DCI is further associated with a second LBT trigger opportunity;

the method further comprises:

receiving, by the UE from a first wireless communication device, a second LBT trigger associated with a second LBT time based on the second LBT trigger opportunity;

determining, by the UE, a second sidelink transmission opportunity for communicating in the unlicensed frequency band at the second LBT time based on the communicated second LBT trigger; and

transmitting, by the UE to a second wireless communication device, in an unlicensed-band a first transmission in a physical sidelink shared channel (PSSCH) at one of the first sidelink transmission opportunity or the second sidelink transmission opportunity.

3. The method of claim 2 , wherein:

the second LBT trigger opportunity is associated with a time-frequency resource for detecting the second LBT trigger based on the first DCI;

the second LBT trigger opportunity is associated with a trigger format based on the first DCI;

and

the first wireless communication device is one of the BS, a transmission-and-reception point, or a proxy sidelink UE.

4. The method of claim 2 , wherein the second sidelink transmission opportunity is associated with a type-2 LBT procedure.

5. The method of claim 2 , wherein:

the second LBT trigger opportunity is further associated with a pre-configured sidelink-band trigger; and

the pre-configured sidelink-band trigger is based on one of a system information block configuration, a radio resource control (RRC) message configuration, or a media access control control element (MAC-CE) message configuration.

6. The method of claim 2 , further comprising:

determining, by the UE, a set of one or more sidelink transmission opportunities contiguous with the determined second sidelink transmission opportunity based on the first DCI,

wherein a group of contiguous transmission opportunities includes each of the determined second sidelink transmission opportunity and the set of one or more sidelink transmission opportunities; and

transmitting, by the UE to a second wireless communication device, in an unlicensed-band a plurality of transmissions in the group of contiguous transmission opportunities, wherein the plurality of transmissions is associated with a plurality of different transport blocks (TBs), and wherein each of the plurality of different TB s is associated with a hybrid automatic repeat request (HARQ) process identifier, a new data indicator (NDI), and a redundancy version (RV).

7. The method of claim 2 , wherein:

the second LBT time is prior to the first LBT time;

the first sidelink transmission opportunity is associated with a type-1 LBT procedure;

the second sidelink transmission opportunity is associated a type-2 LBT procedure; and

the transmitting the first transmission comprises one of:

transmitting the first transmission in a physical sidelink shared channel (PSSCH) at the second sidelink transmission opportunity based on the type-2 LBT procedure associated with second first sidelink transmission opportunity being successful; or

transmitting the first transmission in a physical sidelink shared channel (PSSCH) at the first sidelink transmission opportunity based on the type-2 LBT procedure associated with the second sidelink transmission opportunity being unsuccessful.

8. The method of claim 2 , wherein:

the first LBT time is prior to the second LBT time;

an ending time of the determined second sidelink transmission opportunity is based on one of an ending time of the first sidelink transmission opportunity or an overriding ending time of the second sidelink transmission opportunity; and

the ending time of the determined second sidelink transmission opportunity is based on one of the first DCI, a system information block, or a radio resource configuration (RRC) message.

9. The method of claim 2 , wherein:

the second LBT trigger is associated with a simplified type 2-0 DCI;

the receiving the second LBT trigger comprises:

receiving the second LBT trigger based on a common search space (CSS) configuration in the unlicensed frequency band;

the CSS configuration is based on an enhanced system information block; and

the first wireless communication device is the BS.

10. The method of claim 1 , wherein:

the first DCI is associated with an enhanced type 3-0 DCI; and

the first sidelink transmission opportunity is associated with a type-1 LBT procedure.

11. The method of claim 1 , further comprising:

determining, by the UE, a cyclic prefix (CP) extension configuration for the first sidelink transmission opportunity based on one of a system information block configuration or a radio resource control (RRC) message configuration.

12. The method of claim 1 , further comprising:

determining, by the UE, a channel access priority class (CAPC) configuration for the first sidelink transmission opportunity based on one of a system information block configuration or a radio resource control (RRC) message configuration.

13. The method of claim 1 , further comprising:

determining, by the UE, a set of one or more sidelink transmission opportunities contiguous with the determined first sidelink transmission opportunity based on the first DCI, wherein a group of contiguous transmission opportunities includes each of the determined first sidelink transmission opportunity and the set of one or more sidelink transmission opportunities; and

transmitting, by the UE to a second wireless communication device, in an unlicensed-band a first plurality of transmissions in the group of contiguous transmission opportunities, wherein the first plurality of transmissions is associated with a plurality of different transport blocks (TBs), wherein each of the plurality of different TBs is associated with a hybrid automatic repeat request (HARQ) process identifier, new data indicator (NDI), and a redundancy version (RV), and wherein each of the set of one or more sidelink transmission opportunities is associated with a type-1 LBT procedure.

14. The method of claim 1 , wherein:

the receiving the first DCI comprises:

receiving the first DCI in an unlicensed frequency band;

the first DCI is associated with an enhanced type 3-0 DCI; and

the first sidelink transmission opportunity is associated with a type-2 listen-before-talk (LBT) procedure.

15. A first user equipment (UE) comprising:

a transceiver configured to:

receive, from a base station (BS), a first downlink control information (DCI) associated with a first listen-before-talk (LBT) time, wherein the first DCI is associated with a cyclic prefix (CP) extension, and wherein the CP extension is associated with a traffic priority;

and

a processor coupled to the transceiver, wherein the processor is configured to:

determine a start time of a first sidelink transmission opportunity for communicating in an unlicensed frequency band at the first LBT time based on the traffic priority associated with the CP extension.

16. The first UE of claim 15 , wherein:

the transceiver is further configured to:

receive the first DCI in a licensed frequency band, wherein the first DCI is further associated with a second LBT trigger opportunity; and

receive, from a first wireless communication device, a second LBT trigger associated with a second LBT time based on the second LBT trigger opportunity;

the processor is further configured to:

determine a second sidelink transmission opportunity for communicating in the unlicensed frequency band at the second LBT time based on the communicated second LBT trigger; and

the transceiver is further configured to:

transmit, to a second wireless communication device, in an unlicensed-band a first transmission in a physical sidelink shared channel (PSSCH) at one of the first sidelink transmission opportunity or the second sidelink transmission opportunity.

17. The first UE of claim 16 wherein:

the second LBT trigger opportunity is associated with a time-frequency resource for detecting the second LBT trigger based on the first DCI;

the second LBT trigger opportunity is associated with a trigger format based on the first DCI;

and

the first wireless communication device is one of the BS, a transmission-and-reception point, or a proxy sidelink UE.

18. The first UE of claim 15 , wherein:

the first DCI is associated with an enhanced type 3-0 DCI; and

the first sidelink transmission opportunity is associated with a type-1 LBT procedure.

19. The first UE of claim 16 , wherein:

the second LBT trigger opportunity is further associated with a pre-configured sidelink-band trigger; and

the pre-configured sidelink-band trigger is based on one of a system information block configuration, a radio resource control (RRC) message configuration, or a media access control control element (MAC-CE) message configuration.

20. The first UE of claim 16 , wherein:

the second LBT time is prior to the first LBT time;

the first sidelink transmission opportunity is associated with a type-1 LBT procedure;

the second sidelink transmission opportunity is associated a type-2 LBT procedure; and

the transceiver is further configured to:

transmit the first transmission in a physical sidelink shared channel (PSSCH) at the second sidelink transmission opportunity based on the type-2 LBT procedure associated with second first sidelink transmission opportunity being successful; or

transmit the first transmission in a physical sidelink shared channel (PSSCH) at the first sidelink transmission opportunity based on the type-2 LBT procedure associated with the second sidelink transmission opportunity being unsuccessful.

21. The first UE of claim 16 , wherein:

the first LBT time is prior to the second LBT time;

an ending time of the determined second sidelink transmission opportunity is based on one of an ending time of the first sidelink transmission opportunity or an overriding ending time of the second sidelink transmission opportunity; and

the ending time of the determined second sidelink transmission opportunity is based on one of the first DCI, a system information block, or a radio resource configuration (RRC) message.

22. The first UE of claim 16 , wherein:

the second LBT trigger is associated with a simplified type 2-0 DCI;

the transceiver is further configured to:

receive the second LBT trigger based on a common search space (CSS) configuration in the unlicensed frequency band;

the CSS configuration is based on an enhanced system information block; and

the first wireless communication device is the BS.

23. The first UE of claim 16 , wherein the second sidelink transmission opportunity is associated with a type-2 LBT procedure.

24. The first UE of claim 15 , wherein the processor is further configured to:

determine a cyclic prefix (CP) extension configuration for the first sidelink transmission opportunity based on one of a system information block configuration or a radio resource control (RRC) message configuration.

25. The first UE of claim 15 , wherein the processor is further configured to:

determine a channel access priority class (CAPC) configuration for the first sidelink transmission opportunity based on one of a system information block configuration or a radio resource control (RRC) message configuration.

26. The first UE of claim 15 , wherein the transceiver is further configured to:

receive the first DCI in an unlicensed frequency band;

wherein the first DCI is associated with an enhanced type 3-0 DCI; and

wherein the first sidelink transmission opportunity is associated with a type-2 listen-before-talk (LBT) procedure.

27. A first user equipment (UE), comprising:

means for receiving, from a base station (BS), a first downlink control information (DCI) associated with a first listen-before-talk (LBT) time, wherein the first DCI is associated with a cyclic prefix (CP) extension, and wherein the CP extension is associated with a traffic priority; and

means for determining a start time of a first sidelink transmission opportunity for communicating in an unlicensed frequency band at the first LBT time based on the traffic priority associated with the CP extension.

28. The first UE of claim 27 , wherein:

the means for receiving the first DCI comprises:

means for receiving the first DCI in a licensed frequency band;

the first DCI is further associated with a second LBT trigger opportunity;

the first UE further comprises:

means for receiving, from a first wireless communication device, a second LBT trigger associated with a second LBT time based on the second LBT trigger opportunity;

means for determining a second sidelink transmission opportunity for communicating in the unlicensed frequency band at the second LBT time based on the communicated second LBT trigger; and

means for transmitting, to a second wireless communication device, in an unlicensed-band a first transmission in a physical sidelink shared channel (PSSCH) at one of the first sidelink transmission opportunity or the second sidelink transmission opportunity.

29. The first UE of claim 28 , wherein:

the second LBT trigger opportunity is associated with a time-frequency resource for detecting the second LBT trigger based on the first DCI;

the second LBT trigger opportunity is associated with a trigger format based on the first DCI;

and

the first wireless communication device is one of the BS, a transmission-and-reception point, or a proxy sidelink UE.

30. A base station (BS), comprising:

a processor configured to:

determine a start time of a first sidelink transmission opportunity for communicating in an unlicensed frequency band at a first listen-before-talk (LBT) time;

and

a transceiver coupled to the processor, wherein the transceiver is configured to:

transmit, to a user equipment (UE) in a licensed frequency band, a first downlink control information (DCI) associated with the determined first sidelink transmission opportunity, the DCI indicating a cyclic prefix (CP) extension, wherein the start time of the first sidelink transmission opportunity is based on a traffic priority associated with the CP extension.