Multi-TTI selective grant for sidelink communication in unlicensed spectrum
Certain aspects of the present disclosure provide a method for wireless communications by a transmitter UE. The method generally includes receiving, from a network entity, a downlink control information (DCI) allocating resources in an unlicensed frequency band for multiple physical sidelink shared channel (PSSCH) transmissions across multiple transmission time intervals (TTIs), performing a listen-before-talk (LBT) channel access procedure in the TTIs, and transmitting, to at least one receiver UE, one or more PSSCHs in one or more of the TTIs being indicated as passing the LBT channel access procedure based on the performance.
1. A method for wireless communications by a transmitter user equipment (UE), comprising:
receiving, from a network entity, a downlink control information (DCI) allocating resources in an unlicensed frequency band for multiple physical sidelink shared channel (PSSCH) transmissions across multiple transmission time intervals (TTIs);
performing a listen-before-talk (LBT) channel access procedure in the multiple TTIs; and
transmitting, to at least one receiver UE, one or more PSSCHs in one or more of the multiple TTIs being indicated as passing the LBT channel access procedure based on the performance.
2. The method of claim 1 , wherein the multiple TTIs comprise continuous slots.
3. The method of claim 2 , wherein the continuous slots are indicated by a time domain resource allocation (TDRA) table or a time resource assignment in a sidelink control information (SCI) field of the DCI.
4. The method of claim 1 , wherein:
the DCI indicates a hybrid automatic repeat request (HARQ) identifier (HARQ ID); and
the method further comprises deriving a HARQ ID for each of the one or more PSSCHs based on the HARQ ID indicated in the DCI.
5. The method of claim 1 , wherein:
each of the one or more PSSCHs is scheduled with sidelink control information (SCI) associated with a new data indicator (NDI) bit to indicate whether a corresponding transport block (TB) contains new data or is a retransmission.
6. The method of claim 1 , wherein:
an initial transmission of each of the one or more PSSCHs is transmitted on a same starting subchannel.
7. The method of claim 1 , wherein:
each retransmission of the one or more PSSCHs has a same frequency allocation as an initial transmission of the same PSSCH.
8. The method of claim 1 , wherein:
each of the one or more PSSCH transmissions shares a same time resource assignment field; and
the method further comprises determining time domain resources for a retransmission of the one or more PSSCHs based on at least one rule.
9. The method of claim 8 , wherein:
the DCI allocates time domain resources for a first burst of PSSCHs for initial transmission and indicates a time domain offset between a first PSSCH of the first burst and a first PSSCH of a first burst of a second burst of PSSCHs for retransmission; and
the at least one rule indicates that each PSSCH in the second burst is offset by the same time domain offset from a corresponding PSSCH in the first burst.
10. The method of claim 1 , wherein:
the DCI indicates a sidelink assignment index (SAI) value for a first PSSCH of the one or more PSSCHs; and
the method further comprises deriving a SAI value for each of the remaining one or more PSSCHs based on the SAI value indicated in the DCI.
11. The method of claim 1 , further comprising:
receiving, from the receiver UE, one or more physical sidelink feedback channels (PSFCHs) associated with the one or more PSSCH transmissions;
mapping hybrid automatic repeat request (HARQ) bits in the one or more PSFCHs to a HARQ codebook used for providing physical uplink shared channel (PUSCH) physical uplink control channel (PUCCH) HARQ feedback; and
transmitting, to the network entity, a feedback for the one or more PSSCH transmissions based on the mapping.
12. The method of claim 11 , wherein:
when one of the multiple TTIs fails the LBT channel access procedure based on the performance, the UE sends a negative acknowledgment (NAK) for the corresponding HARQ bit being mapped to the HARQ codebook.
13. A method for wireless communications by a network entity, comprising:
transmitting, to a transmitter user equipment (UE), a downlink control information (DCI) allocating resources in an unlicensed frequency band for multiple physical sidelink shared channel (PSSCH) transmissions across multiple transmission time intervals (TTIs); and
receiving, from the transmitter UE, hybrid automatic repeat request (HARQ) feedback for the one or more PSSCH transmissions.
14. The method of claim 13 , wherein the multiple TTIs comprise continuous slots.
15. The method of claim 14 , wherein the continuous slots are indicated by a time domain resource allocation (TDRA) table or a time resource assignment in a sidelink control information (SCI) field of the DCI.
16. The method of claim 13 , wherein:
the DCI indicates a hybrid automatic repeat request (HARQ) identifier (HARQ ID) for use by the transmitter UE in deriving a HARQ ID for each of the one or more PSSCHs based on the HARQ ID indicated in the DCI.
17. The method of claim 13 , wherein:
each of the one or more PSSCHs is scheduled with sidelink control information (SCI) associated with a new data indicator (NDI) bit to indicate whether a corresponding transport block (TB) contains new data or is a retransmission.
18. The method of claim 13 , wherein:
an initial transmission of each of the one or more PSSCHs is scheduled for transmission on a same starting subchannel.
19. The method of claim 13 , wherein:
each retransmission of the one or more PSSCHs is scheduled for transmission with a same frequency allocation as an initial transmission of the same PSSCH.
20. The method of claim 13 , wherein:
each of the one or more PSSCH transmissions shares a same time resource assignment field for use by the transmitter UE in determining time domain resources for a retransmission of the one or more PSSCHs based on at least one rule.
21. The method of claim 20 , wherein:
the DCI allocates time domain resources for a first burst of PSSCHs for initial transmission and indicates a time domain offset between a first PSSCH of the first burst and a first PSSCH of a first burst of a second burst of PSSCHs for retransmission; and
the at least one rule indicates that each PSSCH in the second burst is offset by the same time domain offset from a corresponding PSSCH in the first burst.
22. The method of claim 13 , wherein:
the DCI indicates a sidelink assignment index (SAI) value for a first PSSCH of the one or more PSSCHs for use by the transmitter UE in deriving a SAI value for each of the remaining one or more PSSCHs based on the SAI value indicated in the DCI.
23. A transmitter user equipment (UE), comprising:
a receiver configured to receive, from a network entity, a downlink control information (DCI) allocating resources in an unlicensed frequency band for multiple physical sidelink shared channel (PSSCH) transmissions across multiple transmission time intervals (TTIs);
a processing system configured to perform a listen-before-talk (LBT) channel access procedure in the multiple TTIs; and
a transmitter configured to transmit, to at least one receiver UE, one or more PSSCHs in one or more of the multiple TTIs being indicated as passing the LBT channel access procedure based on the performance.
24. The transmitter UE of claim 23 , wherein at least one of:
the multiple TTIs comprise continuous slots; or
the continuous slots are indicated by a time domain resource allocation (TDRA) table or a time resource assignment in a sidelink control information (SCI) field of the DCI.
25. The transmitter UE of claim 23 , wherein:
each of the one or more PSSCH transmissions shares a same time resource assignment field; and
the processing system is further configured to determine time domain resources for a retransmission of the one or more PSSCHs based on at least one rule.
26. The transmitter UE of claim 25 , wherein:
the DCI allocates time domain resources for a first burst of PSSCHs for initial transmission and indicates a time domain offset between a first PSSCH of the first burst and a first PSSCH of a first burst of a second burst of PSSCHs for retransmission; and
the at least one rule indicates that each PSSCH in the second burst is offset by the same time domain offset from a corresponding PSSCH in the first burst.
27. The transmitter UE of claim 23 , wherein:
the receiver is further configured to receive, from the receiver UE, one or more physical sidelink feedback channels (PSFCHs) associated with the one or more PSSCH transmissions;
the processing system is further configured to map hybrid automatic repeat request (HARQ) bits in the one or more PSFCHs to a HARQ codebook used for providing physical uplink shared channel (PUSCH) physical uplink control channel (PUCCH) HARQ feedback; and
the transmitter is further configured to transmit, to the network entity, a feedback for the one or more PSSCH transmissions based on the mapping.
28. The transmitter UE of claim 27 , wherein:
when one of the multiple TTIs fails the LBT channel access procedure based on the performance, the UE sends a negative acknowledgment (NAK) for the corresponding HARQ bit being mapped to the HARQ codebook.
29. A network entity, comprising:
a transmitter configured to transmit, to a transmitter user equipment (UE), a downlink control information (DCI) allocating resources in an unlicensed frequency band for multiple physical sidelink shared channel (PSSCH) transmissions across multiple transmission time intervals (TTIs); and
a receiver configured to receive, from the transmitter UE, hybrid automatic repeat request (HARQ) feedback for the one or more PSSCH transmissions.
30. The network entity of claim 29 , wherein at least one of:
the multiple TTIs comprise continuous slots; or
the continuous slots are indicated by a time domain resource allocation (TDRA) table or a time resource assignment in a sidelink control information (SCI) field of the DCI.