Semi-static HARQ-ACK codebook with multiple PDSCH transmissions per slot

1. A method for wireless communications by a user equipment (UE), comprising:

receiving first signaling defining time domain resources for a number of physical downlink shared channel (PDSCH) candidates within a transmission time interval (TTI);

receiving second signaling scheduling the UE to receive at least two PDSCH transmissions according to the PDSCH candidates;

determining which acknowledgment/negative acknowledgement (ACK/NACK) fields, of a codebook with fewer ACK/NACK fields than the number of PDSCH candidates, to use to provide ACK/NACK feedback for which of the scheduled PDSCH transmissions, wherein the determination comprises:

determining whether at least one PDSCH candidate overlaps in time with at least two other PDSCH candidates;

picking, as a reference set, a maximum number of non-overlapping PDSCH candidates per slot as defined by the first signaling, wherein each PDSCH candidate in the reference set is mapped to one of the ACK/NACK fields;

for each PDSCH candidate not in the reference set, mapping that PDSCH candidate to an ACK/NACK field of a PDSCH candidate in the reference set when that PDSCH candidate starting symbol is:

within a duration of the PDSCH candidate in the reference set or occurs in a gap between the PDSCH candidate in the reference set and the end of a previous PDSCH candidate in the reference set; and

providing ACK/NACK feedback for the scheduled PDSCH transmissions according to the determination.

2. The method of claim 1 , wherein the TTI comprises a time slot within a subframe or a portion of a time slot.

3. The method of claim 1 , further comprising, if the same ACK/NACK field is determined for more than one scheduled PDSCH candidate, bundling the corresponding ACK/NACK feedback for those PDSCH candidates.

4. The method of claim 1 , wherein the determination is based on a function that maps each PDSCH candidate to one of the ACK/NACK fields.

5. The method of claim 4 , wherein the function comprises a hashing function that takes a start and length indicator vector (SLIV) as an input and outputs a location corresponding to one of the ACK/NACK fields.

6. The method of claim 1 , further comprising:

grouping the PDSCH candidates into at least first and second groups of PDSCH candidates whose time domain resources do not overlap; and

wherein the determination of which ACK/NACK field to use for a given PDSCH candidate is based on a location of that PDSCH candidate within its group.

7. The method of claim 6 , wherein a scheduling rule prevents PDSCH candidates from both the first and second groups from being scheduled in the same TTI.

8. The method of claim 1 , wherein:

the first signaling conveys a table with entries corresponding to PDSCH candidates; and

the reference set is obtained based on the order of occurrence of entries in the table.

9. A method for wireless communications by a network entity, comprising:

providing, to a user equipment (UE), first signaling defining time domain resources for a number of physical downlink shared channel (PDSCH) candidates within a transmission time interval (TTI);

providing second signaling scheduling the UE to receive at least two PDSCH transmissions according to the PDSCH candidates;

determining which acknowledgment/negative acknowledgement (ACK/NACK) fields, of a codebook with fewer ACK/NACK fields than the number of PDSCH candidates, to use to provide ACK/NACK feedback for which of the scheduled PDSCH transmissions, wherein the determination comprises:

determining whether at least one PDSCH candidate overlaps in time with at least two other PDSCH candidates;

picking, as a reference set, a maximum number of non-overlapping PDSCH candidates per slot as defined by the first signaling, wherein each PDSCH candidate in the reference set is mapped to one of the ACK/NACK fields; and

for each PDSCH candidate not in the reference set, mapping that PDSCH candidate to an ACK/NACK field of a PDSCH candidate in the reference set when that PDSCH candidate starting symbol is:

within a duration of the PDSCH candidate in the reference set or occurs in a gap between the PDSCH candidate in the reference set and the end of a previous PDSCH candidate in the reference set; and

processing ACK/NACK feedback, received from the UE, for the scheduled PDSCH transmissions according to the determination.

10. The method of claim 9 , wherein the TTI comprises a time slot within a subframe or a portion of a time slot.

11. The method of claim 9 , further comprising, determining that, if the same ACK/NACK field is determined for more than one scheduled PDSCH candidate, the UE bundled the corresponding ACK/NACK feedback for those PDSCH candidates.

12. The method of claim 9 , wherein the determination is based on a function that maps each PDSCH candidate to one of the ACK/NACK fields.

13. The method of claim 12 , wherein the function comprises a hashing function that takes a start and length indicator vector (SLIV) as an input and outputs a location corresponding to one of the ACK/NACK fields.

14. The method of claim 9 , further comprising:

grouping the PDSCH candidates into at least first and second groups of PDSCH candidates whose time domain resources do not overlap; and

wherein the determination of which ACK/NACK field to use for a given PDSCH candidate is based on a location of that PDSCH candidate within its group.

15. The method of claim 14 , further comprising avoiding scheduling PDSCH candidates from both the first and second groups in the same TTI.

16. The method of claim 9 , wherein:

the first signaling conveys a table with entries corresponding to PDSCH candidates; and

the reference set is obtained based on the order of occurrence of entries in the table.

17. An apparatus for wireless communications by a user equipment (UE), comprising:

means for receiving first signaling defining time domain resources for a number of physical downlink shared channel (PDSCH) candidates within a transmission time interval (TTI);

means for receiving second signaling scheduling the UE to receive at least two PDSCH transmissions according to the PDSCH candidates;

means for determining which acknowledgment/negative acknowledgement (ACK/NACK) fields, of a codebook with fewer ACK/NACK fields than the number of PDSCH candidates, to use to provide ACK/NACK feedback for which of the scheduled PDSCH transmissions, wherein the means for determining comprises:

means for determining whether at least one PDSCH candidate overlaps in time with at least two other PDSCH candidates;

means for picking, as a reference set, a maximum number of non-overlapping PDSCH candidates per slot as defined by the first signaling, wherein each PDSCH candidate in the reference set is mapped to one of the ACK/NACK fields; and

for each PDSCH candidate not in the reference set, means for mapping that PDSCH candidate to an ACK/NACK field of a PDSCH candidate in the reference set when that PDSCH candidate starting symbol is:

within a duration of the PDSCH candidate in the reference set or occurs in a gap between the PDSCH candidate in the reference set and the end of a previous PDSCH candidate in the reference set; and

means for providing ACK/NACK feedback for the scheduled PDSCH transmissions according to the determination.

18. The apparatus of claim 17 , wherein the determination is based on a function that maps each PDSCH candidate to one of the ACK/NACK fields.

19. The apparatus of claim 17 , further comprising:

means for grouping the PDSCH candidates into at least first and second groups of PDSCH candidates whose time domain resources do not overlap; and

wherein the determination of which ACK/NACK field to use for a given PDSCH candidate is based on a location of that PDSCH candidate within its group.

20. An apparatus for wireless communications by a network entity, comprising:

means for providing, to a user equipment (UE), first signaling defining time domain resources for a number of physical downlink shared channel (PDSCH) candidates within a transmission time interval (TTI);

means for providing second signaling scheduling the UE to receive at least two PDSCH transmissions according to the PDSCH candidates;

means for determining which acknowledgment/negative acknowledgement (ACK/NACK) fields, of a codebook with fewer ACK/NACK fields than the number of PDSCH candidates, to use to provide ACK/NACK feedback for which of the scheduled PDSCH transmissions, wherein the means for determining comprises:

means for determining whether at least one PDSCH candidate overlaps in time with at least two other PDSCH candidates;

means for picking, as a reference set, a maximum number of non-overlapping PDSCH candidates per slot as defined by the first signaling, wherein each PDSCH candidate in the reference set is mapped to one of the ACK/NACK fields; and

for each PDSCH candidate not in the reference set, means for mapping that PDSCH candidate to an ACK/NACK field of a PDSCH candidate in the reference set when that PDSCH candidate starting symbol is:

within a duration of the PDSCH candidate in the reference set or occurs in a gap between the PDSCH candidate in the reference set and the end of a previous PDSCH candidate in the reference set; and

means for processing ACK/NACK feedback, received from the UE, for the scheduled PDSCH transmissions according to the determination.

21. The apparatus of claim 20 , wherein the determination is based on a function that maps each PDSCH candidate to one of the ACK/NACK fields.

22. The apparatus of claim 20 , further comprising:

means for grouping the PDSCH candidates into at least first and second groups of PDSCH candidates whose time domain resources do not overlap; and

wherein the determination of which ACK/NACK field to use for a given PDSCH candidate is based on a location of that PDSCH candidate within its group.