Triggering HARQ-ACK feedback for a downlink slot set

1. An apparatus comprising:

a receiver that receives a first control signal from a base unit for triggering hybrid automatic repeat request acknowledgement (HARQ-ACK) feedback for a downlink slot set, wherein the downlink slot set comprises multiple downlink slots and the HARQ-ACK feedback for the downlink slot set corresponds to all downlink transmissions in the downlink slot set and is transmitted in one uplink control information (UCI) and the first control signal indicates one or more of: a starting slot index for the downlink slot set, an ending slot index for the downlink slot set, and a number of slots of the downlink slot set;

a processor that identifies the downlink slot set in response to the first control signal using the indication received in the first control signal; and

a transmitter that transmits UCI to the base unit in a slot determined by the first control signal, wherein the UCI comprises the HARQ-ACK feedback for the identified downlink slot set.

2. The apparatus of claim 1 , wherein the receiver also receives a radio resource control (RRC) signal and the processor enters a triggered reporting mode, wherein the apparatus does not transmit HARQ-ACK feedback until an UCI transmission request is received, wherein the first control signal contains an UCI transmission request.

3. The apparatus of claim 2 , wherein the first control signal is an uplink grant that includes a flag to indicate the UCI transmission request.

4. The apparatus of claim 1 , wherein the first control signal is an uplink grant for UCI transmission, and wherein the processor detects an uplink grant for data transmission using a first radio network temporary identifier (RNTI) and detects the uplink grant for UCI transmission using a second RNTI.

5. The apparatus of claim 1 , wherein the downlink slot set comprises one or more of: multiple PDSCH transmissions on multiple slots, multiple PDSCH transmissions on multiple mini-slots, and multiple PDSCH transmissions on multiple carriers.

6. The apparatus of claim 1 , wherein the first control signal indicates one or more of: a HARQ-ACK codebook size, a timing offset for UCI transmission, a UCI transmission resource in time domain, a UCI transmission resource in frequency domain, a Polar coding rate for UCI encoding, and a UCI transmission format.

7. The apparatus of claim 1 , wherein the first control signal indicates a carrier index indicating a scheduled carrier for the UCI transmission.

8. The apparatus of claim 1 , wherein the downlink slot set ends a determined number of slots prior to a slot where the first control signal is received.

9. The apparatus of claim 1 , wherein the downlink slot set ends at a slot where the first control signal is received.

10. The apparatus of claim 1 , wherein the receiver further receives a RRC signal for configuring a maximum number of slots of the downlink slot set, wherein the first control signal is received in the last slot of the downlink slot set.

11. A method comprising:

receiving a first control signal from a base unit for triggering hybrid automatic repeat request acknowledgement (HARQ-ACK) feedback for a downlink slot set, wherein the downlink slot set comprises multiple downlink slots and the HARQ-ACK feedback for the downlink slot set corresponds to all downlink transmissions in the downlink slot set and is transmitted in one uplink control information (UCI) and the first control signal indicates one or more of: a starting slot index for the downlink slot set, an ending slot index for the downlink slot set, and a number of slots of the downlink slot set;

identifying the downlink slot set in response to the first control signal using the indication received in the first control signal; and

transmitting UCI to the base unit in a slot determined by the first control signal, wherein the UCI comprises the HARQ-ACK feedback for the identified downlink slot set.

12. The method of claim 11 , further comprising receiving a radio resource control (RRC) signal and entering a triggered reporting mode, wherein HARQ-ACK feedback is only transmitted to the base unit, while in the triggered reporting mode, in response to receiving a UCI transmission request, wherein the first control signal contains a UCI transmission request.

13. The method of claim 12 , wherein the first control signal is an uplink grant that includes a flag to indicate the UCI transmission request.

14. The method of claim 11 , wherein the first control signal is an uplink grant for UCI transmission, the method further comprising detecting an uplink grant for data transmission using a first radio network temporary identifier (RNTI) and detecting the uplink grant for UCI transmission using a second RNTI.

15. The method of claim 11 , wherein the downlink slot set comprises one or more of: multiple PDSCH transmissions on multiple slots, multiple PDSCH transmissions on multiple mini-slots, and multiple PDSCH transmissions on multiple carriers.

16. The method of claim 11 , wherein the first control signal indicates one or more of: HARQ-ACK codebook size, timing offset for UCI transmission, UCI transmission resource in time domain, UCI transmission resource in frequency domain, Polar coding rate for UCI encoding, UCI transmission format.

17. The method of claim 11 , wherein the first control signal indicates a carrier index indicating a scheduled carrier for the UCI transmission.

18. The method of claim 11 , wherein the downlink slot set ends a determined number of slots prior to a slot where the first control signal is received.