Method and apparatus for HARQ-ACK feedback for carrier aggregation

1. A method comprising:

receiving at least one downlink transmission;

generating a first hybrid automatic repeat request-acknowledgement sub-codebook for the at least one downlink transmission;

determining whether to generate a second hybrid automatic repeat request-acknowledgement sub-codebook, wherein determining whether to generate the second hybrid automatic repeat request-acknowledgement sub-codebook is based on whether the at least one downlink transmission is mapped to the first hybrid automatic repeat request-acknowledgement sub-codebook;

receiving an indicator for indicating whether the second hybrid automatic repeat request-acknowledgement sub-codebook exists;

generating the second hybrid automatic repeat request-acknowledgement sub-codebook based on the received indicator; and

transmitting a hybrid automatic repeat request-acknowledgement codebook, wherein the hybrid automatic repeat request-acknowledgement codebook comprises the first hybrid automatic repeat request-acknowledgement sub-codebook in response to the second hybrid automatic repeat request-acknowledgement sub-codebook determined not to be generated, or comprises the first hybrid automatic repeat request-acknowledgement sub-codebook and the second hybrid automatic repeat request-acknowledgement sub-codebook in response to the second hybrid automatic repeat request-acknowledgement sub-codebook determined to be generated.

2. The method of claim 1 , wherein each bit in the first hybrid automatic repeat request-acknowledgement sub-codebook corresponds to one transport block of the at least one downlink transmission, and each bit in the second hybrid automatic repeat request-acknowledgement sub-codebook corresponds to one code block group of one transport block of the at least one downlink transmission.

3. The method of claim 2 , comprising: in response to the second hybrid automatic repeat request-acknowledgement sub-codebook determined to be generated, generating M bits for the second hybrid automatic repeat request-acknowledgement sub-codebook, wherein M is the configured maximum number of code block groups per transport block across all the carriers configured with code block group-based retransmission.

4. The method of claim 1 , wherein each bit in the first hybrid automatic repeat request-acknowledgement sub-codebook corresponds to one code block group of one transport block of the at least one downlink transmission, and each bit in the second hybrid automatic repeat request-acknowledgement sub-codebook corresponds to one transport block of the at least one downlink transmission.

5. The method of claim 4 , comprising: in response to the second hybrid automatic repeat request-acknowledgement sub-codebook determined to be generated, generating one bit for the second hybrid automatic repeat request-acknowledgement sub-codebook.

6. The method of claim 1 , comprising in response to the second hybrid automatic repeat request-acknowledgement sub-codebook determined to be generated, generating at least one bit for the second hybrid automatic repeat request-acknowledgement sub-codebook.

7. The method of claim 1 , wherein determining whether to generate the second hybrid automatic repeat request-acknowledgement sub-codebook is based on whether the at least one downlink transmission is only mapped to the first hybrid automatic repeat request-acknowledgement sub-codebook.

8. The method of claim 1 , further comprising: receiving an indicator for indicating a number of hybrid automatic repeat request-acknowledgement sub-codebooks, and generating the second hybrid automatic repeat request-acknowledgement sub-codebook based on the received indicator.

9. The method of claim 8 , wherein the indicator is included in downlink control information.

10. A method comprising:

transmitting at least one downlink transmission;

transmitting an indicator for indicating whether a second hybrid automatic repeat request-acknowledgement sub-codebook exists;

determining whether a hybrid automatic repeat request-acknowledgement codebook for the at least one downlink transmission comprises only a first hybrid automatic repeat request-acknowledgement sub-codebook, or comprises a first hybrid automatic repeat request-acknowledgement sub-codebook and the second hybrid automatic repeat request-acknowledgement sub-codebook, wherein the second hybrid automatic repeat request-acknowledgement sub-codebook is generated is based on whether the at least one downlink transmission is mapped to the first hybrid automatic repeat request-acknowledgement sub-codebook; and

receiving the hybrid automatic repeat request-acknowledgement codebook.

11. The method of claim 10 , wherein the first hybrid automatic repeat request-acknowledgement sub-codebook includes hybrid automatic repeat request-acknowledgement bits with each bit corresponding to one transport block of the at least one downlink transmission, and the second hybrid automatic repeat request-acknowledgement sub-codebook includes hybrid automatic repeat request-acknowledgement bits with each bit corresponding to one code block group of one transport block of the at least one downlink transmission.

12. The method of claim 10 , wherein the first hybrid automatic repeat request-acknowledgement sub-codebook includes hybrid automatic repeat request-acknowledgement bits with each bit corresponding to one code block group of one transport block of the at least one downlink transmission, and the second hybrid automatic repeat request-acknowledgement sub-codebook includes hybrid automatic repeat request-acknowledgement bits with each bit corresponding to one transport block of the at least one downlink transmission.

13. The method of claim 10 , wherein the transmitted indicator is included in downlink control information.

14. The method of claim 10 , comprising:

in response to there being a single downlink transmission, determining the hybrid automatic repeat request-acknowledgement codebook to comprise only the first hybrid automatic repeat request-acknowledgement sub-codebook;

in response to there being more than one downlink transmission transmitted on a carrier configured with transport block-based retransmission or on a carrier configured with code block group-based retransmission and scheduled by downlink control information format 1_0, determining the hybrid automatic repeat request-acknowledgement codebook to comprise only the first hybrid automatic repeat request-acknowledgement sub-codebook;

in response to there being more than one downlink transmission transmitted on a carrier configured with code block group-based retransmission and scheduled by downlink control information format 1_1, determining the hybrid automatic repeat request-acknowledgement codebook to comprise only the first hybrid automatic repeat request-acknowledgement sub-codebook; and

in response to there being more than one downlink transmission, partly transmitted on a carrier configured with transport block-based retransmission or on a carrier configured with code block group-based retransmission and scheduled by downlink control information format 1_0, and partly transmitted on a carrier configured with code block group-based retransmission and scheduled by downlink control information format 1_1, determining the hybrid automatic repeat request-acknowledgement codebook to comprise the first hybrid automatic repeat request-acknowledgement sub-codebook and the second hybrid automatic repeat request-acknowledgement sub-codebook.

15. An apparatus comprising:

a receiver that receives at least one downlink transmission;

a processor that generates a first hybrid automatic repeat request-acknowledgement sub-codebook for the at least one downlink transmission, and determines whether to generate a second hybrid automatic repeat request-acknowledgement sub-codebook, wherein determining whether to generate the second hybrid automatic repeat request-acknowledgement sub-codebook is based on whether the at least one downlink transmission is mapped to the first hybrid automatic repeat request-acknowledgement sub-codebook; and

a transmitter that transmits a hybrid automatic repeat request-acknowledgement codebook, wherein the hybrid automatic repeat request-acknowledgement codebook comprises the first hybrid automatic repeat request-acknowledgement sub-codebook in response to the second hybrid automatic repeat request-acknowledgement sub-codebook determined not to be generated, or comprises the first hybrid automatic repeat request-acknowledgement sub-codebook and the second hybrid automatic repeat request-acknowledgement sub-codebook in response to the second hybrid automatic repeat request-acknowledgement sub-codebook determined to be generated, wherein:

the receiver receives an indicator for indicating whether the second hybrid automatic repeat request-acknowledgement sub-codebook exists; and

the processor generates the second hybrid automatic repeat request-acknowledgement sub-codebook based on the received indicator.

16. An apparatus comprising:

a transmitter that:

transmits at least one downlink transmission; and

transmits an indicator for indicating whether a second hybrid automatic repeat request-acknowledgement sub-codebook exists;

a processor that determines whether a hybrid automatic repeat request-acknowledgement codebook for the at least one downlink transmission comprises only a first hybrid automatic repeat request-acknowledgement sub-codebook, or comprises a first hybrid automatic repeat request-acknowledgement sub-codebook and the second hybrid automatic repeat request-acknowledgement sub-codebook, wherein the second hybrid automatic repeat request-acknowledgement sub-codebook is generated is based on whether the at least one downlink transmission is mapped to the first hybrid automatic repeat request-acknowledgement sub-codebook; and

a receiver that receives the hybrid automatic repeat request-acknowledgement codebook.