5G • RAN
HARQ-ACK Codebook Type 2
Dynamic HARQ-ACK Codebook
Adaptive HARQ feedback codebook where feedback size dynamically matches actually scheduled transmissions via DAI.
Technical Explanation
Type 2 (Dynamic) codebook sizes the HARQ-ACK payload based on Counter DAI and Total DAI values in received DCIs. The UE transmits only as many ACK/NACK bits as there were actually scheduled PDSCHs, dramatically reducing PUCCH bit overhead in Carrier Aggregation and bursty data traffic.
Key Functions
- Dynamically sizes HARQ feedback bits based on received DAI values
- Eliminates empty NACK bits for unscheduled candidate slots
- Standard feedback mode in multi-carrier 5G mobile networks
Specifications
3GPP TS 38.213
Interfaces
Uu
Related 5G Concepts
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