5G • RAN
HARQ-ACK Codebook Type 1
Semi-Static HARQ-ACK Codebook
Pre-calculated HARQ feedback codebook with fixed bit positions for every candidate PDSCH occasion.
Technical Explanation
Type 1 (Semi-Static) codebook creates a fixed-size bit sequence based on configured RRC parameters (candidate slots, carrier aggregation cells, time-domain allocation tables). The UE generates an ACK or NACK for every possible occasion—reporting NACK for occasions where no PDCCH was received. It is simple but introduces unnecessary feedback overhead.
Key Functions
- Pre-computed fixed bit layout based strictly on RRC configuration
- Reports ACK or NACK for every possible candidate transmission occasion
- Robust against missed PDCCHs but has higher uplink feedback overhead
Specifications
3GPP TS 38.213
Interfaces
Uu
Related 5G Concepts
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