5G • RAN
IR-HARQ
Incremental Redundancy HARQ
HARQ mechanism where retransmissions send different parity bit subsets to progressively lower effective code rate.
Technical Explanation
Under Incremental Redundancy, if a transport block fails CRC verification, the receiver buffers the soft Log-Likelihood Ratios (LLRs). The retransmission transmits a different Redundancy Version (e.g. RV2 following RV0). The receiver combines both transmissions, accumulating coding gain and dramatically reducing retransmission counts.
Key Functions
- Transmits complementary parity bits on each successive retransmission
- Accumulates soft energy and coding gain in receiver LLR memory
- Standard operating mode for 5G PDSCH and PUSCH
Specifications
3GPP TS 38.212, TS 38.214
Interfaces
Uu
Related 5G Concepts
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