5G • RAN
Chase Combining (CC)
Chase Combining HARQ
HARQ retransmission mode where identical coded bits are retransmitted to accumulate pure signal energy (Eb/N0).
Technical Explanation
In Chase Combining (equivalent to retransmitting RV0 repeatedly), the exact same coded bits are sent again. The receiver averages the received symbols across retransmissions to achieve maximal ratio combining (pure energy gain). While simpler than IR-HARQ, it yields less coding gain for a given bandwidth expenditure.
Key Functions
- Retransmits identical bit sequences to build received symbol SNR
- Performs soft symbol averaging across retransmission attempts
- Used in legacy fallbacks or when systematic bit energy is dominant
Specifications
3GPP TS 38.212, TS 38.214
Interfaces
Uu
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