5G • Services
PSFCH
Physical Sidelink Feedback Channel
Physical channel carrying HARQ ACK/NACK feedback between vehicles over the direct PC5 sidelink.
Technical Explanation
Introduced in 5G NR V2X, the PSFCH transmits dedicated HARQ feedback for sidelink groupcast and unicast transmissions. Vehicles send 1-bit ACK/NACK using sequence cyclic shifts over a single PRB in the slot's second-to-last symbol, ensuring high reliability for critical collision warnings.
Key Functions
- Provides over-the-air HARQ ACK/NACK feedback between peer vehicles
- Enables retransmission of lost vehicle safety packets over PC5
- Employs sequence cyclic shifts across single PRB in designated feedback slots
Specifications
3GPP TS 38.211, TS 38.213
Interfaces
PC5
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