5G • RAN
Scheduling Request (SR)
Uplink Scheduling Request
Physical layer signal sent on PUCCH by UE to request PUSCH uplink resources when no grant is available.
Technical Explanation
When new data arrives in an empty UE buffer and triggers a regular Buffer Status Report (BSR), the UE transmits a Scheduling Request (SR) on configured periodic PUCCH Format 0 or Format 1 resources. The gNodeB responds with an uplink grant (DCI Format 0_0/0_1), allowing the UE to transmit its BSR and payload.
Key Functions
- Transmits 1-bit resource request on dedicated PUCCH occasions
- Triggered by arrival of high-priority data in empty uplink buffer
- Prompts gNodeB to issue dynamic PUSCH grant via DCI
Specifications
3GPP TS 38.213, TS 38.321
Interfaces
Uu
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