5G NR Scheduling Request Procedure and Uplink Grant

This page describes the 5G NR Scheduling Request Procedure between the User Equipment (UE) and the gNB (base station). It outlines the messages exchanged between them, specifically the Scheduling Request (SR) and the Uplink Grant, as defined in the 3GPP Physical (PHY) and Medium Access Control (MAC) layer specifications.

5G NR Scheduling Procedure

Here’s a breakdown of the procedure:

• It’s one of the fundamental services the MAC layer expects from the Physical layer.
• When the UE has data to send, it requests an uplink grant from the gNB (the network) by sending a “scheduling request” message over the PUCCH channel (Physical Uplink Control Channel).
• The network (gNB) responds to the UE with the uplink grant. This grant is delivered in a DCI (Downlink Control Information) message, either DCI 0_0 or DCI 0_1, transmitted over the PDCCH channel (Physical Downlink Control Channel).
• Following the grant, the UE begins transmitting its data over the PUSCH channel (Physical Uplink Shared Channel).
• Certain PUCCH formats are specifically used to carry the Scheduling Request message.
• The entire scheduling procedure is managed by MAC layer processes, detailed in section 5.4.4 of the 3GPP TS 38.321 document.

References

• 3GPP TS 38.321 V15.2.0 (2018-06), MAC specification (Release 15)
• 3GPP TS 38.211 V15.2.0 (2018-06), Physical channels and modulation
• 3GPP TS 38.300 V15.2.0 (2018-06), NR and NG-RAN Overall Description