5G RRC Connection Setup Procedure | Between UE and 5G RAN

This page describes 5G RRC Connection Setup Procedure between UE and 5G RAN. The 5G RRC connection setup procedure covers messages exchanged between UE and 5G RAN (5G Radio Access Network).

The Figure-1 depicts 5G User Plane protocol stack and Control Plane protocol stack. As shown 5G user plane consists of PHY, MAC, RLC and PDCP layers. Here PHY is physical layer i.e. layer-1 and rest are layer-2 as per OSI stack.

5G Protocol Stack- User Plane and Control Plane

As shown 5G control plane consists of PHY, MAC, RLC, PDCP, RRC and NAS (between UE and NG Core). RRC stands for Radio Resource Control. It is protocol used for signaling between 5G radio network and UE.

RRC has two states and state transitions viz. RRC_IDLE and RRC_CONNECTED. Following are the basic functions performed by RRC sublayer.
• Broadcasting of system informations to NAS and AS.
• Establishment, maintenance and release of RRC connection.
• Security including key management
• Establishment, configuration, maintenance and release of point-point radio bearers.
• Mobility functions, measurement reporting etc.

5G RRC Connection Setup Procedure

5G RRC Connection Setup Procedure

➨The figure-2 depicts 5G RRC connection setup procedure.
➨As shown UE receives SS (Synchronization Signal) broadcasted by 5G-RAN. UE performs synchronization using SS.
➨UE decodes MIB and measures BRS to determine downlink beam pair. UE also decodes SIB. Refer 5G MIB and SIB >>.
➨UE transmits RACH preamble towards RAN. 5G-RAN replies with RACH response to UE.
➨UE transmits RRC connection request to 5G-RAN.
➨5G-RAN replies RRC connection setup complete to UE.
➨After the RRC connection is established between UE and 5G-RAN, re-configuration may happen between them as and when required.

Reference: TS V5G.300: "Network and Signaling Working Group; Verizon 5th Generation Radio Access; Overall Description"

5G NR Numerology | 5G NR Terminology

5G NR Control channels | 5G NR Traffic Channels | 5G NR Reference Signals and sequences


This 5G tutorial also covers following sub topics on the 5G technology:
5G basic tutorial
5G Frequency Bands
5G millimeter wave tutorial
5G mm wave frame
5G millimeter wave channel sounding
Difference between 4G and 5G
5G testing and test equipments
5G network architecture
5G NR Physical layer
5G NR MAC layer
5G NR RLC layer
5G NR PDCP layer

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