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5G Reference

5G Protocols

The 5G protocol stack defines how data and signaling are transmitted across the physical layer, radio interface, and core network.

This page provides a structured reference of key 5G protocols, including PHY, RRC, PDCP, SDAP, NAS, and NGAP, with explanations aligned to 3GPP specifications.

The content is organized from lower layers to higher layers, helping you understand how physical transmission, radio resource control, and core network signaling work together in 5G systems.

NGAPNASRRCPDCPSDAPPHY

Released Protocols

Interface: NG Open

NGAP

NG interface signaling between NG-RAN and AMF.
Layer: Control plane Open

NAS

5GMM and 5GSM procedures, messages, and session control.
Layer: Access stratum Open

RRC

Radio resource control and access-stratum procedures.
Layer: User and control plane Open

PDCP

Packet handling, duplication, header compression, and recovery behavior.
Layer: QoS adaptation Open

SDAP

QoS flow mapping and service data adaptation.
Layer: Physical Open

PHY

Physical layer procedures and radio transmission topics.

Recently Added Protocol Pages

5G NAS QoS Rules, IP Addressing, and Session Context

Release 18 reference for 5G NAS IP address allocation, QoS rules, QoS flow descriptions, Session-AMBR, reflective QoS, and the session context created at establishment and updated during modification.

 5G NR RRC Timers and Constants: T300, T302, T304, T310, T311, T319, T320, T380, T390, T430, N310, N311

5G NR RRC timers and constants reference based on 3GPP TS 38.331 Release 18. Check T300, T301, T302, T304, T310, T311, T319, T320, T380, T390, T430, N310, and N311 for setup, reject wait, handover, radio link failure, resume supervision, release, and barring handling.

 5G NR ARFCN

Complete 5G NR ARFCN reference based on Release 18 band and raster rules. Learn global frequency raster mapping, channel raster, FR1 and FR2 ranges, formulas, band context, GSCN comparison, and troubleshooting checks.

 NGAP Identifiers and Logical Connections

Complete NGAP identifiers and logical connections reference covering AMF UE NGAP ID, RAN UE NGAP ID, UE-associated logical NG-connection, identifier lifecycle, trace correlation, reset behavior, and troubleshooting.

 5G PDCP Ciphering and Integrity Protection | COUNT, MAC-I and PDCP Security in NR

Learn 5G NR PDCP ciphering and integrity protection with COUNT, BEARER, DIRECTION, KEY, MAC-I, DAPS bearer handling, and how PDCP applies security in transmit and receive paths.

 5G SDAP Architecture, Services, and Functions

5G SDAP architecture reference covering SDAP entities, protocol placement, services to upper layers, lower-layer expectations, QoS flow mapping, reflective QoS, MRB handling, and sidelink functions.