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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 Sidelink SDAP Overview and SL-DRB Mapping

5G SDAP reference covering sidelink SDAP over PC5, SDAP entity model per destination and cast type, PC5 QoS flow to SL-DRB mapping, default SL-DRB behavior, and sidelink limits such as no Reflective QoS over PC5.

 5GS UE and Network Identities: SUPI, SUCI, 5G-GUTI, GUAMI, PEI, GPSI, and More

Understand 5GS identities and identifiers including SUPI, SUCI, 5G-GUTI, 5G-S-TMSI, 5G-TMSI, GUAMI, PEI, GPSI, IMSI-based and NAI-based forms, with structures, examples, and usage in 5G procedures.

 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 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.

 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 Frame Structure

Complete 5G NR frame structure reference based on Release 18 PHY specifications. Learn frames, subframes, slots, mini-slots, OFDM symbols, TDD timing, scheduling context, and troubleshooting checks.