Technical reference hub for telecom engineers

Structured protocol references, message databases, call flows, troubleshooting guides, releases, and engineering tools for wireless and telecom engineers.

Search the platform

Search by protocol, message, procedure, symptom, tool, or release.

Initial Context Setup Failure NGAP Downlink NAS Transport RRC Setup Failure PDU Session Establishment Failure

Explore by Technology

5G

Architecture, interfaces, protocols, procedures, and technical reference pages for NR.

LTE

LTE protocol references, mobility procedures, messages, and engineering lookup pages.

6G

Early-stage 6G concepts, standardization status, and next-generation wireless reference material.

Troubleshooting Guides

5G Initial Access Troubleshooting

Isolate failures in cell search, PBCH decode, SIB1 acquisition, suitability checks, camping, and pre-random-access gating.

TAI and Tracking Area Mismatch Troubleshooting

Troubleshoot TAC broadcast errors, tracking-area restrictions, roaming-area mismatch, and area-related registration reject causes.

AMF Selection and GUAMI Issues

Troubleshoot wrong AMF targeting, stale GUAMI or 5G-GUTI context, and broken AMF-selection hints across RRC and NGAP.

5G Registration Failure Troubleshooting

End-to-end guide for registration reject, incomplete registration, AMF selection issues, and first-access failures.

Initial Context Setup Failure Analysis

Diagnose failures during Initial Context Setup and isolate core, policy, or radio-side blockers.

PDU Session Establishment Failure

Diagnose failed session setup, 5GSM reject causes, policy gaps, and missing path creation.

Latest Updates

Protocol 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.

Protocol 5G NAS Protocol Overview

Complete 5G NAS protocol overview covering N1 placement, 5GMM and 5GSM, UE to AMF and UE to SMF signaling roles, NAS security, major procedure families, and related message, call flow, and troubleshooting paths.

Protocol 5G NR RRC Overview: 38.331 Release 18 Reference

Complete 5G NR RRC overview based on 3GPP TS 38.331 Release 18. Learn RRC states, procedures, messages, system information, measurements, mobility, security, troubleshooting, and related call flows.

Protocol 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.

Protocol 5G RLC Acknowledged Mode | AM RLC, AMD PDUs, STATUS and ARQ in NR

Learn 5G NR RLC acknowledged mode with AM architecture, AMD and STATUS PDUs, transmit and receive windows, ARQ retransmission, polling, reassembly, timers, and trace analysis guidance.

Protocol 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.