What is 3GLTEInfo?
3GLTEInfo is a technical telecom reference site covering 5G, LTE, IMS, protocol messages, call flows, troubleshooting, 3GPP releases, and wireless engineering tools.
5G, LTE, IMS & Telecom Engineering Reference
3GLTEInfo is a practical telecom engineering reference for 5G, LTE, IMS, radio access, core network signalling, protocol messages, architecture, interfaces, call flows, troubleshooting, 3GPP releases, and wireless tools.
Use the site to understand how mobile networks work, browse protocol messages, study call flows, troubleshoot signalling problems, and use engineering calculators and decoders.
Primary reference areas
5G Reference
Architecture, interfaces, protocols, call flows, messages, troubleshooting, tools, and releases for 5G.
LTE Reference
LTE architecture, RRC, NAS, S1AP, call flows, radio procedures, and troubleshooting.
IMS / SIP
IMS SIP requests, responses, registration, VoLTE, VoNR, call setup, early media, and call release.
Protocol Messages
Search and browse 5G, LTE, IMS, RRC, NAS, NGAP, F1AP, E1AP, XnAP, and S1AP messages.
Tools
NR-ARFCN, LTE EARFCN, throughput, GSCN, TBS, and protocol decoding tools.
Troubleshooting
Troubleshooting guides for registration, access, RRC, mobility, throughput, IMS, and protocol failures.
5G Engineering Reference
Start here for 5G architecture, interfaces, protocols, call flows, messages, troubleshooting, tools, and release-level features.
5G Architecture
System architecture, RAN, 5GC, and functional building blocks.
5G Interfaces
N1, N2, N3, N4, N6, N9, F1, E1, Xn, and service-based interfaces.
5G Protocols
NR, RRC, NAS, NGAP, SDAP, PDCP, RLC, MAC, and PHY references.
5G Call Flows
Registration, PDU session, handover, security, paging, and VoNR procedures.
5G Messages
Searchable 5G protocol message hubs and procedure groupings.
5G Troubleshooting
Access, registration, paging, session, security, and NGAP troubleshooting.
5G Tools
NR-ARFCN, GSCN, TBS, throughput, and engineering calculators.
3GPP Releases
Release 15 through Release 20 context for 5G and 5G-Advanced.
LTE Engineering Reference
Use the LTE library for architecture, EPC interfaces, RRC and NAS protocol references, S1AP messages, call flows, VoLTE context, and practical radio tools.
LTE Architecture
E-UTRAN, EPC, eNodeB, MME, SGW, PGW, PCRF, and VoLTE architecture.
LTE Interfaces
S1-MME, S1-U, S11, S5/S8, S6a, SGi, and X2 interface references.
LTE Protocols
LTE RRC, NAS, protocol stack, timers, states, and cause-value references.
LTE Call Flows
Attach, TAU, service request, detach, bearers, handover, CSFB, and VoLTE flows.
LTE RRC Messages
Radio connection, mobility, measurement, and system-information messages.
LTE NAS Messages
EPS mobility and session-management messages for attach, TAU, and bearers.
S1AP Messages
S1-MME procedures between eNodeB and MME for UE context and E-RAB handling.
LTE Tools
Start with LTE EARFCN conversion and related RF engineering tools.
Protocol Message Libraries
Start with the message family you are analyzing. Each hub includes searchable messages, procedure grouping, directions, key fields, and troubleshooting context.
5G Messages
Start from the complete 5G message library.
NGAP Messages
N2 control-plane messages between gNB and AMF.
5G RRC Messages
Radio-resource control messages for NR.
5G NAS Messages
5GMM and 5GSM signalling between UE and core.
F1AP Messages
CU-DU F1 control-plane procedure messages.
E1AP Messages
CU-CP and CU-UP E1 control-plane messages.
XnAP Messages
Inter-gNB mobility and coordination messages.
LTE Messages
Entry point for LTE message families.
LTE RRC Messages
LTE radio connection, mobility, and measurement messages.
LTE NAS Messages
EPS mobility and session-management messages.
S1AP Messages
S1-MME messages between eNodeB and MME.
IMS SIP Messages
IMS SIP requests and responses for VoLTE and VoNR.
Popular Engineering Tools
Keep the common calculators and protocol helpers close to hand.
3GPP Decoder
Decode and inspect protocol-oriented 3GPP data.
5G NR-ARFCN Calculator
Convert NR-ARFCN, bands, and frequencies.
LTE EARFCN Calculator
Convert LTE EARFCN values and bands.
5G NR Throughput Calculator
Estimate NR downlink and uplink throughput.
5G NR GSCN Calculator
Calculate synchronization raster and GSCN values.
5G NR TBS Calculator
Estimate NR transport block size.
Troubleshooting Guides
Find practical guides for debugging radio access, registration, mobility, session setup, throughput, and IMS signalling issues.
5G Registration and Access Failures
Trace registration rejection, access failure, TAI mismatch, and emergency access issues.
5G PHY Throughput Troubleshooting
Check radio, scheduling, MCS, PRB, and layer-related causes of low throughput.
RRC Troubleshooting
Map common RRC symptoms to likely radio and procedure causes.
IMS / VoLTE Troubleshooting
Use IMS SIP session flow context to isolate VoLTE setup and release issues.
General Troubleshooting Hub
Browse troubleshooting references by symptom, cause, and protocol area.
Learning Paths and Tutorials
Use structured tutorials and learning paths to understand LTE, VoLTE, IMS, and 5G from architecture to message-level troubleshooting.
LTE Tutorial / LTE Training
Learn LTE architecture, access, mobility, bearers, and signalling fundamentals.
VoLTE Tutorial
Follow IMS voice over LTE concepts, registration, bearer setup, and call procedures.
5G Learning Path
Use guided study paths for 5G architecture, protocols, and troubleshooting.
IMS / SIP Basics
Start with SIP requests and responses used in IMS service signalling.
3GPP Protocol Basics
Review what 3GPP is and how telecom standards fit together.
3G Tutorials
Review UMTS and 3G fundamentals when working across legacy networks.
3GPP Releases and Advanced Topics
Explore release-level changes and advanced wireless topics such as 5G-Advanced, NTN, MBS, private 5G, O-RAN, sidelink, positioning, and slicing.
3GPP Releases
Browse release-level changes from LTE through 5G-Advanced.
Release 18
Study the first 5G-Advanced baseline.
Release 19
Follow the second 5G-Advanced release wave.
Release 20
Track the bridge toward later 5G evolution and 6G study work.
5G-Advanced
Explore advanced 5G feature areas and engineering impact.
NTN
Review non-terrestrial network concepts and procedure context.
MBS
Read multicast and broadcast service mapping into radio bearers.
Network Slicing
Understand slicing, NSSAI, selection, and session behavior.
Sidelink
Review sidelink SDAP and SL-DRB mapping context.
Reference areas: 3GPP protocol specifications, LTE and 5G signalling procedures, IMS SIP and SDP references, and practical telecom engineering tools.
Latest Updates
Recent protocol, call-flow, message, and architecture updates from the reference library.
Initial UL RRC Message Transfer
Initial UL RRC Message Transfer is the F1AP message the gNB-DU sends to the gNB-CU to forward the first uplink RRC message received from a UE, including early cell and radio identifiers needed for CU-side access handling.
UE Context Release Request
UE Context Release Request is the F1AP UE-associated message the gNB-DU sends to the gNB-CU when the DU requests release of an existing UE-associated logical F1 connection or prepared release branch.
UL RRC Message Transfer
UL RRC Message Transfer is the F1AP UE-associated message the gNB-DU sends to the gNB-CU to deliver an uplink RRC message received from the UE over the selected SRB.
DL RRC Message Transfer
DL RRC Message Transfer is the F1AP UE-associated message the gNB-CU sends to the gNB-DU to deliver a downlink RRC message toward the UE over the selected SRB.
UE Context Modification Confirm
UE Context Modification Confirm is the F1AP message the gNB-CU sends to the gNB-DU to report successful update of the UE context after UE Context Modification Required.
UE Context Modification Required
UE Context Modification Required is the F1AP initiating message sent by the gNB-DU to the gNB-CU when the DU needs changes to an existing UE context.
UE Context Setup Failure
UE Context Setup Failure is the F1AP unsuccessful outcome sent by the gNB-DU to the gNB-CU when the DU cannot establish the requested UE context.
5G NAS - Service Request
Service Request is the NAS message the UE uses to request service resumption when it already has a valid registration context but needs active signaling again.
5G NAS - UL NAS Transport
UL NAS Transport is the NAS wrapper message the UE uses to send a payload upward toward the core when the NAS procedure needs to carry additional information transparently.
5G NAS - Security Mode Reject
Security Mode Reject is the NAS message the UE sends when it cannot accept the NAS security configuration selected by the AMF in Security Mode Command.
FAQ
What topics does 3GLTEInfo cover?
3GLTEInfo covers 5G, LTE, IMS, architecture, interfaces, protocol stacks, protocol messages, call flows, troubleshooting, releases, tutorials, and engineering tools.
Where can I find protocol messages?
Start at the Protocol Messages hub to browse 5G, LTE, IMS SIP, RRC, NAS, NGAP, F1AP, E1AP, XnAP, S1AP, LTE RRC, and LTE NAS messages.
Where can I find 5G architecture and interface references?
Use the 5G Architecture and 5G Interfaces sections for RAN, 5GC, N1, N2, N3, N4, N6, N9, F1, E1, Xn, and service-based interface references.
Which tools are available?
Popular tools include 3GPP Decoder, LTE EARFCN Calculator, 5G NR-ARFCN Calculator, 5G NR Throughput Calculator, 5G NR GSCN Calculator, and 5G NR TBS Calculator.
Who is this site for?
The site is for telecom engineers, RAN engineers, core network engineers, protocol testers, log analysts, students, and anyone troubleshooting LTE, 5G, IMS, or radio access signalling.