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UPDATED (2016-11-15): Yvette Koza (Deutsche Telekom AG / ETSI) was elected Vice Chairman of CT WG4 by acclamation.

The TSG Core Network and Terminals WG4 (CT WG4) standardizes stage 2 and stage 3 aspects within the Core Network focusing on Supplementary Services, Basic Call Processing, Mobility Management within the Core Network, Bearer Independent Architecture, GPRS between network entities, Transcoder Free Operation, CAMEL, Generic User Profile, Wireless LAN - UMTS interworking and descriptions of IP Multimedia Subsystem. CT WG4 is also responsible as a "protocol steward" for the some IP related protocols (this involves analyzing, validating, extending if necessary, clarifying how they are used, specifying packages and parameter values).

Terms of reference 

The latest terms of reference were appoved at CT#58 in document 

3GPP CT4’s mandate is to specify the protocols within the Core Network including specifications describing the protocol requirements. 

3GPP TSG CT WG4 (CT4) is responsible for the standardization of the stage 2 aspects within the Core Network including: 

  • Supplementary Services in the CS Domain,
  • Basic Call Processing in the CS Domain,
  • Mobility Management within the Core Network,
  • Bearer Independent Architecture
  • CAMEL.


CT4 is also responsible for the specification of the mobile specific protocol specifications within the mobile core network.


A number of protocols within the core network are specified by external bodies such as: the ITU-T and the IETF. In these cases, CT4 are involved in “profiling”, i.e. describing how and which part of these “external protocols” are to be used, setting default behaviour, restricting options and ensuring Backwards Compatibility. Specifying the protocol profiling between 3GPP specified protocols and these external protocols.


CT4 is responsible for the following core network feature specifications:


  • Stage 2 and (jointly with CT3) stage 3 specifications of the Bearer Independent Architecture;
  • Stage 2 and stage 3 (between Core Network entities) of Mobility Management within the Core Network;
  • Stage 2 and stage 3 (between Core Network entities) of Circuit-Switched Call Control within the Core Network, e.g. Basic Call Handling;
  • Stage 2 of the restoration procedures of the Core Network entities;
  • Profiling of Call Control Protocols defined outside 3GPP to be used within the Core Network, e.g. BICC, SIP-I;
  • Stage2 (jointly with CT3) and Stage 3 of MGW control protocol and profile definition (H.248 based);
  • Stage 3 (between network entities) of GPRS (e.g. Interfaces based on GTP, MAP and Diameter);
  • Stage 3 (between network entities) of EPC (e.g. Interfaces based on GTP, PMIP and Diameter);
  • Stage 2 and stage 3 of Supplementary Services in the CS Domain;
  • Stage 2 and stage 3 of Mobile Number Portability;
  • Stage 2 and stage 3 of Subscriber Data Management i.e. Numbering, Addressing and Identification and the Organisation of the Subscribers Data;
  • Stage 2 and stage 3 of Transcoder Free Operation (TrFO) - OoBTC (in conjunction with SA4);
  • Stage 2 and stage 3 of CAMEL;
  • Stage 3 of Location Services;
  • Stage 3 of Security (Authentication, Authorisation, Administration);
  • Stage 3 of WLAN – UMTS, EPS - WLAN interworking;
  • Stage 3 of Subscriber Certificates for Generic Authentication and Authorisation;
  • Stage 2 (jointly with SA2) and Stage 3 of the Generic User Profile (GUP);
  • Stage 3 (jointly with CT3) specifications of the IP Multimedia Subsystem (IMS); and
  • Stage 3 on DNS procedures within 3GPP


CT4 is responsible as a “protocol steward” for the following IP related protocols. This involves: analyzing, validating,
extending (if necessary), clarifying how they are used, specifying packages and their parameter values:


  • AAA protocols;
  • Security protocols;
  • Subscriber Data Management in the HSS and HSS-Core Network entities and the protocols to support it;
  • Diameter protocol codes, in particular requesting Application IDs from IANA;
  • AVP result codes and, in particular, reserving AVP codes from the 3GPP specific range;
  • Experimental result codes, in particular, reserving Experimental Result Codes from the 3GPP specific range.

Useful links and information

About CT WG4 List of elected officials
Documents Meeting documents
  Work items
Meetings Next meeting information & previous meeting reports and documents
  Liaisons Statements
  Full CT WG4 meeting calendar
General info 3GPP IETF Dependencies - from TSG#52 Jun 2011 onwards the 3GPP-IETF Dependencies are included in the 3GPP Work Plan
  Email exploder lists


CT Working groups 
TSG CT Plenary  
[No WG2] See Old Terminals Group 2
TSG CT WG3 Interworking with external networks
TSG CT WG5 OSA (Now transferred to OMA)
TSG CT WG6 Smart Card Application Aspects
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