TICC

Transport Independent Call Control

Protocol
Introduced in Rel-5
Transport Independent Call Control (TICC) is a 3GPP architecture and protocol framework that separates call control logic from the underlying transport technology. It enables the creation and management of multimedia sessions (like voice and video calls) over various IP-based and circuit-switched networks, providing network convergence and service flexibility.

Description

Transport Independent Call Control (TICC) is a core architectural principle and protocol framework defined in 3GPP TS 23.153. Its fundamental design decouples the call control and service logic from the specific details of the underlying transport network, whether it is IP-based (like IMS) or traditional circuit-switched. This is achieved through a layered approach where the call control layer manages the state and signaling for multimedia sessions, while the transport layer handles the actual bearer establishment and media flow. Key components include the Call State Control Function (CSCF) in the IMS for IP transport control and the Media Gateway Control Function (MGCF) for interworking with circuit-switched domains. TICC utilizes and extends the Session Initiation Protocol (SIP) as its primary signaling protocol for session establishment, modification, and termination. It defines how SIP messages are mapped to and from other signaling systems, such as ISDN User Part (ISUP) or Bearer Independent Call Control (BICC), to ensure seamless service delivery across heterogeneous networks. The framework is essential for enabling fixed-mobile convergence, allowing services like Voice over LTE (VoLTE) to interoperate with legacy PSTN/PLMN networks.

Purpose & Motivation

TICC was developed to address the challenge of network evolution and convergence. Traditional telecommunications were built on circuit-switched networks with tightly integrated call control and transport. The emergence of packet-switched IP networks created a need to support existing telephony services over new infrastructure without a complete, instantaneous overhaul. TICC solves this by providing a unified call control model that is agnostic to the transport layer. This allows network operators to introduce IP-based core networks (like IMS) gradually while maintaining interoperability with the vast installed base of circuit-switched equipment and subscribers. It was motivated by the desire to reduce operational costs, enable new multimedia services, and create a future-proof architecture. By separating control from transport, TICC facilitates the introduction of new access technologies (e.g., LTE, 5G NR) and transport mechanisms without requiring fundamental changes to the service logic, thereby protecting investments and accelerating innovation.

Key Features

  • Decouples call/session control logic from underlying transport technology
  • Utilizes SIP as the primary signaling protocol for session control
  • Defines interworking functions (e.g., MGCF) for connectivity with circuit-switched networks
  • Supports the Bearer Independent Call Control (BICC) protocol for trunking
  • Enables seamless fixed-mobile convergence (FMC)
  • Provides a foundation for IMS-based services like VoLTE and ViLTE

Evolution Across Releases

Rel-5 Initial

TICC was initially introduced in Release 5 as part of the IP Multimedia Subsystem (IMS) architecture. It established the core principle of transport-independent session control using SIP, primarily focusing on enabling multimedia services over GPRS/UMTS packet-switched domains and defining interworking with CS domains via the MGCF.

TS 23.153

Defining Specifications

SpecificationTitle
TS 23.153 3GPP TS 23.153