Bearer Independent Call Control

The Bearer Independent Call Control (BICC) is a signaling protocol based on N-ISUP that is used to support narrowband ISDN service over a broadband backbone network without interfering with interfaces to the existing network and end-to-end services.

Specified by the International Telecommunications Union - Telecommunications Standardization Sector (ITU-T) in recommendation Q.1901, BICC was designed to be fully compatible with existing networks and any system capable of carrying voice messages.

BICC supports narrowband ISDN services independently of bearer and signaling message transport technology. ISUP messages carry both call control and bearer control information, identifying the physical bearer circuit by a Circuit Identification Code (CIC). The narrowband ISDN service also uses a CIC of a lower range referred to as the Circuit Identification Code.

However, CIC is specific to time-division multiplexed (TDM) networks. BICC was developed to be interoperable with any type of bearer, such as those based on asynchronous transfer mode (ATM) and Internet Protocol (IP) technologies, as well as TDM. BICC separates call control and bearer connection control, transporting BICC signaling independently of bearer control signaling.

The actual bearer transport used is transparent to the BICC signaling protocol - BICC has no knowledge of the specific bearer technology, which is referenced in the binding information.

Bearer setup directionIf the bearer is established in the same direction as the IAM sender then the bearer setup is said to be in the forward direction. If the bearer is established in the opposite direction as the IAM sender then the bearer setup is said to be in the backward direction.

The ITU announced the completion of the second set of BICC protocols (BICC Capability Set 2, or CS 2) in July 2001; these are expected to help move networks from the current model - which is based on public-switching systems - to a server-based model.

The BICC deployment architecture comprises a server, proxy, and a media gateway to support the current services over networks based on circuit-switched, ATM, and Internet Protocol (IP) technologies, including third-generation wireless.

According to the ITU, the completion of the BICC protocols is a historic step toward broadband multimedia networks, because it will enable the seamless migration of circuit-switched TDM networks to high-capacity broadband multimedia networks.

The Third Generation Partnership Project (3GPP) has included BICC CS 2 in the Universal Mobile Telecommunications Service (UMTS) release 4. Among the future ITU-T plans for BICC are the inclusion of more advanced service support and more utilization of proxies, such as the Session Initiation Protocol (SIP) proxy.

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