BICC (Bearer independent call control)

Bearer Independent Call Control (BICC) is a protocol used in telecommunications networks to control the setup, maintenance, and release of voice and data calls. It was first introduced by the International Telecommunication Union (ITU) in 1993 as an extension of the ISDN User Part (ISUP) protocol used in circuit-switched networks.

BICC is a signaling protocol that operates at the signaling network layer of the Open Systems Interconnection (OSI) model. It is used to provide end-to-end signaling between network elements, including the user's terminal equipment, the access network, and the core network. BICC is particularly well-suited for use in mobile networks, where it provides support for both circuit-switched and packet-switched calls.

BICC is designed to be bearer-independent, which means that it can be used to control the setup, maintenance, and release of calls using different types of bearers, including circuit-switched, packet-switched, and ATM-based bearers. This makes BICC particularly useful in the context of modern telecommunications networks, which often use a mix of different bearer technologies to support a wide range of services.

The BICC protocol defines a number of messages that are used to control the setup, maintenance, and release of calls. These messages are exchanged between network elements using the Signaling Connection Control Part (SCCP) protocol, which provides reliable transport of signaling messages between network elements. BICC messages include:

• Initial Address Message (IAM): This message is used to initiate a call and includes information about the calling and called parties, as well as information about the type of bearer being used.
• Address Complete Message (ACM): This message is sent by the called party's network element to indicate that the called party is ready to receive the call.
• Call Progress Message (CPG): This message is sent by the called party's network element to indicate that the call is progressing.
• Connect Message (CON): This message is sent by the called party's network element to indicate that the call has been successfully connected.
• Release Message (REL): This message is used to release a call.
• Release Complete Message (RLC): This message is sent by the releasing party's network element to indicate that the call has been successfully released.

BICC also includes a number of other messages that are used to handle call transfers, call diversion, and other advanced call control features.

One of the key advantages of BICC is its ability to support both circuit-switched and packet-switched calls. When used with circuit-switched calls, BICC is typically used in conjunction with the ISUP protocol, which provides the signaling for the circuit-switched portion of the call. When used with packet-switched calls, BICC is typically used in conjunction with the Session Initiation Protocol (SIP) or the Mobile Application Part (MAP) protocol.

Another advantage of BICC is its support for a wide range of bearer technologies, including ATM-based bearers. This makes BICC particularly useful in the context of modern telecommunications networks, which often use a mix of different bearer technologies to support a wide range of services.

In addition to its support for different bearers, BICC also provides a number of advanced call control features. For example, BICC includes support for call transfer, call diversion, call waiting, and call hold. These features allow users to manage their calls more effectively and can improve the overall quality of service in the network.

Despite its advantages, BICC has some limitations. For example, BICC was designed primarily for use in circuit-switched networks and may not be well-suited for use in fully packet-switched networks. Additionally, BICC does not provide support for some advanced call control features, such as call conferencing and call queuing, which may limit its usefulness in certain contexts.

Another limitation of BICC is its complexity. Because BICC is designed to support a wide range of bearers and call control features, it can be quite complex to implement and configure. This can make it difficult for network operators to deploy and maintain BICC-based networks.

Despite these limitations, BICC remains an important protocol in the telecommunications industry. Many legacy networks still rely on BICC for call control, and BICC is often used in conjunction with newer protocols like SIP and MAP to support a wide range of services.

In recent years, there has been a growing trend toward packet-switched networks, which use protocols like SIP and Diameter for call control. As a result, the role of BICC in modern telecommunications networks is likely to diminish over time. However, BICC is still an important protocol for legacy networks and will likely continue to play a role in the industry for years to come.