Convergent Multi-Media Conference

Description

Convergent Multi-Media Conference (CMMC) is a standardized service defined by 3GPP for multimedia conferencing within IP Multimedia Subsystem (IMS) networks. It provides the architectural framework and procedures for establishing, managing, and terminating conferences that combine multiple media types, such as audio, video, and data sharing (like whiteboarding or file transfer), into a single session. The service operates on top of the IMS core, utilizing SIP (Session Initiation Protocol) for session control and negotiation. It leverages IMS capabilities like authentication, authorization, and Quality of Service (QoS) management to ensure a secure and reliable conferencing experience across different access networks, including LTE, 5G NR, and fixed broadband.

The CMMC architecture involves several key functional entities. The Conference Focus is a central SIP user agent that hosts the conference, maintaining the signaling relationships with all participants and mixing or switching media streams. Participants connect to the Conference Focus via their User Equipment (UE) and the IMS core. The Media Resource Function (MRF) is responsible for the actual processing of media streams, including audio mixing, video composition, and transcoding between different codecs to ensure compatibility among diverse endpoints. The service interacts with other IMS entities like the Call Session Control Function (CSCF) for routing and the Home Subscriber Server (HSS) for user profile data.

From a procedural perspective, CMMC supports various conference models, including ad-hoc conferences created during an ongoing call and pre-arranged conferences scheduled in advance. A participant can join a conference via an explicit invitation (SIP INVITE) or by dialing a conference-specific URI. The Conference Focus manages participant roles (e.g., chairperson, participant), controls floor management for speaking rights, and can support features like conference recording and announcements. Media handling is flexible; for example, a video conference might use a centralized media mixing model where the MRF composites a single video layout, or a decentralized model using multicast or selective forwarding.

The role of CMMC in the network is to provide a carrier-grade, interoperable conferencing service that is integral to IMS-based communication offerings. It enables service providers to deploy advanced conferencing features consistently across mobile and fixed networks, facilitating business and consumer applications like virtual meetings, webinars, and collaborative work sessions. By being part of the 3GPP standards, CMMC ensures that implementations from different vendors can interwork, promoting a healthy ecosystem and seamless user experiences in multi-vendor network environments.

Purpose & Motivation

CMMC was created to address the growing demand for standardized, network-provided multimedia conferencing services within the framework of 3GPP's all-IP architecture, particularly IMS. Prior to its standardization, conferencing solutions were often proprietary, siloed systems that lacked interoperability between different networks and terminal types. This fragmentation limited scalability, complicated service provisioning, and hindered the user experience with inconsistent features and quality. The rise of mobile broadband and the convergence of fixed and mobile networks necessitated a unified approach to conferencing that could leverage the control and charging capabilities of the IMS core.

The primary problem CMMC solves is enabling seamless, rich multimedia group communication as a native network service, rather than an over-the-top application. By being integrated into the IMS, CMMC can utilize network-controlled QoS for guaranteed media quality, enforce security policies through IMS authentication, and support integrated billing via the Online Charging System (OCS). This allows operators to offer differentiated, reliable conferencing services with business models like premium conference calling. Furthermore, it supports convergence by allowing participants to join from various access networks (e.g., a 4G smartphone, a 5G tablet, or a wired VoIP desk phone) using the same service logic.

Historically, multimedia conferencing was often handled by standalone systems or internet-based applications that operated independently of the underlying network. These approaches lacked the ability to guarantee performance, deeply integrate with operator services (like number translation or emergency calling), or efficiently manage network resources. CMMC, introduced in 3GPP Release 8 alongside the maturation of IMS for mobile networks, provided a standards-based blueprint for operators to build conferencing into their service portfolios. It addressed limitations of previous non-standardized or access-specific conferencing by defining a clear architecture that works harmoniously with other IMS services like Voice over LTE (VoLTE) and Rich Communication Services (RCS), ensuring a consistent and managed user experience.

Key Features

• Support for mixed media types (audio, video, data) within a single conference session
• Integration with IMS core for authentication, authorization, and QoS management
• Flexible conference models including ad-hoc and pre-arranged conferences
• Centralized media processing via Media Resource Function (MRF) for mixing and transcoding
• Floor control and participant role management (e.g., chairperson privileges)
• Interoperability across diverse user equipment and network access types

Evolution Across Releases

Defining Specifications