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IP-Multimedia Subsystem

IMS is one of 3GPP’s greatest success stories.

Originally designed to evolve UMTS networks to deliver Internet Protocol multimedia to mobile users, IMS has become the core component within 3G, cable TV and next generation fixed telecoms networks.

IMS specification began in 3GPP Release 5 as part of the core network evolution from circuit-switching to packet-switching and was refined by subsequent Releases 6 and 7.


Initially, IMS was an all-IP system designed to assist mobile operators deliver next generation interactive and interoperable services, cost-effectively, over an architecture providing the flexibility of the Internet.

Standardisers now base their core network evolution on Common IMS

Session Initiation Protocol was selected as the signalling mechanism for IMS, thereby allowing voice, text and multimedia services to traverse all connected networks. 3GPP works closely with experts in the IETF to ensure maximum re-usability of internet standards, preventing fragmentation of IMS standards.

With the adoption of IMS by other industry sectors, the potential of a mass market to bring about substantial economies of scale will provide affordable broadband wireless access regardless of how and where users connect.

The responsibility for producing the Common IMS specifications in 3GPP lies largely with the Services and System Aspects (SA) group.

Reading should start with;

  • 22.228 Service requirements for an IMS system.
  • 23.228 Archtecture and main flows for an IMS system.
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