Written by: Daniel Enström, Anders Nohlgren, Håkan Olofsson, Janne Peisa and Per Synnergren

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ETSI and 3GPP have standardized a new multimedia telephony service. The objective is to give operators the tools with which to build a converged fixed and mobile VoIP service offering with multimedia support. Multimedia telephony combines the quality, interoperability, reliability, efficiency, and regulatory and supplementary services of traditional telephony with the rich, flexible media capabilities of internet community-based services. And because the service is built on IMS, it is access-agnostic - that is, it can run over a variety of access networks.

The authors describe the service in terms of its media-handling capabilities and its set of supplementary services. They also show that WCDMA with HSPA is well suited to transport multimedia telephony.

Introduction
A new, rich communication culture is emerging as a consequence of community interaction on the internet. Communication has evolved into and revolves around the sharing of everyday experiences anywhere and at any time. Operators who choose to ride this wave to maintain their position in the value chain can employ IMS and benefit from rapid and innovative application development.

Global interconnect agreements for services (such as telephony and SMS) between operators constitute a key pillar of the telecommunications industry. Indeed, successful mass-market uptake of new services requires interoperability between operators, networks and devices. Being able to make a telephone call or to send an SMS to anyone, and knowing that the communication will work even across multiple operators and service providers, is a powerful concept that can only be achieved through global standards.

Therefore, in addition to the emergence of IMS as the service engine for next-generation IP networks, the industry has identified a need for detailed standardization of key IMS-based services, in particular for person-to-person communication. Standardizing such services facilitates multi-vendor interoperability and operator interconnect, and thus creates a potential for truly global, mass-market uptake.