As opposed to "mobile Next Generation Network" approach aiming at just carrying circuit services on top of the Internet Protocol (IP), the IP Multimedia Subsystem (IMS) offers operators the opportunity to build an open IP based service infrastructure that will enable an easy deployment of new rich multimedia communication services mixing telecom and data services. Alcatel IMS solution is based on 3GPP specifications but is also able to provide common IMS services for mobile and other access networks including fixed ones. Before trying to emulate circuit switched domain, IMS will first provide new services (such as Instant Messaging, Presence, Push to Talk over Cellular (PoC)) that are not too demanding for the underlying radio access network. These services will attract customers and create new telecommunication needs without inducing the technical risks and costs of speech with stringent quality over packet radio.