A Key Point Towards the NGN Evolution:The IP Subsystem

摘要

Operators are looking to migrate their mobile and fixed markets to IP-based multimedia applications and services with end-to-end quality-of-service (QoS) guarantee for cost and revenue generating advantages. As wireline and wireless services (including voice) migrate to IP, they will become part of a suite of real-time communication services running on IP networks that share a common client-server arrangement. In addition, the evolution to IP networks opens the door for several classes of new services in person-to-person communications (video-MMS, instant messaging, push to talk, enriched contact book...), and access to content (browsing, rich media, Java/active content, download/digital rights management...), and will regulate the relationship with the value-added service providers (location, kiosk, presence...). However, to implement these converged and new classes of services, and to ensure QoS, the network must have a consistent and robust services architecture which should be based on IMS. IMS, standardised by 3GPP and reused by TISPAN (ETSI), as the basis of the next-generation network (NGN), is an integrated and common architecture to manage a wide range of services and various modes of interconnection (UMTS, IP VPN, xDSL, WLAN...). It brings back the control session under the scope of the operator (SIP-based protocol, separation of data and signalling, call/session control layer...).The operator can charge users according to session content and this brings a better usage of data session content. To summarise, IMS should allow the establishment of several multimedia packet sessions with a policy QoS between two end-users. The paper discusses the IMS architecture based on a standards point of view and the IMS main features. The paper also provides an overview of IMS industrial proposals and the mutual action in standardisation.