IMS as a key enabler

One of the main features of SATNAC are the various panel discussions where experts from around the world discuss aspects of emerging telecommunication technologies. While often agreeing on the technologies, their perspectives of pervasiveness and implementation may vary dramatically. IP multimedia subsystem (IMS) is in this category.

The subject was introduced by Prof. Thomas Magedanze, Fraunhofer Institute FOKUS, with Malcolm Johnson of the ITU and Falk Schröder, head of Mobile Architecture and Services Group and managing partner Detecon International Gmbh. While all agreed that is has a major contribution to make to the future success of telcos, not all agreed that it will be a killer application.

Prof. Megadanz introduced the subject by positioning IMS against the “over the top” (OTT) approach (see side panel). “OTT is a stand-alone once-off fast deployment solution offering fragmented user experience, whereas IMS offers an integrated end-user experience. IMS offers faster integration of subsequent applications. It re-uses deployed infrastructure with OPEX shared across the whole solution.

“IMS harmonises the session signalling over IP networks based on SIP but does not standardise specific services. It however provides common functionalities for many multimedia services, such as single sign on, security, charging, QoS, customer administration, etc.

“IMS represents a “natural” system evolution, that is, a combination of internet technologies and protocols with well-known intelligent networking concepts from the classic telecommunications world. In this regard, the IMS primarily defines a harmonised session control and AAA overlay architecture based on “carrier grade extensions” of flexible general purpose IETF protocols, such as the session initiation protocol (SIP) and Diameter protocols, to maintain control of IP-based service provision on top of mobile and fixed networks.

“To respect the competitive nature of the emerging multimedia services world, no specific services have been standardised in IMS.

“IMS today defines just a “docking station” for application servers, in order to control IP-based communication and information services and implement applications flexibly, to meet any emerging service demands. The SIP-based ISC interface for session control and the Diameter-based Sh interface for application server administration, as well as the Diameter-based Ro and Rf interfaces for online and offline charging, provide a minimum standardised “plug and play” capability so as to avoid a vendor lock.”

“IMS is an overlay architecture defining a standardised “docking station” for applications. It is built on existing IETF and ITU-T standards and is standardised by 3GPP, 3PGG2, ETSI, TISPAN and cable labs amongst many others. IMS provides compared to standard internet better security, service based quality of service (QoS), flexible charging and single sign on.

“Before IMS we had service island with voice, SMS, instant messaging and multimedia messaging as stand-alones. With IMS the end-user experiences a combinational service with all the services plus video available on a single handset.”

“Today differentiation and efficiency is needed for telcos to survive. The NGN service platforms and IMS have the potential to link internet / web 2.0 and telecommunications seamlessly.

“The question is IMS a key enabler? Can the IMS architecture deliver real network programmability? But what is the network? An IP-based carrier network? An access network – to the internet? The internet itself – as a set of interconnected networks? In principle, yes! SIP and Diameter are powerful and flexible enough to provide for control and flexible charging of any voice, video, messaging, or content sharing sessions, as well as enabling group management, presence and location services on top of any IP-based network. In contrast to any legacy network programming approach, IMS provides the necessary flexibility and openness.

“However, the major challenge is the internet as a programmable network itself! And here the question is – who is actually programming it? And who is able to develop revenue bringing services? And what will end users finally pay for? The IMS is a reasonable, but probably the last, unified approach of the telco industry to implement a controllable internet. If the IMS fails, the open internet and related application and content providers will take over and the network operators will provide the bit pipes. But not for free!”

During the panel discussion participants agreed with Prof. Magedanz that IMS is a key enabler. The one issue that emerged is the question of standardisation. The ITU process in standardising IMS was too slow which may have affected the intended impact on telecoms and did not achieve the position of killer application.

IMS discussion



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IMS as a key enabler