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IMS Feature Article

Transitioning to an IMS Services Environment

By Ian Moraes, Ph.D.            October 2006, Volume 1/Number 5

IMS Magazine

The IP Multimedia Subsystem (IMS) (News - Alert) architecture promises a vehicle for fixed/mobile network convergence, user mobility, access-agnostic application development, and a service-centric framework where new revenue-generating communication and messaging services can be developed on an
open architecture. An important component of the IMS architecture is the IMS Application Server where services are deployed and executed.
Operators appreciate the importance and value of an IMS architecture that offers a rapid service creation environment, lower operational expense, and new applications to increase their service offerings. But, today, a large number of operators currently offer messaging and communication services using legacy platforms comprising proprietary hardware and software with silo architectures. While the need to respond quickly to new market opportunities and to reduce operational costs are major drivers for operators seeking to transition to IMS, many are not ready to migrate to a complete IMS deployment immediately, but, instead, prefer a phased gradual movement to IMS.

Deploy a Next-Generation Communication Platform

To support this transition, an operator can begin by deploying a single next-generation communication services platform that functions as an IMS Application Server, offers an open access-agnostic architecture for service creation, provides for flexible bundling of services, and supports a broad set of new services for both fixed and mobile subscribers. This services framework is built using common off-the-shelf (COTS) hardware and software components and is designed to provide the robustness and performance required of carrier-grade systems.

Deploying a next-generation services platform in an initial phase is an appropriate transitional step for operators in their quest toward an IMS architecture. This type of application development environment can support existing services (voice mail, voice services, unified communications), and accelerates time-to-market for new differentiated services (video mail, video portal, advanced IP-based enhanced services) on a single platform. Its function as an IMS SIP Application Server (AS) enables a seamless integration with other IMS core network components as they are introduced into the network.

Benefits of Deploying a Next-Generation Communication Platform
Investing in a complete IMS deployment using a forklift approach is not feasible for many operators because of the significant cost and risk. There is a significant expense incurred by an operator for acquiring, migrating and integrating new IMS components such as Breakout Gateway (News - Alert) Control Function (BGCF), Call Session Control Function (CSCF), Home Subscriber Server (HSS), Subscription Locator Function (SLF), Policy Decision Function (PDF), and Media Gateway Control Function (MGCF). Also, the lack of complete definition and the evolving nature of the specifications coupled with the lack of proven multi-vendor interoperability and maturity of the components is a major risk.

Deploying an IMS AS platform initially allows an operator to gain a better insight and evaluation of the type of organizational structure, roles, and business processes required to create, market and support IMS services in advance of a more comprehensive IMS deployment. Using a phased approach of initially introducing an IMS AS platform offers a timelier path for service innovation, enables adoption of an incremental funding model, and lowers the barrier for entry into the IMS arena. This allows an operator to achieve a better return on investment compared to rolling out an entire IMS deployment.
...many [operators] are not ready to migrate to a complete IMS deployment immediately, but, instead, prefer a phased gradual movement to IMS.
The capability to quickly develop new personalized multimedia services to attract new subscribers and reduce customer churn is paramount. An inherent benefit of next-generation communication services platforms is that one can quickly develop new 2.5G/3G services using standard technology enablers such as Java and VoiceXML. Java facilitates rapid development of applications through a broad set of standard APIs such as JavaServer Pages (JSP) for generating dynamic Web pages, Java Database Connectivity (JDBC) for database access, the Java Naming and Directory Interface (JNDI) for access to directory servers, JavaMail for interfacing with email stores, and the Java API for XML-based RPC (JAX-RPC) for Web services. Java enables easy integration with the back-end data infrastructure (such as LDAP directory servers, SMTP/IMAP email stores, SOAP/RTSP content management and streaming services, and SQL databases), and SOAP/WSDL web services. Moreover, there are Java standards that specifically support SIP and IMS such as SIP Servlets and emerging APIs for Java-enabled handsets.

Another technology enabler that forms a core of next-generation services frameworks is VoiceXML. VoiceXML is an industry standard presentation technology used in telephony applications. It provides a powerful, easy-to-use, web-oriented, XML-based scripting language for voice, video and multimedia applications. When VoiceXML applications are used with Media Resource Control Protocol (MRCP)-based industry standard speech recognition and text-to-speech servers, a speech dimension can be added to multimedia applications. VoiceXML has been widely deployed and used to quickly develop rich multimedia applications. A new version of VoiceXML is being developed that promises new features and flexibility to support the next-generation of converged services.

Today, operators need to be able to offer a broad spectrum of messaging and communications services on different types of access networks. A next-gen communication platform can support TDM, IP and 3G services on a single platform comprising core multimedia application logic that is abstracted from the access mechanism. For example, basic services such as voice mail can be supported via TDM or SIP while newer services such as mobile video portals can be supported using the 3G-324M standard and SIP. Thus, the support for multiple access mechanisms on a single platform fits well with the access-agnostic IMS vision and enables a smoother transition when a complete IMS network is deployed.

A next-generation services platform enables an operator to take advantage of innovative features not available in legacy platforms. For example, operators can quickly create interactive multimedia applications using VoiceXML and Java that can then be deposited in subscribers’ mailboxes. After the subscriber authenticates and retrieves the message in his/her mailbox, the interactive application is executed allowing a subscriber to take actions on the content and information presented. This enables creating targeted offers (e.g., music or video offers) embedded in a message that the subscriber can then act on by making purchases, subscribing to new services, requesting more information or forwarding the offer to a friend. Thus, the ability to quickly create new targeted, short-lived applications is available on this type of platform and does not require a complete IMS network overhaul.

Legacy messaging deployments typically maintain subscriber data within each application platform with little opportunity to share data across applications. Next-generation communication platforms comprise a single authentication and authorization point and logical repository for subscriber data. They provide an open interface (HTTP/XML or SOAP) to access this data so that it can be shared across different applications. This design approach aligns well with the IMS generic user profile concept that provides a single point of access for subscriber data and a centralized server with access to multiple data repositories via protocols such as SOAP to provide a unified conceptual view of subscriber data. Thus, this type of strategy enables a smooth transition to realizing the IMS vision of subscriber data management.

A phased transitional strategy implies that an AS platform will be able to integrate with other IMS network components as they are introduced into the network. The integration of IMS functions using standard interfaces is a central tenet of the IMS architecture. An AS platform offers a SIP-based interface that can support the IMS Service Control (ISC) interface to the Serving CSCF (S-CSCF), the “Sh” interface that uses DIAMETER to interface with an HSS, and, the “Ut” interface that uses HTTP/XML to enable subscribers to manage service-specific data. Additionally, applications can access online and offline-charging functions with IMS “Ro/Rf” interfaces using DIAMETER. An AS platform can also be used along with the IMS Service Capability Interaction Manager (SCIM) function, in the future, to create composite services (akin to Web mashups that realize innovative services by blending data from different web sources) through service orchestration across IMS AS platforms.

Operators want to evolve their networks in an IMS direction as it matures. An initial deployment of a next-generation communication services platform that can function as an IMS Application Server provides a phased transition to an IMS architecture. A standards-based application architecture liberates operators from vendor lock-in, lowers operational costs, accelerates the time-to-market for new services and supports a broad set of access networks. This open architectural framework also enables third party developers to participate in this burgeoning ecosystem. These benefits clearly reflect the essence and promise of the IMS value proposition.

Ian Moraes, Ph.D., is a Principal Engineer in the CTO Office at Glenayre Messaging. For more information on Glenayre, visit

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