Q&A: IMS
What is IMS?
What are the main benefits of IMS?
How does IMS complement UMTS/HSPA networks?
What are some possible applications of IMS?
How are service applications developed for IMS?
What is A-IMS?
What is IMS?
IP Multi-media Subsystem (IMS) is a cost-effective architecture that allows operators to expand their current operations and leverage their investments in Internet Protocol (IP) technologies. IMS was created by wireless operators and vendors in order to enable rapid, reliable introduction of IP and SIP (Session Initiation Protocol) services into their existing and new networks. IMS is designed to provide operators with the means to satisfy the growing demand for diverse and rich communications services that provide direct revenue streams to service providers. Specifically, IMS defines a SIP-based session and service control platform that enables delivery of multimedia applications across different access networks, such as cellular, wireline and cable. It clearly defines a standard architecture and interfaces that not only separate the transport, session, and application layers, but also accommodate mobility, component reuse, and roaming.
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What are the main benefits of IMS?
IMS offers advantages for service providers, equipment manufacturers, independent software vendors (ISV), and end users. The standards impose a logical architecture that makes it cost-effective for operators to roll out new and increasingly personalized services in their networks without disrupting existing services and capabilities. Standard interfaces allow the service provider to offer new services by utilizing previously deployed assets. The model provides for QoS control for individual services, while at the same time protecting the integrity of overall network performance. IMS services can even be integrated with the existing CS services without disruption to the existing circuit base and can provide a smooth evolution of existing applications and services.
The IMS architecture is designed for combining multiple SIP applications so that capabilities – including common subscriber data, service activation, charging, load balancing, handoffs, and roaming – are implemented in a standard way. IMS, as a standard, puts in place a framework where SIP applications from multiple vendors can be integrated into a service provider’s network faster. The benefits of IMS when compared with other next-generation architectures or similar vertically integrated applications and services include:
- Cost advantages: Session control, subscriber data, and transport assets can be shared between applications making IMS cost-efficient for operators.
- Re-use of applications: The sharing of session control, subscriber data, and transport assets makes service and application development fast and efficient, as new applications do not need to re-develop these assets.
- Ease of new application deployment: New applications can be quickly and efficiently deployed because they fit into the existing network of session, subscriber data, and transport assets.
- Variety of vendors: Multi-vendor networks are practical and efficient. Session, transport, and application can be provided by different vendors for a given network or even application.
IMS also supports multiple access technologies, separating transport, session, and application planes to make them independent of access type. This provides efficiency for the service provider and an enhanced experience for the end user.
Service providers can then offer common services to customers over wireline or wireless access methods using the same assets. For operators and their vendors, the IMS architecture supports rapid and efficient service creation. For users, IMS makes it possible to access multiple services in the course of the same call or session.
IMS-based solutions provide both telephony services and multimedia telephony for fixed operators today. This enables service providers to pursue revenue growth opportunities and fixed-mobile convergence strategies. For pure mobile operators, IMS will enable a secure migration of today’s telephony services and users from circuit-switched to packet-switched bearers over time, once radio and packet core networks have evolved to enable efficient mobile telephony over IP.
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How does IMS complement UMTS/HSPA networks?
UMTS/HSPA is evolving toward a future wireless all-IP network, including access network capabilities that enable a multitude of new, mobile multimedia applications. UMTS/HSPA networks will provide the increased bandwidth necessary for a user to access services while on the move. An IMS-based multimedia service ecosystem is able to take maximum advantage of UMTS/HSPA network technology and its ability to supply high-speed data access, coupled with other key value-added characteristics such as an ‘always on’ connection, unprecedented quality of service, security and regulatory support.
IMS provides an architecture that facilitates the creation and deployment of complex multimedia applications, and provides service transparency and integration between networks and services. All these combine to ensure a rewarding user experience for the emerging generation of online services. These services integrate deeply into the user’s lifestyle and give the user more variety and greater control. Together, UMTS/HSPA and IMS will drive mobile data growth and user adoption.
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What are some possible applications of IMS?
IMS supports the concept of an open service creation model that allows the inclusion of third-party applications and application servers, enabling operators to tailor services and applications for their customers. Operators can develop the new services themselves, outsource the development work, or purchase IMS-compliant applications from external sources.
More than a thousand software development companies worldwide are estimated to be currently working on Session Initiation Protocol (SIP) applications, bringing innovation far beyond most previous expectations.
IMS services can provide a richer user experience by seamlessly integrating various media components such as messaging, video, streaming media, and others. Examples of these services include Push-to-Talk over Cellular (PoC) and Video Share. These services are designed to enrich the person-to-person communication experience.
Some services provide access to content and entertainment. These are classified as person-to-machine services. In this case, IMS becomes a secure vehicle for distributing premium content. Examples of these types of services include mobile music, streaming content and news, and others.
Other sets of services include machine-to-machine or collaborative services developed to address context-sensitive and/or community-based applications such as enterprise workflow processes.
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How are service applications developed for IMS?
To leverage the potential of multimedia services in a timely manner, be it rich communication and entertainment services or collaborative services – many of which are not yet known today – it is necessary to have a flexible service creation and execution environment. The 3GPP reference model that allows for an ecosystem composed of flexible and diverse services is shown in the figure below. It shows three basic classifications of service applications that can be implemented in an IMS-based environment. The top portion of the diagram shows native SIP applications deployed in SIP application servers. The right side of the diagram shows how Open Service Architecture (OSA) application services can interact with the IMS core through the OSA Service Capability Server (SCS) construct. The lower portion of the diagram depicts the integration of legacy services through an inter-working gateway or IP-Multimedia Service Switching Function (IM-SSF).
Functional architecture for support of service provision for IP multimedia subsystem
Through a SIP A/S container, developers can influence and impact the SIP session on behalf of the services, yet focus on the application business logic, while the container handles the non-essential complexity of the SIP signaling. It is possible for containers to support application composition and/or converged applications, e.g., applications that span multiple protocols and media types, be it web services or SIP.
Key to IMS and SIP architecture is the ability to integrate with other Internet-based protocols such as HTTP (Hypertext Transfer Protocol). After all, SIP is modeled after the HTTP and Internet paradigm of extensibility and flexibility. Thus, IMS applications can integrate with other non SIP-based services such as RTSP-based media streaming and SOAP/XML web-based services.
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What is A-IMS?
Advances to Multimedia Subsystem (A-IMS) is an additional IMS architecture with several new components that is being promoted by Verizon Wireless and several of its main IP core network vendors. It currently is not standardized by 3GPP. According to some proponents of A-IMS, it provides a set of enhancements to the 3GPP2 Multimedia Domain architecture that are related to 3GPP’s IMS. In order to uniformly manage both SIP and non-SIP services, A-IMS introduces two new elements: a Service Broker to manage the invocation of services and a Policy Manager, which allows the service provider to manage the usage of network resources on behalf of both types of applications.
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