Making IMS Work in Your Network
By Duane Sword, Empirix
IP Multimedia Subsystem (IMS) simplifies the deployment of new services by providing a common set of content-rich multimedia applications across any IP-enabled network including DSL, cellular, cable, and WiFi. However, although the idea is to simplify the network, migration to IMS is complex and error-prone. Experience working with infrastructure vendors and carriers in laboratories and operating networks has revealed two primary challenges delaying real-world IMS deployments, namely: device interoperability and service interworking.

Device Interoperability

Interoperability problems stem from three major causes:

• IMS is still often being updated.
• Over a dozen groups are working on aspects of IMS, often with different approaches.
• · Standards for particular aspects of IMS are often unclear or unavailable.

Without a single reference point, there is obviously no such thing as "IMS certified." As a result, it is not surprising that most IMS products do not interoperate out of the box. Unfortunately, this lengthens implementation timelines and delays revenue realization for all parties.

Infrastructure vendors can get a head start on interoperability problems by testing during the development process. Testing is typically conducted with other vendors' products or with emulation devices that can simulate various IMS components. Similarly, service providers can conduct interoperability tests in their laboratories to identify issues and aid in vendor selection.

Service Interworking

As providers deploy new applications and services, they must ensure they not only interact correctly with each other, but also across other carriers' networks. For example, a carrier implementing fixed-mobile convergence needs to ensure its users can roam seamlessly between environments while maintaining basic features such as call forwarding and call waiting. In addition, they must ensure that calls to and from less advanced networks do not cause problems.

One way to identify interworking issues is to conduct specialized, end-to-end tests of new IP-enabled services to evaluate media quality (voice, video, data) and feature functionality. Even after the system is fully deployed and running, on-going monitoring of quality and functionality is vital to ensure that issues do not surface later.

The right set of test and measurement tools, such as Empirix's Hammer products, can help at all phases of development to simplify deployment and ensure the best experience for the end user. The Hammer product line provides media quality, load, feature, and device emulation testing and monitoring. Empirix has extensive experience in helping NEMs, service providers, and enterprises successfully transition to new telecom technologies, including CTI, TDM/PSTN, VoIP, next-generation networks, and now IMS.

Conclusion

Done right, IMS will enable faster deployment of new content-rich services. Done wrong, it can prevent NEMs and service providers from launching new products and services on time, and wreak havoc on basic network functions such as dial tone, voice quality, security, integrity, and transaction reliability. Maintaining or improving quality of experience for the end user during each migration step is critical.

Duane Sword is Vice President of Product Management for Empirix (Waltham, MA).