Cingular Wireless has awarded Lucent a four-year agreement to help the largest U.S. mobile operator build an IP Multimedia Subsystem (IMS) for developing and delivering subscriber services, the companies said Monday.

An IMS defines how an IP network should handle voice calls and data sessions. It essentially takes the place of the control infrastructure in a traditional circuit-switched phone network, but it separates services from the networks that carry them. That way, services can reside on central application servers and be delivered over any type of network connection. Based on open standards, it has been embraced by several key telecommunications standards bodies around the world.

Once implemented, Lucent's technology will let Cingular develop new, easy-to-use services that customers can access from anywhere on almost any device, the companies said in a statement. It will also be a more cost-effective system for delivering new services, according to Cingular.

Under the agreement, Lucent will provide components of its Accelerate Next Generation Communications Solutions portfolio and the Lucent Technologies Bell Labs Service Enhancement Layer, a set of software elements developed by Lucent's Bell Labs division. Lucent Worldwide Services will help Cingular with deployment and integration of the infrastructure, including multivendor integration and technical support services, the companies said.

Cingular has a nationwide voice and data network based on GSM/GPRS (Global System for Mobile Communications/General Packet Radio Service) with more than 51 million customers and is building out a high-speed UMTS (Universal Mobile Telecommunications System) infrastructure in several markets. Lucent grew out of AT&T's Bell Labs with a spin-off in the late 1990s.

The companies are not disclosing financial terms of the agreement, said Lucent spokesman Mike Alva.

Cingular, a joint venture of wireline carriers SBC and BellSouth, may use IMS to build a mobile roaming service using a dual-mode handset that lets users go between a home line and the cellular network, said Tom Nolle, president of telecommunications consulting and products company CIMI. Lucent's Alva confirmed the company's technology could be used for this. Cingular representatives could not immediately be reached for comment.

The IDG News Service is a Network World affiliate.