Nokia Siemens Networks is partnering with an unlikely companion for its femtocell platform: CDMA technologist Airvana. The two companies said this week they were offering up a joint UMTS femtocell platform using Airvana’s radio access point technology and Nokia’s gateway.

Airvana was one of the primary companies to drive CDMA 1X EV-DO technologies, eventually reselling its software and equipment through the major CDMA vendors. But in the last year the company has been branching out from CDMA and exploring not only alternate technologies like WiMAX, but the much bigger world of GSM. At the 3GSM World Congress this year, Airvana launched its first universal access gateway, an access-agnostic IP platform designed to work with GSM, CDMA or WiMAX platforms. In May Airvana acquired 3Way Networks, a UMTS picocell and femtocell maker.

While UMTS may not be Airvana’s traditional area of expertise, radio access networks are as is the software that manages the complex functions of handoff and QoS, both of which give Airvana an edge in designing the tiny home base stations, which theoretically could be used to form a network of hundreds of thousands of tiny micro-cells in any given market.

Femtocells are basically home or indoor base stations designed to handle two or three calls simultaneously. Like other indoor fixed mobile convergence solutions, the femtocell uses a broadband pipe such as a DSL or cable modem connection to backhaul the cellular signal to a gateway—which is where Nokia Siemens comes in—linked to the core network. But unlike Wi-Fi-based technologies like unlicensed mobile access—recently launched by T-Mobile--the femtocell uses a carrier’s own spectrum, allowing the operator to extend its network without adding any new infrastructure.

Sprint on Monday announced its own limited commercial launch of Samsung-built femtocells in Indianapolis and Denver, becoming the first operator in the U.S. to pursue the technology and the first operator in the world to commercially deploy it.

Airvana and Nokia said they have successfully completed end-to-end trials over their combined architecture, making a call through the femtocell and back onto a Nokia core network. The companies will market and sell their joint solution to operators, but do not appear to be making their relationship exclusive. Airvana will certify its product to interoperate with the Nokia core, but they will ship their gear separately. The two companies expect to have trails of the platform running by the end of the year and deployments in 2008.