Alcatel-Lucent SA has closed its acquisition of Nortel Networks Corp.’s UMTS (Universal Mobile Telecommunications System) mobile infrastructure business, the companies announced Tuesday.

Alcatel-Lucent announced plans to buy the 3G (third-generation) networks business in September for $320 million less transaction costs. It has cleared the final regulatory approvals and closed the purchase on Dec. 31, it said.

The deal makes Alcatel-Lucent one of the largest providers of UMTS gear, with one in four UMTS operators worldwide using its products, the company said.

Nortel had failed to establish a leading position in the 3G market and will now focus instead on what it calls 4G mobile technologies, including WiMax, EV-DO (Evolution-Data Optimized) Revision C, and the LTE (Long-Term Evolution) generations of UMTS. It will also continue to support customers using earlier CDMA (Code Division Multiple Access) and GSM (Global System for Mobile Communications) technologies.

About 1,700 employees from Nortel’s UMTS unit are moving to Alcatel-Lucent, including most of the research and development team, the companies have said.

Alcatel and Lucent completed their merger in November.