T-Mobile USA to use Ericsson, Nokia Siemens gear 4 U.S. mobile provider, said on Monday that it plans to use network equipment from Sweden's Ericsson and Nokia Siemens Networks for a $4 billion network upgrade it is planning for 2013. T-Mobile USA, a unit of Deutsche Telekom, did not disclose the value of the total project budget to be allotted to the two European vendors. Nokia Siemens is a venture of Finland's Nokia and Germany's Siemens. The company expects the two vendors to install equipment for its upgrade in all the 37,000 cell towers in its network, it said at the annual CTIA Wireless industry conference here. Since T-Mobile USA's plan to sell itself to No. 2 U.S. mobile service AT&T Inc fell apart last year, the smaller operator is scrambling to catch up with high-speed wireless upgrades at its bigger rivals, including AT&T. T-Mobile USA is following its rivals' footsteps with an upgrade to a high-speed technology known as Long Term Evolution (LTE). Wireless network upgrades are expected to provide a boost for equipment vendors. Ericsson is the market leader in wireless network equipment and is double the size of its nearest rivals, Nokia Siemens and Huawei Technologies. Reporting By Sinead Carew; Editing by Richard Chang