Since announcing its’ $4 billion 4G network evolution plan, T-Mobile has made substantial progress, operator has reported. T-Mobile LTE trials are underway and this summer it plans to begin using Release-10 equipment in these trials.

Operator has already selected Ericsson and Nokia Siemens Networks (NSN) to support It’s 4G network evolution plan, including network modernization and LTE deployment in 2013. Operator plans to modernize 37,000 cell sites and a move to the latest, LTE release 10 capable equipment.

According to T-Mobile, initially, this effort will improve existing voice and data coverage, make their 4G network compatible with a broader range of devices (including the iPhone), and pave the way for LTE service next year.

By the end of June, operator expects new equipment to be installed at its first 400 modernized GSM / HSPA+ sites and plans to grow this to over 2,500 sites by the end of July.

As new equipment is in place, T-Mobile is turning up some small scale tests 4G HSPA+ service in 1900 MHz spectrum. Operator is working toward introducing HSPA+ service in 1900 MHz spectrum in a large number of markets later this year.