T-Mobile, which is expected to be the last major carrier in the United States to launch 4G LTE services presuming Sprint actually gets its act together and launches LTE this year, has delivered an update on its progress through its official blog. Here are the basic highlights: T-Mobile will be conducting trials of LTE Release 10 equipment this summer and is still on track to launch its LTE network next year. T-Mobile is upgrading 37,000 cell sites to LTE and has already secured zoning approval for 19,500 sites. The carrier expects to have 400 sites upgraded to LTE by the end of June and 2,500 sites upgraded by the end of July. In all, T-Mobile is spending $4 billion to deploy LTE across its network.